2021-07-04 20:29:21

by Miguel Ojeda

Subject: [PATCH 00/17] Rust support

From: Miguel Ojeda <[email protected]>

Rust support

This is the patch series to add support for Rust as a second language
to the Linux kernel.

If you are interested in following this effort, please join us in
the mailing list at:

[email protected]

and take a look at the project itself at:

https://github.com/Rust-for-Linux

Cheers,
Miguel

--

# Rust support

This cover letter explains the major changes and updates done since
the RFC sent in the previous merge window back in April, plus a few
extra notes and announcements. For the RFC, please see:

https://lore.kernel.org/lkml/[email protected]/


## Rust infrastructure updates

There have been several major improvements to the overall Rust
support. The following subsections cover these.


### Removed panicking allocations

We have removed infallible allocations. In order to do so, we have
integrated a subset of the `alloc` standard library crate, with some
additions on top. This allows us to customize things to our needs,
while giving upstream the time they need to evaluate our changes.

Eventually, the goal is to have everything the kernel needs in
upstream `alloc` and drop it from the kernel tree. We have already
started this process and some changes have been already accepted
upstream.

On top of that, `alloc` is now compiled with panicking allocation
methods disabled, thus they cannot be used within the kernel by
mistake either.

Moreover, the documentation for this customized `alloc` crate (as well
as for `core`) is now generated alongside the rest of the Rust kernel
documentation. Thus kernel developers can now easily browse the subset
that is available within the kernel. Like last time, you can take
a look at a preview of the documentation at:

https://rust-for-linux.github.io/docs/alloc/

Note that the `compiler_builtins` panicking intrinsics are still
there, but those will be solved by partitioning `core` via feature
gates. The first one, for disabling floating-point functionality,
has just been accepted upstream.


### Beta compiler supported

Up until now, we have been using nightly releases of `rustc` because
we need some of the latest fixes and unstable features.

However, the kernel can now be compiled with beta and stable `rustc`
releases. At the moment, we are using the 1.54-beta1 version as our
reference compiler. At the end of this month, `rustc` 1.54 will be
released, and we will move to that version as our reference.

Note that the kernel still requires unstable features, even if it is
compiled with a stable `rustc` release, thus we cannot guarantee that
future `rustc` versions will work without changes to the kernel tree.

Thus, until all the unstable features we need are stabilized, we will
support a single `rustc` version for each kernel release.


### Testing support

Another big addition has been the support for testing. We now support
the standard Rust `#[test]` attribute to easily write tests, e.g.:

#[test]
fn f() {
let a = 20;
let b = 22;
assert_eq!(a + b, 42);
}

Furthermore, we are now also supporting Rust documentation tests
("doctests"). These allow us to make sure our examples remain up to
date, and also double as tests too, e.g.:

/// ```
/// assert_eq!(foo::f(), 42);
/// ```
pub fn f() -> i32 {
42
}

For the moment, both kinds of tests are run in the host only, but
the goal is to have them running in kernel space, so that we can
test code that depends on kernel features, and to allow any kernel
module to declare and use them.


### Architectures and compiler support

`arm` (i.e. 32-bit) and `riscv` are now also supported.

On compilers, we would like to mention all the work that has been
going in GCC Rust (a GCC frontend for the Rust language) and
`rustc_codegen_gcc` (a `rustc` backend for GCC). The latter now passes
all `core` tests, and the former is now working on traits. We continue
to track their progress as they may become the best way to have
GCC-built kernels with Rust support enabled. Their latest reports
can be found at:

https://blog.antoyo.xyz/rustc_codegen_gcc-progress-report-1
https://thephilbert.io/2021/06/28/gcc-rust-weekly-status-report-20/

On top of that, we requested Compiler Explorer to add support to all
the alternative compilers. At the time of writing, they have already
added `mrustc` and GCC Rust; and `rustc_codegen_gcc` is coming soon.
See a live example at:

https://godbolt.org/z/8o74c57Yj


## Rust abstractions and driver updates

We have developed new Rust abstractions that use the kernel C
implementations: red-black trees, reference-counted objects, file
descriptor creation, tasks, files, io vectors...

Additionally, we have improved driver support: improvements to
`file_operations` (more operations supported, arbitrary state),
reduced boiler-plate code, improved `module!` macro, registration
macros, rudimentary (`probe` and `remove`) platform drivers...

On Binder, there is now support for transferring files descriptors
and LSM hooks; and we are working on preliminary performance numbers.

Moreover, there is ongoing work on a Rust example driver,
`bcm2835-rng`. This is the hardware random-number generator present
on Raspberry Pi Zero(W), Classic, Two, and Three.

There are other small improvements, such as drivers being restricted
on what unstable features they can use.


## Patch series status

Like it was mentioned in the RFC, the Rust support is still to be
considered experimental. However, as noted back in April, support is
good enough that kernel developers can start working on the Rust
abstractions for subsystems and write drivers and other modules.

Please note that the current series have just arrived in `linux-next`,
thus the first run will happen on Tuesday.


## Industry and academia support

We have been in contact with a set of companies and academia members
that would like to use Rust as a second language in the kernel. Some
of them have already started to evaluate Rust for their needs using
the infrastructure we have already in place.

In particular, we have got a few statements from major companies.
In no particular order:

Microsoft's Linux Systems Group is interested in contributing to
getting Rust into Linux kernel. Hopefully we will be able to submit
select Hyper-V drivers written in Rust in the coming months.

Arm recognises the Rust value proposition and is actively working
with the Rust community to improve Rust for Arm based systems.
A good example is Arm’s RFC contribution to the Rust language which
made Linux on 64-bit Arm systems a Tier-1 Rust supported platform.
Rustaceans at Arm are excited about the Rust for Linux initiative
and look forward to assisting in this effort.

Google supports and contributes directly to the Rust for Linux
project. Our Android team is evaluating a new Binder implementation
and considering other drivers where Rust could be adopted.

In addition, IBM contributed the Rust kernel support for PowerPC
which was already included in the RFC.

In addition, from academia, there are already several projects around
Rust for Linux going on. As an example, members of LSE (Systems
Research Laboratory) at EPITA (École pour l'informatique et les
techniques avancées) are developing an SPI Rust driver.

And, of course, special thanks go to ISRG (Internet Security Research
Group) and Google for their financial support on this endeavor.


## Conferences and talks

We have submitted talk proposals for LPC (Linux Plumbers Conference).

The main one will describe the work we have done so far and ideally
will also serve as an introduction for other kernel developers
interested in using Rust in the kernel. It will cover an introduction
of the language within the context of the kernel, how the overall Rust
support works, how code is documented, how tests are written, a tour
of available tooling, an explanation of coding guidelines, how kernel
driver code looks like, etc.

In addition, we would like to announce that we are organizing a new
conference that focuses on Rust and the Linux kernel. The first
edition will be virtual and will take place before LPC. Details will
be announced soon.


## Acknowledgements

The signatures in the main commits correspond to the people that
wrote code that has ended up in them at the present time. For details
on contributions to code and discussions, please see our repository:

https://github.com/Rust-for-Linux/linux

However, we would like to give credit to everyone that has contributed
in one way or another to the Rust for Linux project. Since the RFC:

- bjorn3 for all the input on Rust compiler details and all
the reviews and suggestions.

- Arthur Cohen, Esteban Blanc and Martin Schmidt for their ongoing
work on the SPI abstractions and driver.

- Dan Robertson for his ongoing work on softdeps in the `module!`
macro and the addition of a few safety comments.

- Paul Römer for his ongoing experiment on using `NonNull` as much
as possible.

- Sladyn Nunes for his ongoing sorting of error constants.

- Jonathan Corbet and the LPC organizers for lending us the Linux
Plumbers Conference infrastructure so that we can have an easy
time setting up the new conference.

- John Ericson for quickly implementing the `no_global_oom_handling`
`cfg` feature in upstream `alloc` to easily disable all
functionality that relies on panicking allocations.

- Josh Triplett and John Ericson for their input on `alloc` which
helped us decide what to do with it (i.e. fully custom vs.
slightly custom in-tree copy vs. upstream), as well as offering
to help moving forward some needed features on the Rust side.

- Mark Rousskov for answering some questions about beta backports
and scheduling, as well as working on unsticking `1.54.0-beta.1`.

- Philipp Krones for his input on Clippy lints and discussing
extensions for developing custom lints.

- Antoni Boucher for his work on `rustc_codegen_gcc`.

- Philip Herrons (and his supporters Open Source Security and
Embecosm) for his work on GCC Rust.

- Marc Poulhiès for his work on Compiler Explorer to add the
alternative Rust compilers we requested.

- Many folks that have reported issues, tested the project,
helped spread the word, joined discussions and contributed in
other ways! In no particular order: Chenguang Wang, Greg Morenz,
John Baublitz, Leah Leshchinsky, Caedin Cook, Liam Arzola,
Fabio Aiuto, Hanqing Zhao, Robin Randhawa, Michal Rostecki,
Wei Liu...

For additional acknowledgements, please see the RFC from April.

Miguel Ojeda (17):
kallsyms: support big kernel symbols (2-byte lengths)
kallsyms: increase maximum kernel symbol length to 512
Makefile: generate `CLANG_FLAGS` even in GCC builds
vsprintf: add new `%pA` format specifier
rust: add C helpers
rust: add `compiler_builtins` crate
rust: add `alloc` crate
rust: add `build_error` crate
rust: add `macros` crate
rust: add `kernel` crate
rust: export generated symbols
Kbuild: add Rust support
docs: add Rust documentation
samples: add Rust examples
scripts: add `generate_rust_analyzer.py`
MAINTAINERS: Rust
Android: Binder IPC in Rust (WIP)

.gitignore | 5 +
.rustfmt.toml | 12 +
Documentation/doc-guide/kernel-doc.rst | 3 +
Documentation/index.rst | 1 +
Documentation/kbuild/kbuild.rst | 4 +
Documentation/process/changes.rst | 13 +
Documentation/rust/arch-support.rst | 35 +
Documentation/rust/assets/favicon-16x16.png | Bin 0 -> 798 bytes
Documentation/rust/assets/favicon-32x32.png | Bin 0 -> 2076 bytes
Documentation/rust/assets/rust-logo.png | Bin 0 -> 53976 bytes
Documentation/rust/coding.rst | 92 +
Documentation/rust/docs.rst | 110 +
Documentation/rust/index.rst | 20 +
Documentation/rust/quick-start.rst | 222 ++
MAINTAINERS | 14 +
Makefile | 176 +-
arch/arm/rust/target.json | 28 +
arch/arm64/rust/target.json | 35 +
arch/powerpc/rust/target.json | 30 +
arch/riscv/Makefile | 1 +
arch/riscv/rust/rv32ima.json | 37 +
arch/riscv/rust/rv32imac.json | 37 +
arch/riscv/rust/rv64ima.json | 37 +
arch/riscv/rust/rv64imac.json | 37 +
arch/x86/rust/target.json | 37 +
drivers/android/Kconfig | 7 +
drivers/android/Makefile | 2 +
drivers/android/allocation.rs | 264 ++
drivers/android/context.rs | 80 +
drivers/android/defs.rs | 99 +
drivers/android/node.rs | 476 +++
drivers/android/process.rs | 972 ++++++
drivers/android/range_alloc.rs | 189 ++
drivers/android/rust_binder.rs | 114 +
drivers/android/thread.rs | 857 +++++
drivers/android/transaction.rs | 328 ++
include/linux/kallsyms.h | 2 +-
include/linux/spinlock.h | 17 +-
include/uapi/linux/android/binder.h | 28 +-
init/Kconfig | 28 +
kernel/kallsyms.c | 7 +
kernel/livepatch/core.c | 4 +-
kernel/printk/printk.c | 5 +-
lib/Kconfig.debug | 144 +
lib/vsprintf.c | 12 +
rust/.gitignore | 6 +
rust/Makefile | 316 ++
rust/alloc/README.md | 32 +
rust/alloc/alloc.rs | 425 +++
rust/alloc/borrow.rs | 493 +++
rust/alloc/boxed.rs | 1728 ++++++++++
rust/alloc/collections/mod.rs | 116 +
rust/alloc/fmt.rs | 587 ++++
rust/alloc/lib.rs | 197 ++
rust/alloc/macros.rs | 128 +
rust/alloc/prelude/mod.rs | 17 +
rust/alloc/prelude/v1.rs | 16 +
rust/alloc/raw_vec.rs | 612 ++++
rust/alloc/rc.rs | 2539 +++++++++++++++
rust/alloc/slice.rs | 1271 ++++++++
rust/alloc/str.rs | 614 ++++
rust/alloc/string.rs | 2847 ++++++++++++++++
rust/alloc/sync.rs | 2631 +++++++++++++++
rust/alloc/vec/drain.rs | 157 +
rust/alloc/vec/drain_filter.rs | 145 +
rust/alloc/vec/into_iter.rs | 296 ++
rust/alloc/vec/is_zero.rs | 106 +
rust/alloc/vec/mod.rs | 3255 +++++++++++++++++++
rust/alloc/vec/partial_eq.rs | 49 +
rust/alloc/vec/set_len_on_drop.rs | 30 +
rust/alloc/vec/spec_extend.rs | 170 +
rust/bindgen_parameters | 13 +
rust/build_error.rs | 33 +
rust/compiler_builtins.rs | 146 +
rust/exports.c | 16 +
rust/helpers.c | 235 ++
rust/kernel/allocator.rs | 63 +
rust/kernel/bindings.rs | 28 +
rust/kernel/bindings_helper.h | 24 +
rust/kernel/buffer.rs | 39 +
rust/kernel/build_assert.rs | 80 +
rust/kernel/c_types.rs | 119 +
rust/kernel/chrdev.rs | 212 ++
rust/kernel/error.rs | 272 ++
rust/kernel/file.rs | 130 +
rust/kernel/file_operations.rs | 698 ++++
rust/kernel/io_buffer.rs | 153 +
rust/kernel/iov_iter.rs | 95 +
rust/kernel/lib.rs | 220 ++
rust/kernel/linked_list.rs | 245 ++
rust/kernel/miscdev.rs | 113 +
rust/kernel/module_param.rs | 497 +++
rust/kernel/of.rs | 101 +
rust/kernel/pages.rs | 176 +
rust/kernel/platdev.rs | 166 +
rust/kernel/prelude.rs | 28 +
rust/kernel/print.rs | 412 +++
rust/kernel/random.rs | 50 +
rust/kernel/raw_list.rs | 361 ++
rust/kernel/rbtree.rs | 570 ++++
rust/kernel/security.rs | 79 +
rust/kernel/static_assert.rs | 39 +
rust/kernel/str.rs | 259 ++
rust/kernel/sync/arc.rs | 227 ++
rust/kernel/sync/condvar.rs | 136 +
rust/kernel/sync/guard.rs | 82 +
rust/kernel/sync/locked_by.rs | 112 +
rust/kernel/sync/mod.rs | 84 +
rust/kernel/sync/mutex.rs | 101 +
rust/kernel/sync/spinlock.rs | 109 +
rust/kernel/sysctl.rs | 198 ++
rust/kernel/task.rs | 193 ++
rust/kernel/traits.rs | 26 +
rust/kernel/types.rs | 249 ++
rust/kernel/user_ptr.rs | 191 ++
rust/macros/lib.rs | 127 +
rust/macros/module.rs | 754 +++++
samples/Kconfig | 2 +
samples/Makefile | 1 +
samples/rust/Kconfig | 113 +
samples/rust/Makefile | 12 +
samples/rust/rust_chrdev.rs | 51 +
samples/rust/rust_minimal.rs | 38 +
samples/rust/rust_miscdev.rs | 150 +
samples/rust/rust_module_parameters.rs | 72 +
samples/rust/rust_print.rs | 57 +
samples/rust/rust_random.rs | 61 +
samples/rust/rust_semaphore.rs | 177 +
samples/rust/rust_semaphore_c.c | 212 ++
samples/rust/rust_stack_probing.rs | 40 +
samples/rust/rust_sync.rs | 81 +
scripts/Makefile.build | 22 +
scripts/Makefile.lib | 12 +
scripts/generate_rust_analyzer.py | 143 +
scripts/kallsyms.c | 33 +-
scripts/kconfig/confdata.c | 67 +-
scripts/rust-version.sh | 31 +
tools/include/linux/kallsyms.h | 2 +-
tools/include/linux/lockdep.h | 2 +-
tools/lib/perf/include/perf/event.h | 2 +-
tools/lib/symbol/kallsyms.h | 2 +-
141 files changed, 33003 insertions(+), 45 deletions(-)
create mode 100644 .rustfmt.toml
create mode 100644 Documentation/rust/arch-support.rst
create mode 100644 Documentation/rust/assets/favicon-16x16.png
create mode 100644 Documentation/rust/assets/favicon-32x32.png
create mode 100644 Documentation/rust/assets/rust-logo.png
create mode 100644 Documentation/rust/coding.rst
create mode 100644 Documentation/rust/docs.rst
create mode 100644 Documentation/rust/index.rst
create mode 100644 Documentation/rust/quick-start.rst
create mode 100644 arch/arm/rust/target.json
create mode 100644 arch/arm64/rust/target.json
create mode 100644 arch/powerpc/rust/target.json
create mode 100644 arch/riscv/rust/rv32ima.json
create mode 100644 arch/riscv/rust/rv32imac.json
create mode 100644 arch/riscv/rust/rv64ima.json
create mode 100644 arch/riscv/rust/rv64imac.json
create mode 100644 arch/x86/rust/target.json
create mode 100644 drivers/android/allocation.rs
create mode 100644 drivers/android/context.rs
create mode 100644 drivers/android/defs.rs
create mode 100644 drivers/android/node.rs
create mode 100644 drivers/android/process.rs
create mode 100644 drivers/android/range_alloc.rs
create mode 100644 drivers/android/rust_binder.rs
create mode 100644 drivers/android/thread.rs
create mode 100644 drivers/android/transaction.rs
create mode 100644 rust/.gitignore
create mode 100644 rust/Makefile
create mode 100644 rust/alloc/README.md
create mode 100644 rust/alloc/alloc.rs
create mode 100644 rust/alloc/borrow.rs
create mode 100644 rust/alloc/boxed.rs
create mode 100644 rust/alloc/collections/mod.rs
create mode 100644 rust/alloc/fmt.rs
create mode 100644 rust/alloc/lib.rs
create mode 100644 rust/alloc/macros.rs
create mode 100644 rust/alloc/prelude/mod.rs
create mode 100644 rust/alloc/prelude/v1.rs
create mode 100644 rust/alloc/raw_vec.rs
create mode 100644 rust/alloc/rc.rs
create mode 100644 rust/alloc/slice.rs
create mode 100644 rust/alloc/str.rs
create mode 100644 rust/alloc/string.rs
create mode 100644 rust/alloc/sync.rs
create mode 100644 rust/alloc/vec/drain.rs
create mode 100644 rust/alloc/vec/drain_filter.rs
create mode 100644 rust/alloc/vec/into_iter.rs
create mode 100644 rust/alloc/vec/is_zero.rs
create mode 100644 rust/alloc/vec/mod.rs
create mode 100644 rust/alloc/vec/partial_eq.rs
create mode 100644 rust/alloc/vec/set_len_on_drop.rs
create mode 100644 rust/alloc/vec/spec_extend.rs
create mode 100644 rust/bindgen_parameters
create mode 100644 rust/build_error.rs
create mode 100644 rust/compiler_builtins.rs
create mode 100644 rust/exports.c
create mode 100644 rust/helpers.c
create mode 100644 rust/kernel/allocator.rs
create mode 100644 rust/kernel/bindings.rs
create mode 100644 rust/kernel/bindings_helper.h
create mode 100644 rust/kernel/buffer.rs
create mode 100644 rust/kernel/build_assert.rs
create mode 100644 rust/kernel/c_types.rs
create mode 100644 rust/kernel/chrdev.rs
create mode 100644 rust/kernel/error.rs
create mode 100644 rust/kernel/file.rs
create mode 100644 rust/kernel/file_operations.rs
create mode 100644 rust/kernel/io_buffer.rs
create mode 100644 rust/kernel/iov_iter.rs
create mode 100644 rust/kernel/lib.rs
create mode 100644 rust/kernel/linked_list.rs
create mode 100644 rust/kernel/miscdev.rs
create mode 100644 rust/kernel/module_param.rs
create mode 100644 rust/kernel/of.rs
create mode 100644 rust/kernel/pages.rs
create mode 100644 rust/kernel/platdev.rs
create mode 100644 rust/kernel/prelude.rs
create mode 100644 rust/kernel/print.rs
create mode 100644 rust/kernel/random.rs
create mode 100644 rust/kernel/raw_list.rs
create mode 100644 rust/kernel/rbtree.rs
create mode 100644 rust/kernel/security.rs
create mode 100644 rust/kernel/static_assert.rs
create mode 100644 rust/kernel/str.rs
create mode 100644 rust/kernel/sync/arc.rs
create mode 100644 rust/kernel/sync/condvar.rs
create mode 100644 rust/kernel/sync/guard.rs
create mode 100644 rust/kernel/sync/locked_by.rs
create mode 100644 rust/kernel/sync/mod.rs
create mode 100644 rust/kernel/sync/mutex.rs
create mode 100644 rust/kernel/sync/spinlock.rs
create mode 100644 rust/kernel/sysctl.rs
create mode 100644 rust/kernel/task.rs
create mode 100644 rust/kernel/traits.rs
create mode 100644 rust/kernel/types.rs
create mode 100644 rust/kernel/user_ptr.rs
create mode 100644 rust/macros/lib.rs
create mode 100644 rust/macros/module.rs
create mode 100644 samples/rust/Kconfig
create mode 100644 samples/rust/Makefile
create mode 100644 samples/rust/rust_chrdev.rs
create mode 100644 samples/rust/rust_minimal.rs
create mode 100644 samples/rust/rust_miscdev.rs
create mode 100644 samples/rust/rust_module_parameters.rs
create mode 100644 samples/rust/rust_print.rs
create mode 100644 samples/rust/rust_random.rs
create mode 100644 samples/rust/rust_semaphore.rs
create mode 100644 samples/rust/rust_semaphore_c.c
create mode 100644 samples/rust/rust_stack_probing.rs
create mode 100644 samples/rust/rust_sync.rs
create mode 100755 scripts/generate_rust_analyzer.py
create mode 100755 scripts/rust-version.sh

--
2.32.0

2021-07-04 20:29:30

by Miguel Ojeda

Subject: [PATCH 02/17] kallsyms: increase maximum kernel symbol length to 512

From: Miguel Ojeda <[email protected]>

Rust symbols can become quite long due to namespacing introduced
by modules, types, traits, generics, etc. For instance, for:

pub mod my_module {
pub struct MyType;
pub struct MyGenericType<T>(T);

pub trait MyTrait {
fn my_method() -> u32;
}

impl MyTrait for MyGenericType<MyType> {
fn my_method() -> u32 {
42
}
}
}

generates a symbol of length 96 when using the upcoming v0 mangling scheme:

_RNvXNtCshGpAVYOtgW1_7example9my_moduleINtB2_13MyGenericTypeNtB2_6MyTypeENtB2_7MyTrait9my_method

At the moment, Rust symbols may reach up to 300 in length.
Setting 512 as the maximum seems like a reasonable choice to
keep some headroom.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
include/linux/kallsyms.h | 2 +-
kernel/livepatch/core.c | 4 ++--
scripts/kallsyms.c | 2 +-
tools/include/linux/kallsyms.h | 2 +-
tools/include/linux/lockdep.h | 2 +-
tools/lib/perf/include/perf/event.h | 2 +-
tools/lib/symbol/kallsyms.h | 2 +-
7 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 465060acc98..5cdc6903abc 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -14,7 +14,7 @@

#include <asm/sections.h>

-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
#define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + (KSYM_NAME_LEN - 1) + \
2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + 1)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 335d988bd81..73874e5edfd 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -213,7 +213,7 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
* we use the smallest/strictest upper bound possible (56, based on
* the current definition of MODULE_NAME_LEN) to prevent overflows.
*/
- BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
+ BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);

relas = (Elf_Rela *) relasec->sh_addr;
/* For each rela in this klp relocation section */
@@ -227,7 +227,7 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,

/* Format: .klp.sym.sym_objname.sym_name,sympos */
cnt = sscanf(strtab + sym->st_name,
- ".klp.sym.%55[^.].%127[^,],%lu",
+ ".klp.sym.%55[^.].%511[^,],%lu",
sym_objname, sym_name, &sympos);
if (cnt != 3) {
pr_err("symbol %s has an incorrectly formatted name\n",
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index bcdabee13aa..9bab5f55ade 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -27,7 +27,7 @@

#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))

-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512

struct sym_entry {
unsigned long long addr;
diff --git a/tools/include/linux/kallsyms.h b/tools/include/linux/kallsyms.h
index efb6c3f5f2a..5a37ccbec54 100644
--- a/tools/include/linux/kallsyms.h
+++ b/tools/include/linux/kallsyms.h
@@ -6,7 +6,7 @@
#include <stdio.h>
#include <unistd.h>

-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512

struct module;

diff --git a/tools/include/linux/lockdep.h b/tools/include/linux/lockdep.h
index e56997288f2..d9c163f3ab2 100644
--- a/tools/include/linux/lockdep.h
+++ b/tools/include/linux/lockdep.h
@@ -47,7 +47,7 @@ static inline int debug_locks_off(void)

#define task_pid_nr(tsk) ((tsk)->pid)

-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
#define printk(...) dprintf(STDOUT_FILENO, __VA_ARGS__)
#define pr_err(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
#define pr_warn pr_err
diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index 4d0c02ba3f7..095d60144a7 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -95,7 +95,7 @@ struct perf_record_throttle {
};

#ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
#endif

struct perf_record_ksymbol {
diff --git a/tools/lib/symbol/kallsyms.h b/tools/lib/symbol/kallsyms.h
index 72ab9870454..542f9b059c3 100644
--- a/tools/lib/symbol/kallsyms.h
+++ b/tools/lib/symbol/kallsyms.h
@@ -7,7 +7,7 @@
#include <linux/types.h>

#ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
#endif

static inline u8 kallsyms2elf_binding(char type)
--
2.32.0

2021-07-04 20:29:32

by Miguel Ojeda

Subject: [PATCH 03/17] Makefile: generate `CLANG_FLAGS` even in GCC builds

From: Miguel Ojeda <[email protected]>

To support Rust under GCC-built kernels, we need to save the flags that
would have been passed if the kernel was being compiled with Clang.

The reason is that `bindgen` -- the tool we use to generate Rust
bindings to the C side of the kernel -- relies on `libclang` to
parse C. Ideally:

- `bindgen` would support a GCC backend (requested at [1]),

- or the Clang driver would be perfectly compatible with GCC,
including plugins. Unlikely, of course, but perhaps a big
subset of configs may be possible to guarantee to be kept
compatible nevertheless.

This is also the reason why GCC builds are very experimental and some
configurations may not work (e.g. `GCC_PLUGIN_RANDSTRUCT`). However,
we keep GCC builds working (for some example configs) in the CI
to avoid diverging/regressing further, so that we are better prepared
for the future when a solution might become available.

[1] https://github.com/rust-lang/rust-bindgen/issues/1949

Link: https://github.com/Rust-for-Linux/linux/issues/167
Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
Makefile | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 0565caea036..6e823d8bd64 100644
--- a/Makefile
+++ b/Makefile
@@ -573,18 +573,23 @@ endif
# and from include/config/auto.conf.cmd to detect the compiler upgrade.
CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1))

-ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
+TENTATIVE_CLANG_FLAGS := -Werror=unknown-warning-option
+
ifneq ($(CROSS_COMPILE),)
-CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
+TENTATIVE_CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
endif
ifeq ($(LLVM_IAS),1)
-CLANG_FLAGS += -integrated-as
+TENTATIVE_CLANG_FLAGS += -integrated-as
else
-CLANG_FLAGS += -no-integrated-as
+TENTATIVE_CLANG_FLAGS += -no-integrated-as
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
-CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
+TENTATIVE_CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
endif
-CLANG_FLAGS += -Werror=unknown-warning-option
+
+export TENTATIVE_CLANG_FLAGS
+
+ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
+CLANG_FLAGS += $(TENTATIVE_CLANG_FLAGS)
KBUILD_CFLAGS += $(CLANG_FLAGS)
KBUILD_AFLAGS += $(CLANG_FLAGS)
export CLANG_FLAGS
--
2.32.0

2021-07-04 20:30:06

by Miguel Ojeda

Subject: [PATCH 08/17] rust: add `build_error` crate

From: Miguel Ojeda <[email protected]>

The `build_error` crate provides the `build_error` function which
is then used to provide the `build_error!` and the `build_assert!`
macros.

`build_assert!` is intended to be used when `static_assert!` cannot
be used, e.g. when the condition refers to generic parameters or
parameters of an inline function.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/build_error.rs | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
create mode 100644 rust/build_error.rs

diff --git a/rust/build_error.rs b/rust/build_error.rs
new file mode 100644
index 00000000000..d47fa8393cb
--- /dev/null
+++ b/rust/build_error.rs
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Build-time error.
+//!
+//! This crate provides a function `build_error`, which will panic in
+//! compile-time if executed in const context, and will cause a build error
+//! if not executed at compile time and the optimizer does not optimise away the
+//! call.
+//!
+//! It is used by `build_assert!` in the kernel crate, allowing checking of
+//! conditions that could be checked statically, but could not be enforced in
+//! Rust yet (e.g. perform some checks in const functions, but those
+//! functions could still be called in the runtime).
+
+#![no_std]
+#![feature(const_panic, core_panic)]
+
+/// Panics if executed in const context, or triggers a build error if not.
+#[inline(never)]
+#[cold]
+#[no_mangle]
+#[track_caller]
+pub const fn build_error(msg: &'static str) -> ! {
+ // Could also be `panic!(msg)` to avoid using unstable feature `core_panic`,
+ // but it is not allowed in Rust 2021, while `panic!("{}", msg)` could not
+ // yet be used in const context.
+ core::panicking::panic(msg);
+}
+
+#[cfg(CONFIG_RUST_BUILD_ASSERT_WARN)]
+#[link_section = ".gnu.warning.build_error"]
+#[used]
+static BUILD_ERROR_WARNING: [u8; 45] = *b"call to build_error present after compilation";
--
2.32.0

2021-07-04 20:30:12

by Miguel Ojeda

Subject: [PATCH 04/17] vsprintf: add new `%pA` format specifier

From: Miguel Ojeda <[email protected]>

This patch adds a format specifier `%pA` to `vsprintf` which formats
a pointer as `core::fmt::Arguments`. Doing so allows us to directly
format to the internal buffer of `printf`, so we do not have to use
a temporary buffer on the stack to pre-assemble the message on
the Rust side.

This specifier is intended only to be used from Rust and not for C, so
`checkpatch.pl` is intentionally unchanged to catch any misuse.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
lib/vsprintf.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index f0c35d9b65b..e7afe954004 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2182,6 +2182,10 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
return widen_string(buf, buf - buf_start, end, spec);
}

+#ifdef CONFIG_RUST
+char *rust_fmt_argument(char* buf, char* end, void *ptr);
+#endif
+
/* Disable pointer hashing if requested */
bool no_hash_pointers __ro_after_init;
EXPORT_SYMBOL_GPL(no_hash_pointers);
@@ -2335,6 +2339,10 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
*
* Note: The default behaviour (unadorned %p) is to hash the address,
* rendering it useful as a unique identifier.
+ *
+ * There is also a '%pA' format specifier, but it is only intended to be used
+ * from Rust code to format core::fmt::Arguments. Do *not* use it from C.
+ * See rust/kernel/print.rs for details.
*/
static noinline_for_stack
char *pointer(const char *fmt, char *buf, char *end, void *ptr,
@@ -2407,6 +2415,10 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
return device_node_string(buf, end, ptr, spec, fmt + 1);
case 'f':
return fwnode_string(buf, end, ptr, spec, fmt + 1);
+#ifdef CONFIG_RUST
+ case 'A':
+ return rust_fmt_argument(buf, end, ptr);
+#endif
case 'x':
return pointer_string(buf, end, ptr, spec);
case 'e':
--
2.32.0

2021-07-04 20:30:20

by Miguel Ojeda

Subject: [PATCH 09/17] rust: add `macros` crate

From: Miguel Ojeda <[email protected]>

This crate contains all the procedural macros ("proc macros")
shared by all the kernel.

Procedural macros allow to create syntax extensions. They run at
compile-time and can consume as well as produce Rust syntax.

For instance, the `module!` macro that is used by Rust modules
is implemented here. It allows to easily declare the equivalent
information to the `MODULE_*` macros in C modules, e.g.:

module! {
type: RustMinimal,
name: b"rust_minimal",
author: b"Rust for Linux Contributors",
description: b"Rust minimal sample",
license: b"GPL v2",
}

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/macros/lib.rs | 127 +++++++
rust/macros/module.rs | 754 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 881 insertions(+)
create mode 100644 rust/macros/lib.rs
create mode 100644 rust/macros/module.rs

diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
new file mode 100644
index 00000000000..cb7a4f12f3b
--- /dev/null
+++ b/rust/macros/lib.rs
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Crate for all kernel procedural macros.
+
+mod module;
+
+use proc_macro::TokenStream;
+
+/// Declares a kernel module.
+///
+/// The `type` argument should be a type which implements the [`KernelModule`]
+/// trait. Also accepts various forms of kernel metadata.
+///
+/// C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
+///
+/// [`KernelModule`]: ../kernel/trait.KernelModule.html
+///
+/// # Examples
+///
+/// ```ignore
+/// use kernel::prelude::*;
+///
+/// module!{
+/// type: MyKernelModule,
+/// name: b"my_kernel_module",
+/// author: b"Rust for Linux Contributors",
+/// description: b"My very own kernel module!",
+/// license: b"GPL v2",
+/// params: {
+/// my_i32: i32 {
+/// default: 42,
+/// permissions: 0o000,
+/// description: b"Example of i32",
+/// },
+/// writeable_i32: i32 {
+/// default: 42,
+/// permissions: 0o644,
+/// description: b"Example of i32",
+/// },
+/// },
+/// }
+///
+/// struct MyKernelModule;
+///
+/// impl KernelModule for MyKernelModule {
+/// fn init() -> Result<Self> {
+/// // If the parameter is writeable, then the kparam lock must be
+/// // taken to read the parameter:
+/// {
+/// let lock = THIS_MODULE.kernel_param_lock();
+/// pr_info!("i32 param is: {}\n", writeable_i32.read(&lock));
+/// }
+/// // If the parameter is read only, it can be read without locking
+/// // the kernel parameters:
+/// pr_info!("i32 param is: {}\n", my_i32.read());
+/// Ok(MyKernelModule)
+/// }
+/// }
+/// ```
+///
+/// # Supported argument types
+/// - `type`: type which implements the [`KernelModule`] trait (required).
+/// - `name`: byte array of the name of the kernel module (required).
+/// - `author`: byte array of the author of the kernel module.
+/// - `description`: byte array of the description of the kernel module.
+/// - `license`: byte array of the license of the kernel module (required).
+/// - `alias`: byte array of alias name of the kernel module.
+/// - `alias_rtnl_link`: byte array of the `rtnl_link_alias` of the kernel module (mutually exclusive with `alias`).
+/// - `params`: parameters for the kernel module, as described below.
+///
+/// # Supported parameter types
+///
+/// - `bool`: Corresponds to C `bool` param type.
+/// - `i8`: No equivalent C param type.
+/// - `u8`: Corresponds to C `char` param type.
+/// - `i16`: Corresponds to C `short` param type.
+/// - `u16`: Corresponds to C `ushort` param type.
+/// - `i32`: Corresponds to C `int` param type.
+/// - `u32`: Corresponds to C `uint` param type.
+/// - `i64`: No equivalent C param type.
+/// - `u64`: Corresponds to C `ullong` param type.
+/// - `isize`: No equivalent C param type.
+/// - `usize`: No equivalent C param type.
+/// - `str`: Corresponds to C `charp` param type. Reading returns a byte slice.
+/// - `ArrayParam<T,N>`: Corresponds to C parameters created using `module_param_array`. An array
+/// of `T`'s of length at **most** `N`.
+///
+/// `invbool` is unsupported: it was only ever used in a few modules.
+/// Consider using a `bool` and inverting the logic instead.
+#[proc_macro]
+pub fn module(ts: TokenStream) -> TokenStream {
+ module::module(ts)
+}
+
+/// Declares a kernel module that exposes a single misc device.
+///
+/// The `type` argument should be a type which implements the [`FileOpener`] trait. Also accepts
+/// various forms of kernel metadata.
+///
+/// C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
+///
+/// [`FileOpener`]: ../kernel/file_operations/trait.FileOpener.html
+///
+/// # Examples
+///
+/// ```ignore
+/// use kernel::prelude::*;
+///
+/// module_misc_device! {
+/// type: MyFile,
+/// name: b"my_miscdev_kernel_module",
+/// author: b"Rust for Linux Contributors",
+/// description: b"My very own misc device kernel module!",
+/// license: b"GPL v2",
+/// }
+///
+/// #[derive(Default)]
+/// struct MyFile;
+///
+/// impl kernel::file_operations::FileOperations for MyFile {
+/// kernel::declare_file_operations!();
+/// }
+/// ```
+#[proc_macro]
+pub fn module_misc_device(ts: TokenStream) -> TokenStream {
+ module::module_misc_device(ts)
+}
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
new file mode 100644
index 00000000000..1389c53aa22
--- /dev/null
+++ b/rust/macros/module.rs
@@ -0,0 +1,754 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{token_stream, Delimiter, Group, Literal, TokenStream, TokenTree};
+
+fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
+ if let Some(TokenTree::Ident(ident)) = it.next() {
+ Some(ident.to_string())
+ } else {
+ None
+ }
+}
+
+fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
+ if let Some(TokenTree::Literal(literal)) = it.next() {
+ Some(literal.to_string())
+ } else {
+ None
+ }
+}
+
+fn try_byte_string(it: &mut token_stream::IntoIter) -> Option<String> {
+ try_literal(it).and_then(|byte_string| {
+ if byte_string.starts_with("b\"") && byte_string.ends_with('\"') {
+ Some(byte_string[2..byte_string.len() - 1].to_string())
+ } else {
+ None
+ }
+ })
+}
+
+fn expect_ident(it: &mut token_stream::IntoIter) -> String {
+ try_ident(it).expect("Expected Ident")
+}
+
+fn expect_punct(it: &mut token_stream::IntoIter) -> char {
+ if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
+ punct.as_char()
+ } else {
+ panic!("Expected Punct");
+ }
+}
+
+fn expect_literal(it: &mut token_stream::IntoIter) -> String {
+ try_literal(it).expect("Expected Literal")
+}
+
+fn expect_group(it: &mut token_stream::IntoIter) -> Group {
+ if let TokenTree::Group(group) = it.next().expect("Reached end of token stream for Group") {
+ group
+ } else {
+ panic!("Expected Group");
+ }
+}
+
+fn expect_byte_string(it: &mut token_stream::IntoIter) -> String {
+ try_byte_string(it).expect("Expected byte string")
+}
+
+#[derive(Clone, PartialEq)]
+enum ParamType {
+ Ident(String),
+ Array { vals: String, max_length: usize },
+}
+
+fn expect_array_fields(it: &mut token_stream::IntoIter) -> ParamType {
+ assert_eq!(expect_punct(it), '<');
+ let vals = expect_ident(it);
+ assert_eq!(expect_punct(it), ',');
+ let max_length_str = expect_literal(it);
+ let max_length = max_length_str
+ .parse::<usize>()
+ .expect("Expected usize length");
+ assert_eq!(expect_punct(it), '>');
+ ParamType::Array { vals, max_length }
+}
+
+fn expect_type(it: &mut token_stream::IntoIter) -> ParamType {
+ if let TokenTree::Ident(ident) = it
+ .next()
+ .expect("Reached end of token stream for param type")
+ {
+ match ident.to_string().as_ref() {
+ "ArrayParam" => expect_array_fields(it),
+ _ => ParamType::Ident(ident.to_string()),
+ }
+ } else {
+ panic!("Expected Param Type")
+ }
+}
+
+fn expect_end(it: &mut token_stream::IntoIter) {
+ if it.next().is_some() {
+ panic!("Expected end");
+ }
+}
+
+fn get_literal(it: &mut token_stream::IntoIter, expected_name: &str) -> String {
+ assert_eq!(expect_ident(it), expected_name);
+ assert_eq!(expect_punct(it), ':');
+ let literal = expect_literal(it);
+ assert_eq!(expect_punct(it), ',');
+ literal
+}
+
+fn get_byte_string(it: &mut token_stream::IntoIter, expected_name: &str) -> String {
+ assert_eq!(expect_ident(it), expected_name);
+ assert_eq!(expect_punct(it), ':');
+ let byte_string = expect_byte_string(it);
+ assert_eq!(expect_punct(it), ',');
+ byte_string
+}
+
+struct ModInfoBuilder<'a> {
+ module: &'a str,
+ counter: usize,
+ buffer: String,
+}
+
+impl<'a> ModInfoBuilder<'a> {
+ fn new(module: &'a str) -> Self {
+ ModInfoBuilder {
+ module,
+ counter: 0,
+ buffer: String::new(),
+ }
+ }
+
+ fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
+ use std::fmt::Write;
+
+ let string = if builtin {
+ // Built-in modules prefix their modinfo strings by `module.`.
+ format!(
+ "{module}.{field}={content}\0",
+ module = self.module,
+ field = field,
+ content = content
+ )
+ } else {
+ // Loadable modules' modinfo strings go as-is.
+ format!("{field}={content}\0", field = field, content = content)
+ };
+
+ write!(
+ &mut self.buffer,
+ "
+ {cfg}
+ #[doc(hidden)]
+ #[link_section = \".modinfo\"]
+ #[used]
+ pub static __{module}_{counter}: [u8; {length}] = *{string};
+ ",
+ cfg = if builtin {
+ "#[cfg(not(MODULE))]"
+ } else {
+ "#[cfg(MODULE)]"
+ },
+ module = self.module,
+ counter = self.counter,
+ length = string.len(),
+ string = Literal::byte_string(string.as_bytes()),
+ )
+ .unwrap();
+
+ self.counter += 1;
+ }
+
+ fn emit_only_builtin(&mut self, field: &str, content: &str) {
+ self.emit_base(field, content, true)
+ }
+
+ fn emit_only_loadable(&mut self, field: &str, content: &str) {
+ self.emit_base(field, content, false)
+ }
+
+ fn emit(&mut self, field: &str, content: &str) {
+ self.emit_only_builtin(field, content);
+ self.emit_only_loadable(field, content);
+ }
+
+ fn emit_param(&mut self, field: &str, param: &str, content: &str) {
+ let content = format!("{param}:{content}", param = param, content = content);
+ self.emit(field, &content);
+ }
+}
+
+fn permissions_are_readonly(perms: &str) -> bool {
+ let (radix, digits) = if let Some(n) = perms.strip_prefix("0x") {
+ (16, n)
+ } else if let Some(n) = perms.strip_prefix("0o") {
+ (8, n)
+ } else if let Some(n) = perms.strip_prefix("0b") {
+ (2, n)
+ } else {
+ (10, perms)
+ };
+ match u32::from_str_radix(digits, radix) {
+ Ok(perms) => perms & 0o222 == 0,
+ Err(_) => false,
+ }
+}
+
+fn param_ops_path(param_type: &str) -> &'static str {
+ match param_type {
+ "bool" => "kernel::module_param::PARAM_OPS_BOOL",
+ "i8" => "kernel::module_param::PARAM_OPS_I8",
+ "u8" => "kernel::module_param::PARAM_OPS_U8",
+ "i16" => "kernel::module_param::PARAM_OPS_I16",
+ "u16" => "kernel::module_param::PARAM_OPS_U16",
+ "i32" => "kernel::module_param::PARAM_OPS_I32",
+ "u32" => "kernel::module_param::PARAM_OPS_U32",
+ "i64" => "kernel::module_param::PARAM_OPS_I64",
+ "u64" => "kernel::module_param::PARAM_OPS_U64",
+ "isize" => "kernel::module_param::PARAM_OPS_ISIZE",
+ "usize" => "kernel::module_param::PARAM_OPS_USIZE",
+ "str" => "kernel::module_param::PARAM_OPS_STR",
+ t => panic!("Unrecognized type {}", t),
+ }
+}
+
+fn try_simple_param_val(
+ param_type: &str,
+) -> Box<dyn Fn(&mut token_stream::IntoIter) -> Option<String>> {
+ match param_type {
+ "bool" => Box::new(|param_it| try_ident(param_it)),
+ "str" => Box::new(|param_it| {
+ try_byte_string(param_it)
+ .map(|s| format!("kernel::module_param::StringParam::Ref(b\"{}\")", s))
+ }),
+ _ => Box::new(|param_it| try_literal(param_it)),
+ }
+}
+
+fn get_default(param_type: &ParamType, param_it: &mut token_stream::IntoIter) -> String {
+ let try_param_val = match param_type {
+ ParamType::Ident(ref param_type)
+ | ParamType::Array {
+ vals: ref param_type,
+ max_length: _,
+ } => try_simple_param_val(param_type),
+ };
+ assert_eq!(expect_ident(param_it), "default");
+ assert_eq!(expect_punct(param_it), ':');
+ let default = match param_type {
+ ParamType::Ident(_) => try_param_val(param_it).expect("Expected default param value"),
+ ParamType::Array {
+ vals: _,
+ max_length: _,
+ } => {
+ let group = expect_group(param_it);
+ assert_eq!(group.delimiter(), Delimiter::Bracket);
+ let mut default_vals = Vec::new();
+ let mut it = group.stream().into_iter();
+
+ while let Some(default_val) = try_param_val(&mut it) {
+ default_vals.push(default_val);
+ match it.next() {
+ Some(TokenTree::Punct(punct)) => assert_eq!(punct.as_char(), ','),
+ None => break,
+ _ => panic!("Expected ',' or end of array default values"),
+ }
+ }
+
+ let mut default_array = "kernel::module_param::ArrayParam::create(&[".to_string();
+ default_array.push_str(
+ &default_vals
+ .iter()
+ .map(|val| val.to_string())
+ .collect::<Vec<String>>()
+ .join(","),
+ );
+ default_array.push_str("])");
+ default_array
+ }
+ };
+ assert_eq!(expect_punct(param_it), ',');
+ default
+}
+
+fn generated_array_ops_name(vals: &str, max_length: usize) -> String {
+ format!(
+ "__generated_array_ops_{vals}_{max_length}",
+ vals = vals,
+ max_length = max_length
+ )
+}
+
+#[derive(Debug, Default)]
+struct ModuleInfo {
+ type_: String,
+ license: String,
+ name: String,
+ author: Option<String>,
+ description: Option<String>,
+ alias: Option<String>,
+ params: Option<Group>,
+}
+
+impl ModuleInfo {
+ fn parse(it: &mut token_stream::IntoIter) -> Self {
+ let mut info = ModuleInfo::default();
+
+ const EXPECTED_KEYS: &[&str] = &[
+ "type",
+ "name",
+ "author",
+ "description",
+ "license",
+ "alias",
+ "alias_rtnl_link",
+ "params",
+ ];
+ const REQUIRED_KEYS: &[&str] = &["type", "name", "license"];
+ let mut seen_keys = Vec::new();
+
+ loop {
+ let key = match it.next() {
+ Some(TokenTree::Ident(ident)) => ident.to_string(),
+ Some(_) => panic!("Expected Ident or end"),
+ None => break,
+ };
+
+ if seen_keys.contains(&key) {
+ panic!(
+ "Duplicated key \"{}\". Keys can only be specified once.",
+ key
+ );
+ }
+
+ assert_eq!(expect_punct(it), ':');
+
+ match key.as_str() {
+ "type" => info.type_ = expect_ident(it),
+ "name" => info.name = expect_byte_string(it),
+ "author" => info.author = Some(expect_byte_string(it)),
+ "description" => info.description = Some(expect_byte_string(it)),
+ "license" => info.license = expect_byte_string(it),
+ "alias" => info.alias = Some(expect_byte_string(it)),
+ "alias_rtnl_link" => {
+ info.alias = Some(format!("rtnl-link-{}", expect_byte_string(it)))
+ }
+ "params" => info.params = Some(expect_group(it)),
+ _ => panic!(
+ "Unknown key \"{}\". Valid keys are: {:?}.",
+ key, EXPECTED_KEYS
+ ),
+ }
+
+ assert_eq!(expect_punct(it), ',');
+
+ seen_keys.push(key);
+ }
+
+ expect_end(it);
+
+ for key in REQUIRED_KEYS {
+ if !seen_keys.iter().any(|e| e == key) {
+ panic!("Missing required key \"{}\".", key);
+ }
+ }
+
+ let mut ordered_keys: Vec<&str> = Vec::new();
+ for key in EXPECTED_KEYS {
+ if seen_keys.iter().any(|e| e == key) {
+ ordered_keys.push(key);
+ }
+ }
+
+ if seen_keys != ordered_keys {
+ panic!(
+ "Keys are not ordered as expected. Order them like: {:?}.",
+ ordered_keys
+ );
+ }
+
+ info
+ }
+}
+
+pub fn module(ts: TokenStream) -> TokenStream {
+ let mut it = ts.into_iter();
+
+ let info = ModuleInfo::parse(&mut it);
+
+ let name = info.name.clone();
+
+ let mut modinfo = ModInfoBuilder::new(&name);
+ if let Some(author) = info.author {
+ modinfo.emit("author", &author);
+ }
+ if let Some(description) = info.description {
+ modinfo.emit("description", &description);
+ }
+ modinfo.emit("license", &info.license);
+ if let Some(alias) = info.alias {
+ modinfo.emit("alias", &alias);
+ }
+
+ // Built-in modules also export the `file` modinfo string
+ let file =
+ std::env::var("RUST_MODFILE").expect("Unable to fetch RUST_MODFILE environmental variable");
+ modinfo.emit_only_builtin("file", &file);
+
+ let mut array_types_to_generate = Vec::new();
+ if let Some(params) = info.params {
+ assert_eq!(params.delimiter(), Delimiter::Brace);
+
+ let mut it = params.stream().into_iter();
+
+ loop {
+ let param_name = match it.next() {
+ Some(TokenTree::Ident(ident)) => ident.to_string(),
+ Some(_) => panic!("Expected Ident or end"),
+ None => break,
+ };
+
+ assert_eq!(expect_punct(&mut it), ':');
+ let param_type = expect_type(&mut it);
+ let group = expect_group(&mut it);
+ assert_eq!(expect_punct(&mut it), ',');
+
+ assert_eq!(group.delimiter(), Delimiter::Brace);
+
+ let mut param_it = group.stream().into_iter();
+ let param_default = get_default(&param_type, &mut param_it);
+ let param_permissions = get_literal(&mut param_it, "permissions");
+ let param_description = get_byte_string(&mut param_it, "description");
+ expect_end(&mut param_it);
+
+ // TODO: more primitive types
+ // TODO: other kinds: unsafes, etc.
+ let (param_kernel_type, ops): (String, _) = match param_type {
+ ParamType::Ident(ref param_type) => (
+ param_type.to_string(),
+ param_ops_path(param_type).to_string(),
+ ),
+ ParamType::Array {
+ ref vals,
+ max_length,
+ } => {
+ array_types_to_generate.push((vals.clone(), max_length));
+ (
+ format!("__rust_array_param_{}_{}", vals, max_length),
+ generated_array_ops_name(vals, max_length),
+ )
+ }
+ };
+
+ modinfo.emit_param("parmtype", &param_name, &param_kernel_type);
+ modinfo.emit_param("parm", &param_name, &param_description);
+ let param_type_internal = match param_type {
+ ParamType::Ident(ref param_type) => match param_type.as_ref() {
+ "str" => "kernel::module_param::StringParam".to_string(),
+ other => other.to_string(),
+ },
+ ParamType::Array {
+ ref vals,
+ max_length,
+ } => format!(
+ "kernel::module_param::ArrayParam<{vals}, {max_length}>",
+ vals = vals,
+ max_length = max_length
+ ),
+ };
+ let read_func = if permissions_are_readonly(&param_permissions) {
+ format!(
+ "
+ fn read(&self) -> &<{param_type_internal} as kernel::module_param::ModuleParam>::Value {{
+ // SAFETY: Parameters do not need to be locked because they are read only or sysfs is not enabled.
+ unsafe {{ <{param_type_internal} as kernel::module_param::ModuleParam>::value(&__{name}_{param_name}_value) }}
+ }}
+ ",
+ name = name,
+ param_name = param_name,
+ param_type_internal = param_type_internal,
+ )
+ } else {
+ format!(
+ "
+ fn read<'lck>(&self, lock: &'lck kernel::KParamGuard) -> &'lck <{param_type_internal} as kernel::module_param::ModuleParam>::Value {{
+ // SAFETY: Parameters are locked by `KParamGuard`.
+ unsafe {{ <{param_type_internal} as kernel::module_param::ModuleParam>::value(&__{name}_{param_name}_value) }}
+ }}
+ ",
+ name = name,
+ param_name = param_name,
+ param_type_internal = param_type_internal,
+ )
+ };
+ let kparam = format!(
+ "
+ kernel::bindings::kernel_param__bindgen_ty_1 {{
+ arg: unsafe {{ &__{name}_{param_name}_value }} as *const _ as *mut kernel::c_types::c_void,
+ }},
+ ",
+ name = name,
+ param_name = param_name,
+ );
+ modinfo.buffer.push_str(
+ &format!(
+ "
+ static mut __{name}_{param_name}_value: {param_type_internal} = {param_default};
+
+ struct __{name}_{param_name};
+
+ impl __{name}_{param_name} {{ {read_func} }}
+
+ const {param_name}: __{name}_{param_name} = __{name}_{param_name};
+
+ // Note: the C macro that generates the static structs for the `__param` section
+ // asks for them to be `aligned(sizeof(void *))`. However, that was put in place
+ // in 2003 in commit 38d5b085d2 (\"[PATCH] Fix over-alignment problem on x86-64\")
+ // to undo GCC over-alignment of static structs of >32 bytes. It seems that is
+ // not the case anymore, so we simplify to a transparent representation here
+ // in the expectation that it is not needed anymore.
+ // TODO: revisit this to confirm the above comment and remove it if it happened
+ #[repr(transparent)]
+ struct __{name}_{param_name}_RacyKernelParam(kernel::bindings::kernel_param);
+
+ unsafe impl Sync for __{name}_{param_name}_RacyKernelParam {{
+ }}
+
+ #[cfg(not(MODULE))]
+ const __{name}_{param_name}_name: *const kernel::c_types::c_char = b\"{name}.{param_name}\\0\" as *const _ as *const kernel::c_types::c_char;
+
+ #[cfg(MODULE)]
+ const __{name}_{param_name}_name: *const kernel::c_types::c_char = b\"{param_name}\\0\" as *const _ as *const kernel::c_types::c_char;
+
+ #[link_section = \"__param\"]
+ #[used]
+ static __{name}_{param_name}_struct: __{name}_{param_name}_RacyKernelParam = __{name}_{param_name}_RacyKernelParam(kernel::bindings::kernel_param {{
+ name: __{name}_{param_name}_name,
+ // SAFETY: `__this_module` is constructed by the kernel at load time and will not be freed until the module is unloaded.
+ #[cfg(MODULE)]
+ mod_: unsafe {{ &kernel::bindings::__this_module as *const _ as *mut _ }},
+ #[cfg(not(MODULE))]
+ mod_: core::ptr::null_mut(),
+ ops: unsafe {{ &{ops} }} as *const kernel::bindings::kernel_param_ops,
+ perm: {permissions},
+ level: -1,
+ flags: 0,
+ __bindgen_anon_1: {kparam}
+ }});
+ ",
+ name = name,
+ param_type_internal = param_type_internal,
+ read_func = read_func,
+ param_default = param_default,
+ param_name = param_name,
+ ops = ops,
+ permissions = param_permissions,
+ kparam = kparam,
+ )
+ );
+ }
+ }
+
+ let mut generated_array_types = String::new();
+
+ for (vals, max_length) in array_types_to_generate {
+ let ops_name = generated_array_ops_name(&vals, max_length);
+ generated_array_types.push_str(&format!(
+ "
+ kernel::make_param_ops!(
+ {ops_name},
+ kernel::module_param::ArrayParam<{vals}, {{ {max_length} }}>
+ );
+ ",
+ ops_name = ops_name,
+ vals = vals,
+ max_length = max_length,
+ ));
+ }
+
+ format!(
+ "
+ /// The module name.
+ ///
+ /// Used by the printing macros, e.g. [`info!`].
+ const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
+
+ static mut __MOD: Option<{type_}> = None;
+
+ // SAFETY: `__this_module` is constructed by the kernel at load time and will not be freed until the module is unloaded.
+ #[cfg(MODULE)]
+ static THIS_MODULE: kernel::ThisModule = unsafe {{ kernel::ThisModule::from_ptr(&kernel::bindings::__this_module as *const _ as *mut _) }};
+ #[cfg(not(MODULE))]
+ static THIS_MODULE: kernel::ThisModule = unsafe {{ kernel::ThisModule::from_ptr(core::ptr::null_mut()) }};
+
+ // Loadable modules need to export the `{{init,cleanup}}_module` identifiers
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn init_module() -> kernel::c_types::c_int {{
+ __init()
+ }}
+
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn cleanup_module() {{
+ __exit()
+ }}
+
+ // Built-in modules are initialized through an initcall pointer
+ // and the identifiers need to be unique
+ #[cfg(not(MODULE))]
+ #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))]
+ #[doc(hidden)]
+ #[link_section = \"{initcall_section}\"]
+ #[used]
+ pub static __{name}_initcall: extern \"C\" fn() -> kernel::c_types::c_int = __{name}_init;
+
+ #[cfg(not(MODULE))]
+ #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
+ global_asm!(
+ r#\".section \"{initcall_section}\", \"a\"
+ __{name}_initcall:
+ .long __{name}_init - .
+ .previous
+ \"#
+ );
+
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_init() -> kernel::c_types::c_int {{
+ __init()
+ }}
+
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_exit() {{
+ __exit()
+ }}
+
+ fn __init() -> kernel::c_types::c_int {{
+ match <{type_} as kernel::KernelModule>::init() {{
+ Ok(m) => {{
+ unsafe {{
+ __MOD = Some(m);
+ }}
+ return 0;
+ }}
+ Err(e) => {{
+ return e.to_kernel_errno();
+ }}
+ }}
+ }}
+
+ fn __exit() {{
+ unsafe {{
+ // Invokes `drop()` on `__MOD`, which should be used for cleanup.
+ __MOD = None;
+ }}
+ }}
+
+ {modinfo}
+
+ {generated_array_types}
+ ",
+ type_ = info.type_,
+ name = info.name,
+ modinfo = modinfo.buffer,
+ generated_array_types = generated_array_types,
+ initcall_section = ".initcall6.init"
+ ).parse().expect("Error parsing formatted string into token stream.")
+}
+
+pub fn module_misc_device(ts: TokenStream) -> TokenStream {
+ let mut it = ts.into_iter();
+
+ let info = ModuleInfo::parse(&mut it);
+
+ let module = format!("__internal_ModuleFor{}", info.type_);
+
+ format!(
+ "
+ #[doc(hidden)]
+ struct {module} {{
+ _dev: core::pin::Pin<alloc::boxed::Box<kernel::miscdev::Registration>>,
+ }}
+
+ impl kernel::KernelModule for {module} {{
+ fn init() -> kernel::Result<Self> {{
+ Ok(Self {{
+ _dev: kernel::miscdev::Registration::new_pinned::<{type_}>(
+ kernel::c_str!(\"{name}\"),
+ None,
+ (),
+ )?,
+ }})
+ }}
+ }}
+
+ kernel::prelude::module! {{
+ type: {module},
+ name: b\"{name}\",
+ {author}
+ {description}
+ license: b\"{license}\",
+ {alias}
+ }}
+ ",
+ module = module,
+ type_ = info.type_,
+ name = info.name,
+ author = info
+ .author
+ .map(|v| format!("author: b\"{}\",", v))
+ .unwrap_or_else(|| "".to_string()),
+ description = info
+ .description
+ .map(|v| format!("description: b\"{}\",", v))
+ .unwrap_or_else(|| "".to_string()),
+ alias = info
+ .alias
+ .map(|v| format!("alias: b\"{}\",", v))
+ .unwrap_or_else(|| "".to_string()),
+ license = info.license
+ )
+ .parse()
+ .expect("Error parsing formatted string into token stream.")
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_permissions_are_readonly() {
+ assert!(permissions_are_readonly("0b000000000"));
+ assert!(permissions_are_readonly("0o000"));
+ assert!(permissions_are_readonly("000"));
+ assert!(permissions_are_readonly("0x000"));
+
+ assert!(!permissions_are_readonly("0b111111111"));
+ assert!(!permissions_are_readonly("0o777"));
+ assert!(!permissions_are_readonly("511"));
+ assert!(!permissions_are_readonly("0x1ff"));
+
+ assert!(permissions_are_readonly("0o014"));
+ assert!(permissions_are_readonly("0o015"));
+
+ assert!(!permissions_are_readonly("0o214"));
+ assert!(!permissions_are_readonly("0o024"));
+ assert!(!permissions_are_readonly("0o012"));
+
+ assert!(!permissions_are_readonly("0o315"));
+ assert!(!permissions_are_readonly("0o065"));
+ assert!(!permissions_are_readonly("0o017"));
+ }
+}
--
2.32.0

2021-07-04 20:30:25

by Miguel Ojeda

Subject: [PATCH 11/17] rust: export generated symbols

From: Miguel Ojeda <[email protected]>

All symbols are reexported reusing the `EXPORT_SYMBOL_GPL` macro
from C. The lists of symbols are generated on the fly.

There are three main sets of symbols to distinguish:

- The ones from the `core` and `alloc` crates (from the Rust
standard library). The code is licensed as Apache/MIT.

- The ones from our abstractions in the `kernel` crate.

- The helpers (already exported since they are not generated).

We export everything as GPL. This ensures we do not mistakenly
expose GPL kernel symbols/features as non-GPL, even indirectly.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/exports.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
create mode 100644 rust/exports.c

diff --git a/rust/exports.c b/rust/exports.c
new file mode 100644
index 00000000000..d7dff1b3b91
--- /dev/null
+++ b/rust/exports.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// A hack to export Rust symbols for loadable modules without having to redo
+// the entire `include/linux/export.h` logic in Rust.
+//
+// This requires the Rust's new/future `v0` mangling scheme because the default
+// one ("legacy") uses invalid characters for C identifiers (thus we cannot use
+// the `EXPORT_SYMBOL_*` macros).
+
+#include <linux/module.h>
+
+#define EXPORT_SYMBOL_RUST_GPL(sym) extern int sym; EXPORT_SYMBOL_GPL(sym);
+
+#include "exports_core_generated.h"
+#include "exports_alloc_generated.h"
+#include "exports_kernel_generated.h"
--
2.32.0

2021-07-04 20:30:42

by Miguel Ojeda

Subject: [PATCH 14/17] samples: add Rust examples

From: Miguel Ojeda <[email protected]>

A set of Rust modules that showcase how Rust modules look like
and how to use the abstracted kernel features.

These samples also double as tests in the CI.

The semaphore sample comes with a C version for comparison.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
samples/Kconfig | 2 +
samples/Makefile | 1 +
samples/rust/Kconfig | 113 +++++++++++++
samples/rust/Makefile | 12 ++
samples/rust/rust_chrdev.rs | 51 ++++++
samples/rust/rust_minimal.rs | 38 +++++
samples/rust/rust_miscdev.rs | 150 +++++++++++++++++
samples/rust/rust_module_parameters.rs | 72 +++++++++
samples/rust/rust_print.rs | 57 +++++++
samples/rust/rust_random.rs | 61 +++++++
samples/rust/rust_semaphore.rs | 177 +++++++++++++++++++++
samples/rust/rust_semaphore_c.c | 212 +++++++++++++++++++++++++
samples/rust/rust_stack_probing.rs | 40 +++++
samples/rust/rust_sync.rs | 81 ++++++++++
14 files changed, 1067 insertions(+)
create mode 100644 samples/rust/Kconfig
create mode 100644 samples/rust/Makefile
create mode 100644 samples/rust/rust_chrdev.rs
create mode 100644 samples/rust/rust_minimal.rs
create mode 100644 samples/rust/rust_miscdev.rs
create mode 100644 samples/rust/rust_module_parameters.rs
create mode 100644 samples/rust/rust_print.rs
create mode 100644 samples/rust/rust_random.rs
create mode 100644 samples/rust/rust_semaphore.rs
create mode 100644 samples/rust/rust_semaphore_c.c
create mode 100644 samples/rust/rust_stack_probing.rs
create mode 100644 samples/rust/rust_sync.rs

diff --git a/samples/Kconfig b/samples/Kconfig
index b5a1a7aa7e2..eaa06c05d37 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -223,4 +223,6 @@ config SAMPLE_WATCH_QUEUE
Build example userspace program to use the new mount_notify(),
sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.

+source "samples/rust/Kconfig"
+
endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 087e0988ccc..291663e56a3 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/
subdir-$(CONFIG_SAMPLE_WATCHDOG) += watchdog
subdir-$(CONFIG_SAMPLE_WATCH_QUEUE) += watch_queue
obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak/
+obj-$(CONFIG_SAMPLES_RUST) += rust/
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
new file mode 100644
index 00000000000..183a3c4dc80
--- /dev/null
+++ b/samples/rust/Kconfig
@@ -0,0 +1,113 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menuconfig SAMPLES_RUST
+ bool "Rust samples"
+ depends on RUST
+ help
+ You can build sample Rust kernel code here.
+
+ If unsure, say N.
+
+if SAMPLES_RUST
+
+config SAMPLE_RUST_MINIMAL
+ tristate "Minimal"
+ help
+ This option builds the Rust minimal module sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_minimal.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_PRINT
+ tristate "Printing macros"
+ help
+ This option builds the Rust printing macros sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_print.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_MODULE_PARAMETERS
+ tristate "Module parameters"
+ help
+ This option builds the Rust module parameters sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_module_parameters.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_SYNC
+ tristate "Synchronisation primitives"
+ help
+ This option builds the Rust synchronisation primitives sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_sync.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_CHRDEV
+ tristate "Character device"
+ help
+ This option builds the Rust character device sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_chrdev.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_MISCDEV
+ tristate "Miscellaneous device"
+ help
+ This option builds the Rust miscellaneous device sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_miscdev.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_STACK_PROBING
+ tristate "Stack probing"
+ help
+ This option builds the Rust stack probing sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_stack_probing.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_SEMAPHORE
+ tristate "Semaphore"
+ help
+ This option builds the Rust semaphore sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_semaphore.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_SEMAPHORE_C
+ tristate "Semaphore (in C, for comparison)"
+ help
+ This option builds the Rust semaphore sample (in C, for comparison).
+
+ To compile this as a module, choose M here:
+ the module will be called rust_semaphore_c.
+
+ If unsure, say N.
+
+config SAMPLE_RUST_RANDOM
+ tristate "Random"
+ help
+ This option builds the Rust random sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_random.
+
+ If unsure, say N.
+
+endif # SAMPLES_RUST
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
new file mode 100644
index 00000000000..48bc871ea1f
--- /dev/null
+++ b/samples/rust/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_SAMPLE_RUST_MINIMAL) += rust_minimal.o
+obj-$(CONFIG_SAMPLE_RUST_PRINT) += rust_print.o
+obj-$(CONFIG_SAMPLE_RUST_MODULE_PARAMETERS) += rust_module_parameters.o
+obj-$(CONFIG_SAMPLE_RUST_SYNC) += rust_sync.o
+obj-$(CONFIG_SAMPLE_RUST_CHRDEV) += rust_chrdev.o
+obj-$(CONFIG_SAMPLE_RUST_MISCDEV) += rust_miscdev.o
+obj-$(CONFIG_SAMPLE_RUST_STACK_PROBING) += rust_stack_probing.o
+obj-$(CONFIG_SAMPLE_RUST_SEMAPHORE) += rust_semaphore.o
+obj-$(CONFIG_SAMPLE_RUST_SEMAPHORE_C) += rust_semaphore_c.o
+obj-$(CONFIG_SAMPLE_RUST_RANDOM) += rust_random.o
diff --git a/samples/rust/rust_chrdev.rs b/samples/rust/rust_chrdev.rs
new file mode 100644
index 00000000000..ccdfb2da785
--- /dev/null
+++ b/samples/rust/rust_chrdev.rs
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust character device sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::prelude::*;
+use kernel::{c_str, chrdev, file_operations::FileOperations};
+
+module! {
+ type: RustChrdev,
+ name: b"rust_chrdev",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust character device sample",
+ license: b"GPL v2",
+}
+
+#[derive(Default)]
+struct RustFile;
+
+impl FileOperations for RustFile {
+ kernel::declare_file_operations!();
+}
+
+struct RustChrdev {
+ _dev: Pin<Box<chrdev::Registration<2>>>,
+}
+
+impl KernelModule for RustChrdev {
+ fn init() -> Result<Self> {
+ pr_info!("Rust character device sample (init)\n");
+
+ let mut chrdev_reg =
+ chrdev::Registration::new_pinned(c_str!("rust_chrdev"), 0, &THIS_MODULE)?;
+
+ // Register the same kind of device twice, we're just demonstrating
+ // that you can use multiple minors. There are two minors in this case
+ // because its type is `chrdev::Registration<2>`
+ chrdev_reg.as_mut().register::<RustFile>()?;
+ chrdev_reg.as_mut().register::<RustFile>()?;
+
+ Ok(RustChrdev { _dev: chrdev_reg })
+ }
+}
+
+impl Drop for RustChrdev {
+ fn drop(&mut self) {
+ pr_info!("Rust character device sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_minimal.rs b/samples/rust/rust_minimal.rs
new file mode 100644
index 00000000000..49cfd8cf3aa
--- /dev/null
+++ b/samples/rust/rust_minimal.rs
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust minimal sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::prelude::*;
+
+module! {
+ type: RustMinimal,
+ name: b"rust_minimal",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust minimal sample",
+ license: b"GPL v2",
+}
+
+struct RustMinimal {
+ message: String,
+}
+
+impl KernelModule for RustMinimal {
+ fn init() -> Result<Self> {
+ pr_info!("Rust minimal sample (init)\n");
+ pr_info!("Am I built-in? {}\n", !cfg!(MODULE));
+
+ Ok(RustMinimal {
+ message: "on the heap!".try_to_owned()?,
+ })
+ }
+}
+
+impl Drop for RustMinimal {
+ fn drop(&mut self) {
+ pr_info!("My message is {}\n", self.message);
+ pr_info!("Rust minimal sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_miscdev.rs b/samples/rust/rust_miscdev.rs
new file mode 100644
index 00000000000..df8681af9cc
--- /dev/null
+++ b/samples/rust/rust_miscdev.rs
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust miscellaneous device sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::prelude::*;
+use kernel::{
+ c_str,
+ file::File,
+ file_operations::{FileOpener, FileOperations},
+ io_buffer::{IoBufferReader, IoBufferWriter},
+ miscdev,
+ sync::{CondVar, Mutex, Ref},
+};
+
+module! {
+ type: RustMiscdev,
+ name: b"rust_miscdev",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust miscellaneous device sample",
+ license: b"GPL v2",
+}
+
+const MAX_TOKENS: usize = 3;
+
+struct SharedStateInner {
+ token_count: usize,
+}
+
+struct SharedState {
+ state_changed: CondVar,
+ inner: Mutex<SharedStateInner>,
+}
+
+impl SharedState {
+ fn try_new() -> Result<Pin<Ref<Self>>> {
+ Ok(Ref::pinned(Ref::try_new_and_init(
+ Self {
+ // SAFETY: `condvar_init!` is called below.
+ state_changed: unsafe { CondVar::new() },
+ // SAFETY: `mutex_init!` is called below.
+ inner: unsafe { Mutex::new(SharedStateInner { token_count: 0 }) },
+ },
+ |mut state| {
+ // SAFETY: `state_changed` is pinned when `state` is.
+ let pinned = unsafe { state.as_mut().map_unchecked_mut(|s| &mut s.state_changed) };
+ kernel::condvar_init!(pinned, "SharedState::state_changed");
+ // SAFETY: `inner` is pinned when `state` is.
+ let pinned = unsafe { state.as_mut().map_unchecked_mut(|s| &mut s.inner) };
+ kernel::mutex_init!(pinned, "SharedState::inner");
+ },
+ )?))
+ }
+}
+
+struct Token;
+
+impl FileOpener<Pin<Ref<SharedState>>> for Token {
+ fn open(shared: &Pin<Ref<SharedState>>) -> Result<Self::Wrapper> {
+ Ok(shared.clone())
+ }
+}
+
+impl FileOperations for Token {
+ type Wrapper = Pin<Ref<SharedState>>;
+
+ kernel::declare_file_operations!(read, write);
+
+ fn read<T: IoBufferWriter>(
+ shared: &Ref<SharedState>,
+ _: &File,
+ data: &mut T,
+ offset: u64,
+ ) -> Result<usize> {
+ // Succeed if the caller doesn't provide a buffer or if not at the start.
+ if data.is_empty() || offset != 0 {
+ return Ok(0);
+ }
+
+ {
+ let mut inner = shared.inner.lock();
+
+ // Wait until we are allowed to decrement the token count or a signal arrives.
+ while inner.token_count == 0 {
+ if shared.state_changed.wait(&mut inner) {
+ return Err(Error::EINTR);
+ }
+ }
+
+ // Consume a token.
+ inner.token_count -= 1;
+ }
+
+ // Notify a possible writer waiting.
+ shared.state_changed.notify_all();
+
+ // Write a one-byte 1 to the reader.
+ data.write_slice(&[1u8; 1])?;
+ Ok(1)
+ }
+
+ fn write<T: IoBufferReader>(
+ shared: &Ref<SharedState>,
+ _: &File,
+ data: &mut T,
+ _offset: u64,
+ ) -> Result<usize> {
+ {
+ let mut inner = shared.inner.lock();
+
+ // Wait until we are allowed to increment the token count or a signal arrives.
+ while inner.token_count == MAX_TOKENS {
+ if shared.state_changed.wait(&mut inner) {
+ return Err(Error::EINTR);
+ }
+ }
+
+ // Increment the number of token so that a reader can be released.
+ inner.token_count += 1;
+ }
+
+ // Notify a possible reader waiting.
+ shared.state_changed.notify_all();
+ Ok(data.len())
+ }
+}
+
+struct RustMiscdev {
+ _dev: Pin<Box<miscdev::Registration<Pin<Ref<SharedState>>>>>,
+}
+
+impl KernelModule for RustMiscdev {
+ fn init() -> Result<Self> {
+ pr_info!("Rust miscellaneous device sample (init)\n");
+
+ let state = SharedState::try_new()?;
+
+ Ok(RustMiscdev {
+ _dev: miscdev::Registration::new_pinned::<Token>(c_str!("rust_miscdev"), None, state)?,
+ })
+ }
+}
+
+impl Drop for RustMiscdev {
+ fn drop(&mut self) {
+ pr_info!("Rust miscellaneous device sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_module_parameters.rs b/samples/rust/rust_module_parameters.rs
new file mode 100644
index 00000000000..57e59e80502
--- /dev/null
+++ b/samples/rust/rust_module_parameters.rs
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust module parameters sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::prelude::*;
+
+module! {
+ type: RustModuleParameters,
+ name: b"rust_module_parameters",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust module parameters sample",
+ license: b"GPL v2",
+ params: {
+ my_bool: bool {
+ default: true,
+ permissions: 0,
+ description: b"Example of bool",
+ },
+ my_i32: i32 {
+ default: 42,
+ permissions: 0o644,
+ description: b"Example of i32",
+ },
+ my_str: str {
+ default: b"default str val",
+ permissions: 0o644,
+ description: b"Example of a string param",
+ },
+ my_usize: usize {
+ default: 42,
+ permissions: 0o644,
+ description: b"Example of usize",
+ },
+ my_array: ArrayParam<i32, 3> {
+ default: [0, 1],
+ permissions: 0,
+ description: b"Example of array",
+ },
+ },
+}
+
+struct RustModuleParameters;
+
+impl KernelModule for RustModuleParameters {
+ fn init() -> Result<Self> {
+ pr_info!("Rust module parameters sample (init)\n");
+
+ {
+ let lock = THIS_MODULE.kernel_param_lock();
+ pr_info!("Parameters:\n");
+ pr_info!(" my_bool: {}\n", my_bool.read());
+ pr_info!(" my_i32: {}\n", my_i32.read(&lock));
+ pr_info!(
+ " my_str: {}\n",
+ core::str::from_utf8(my_str.read(&lock))?
+ );
+ pr_info!(" my_usize: {}\n", my_usize.read(&lock));
+ pr_info!(" my_array: {:?}\n", my_array.read());
+ }
+
+ Ok(RustModuleParameters)
+ }
+}
+
+impl Drop for RustModuleParameters {
+ fn drop(&mut self) {
+ pr_info!("Rust module parameters sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_print.rs b/samples/rust/rust_print.rs
new file mode 100644
index 00000000000..c43338fca50
--- /dev/null
+++ b/samples/rust/rust_print.rs
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust printing macros sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::pr_cont;
+use kernel::prelude::*;
+
+module! {
+ type: RustPrint,
+ name: b"rust_print",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust printing macros sample",
+ license: b"GPL v2",
+}
+
+struct RustPrint;
+
+impl KernelModule for RustPrint {
+ fn init() -> Result<Self> {
+ pr_info!("Rust printing macros sample (init)\n");
+
+ pr_emerg!("Emergency message (level 0) without args\n");
+ pr_alert!("Alert message (level 1) without args\n");
+ pr_crit!("Critical message (level 2) without args\n");
+ pr_err!("Error message (level 3) without args\n");
+ pr_warn!("Warning message (level 4) without args\n");
+ pr_notice!("Notice message (level 5) without args\n");
+ pr_info!("Info message (level 6) without args\n");
+
+ pr_info!("A line that");
+ pr_cont!(" is continued");
+ pr_cont!(" without args\n");
+
+ pr_emerg!("{} message (level {}) with args\n", "Emergency", 0);
+ pr_alert!("{} message (level {}) with args\n", "Alert", 1);
+ pr_crit!("{} message (level {}) with args\n", "Critical", 2);
+ pr_err!("{} message (level {}) with args\n", "Error", 3);
+ pr_warn!("{} message (level {}) with args\n", "Warning", 4);
+ pr_notice!("{} message (level {}) with args\n", "Notice", 5);
+ pr_info!("{} message (level {}) with args\n", "Info", 6);
+
+ pr_info!("A {} that", "line");
+ pr_cont!(" is {}", "continued");
+ pr_cont!(" with {}\n", "args");
+
+ Ok(RustPrint)
+ }
+}
+
+impl Drop for RustPrint {
+ fn drop(&mut self) {
+ pr_info!("Rust printing macros sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_random.rs b/samples/rust/rust_random.rs
new file mode 100644
index 00000000000..135325b6ca0
--- /dev/null
+++ b/samples/rust/rust_random.rs
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust random device
+//!
+//! Adapted from Alex Gaynor's original available at
+//! <https://github.com/alex/just-use/blob/master/src/lib.rs>.
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::{
+ file::File,
+ file_operations::FileOperations,
+ io_buffer::{IoBufferReader, IoBufferWriter},
+ prelude::*,
+};
+
+#[derive(Default)]
+struct RandomFile;
+
+impl FileOperations for RandomFile {
+ kernel::declare_file_operations!(read, write, read_iter, write_iter);
+
+ fn read<T: IoBufferWriter>(_this: &Self, file: &File, buf: &mut T, _: u64) -> Result<usize> {
+ let total_len = buf.len();
+ let mut chunkbuf = [0; 256];
+
+ while !buf.is_empty() {
+ let len = chunkbuf.len().min(buf.len());
+ let chunk = &mut chunkbuf[0..len];
+
+ if file.is_blocking() {
+ kernel::random::getrandom(chunk)?;
+ } else {
+ kernel::random::getrandom_nonblock(chunk)?;
+ }
+ buf.write_slice(chunk)?;
+ }
+ Ok(total_len)
+ }
+
+ fn write<T: IoBufferReader>(_this: &Self, _file: &File, buf: &mut T, _: u64) -> Result<usize> {
+ let total_len = buf.len();
+ let mut chunkbuf = [0; 256];
+ while !buf.is_empty() {
+ let len = chunkbuf.len().min(buf.len());
+ let chunk = &mut chunkbuf[0..len];
+ buf.read_slice(chunk)?;
+ kernel::random::add_randomness(chunk);
+ }
+ Ok(total_len)
+ }
+}
+
+module_misc_device! {
+ type: RandomFile,
+ name: b"rust_random",
+ author: b"Rust for Linux Contributors",
+ description: b"Just use /dev/urandom: Now with early-boot safety",
+ license: b"GPL v2",
+}
diff --git a/samples/rust/rust_semaphore.rs b/samples/rust/rust_semaphore.rs
new file mode 100644
index 00000000000..1408d5095b8
--- /dev/null
+++ b/samples/rust/rust_semaphore.rs
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust semaphore sample
+//!
+//! A counting semaphore that can be used by userspace.
+//!
+//! The count is incremented by writes to the device. A write of `n` bytes results in an increment
+//! of `n`. It is decremented by reads; each read results in the count being decremented by 1. If
+//! the count is already zero, a read will block until another write increments it.
+//!
+//! This can be used in user space from the shell for example as follows (assuming a node called
+//! `semaphore`): `cat semaphore` decrements the count by 1 (waiting for it to become non-zero
+//! before decrementing); `echo -n 123 > semaphore` increments the semaphore by 3, potentially
+//! unblocking up to 3 blocked readers.
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use core::sync::atomic::{AtomicU64, Ordering};
+use kernel::{
+ c_str, condvar_init, declare_file_operations,
+ file::File,
+ file_operations::{FileOpener, FileOperations, IoctlCommand, IoctlHandler},
+ io_buffer::{IoBufferReader, IoBufferWriter},
+ miscdev::Registration,
+ mutex_init,
+ prelude::*,
+ sync::{CondVar, Mutex, Ref},
+ user_ptr::{UserSlicePtrReader, UserSlicePtrWriter},
+};
+
+module! {
+ type: RustSemaphore,
+ name: b"rust_semaphore",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust semaphore sample",
+ license: b"GPL v2",
+}
+
+struct SemaphoreInner {
+ count: usize,
+ max_seen: usize,
+}
+
+struct Semaphore {
+ changed: CondVar,
+ inner: Mutex<SemaphoreInner>,
+}
+
+struct FileState {
+ read_count: AtomicU64,
+ shared: Ref<Semaphore>,
+}
+
+impl FileState {
+ fn consume(&self) -> Result {
+ let mut inner = self.shared.inner.lock();
+ while inner.count == 0 {
+ if self.shared.changed.wait(&mut inner) {
+ return Err(Error::EINTR);
+ }
+ }
+ inner.count -= 1;
+ Ok(())
+ }
+}
+
+impl FileOpener<Ref<Semaphore>> for FileState {
+ fn open(shared: &Ref<Semaphore>) -> Result<Box<Self>> {
+ Ok(Box::try_new(Self {
+ read_count: AtomicU64::new(0),
+ shared: shared.clone(),
+ })?)
+ }
+}
+
+impl FileOperations for FileState {
+ declare_file_operations!(read, write, ioctl);
+
+ fn read<T: IoBufferWriter>(this: &Self, _: &File, data: &mut T, offset: u64) -> Result<usize> {
+ if data.is_empty() || offset > 0 {
+ return Ok(0);
+ }
+ this.consume()?;
+ data.write_slice(&[0u8; 1])?;
+ this.read_count.fetch_add(1, Ordering::Relaxed);
+ Ok(1)
+ }
+
+ fn write<T: IoBufferReader>(this: &Self, _: &File, data: &mut T, _offs: u64) -> Result<usize> {
+ {
+ let mut inner = this.shared.inner.lock();
+ inner.count = inner.count.saturating_add(data.len());
+ if inner.count > inner.max_seen {
+ inner.max_seen = inner.count;
+ }
+ }
+
+ this.shared.changed.notify_all();
+ Ok(data.len())
+ }
+
+ fn ioctl(this: &Self, file: &File, cmd: &mut IoctlCommand) -> Result<i32> {
+ cmd.dispatch::<Self>(this, file)
+ }
+}
+
+struct RustSemaphore {
+ _dev: Pin<Box<Registration<Ref<Semaphore>>>>,
+}
+
+impl KernelModule for RustSemaphore {
+ fn init() -> Result<Self> {
+ pr_info!("Rust semaphore sample (init)\n");
+
+ let sema = Ref::try_new_and_init(
+ Semaphore {
+ // SAFETY: `condvar_init!` is called below.
+ changed: unsafe { CondVar::new() },
+
+ // SAFETY: `mutex_init!` is called below.
+ inner: unsafe {
+ Mutex::new(SemaphoreInner {
+ count: 0,
+ max_seen: 0,
+ })
+ },
+ },
+ |mut sema| {
+ // SAFETY: `changed` is pinned when `sema` is.
+ let pinned = unsafe { sema.as_mut().map_unchecked_mut(|s| &mut s.changed) };
+ condvar_init!(pinned, "Semaphore::changed");
+
+ // SAFETY: `inner` is pinned when `sema` is.
+ let pinned = unsafe { sema.as_mut().map_unchecked_mut(|s| &mut s.inner) };
+ mutex_init!(pinned, "Semaphore::inner");
+ },
+ )?;
+
+ Ok(Self {
+ _dev: Registration::new_pinned::<FileState>(c_str!("rust_semaphore"), None, sema)?,
+ })
+ }
+}
+
+impl Drop for RustSemaphore {
+ fn drop(&mut self) {
+ pr_info!("Rust semaphore sample (exit)\n");
+ }
+}
+
+const IOCTL_GET_READ_COUNT: u32 = 0x80086301;
+const IOCTL_SET_READ_COUNT: u32 = 0x40086301;
+
+impl IoctlHandler for FileState {
+ type Target = Self;
+
+ fn read(this: &Self, _: &File, cmd: u32, writer: &mut UserSlicePtrWriter) -> Result<i32> {
+ match cmd {
+ IOCTL_GET_READ_COUNT => {
+ writer.write(&this.read_count.load(Ordering::Relaxed))?;
+ Ok(0)
+ }
+ _ => Err(Error::EINVAL),
+ }
+ }
+
+ fn write(this: &Self, _: &File, cmd: u32, reader: &mut UserSlicePtrReader) -> Result<i32> {
+ match cmd {
+ IOCTL_SET_READ_COUNT => {
+ this.read_count.store(reader.read()?, Ordering::Relaxed);
+ Ok(0)
+ }
+ _ => Err(Error::EINVAL),
+ }
+ }
+}
diff --git a/samples/rust/rust_semaphore_c.c b/samples/rust/rust_semaphore_c.c
new file mode 100644
index 00000000000..cdc121d4030
--- /dev/null
+++ b/samples/rust/rust_semaphore_c.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Rust semaphore sample (in C, for comparison)
+ *
+ * This is a C implementation of `rust_semaphore.rs`. Refer to the description
+ * in that file for details on the device.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/refcount.h>
+#include <linux/wait.h>
+
+#define IOCTL_GET_READ_COUNT _IOR('c', 1, u64)
+#define IOCTL_SET_READ_COUNT _IOW('c', 1, u64)
+
+struct semaphore_state {
+ struct kref ref;
+ struct miscdevice miscdev;
+ wait_queue_head_t changed;
+ struct mutex mutex;
+ size_t count;
+ size_t max_seen;
+};
+
+struct file_state {
+ atomic64_t read_count;
+ struct semaphore_state *shared;
+};
+
+static int semaphore_consume(struct semaphore_state *state)
+{
+ DEFINE_WAIT(wait);
+
+ mutex_lock(&state->mutex);
+ while (state->count == 0) {
+ prepare_to_wait(&state->changed, &wait, TASK_INTERRUPTIBLE);
+ mutex_unlock(&state->mutex);
+ schedule();
+ finish_wait(&state->changed, &wait);
+ if (signal_pending(current))
+ return -EINTR;
+ mutex_lock(&state->mutex);
+ }
+
+ state->count--;
+ mutex_unlock(&state->mutex);
+
+ return 0;
+}
+
+static int semaphore_open(struct inode *nodp, struct file *filp)
+{
+ struct semaphore_state *shared =
+ container_of(filp->private_data, struct semaphore_state, miscdev);
+ struct file_state *state;
+
+ state = kzalloc(sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ kref_get(&shared->ref);
+ state->shared = shared;
+ atomic64_set(&state->read_count, 0);
+
+ filp->private_data = state;
+
+ return 0;
+}
+
+static ssize_t semaphore_write(struct file *filp, const char __user *buffer, size_t count,
+ loff_t *ppos)
+{
+ struct file_state *state = filp->private_data;
+ struct semaphore_state *shared = state->shared;
+
+ mutex_lock(&shared->mutex);
+
+ shared->count += count;
+ if (shared->count < count)
+ shared->count = SIZE_MAX;
+
+ if (shared->count > shared->max_seen)
+ shared->max_seen = shared->count;
+
+ mutex_unlock(&shared->mutex);
+
+ wake_up_all(&shared->changed);
+
+ return count;
+}
+
+static ssize_t semaphore_read(struct file *filp, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct file_state *state = filp->private_data;
+ char c = 0;
+ int ret;
+
+ if (count == 0 || *ppos > 0)
+ return 0;
+
+ ret = semaphore_consume(state->shared);
+ if (ret)
+ return ret;
+
+ if (copy_to_user(buffer, &c, sizeof(c)))
+ return -EFAULT;
+
+ atomic64_add(1, &state->read_count);
+ *ppos += 1;
+ return 1;
+}
+
+static long semaphore_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+ struct file_state *state = filp->private_data;
+ void __user *buffer = (void __user *)arg;
+ u64 value;
+
+ switch (cmd) {
+ case IOCTL_GET_READ_COUNT:
+ value = atomic64_read(&state->read_count);
+ if (copy_to_user(buffer, &value, sizeof(value)))
+ return -EFAULT;
+ return 0;
+ case IOCTL_SET_READ_COUNT:
+ if (copy_from_user(&value, buffer, sizeof(value)))
+ return -EFAULT;
+ atomic64_set(&state->read_count, value);
+ return 0;
+ default:
+ return -EINVAL;
+ }
+}
+
+static void semaphore_free(struct kref *kref)
+{
+ struct semaphore_state *device;
+
+ device = container_of(kref, struct semaphore_state, ref);
+ kfree(device);
+}
+
+static int semaphore_release(struct inode *nodp, struct file *filp)
+{
+ struct file_state *state = filp->private_data;
+
+ kref_put(&state->shared->ref, semaphore_free);
+ kfree(state);
+ return 0;
+}
+
+static const struct file_operations semaphore_fops = {
+ .owner = THIS_MODULE,
+ .open = semaphore_open,
+ .read = semaphore_read,
+ .write = semaphore_write,
+ .compat_ioctl = semaphore_ioctl,
+ .release = semaphore_release,
+};
+
+static struct semaphore_state *device;
+
+static int __init semaphore_init(void)
+{
+ int ret;
+ struct semaphore_state *state;
+
+ pr_info("Rust semaphore sample (in C, for comparison) (init)\n");
+
+ state = kzalloc(sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ mutex_init(&state->mutex);
+ kref_init(&state->ref);
+ init_waitqueue_head(&state->changed);
+
+ state->miscdev.fops = &semaphore_fops;
+ state->miscdev.minor = MISC_DYNAMIC_MINOR;
+ state->miscdev.name = "semaphore";
+
+ ret = misc_register(&state->miscdev);
+ if (ret < 0) {
+ kfree(state);
+ return ret;
+ }
+
+ device = state;
+
+ return 0;
+}
+
+static void __exit semaphore_exit(void)
+{
+ pr_info("Rust semaphore sample (in C, for comparison) (exit)\n");
+
+ misc_deregister(&device->miscdev);
+ kref_put(&device->ref, semaphore_free);
+}
+
+module_init(semaphore_init);
+module_exit(semaphore_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Rust for Linux Contributors");
+MODULE_DESCRIPTION("Rust semaphore sample (in C, for comparison)");
diff --git a/samples/rust/rust_stack_probing.rs b/samples/rust/rust_stack_probing.rs
new file mode 100644
index 00000000000..fcb87a53ce7
--- /dev/null
+++ b/samples/rust/rust_stack_probing.rs
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust stack probing sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+#![feature(bench_black_box)]
+
+use kernel::prelude::*;
+
+module! {
+ type: RustStackProbing,
+ name: b"rust_stack_probing",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust stack probing sample",
+ license: b"GPL v2",
+}
+
+struct RustStackProbing;
+
+impl KernelModule for RustStackProbing {
+ fn init() -> Result<Self> {
+ pr_info!("Rust stack probing sample (init)\n");
+
+ // Including this large variable on the stack will trigger
+ // stack probing on the supported archs.
+ // This will verify that stack probing does not lead to
+ // any errors if we need to link `__rust_probestack`.
+ let x: [u64; 514] = core::hint::black_box([5; 514]);
+ pr_info!("Large array has length: {}\n", x.len());
+
+ Ok(RustStackProbing)
+ }
+}
+
+impl Drop for RustStackProbing {
+ fn drop(&mut self) {
+ pr_info!("Rust stack probing sample (exit)\n");
+ }
+}
diff --git a/samples/rust/rust_sync.rs b/samples/rust/rust_sync.rs
new file mode 100644
index 00000000000..40bbfec9ad2
--- /dev/null
+++ b/samples/rust/rust_sync.rs
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust synchronisation primitives sample
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::prelude::*;
+use kernel::{
+ condvar_init, mutex_init, spinlock_init,
+ sync::{CondVar, Mutex, SpinLock},
+};
+
+module! {
+ type: RustSync,
+ name: b"rust_sync",
+ author: b"Rust for Linux Contributors",
+ description: b"Rust synchronisation primitives sample",
+ license: b"GPL v2",
+}
+
+struct RustSync;
+
+impl KernelModule for RustSync {
+ fn init() -> Result<Self> {
+ pr_info!("Rust synchronisation primitives sample (init)\n");
+
+ // Test mutexes.
+ {
+ // SAFETY: `init` is called below.
+ let mut data = Pin::from(Box::try_new(unsafe { Mutex::new(0) })?);
+ mutex_init!(data.as_mut(), "RustSync::init::data1");
+ *data.lock() = 10;
+ pr_info!("Value: {}\n", *data.lock());
+
+ // SAFETY: `init` is called below.
+ let mut cv = Pin::from(Box::try_new(unsafe { CondVar::new() })?);
+ condvar_init!(cv.as_mut(), "RustSync::init::cv1");
+
+ {
+ let mut guard = data.lock();
+ while *guard != 10 {
+ let _ = cv.wait(&mut guard);
+ }
+ }
+ cv.notify_one();
+ cv.notify_all();
+ cv.free_waiters();
+ }
+
+ // Test spinlocks.
+ {
+ // SAFETY: `init` is called below.
+ let mut data = Pin::from(Box::try_new(unsafe { SpinLock::new(0) })?);
+ spinlock_init!(data.as_mut(), "RustSync::init::data2");
+ *data.lock() = 10;
+ pr_info!("Value: {}\n", *data.lock());
+
+ // SAFETY: `init` is called below.
+ let mut cv = Pin::from(Box::try_new(unsafe { CondVar::new() })?);
+ condvar_init!(cv.as_mut(), "RustSync::init::cv2");
+ {
+ let mut guard = data.lock();
+ while *guard != 10 {
+ let _ = cv.wait(&mut guard);
+ }
+ }
+ cv.notify_one();
+ cv.notify_all();
+ cv.free_waiters();
+ }
+
+ Ok(RustSync)
+ }
+}
+
+impl Drop for RustSync {
+ fn drop(&mut self) {
+ pr_info!("Rust synchronisation primitives sample (exit)\n");
+ }
+}
--
2.32.0

2021-07-04 20:30:47

by Miguel Ojeda

Subject: [PATCH 05/17] rust: add C helpers

From: Miguel Ojeda <[email protected]>

This source file contains forwarders to C macros and inlined
functions.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/helpers.c | 235 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 235 insertions(+)
create mode 100644 rust/helpers.c

diff --git a/rust/helpers.c b/rust/helpers.c
new file mode 100644
index 00000000000..a6e98abb13e
--- /dev/null
+++ b/rust/helpers.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bug.h>
+#include <linux/build_bug.h>
+#include <linux/uaccess.h>
+#include <linux/sched/signal.h>
+#include <linux/gfp.h>
+#include <linux/highmem.h>
+#include <linux/uio.h>
+#include <linux/errname.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/security.h>
+
+void rust_helper_BUG(void)
+{
+ BUG();
+}
+
+unsigned long rust_helper_copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+ return copy_from_user(to, from, n);
+}
+
+unsigned long rust_helper_copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ return copy_to_user(to, from, n);
+}
+
+unsigned long rust_helper_clear_user(void __user *to, unsigned long n)
+{
+ return clear_user(to, n);
+}
+
+void rust_helper_spin_lock_init(spinlock_t *lock, const char *name,
+ struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_SPINLOCK
+ __spin_lock_init(lock, name, key);
+#else
+ spin_lock_init(lock);
+#endif
+}
+EXPORT_SYMBOL_GPL(rust_helper_spin_lock_init);
+
+void rust_helper_spin_lock(spinlock_t *lock)
+{
+ spin_lock(lock);
+}
+EXPORT_SYMBOL_GPL(rust_helper_spin_lock);
+
+void rust_helper_spin_unlock(spinlock_t *lock)
+{
+ spin_unlock(lock);
+}
+EXPORT_SYMBOL_GPL(rust_helper_spin_unlock);
+
+void rust_helper_init_wait(struct wait_queue_entry *wq_entry)
+{
+ init_wait(wq_entry);
+}
+EXPORT_SYMBOL_GPL(rust_helper_init_wait);
+
+int rust_helper_signal_pending(struct task_struct *t)
+{
+ return signal_pending(t);
+}
+EXPORT_SYMBOL_GPL(rust_helper_signal_pending);
+
+struct page *rust_helper_alloc_pages(gfp_t gfp_mask, unsigned int order)
+{
+ return alloc_pages(gfp_mask, order);
+}
+EXPORT_SYMBOL_GPL(rust_helper_alloc_pages);
+
+void *rust_helper_kmap(struct page *page)
+{
+ return kmap(page);
+}
+EXPORT_SYMBOL_GPL(rust_helper_kmap);
+
+void rust_helper_kunmap(struct page *page)
+{
+ return kunmap(page);
+}
+EXPORT_SYMBOL_GPL(rust_helper_kunmap);
+
+int rust_helper_cond_resched(void)
+{
+ return cond_resched();
+}
+EXPORT_SYMBOL_GPL(rust_helper_cond_resched);
+
+size_t rust_helper_copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+{
+ return copy_from_iter(addr, bytes, i);
+}
+EXPORT_SYMBOL_GPL(rust_helper_copy_from_iter);
+
+size_t rust_helper_copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+ return copy_to_iter(addr, bytes, i);
+}
+EXPORT_SYMBOL_GPL(rust_helper_copy_to_iter);
+
+bool rust_helper_is_err(__force const void *ptr)
+{
+ return IS_ERR(ptr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_is_err);
+
+long rust_helper_ptr_err(__force const void *ptr)
+{
+ return PTR_ERR(ptr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_ptr_err);
+
+const char *rust_helper_errname(int err)
+{
+ return errname(err);
+}
+
+void rust_helper_mutex_lock(struct mutex *lock)
+{
+ mutex_lock(lock);
+}
+EXPORT_SYMBOL_GPL(rust_helper_mutex_lock);
+
+void *
+rust_helper_platform_get_drvdata(const struct platform_device *pdev)
+{
+ return platform_get_drvdata(pdev);
+}
+EXPORT_SYMBOL_GPL(rust_helper_platform_get_drvdata);
+
+void
+rust_helper_platform_set_drvdata(struct platform_device *pdev,
+ void *data)
+{
+ return platform_set_drvdata(pdev, data);
+}
+EXPORT_SYMBOL_GPL(rust_helper_platform_set_drvdata);
+
+refcount_t rust_helper_refcount_new(void)
+{
+ return (refcount_t)REFCOUNT_INIT(1);
+}
+EXPORT_SYMBOL_GPL(rust_helper_refcount_new);
+
+void rust_helper_refcount_inc(refcount_t *r)
+{
+ refcount_inc(r);
+}
+EXPORT_SYMBOL_GPL(rust_helper_refcount_inc);
+
+bool rust_helper_refcount_dec_and_test(refcount_t *r)
+{
+ return refcount_dec_and_test(r);
+}
+EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test);
+
+void rust_helper_rb_link_node(struct rb_node *node, struct rb_node *parent,
+ struct rb_node **rb_link)
+{
+ rb_link_node(node, parent, rb_link);
+}
+EXPORT_SYMBOL_GPL(rust_helper_rb_link_node);
+
+struct task_struct *rust_helper_get_current(void)
+{
+ return current;
+}
+EXPORT_SYMBOL_GPL(rust_helper_get_current);
+
+void rust_helper_get_task_struct(struct task_struct * t)
+{
+ get_task_struct(t);
+}
+EXPORT_SYMBOL_GPL(rust_helper_get_task_struct);
+
+void rust_helper_put_task_struct(struct task_struct * t)
+{
+ put_task_struct(t);
+}
+EXPORT_SYMBOL_GPL(rust_helper_put_task_struct);
+
+int rust_helper_security_binder_set_context_mgr(struct task_struct *mgr)
+{
+ return security_binder_set_context_mgr(mgr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_security_binder_set_context_mgr);
+
+int rust_helper_security_binder_transaction(struct task_struct *from,
+ struct task_struct *to)
+{
+ return security_binder_transaction(from, to);
+}
+EXPORT_SYMBOL_GPL(rust_helper_security_binder_transaction);
+
+int rust_helper_security_binder_transfer_binder(struct task_struct *from,
+ struct task_struct *to)
+{
+ return security_binder_transfer_binder(from, to);
+}
+EXPORT_SYMBOL_GPL(rust_helper_security_binder_transfer_binder);
+
+int rust_helper_security_binder_transfer_file(struct task_struct *from,
+ struct task_struct *to,
+ struct file *file)
+{
+ return security_binder_transfer_file(from, to, file);
+}
+EXPORT_SYMBOL_GPL(rust_helper_security_binder_transfer_file);
+
+/* We use bindgen's --size_t-is-usize option to bind the C size_t type
+ * as the Rust usize type, so we can use it in contexts where Rust
+ * expects a usize like slice (array) indices. usize is defined to be
+ * the same as C's uintptr_t type (can hold any pointer) but not
+ * necessarily the same as size_t (can hold the size of any single
+ * object). Most modern platforms use the same concrete integer type for
+ * both of them, but in case we find ourselves on a platform where
+ * that's not true, fail early instead of risking ABI or
+ * integer-overflow issues.
+ *
+ * If your platform fails this assertion, it means that you are in
+ * danger of integer-overflow bugs (even if you attempt to remove
+ * --size_t-is-usize). It may be easiest to change the kernel ABI on
+ * your platform such that size_t matches uintptr_t (i.e., to increase
+ * size_t, because uintptr_t has to be at least as big as size_t).
+*/
+static_assert(
+ sizeof(size_t) == sizeof(uintptr_t) &&
+ __alignof__(size_t) == __alignof__(uintptr_t),
+ "Rust code expects C size_t to match Rust usize"
+);
--
2.32.0

2021-07-04 20:30:48

by Miguel Ojeda

Subject: [PATCH 15/17] scripts: add `generate_rust_analyzer.py`

From: Miguel Ojeda <[email protected]>

The `generate_rust_analyzer.py` script generates the configuration
file (`rust-project.json`) for rust-analyzer.

rust-analyzer is a modular compiler frontend for the Rust language.
It provides an LSP server which can be used in editors such as
VS Code, Emacs or Vim.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
scripts/generate_rust_analyzer.py | 143 ++++++++++++++++++++++++++++++
1 file changed, 143 insertions(+)
create mode 100755 scripts/generate_rust_analyzer.py

diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_analyzer.py
new file mode 100755
index 00000000000..72c453e1aea
--- /dev/null
+++ b/scripts/generate_rust_analyzer.py
@@ -0,0 +1,143 @@
+#!/usr/bin/env python3
+"""generate_rust_analyzer - Generates the `rust-project.json` file for `rust-analyzer`.
+"""
+
+import argparse
+import json
+import logging
+import pathlib
+import sys
+
+def generate_crates(srctree, objtree, sysroot_src, bindings_file):
+ # Generate the configuration list.
+ cfg = []
+ with open(objtree / "include" / "generated" / "rustc_cfg") as fd:
+ for line in fd:
+ line = line.replace("--cfg=", "")
+ line = line.replace("\n", "")
+ cfg.append(line)
+
+ # Now fill the crates list -- dependencies need to come first.
+ #
+ # Avoid O(n^2) iterations by keeping a map of indexes.
+ crates = []
+ crates_indexes = {}
+
+ def append_crate(display_name, root_module, is_workspace_member, deps, cfg):
+ crates_indexes[display_name] = len(crates)
+ crates.append({
+ "display_name": display_name,
+ "root_module": str(root_module),
+ "is_workspace_member": is_workspace_member,
+ "deps": [{"crate": crates_indexes[dep], "name": dep} for dep in deps],
+ "cfg": cfg,
+ "edition": "2018",
+ "env": {
+ "RUST_MODFILE": "This is only for rust-analyzer"
+ }
+ })
+
+ # First, the ones in `rust/` since they are a bit special.
+ append_crate(
+ "core",
+ sysroot_src / "core" / "src" / "lib.rs",
+ False,
+ [],
+ [],
+ )
+
+ append_crate(
+ "compiler_builtins",
+ srctree / "rust" / "compiler_builtins.rs",
+ True,
+ [],
+ [],
+ )
+
+ append_crate(
+ "alloc",
+ srctree / "rust" / "alloc" / "lib.rs",
+ True,
+ ["core", "compiler_builtins"],
+ [],
+ )
+
+ append_crate(
+ "macros",
+ srctree / "rust" / "macros" / "lib.rs",
+ True,
+ [],
+ [],
+ )
+ crates[-1]["proc_macro_dylib_path"] = "rust/libmacros.so"
+
+ append_crate(
+ "build_error",
+ srctree / "rust" / "build_error.rs",
+ True,
+ ["core", "compiler_builtins"],
+ [],
+ )
+
+ append_crate(
+ "kernel",
+ srctree / "rust" / "kernel" / "lib.rs",
+ True,
+ ["core", "alloc", "macros", "build_error"],
+ cfg,
+ )
+ crates[-1]["env"]["RUST_BINDINGS_FILE"] = str(bindings_file.resolve(True))
+ crates[-1]["source"] = {
+ "include_dirs": [
+ str(srctree / "rust" / "kernel"),
+ str(objtree / "rust")
+ ],
+ "exclude_dirs": [],
+ }
+
+ # Then, the rest outside of `rust/`.
+ #
+ # We explicitly mention the top-level folders we want to cover.
+ for folder in ("samples", "drivers"):
+ for path in (srctree / folder).rglob("*.rs"):
+ logging.info("Checking %s", path)
+ name = path.name.replace(".rs", "")
+
+ # Skip those that are not crate roots.
+ if f"{name}.o" not in open(path.parent / "Makefile").read():
+ continue
+
+ logging.info("Adding %s", name)
+ append_crate(
+ name,
+ path,
+ True,
+ ["core", "alloc", "kernel"],
+ cfg,
+ )
+
+ return crates
+
+def main():
+ parser = argparse.ArgumentParser()
+ parser.add_argument('--verbose', '-v', action='store_true')
+ parser.add_argument("srctree", type=pathlib.Path)
+ parser.add_argument("objtree", type=pathlib.Path)
+ parser.add_argument("sysroot_src", type=pathlib.Path)
+ parser.add_argument("bindings_file", type=pathlib.Path)
+ args = parser.parse_args()
+
+ logging.basicConfig(
+ format="[%(asctime)s] [%(levelname)s] %(message)s",
+ level=logging.INFO if args.verbose else logging.WARNING
+ )
+
+ rust_project = {
+ "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src, args.bindings_file),
+ "sysroot_src": str(args.sysroot_src),
+ }
+
+ json.dump(rust_project, sys.stdout, sort_keys=True, indent=4)
+
+if __name__ == "__main__":
+ main()
--
2.32.0

2021-07-04 20:30:45

by Miguel Ojeda

Subject: [PATCH 07/17] rust: add `alloc` crate

From: Miguel Ojeda <[email protected]>

This crate is a subset of the Rust standard library `alloc`, with some
additions on top.

This is needed because upstream support for fallible allocations
is a work in progress (i.e. the `try_*` versions of methods which
return a `Result` instead of panicking).

Having the library in-tree also gives us a bit more freedom to
experiment with new interfaces and allows us to iterate quickly.

Eventually, the goal is to have everything the kernel needs in
upstream `alloc` and drop it from the kernel tree.

Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Michael Ellerman <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Co-developed-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Boris-Chengbiao Zhou <[email protected]>
Signed-off-by: Boris-Chengbiao Zhou <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Ayaan Zaidi <[email protected]>
Signed-off-by: Ayaan Zaidi <[email protected]>
Co-developed-by: Douglas Su <[email protected]>
Signed-off-by: Douglas Su <[email protected]>
Co-developed-by: Yuki Okushi <[email protected]>
Signed-off-by: Yuki Okushi <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/alloc/README.md | 32 +
rust/alloc/alloc.rs | 425 ++++
rust/alloc/borrow.rs | 493 +++++
rust/alloc/boxed.rs | 1728 +++++++++++++++
rust/alloc/collections/mod.rs | 116 +
rust/alloc/fmt.rs | 587 ++++++
rust/alloc/lib.rs | 197 ++
rust/alloc/macros.rs | 128 ++
rust/alloc/prelude/mod.rs | 17 +
rust/alloc/prelude/v1.rs | 16 +
rust/alloc/raw_vec.rs | 612 ++++++
rust/alloc/rc.rs | 2539 ++++++++++++++++++++++
rust/alloc/slice.rs | 1271 +++++++++++
rust/alloc/str.rs | 614 ++++++
rust/alloc/string.rs | 2847 +++++++++++++++++++++++++
rust/alloc/sync.rs | 2631 +++++++++++++++++++++++
rust/alloc/vec/drain.rs | 157 ++
rust/alloc/vec/drain_filter.rs | 145 ++
rust/alloc/vec/into_iter.rs | 296 +++
rust/alloc/vec/is_zero.rs | 106 +
rust/alloc/vec/mod.rs | 3255 +++++++++++++++++++++++++++++
rust/alloc/vec/partial_eq.rs | 49 +
rust/alloc/vec/set_len_on_drop.rs | 30 +
rust/alloc/vec/spec_extend.rs | 170 ++
24 files changed, 18461 insertions(+)
create mode 100644 rust/alloc/README.md
create mode 100644 rust/alloc/alloc.rs
create mode 100644 rust/alloc/borrow.rs
create mode 100644 rust/alloc/boxed.rs
create mode 100644 rust/alloc/collections/mod.rs
create mode 100644 rust/alloc/fmt.rs
create mode 100644 rust/alloc/lib.rs
create mode 100644 rust/alloc/macros.rs
create mode 100644 rust/alloc/prelude/mod.rs
create mode 100644 rust/alloc/prelude/v1.rs
create mode 100644 rust/alloc/raw_vec.rs
create mode 100644 rust/alloc/rc.rs
create mode 100644 rust/alloc/slice.rs
create mode 100644 rust/alloc/str.rs
create mode 100644 rust/alloc/string.rs
create mode 100644 rust/alloc/sync.rs
create mode 100644 rust/alloc/vec/drain.rs
create mode 100644 rust/alloc/vec/drain_filter.rs
create mode 100644 rust/alloc/vec/into_iter.rs
create mode 100644 rust/alloc/vec/is_zero.rs
create mode 100644 rust/alloc/vec/mod.rs
create mode 100644 rust/alloc/vec/partial_eq.rs
create mode 100644 rust/alloc/vec/set_len_on_drop.rs
create mode 100644 rust/alloc/vec/spec_extend.rs

diff --git a/rust/alloc/README.md b/rust/alloc/README.md
new file mode 100644
index 00000000000..a1bcc2cef0e
--- /dev/null
+++ b/rust/alloc/README.md
@@ -0,0 +1,32 @@
+# `alloc`
+
+These source files come from the Rust standard library, hosted in
+the https://github.com/rust-lang/rust repository. For copyright
+details, see https://github.com/rust-lang/rust/blob/master/COPYRIGHT.
+
+Please note that these files should be kept as close as possible to
+upstream. In general, only additions should be performed (e.g. new
+methods). Eventually, changes should make it into upstream so that,
+at some point, this fork can be dropped from the kernel tree.
+
+
+## Rationale
+
+On one hand, kernel folks wanted to keep `alloc` in-tree to have more
+freedom in both workflow and actual features if actually needed
+(e.g. receiver types if we ended up using them), which is reasonable.
+
+On the other hand, Rust folks wanted to keep `alloc` as close as
+upstream as possible and avoid as much divergence as possible, which
+is also reasonable.
+
+We agreed on a middle-ground: we would keep a subset of `alloc`
+in-tree that would be as small and as close as possible to upstream.
+Then, upstream can start adding the functions that we add to `alloc`
+etc., until we reach a point where the kernel already knows exactly
+what it needs in `alloc` and all the new methods are merged into
+upstream, so that we can drop `alloc` from the kernel tree and go back
+to using the upstream one.
+
+By doing this, the kernel can go a bit faster now, and Rust can
+slowly incorporate and discuss the changes as needed.
diff --git a/rust/alloc/alloc.rs b/rust/alloc/alloc.rs
new file mode 100644
index 00000000000..a59d64ffb36
--- /dev/null
+++ b/rust/alloc/alloc.rs
@@ -0,0 +1,425 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Memory allocation APIs
+
+#![stable(feature = "alloc_module", since = "1.28.0")]
+
+#[cfg(not(test))]
+use core::intrinsics;
+use core::intrinsics::{min_align_of_val, size_of_val};
+
+use core::ptr::Unique;
+#[cfg(not(test))]
+use core::ptr::{self, NonNull};
+
+#[stable(feature = "alloc_module", since = "1.28.0")]
+#[doc(inline)]
+pub use core::alloc::*;
+
+#[cfg(test)]
+mod tests;
+
+extern "Rust" {
+ // These are the magic symbols to call the global allocator. rustc generates
+ // them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
+ // (the code expanding that attribute macro generates those functions), or to call
+ // the default implementations in libstd (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
+ // otherwise.
+ // The rustc fork of LLVM also special-cases these function names to be able to optimize them
+ // like `malloc`, `realloc`, and `free`, respectively.
+ #[rustc_allocator]
+ #[rustc_allocator_nounwind]
+ fn __rust_alloc(size: usize, align: usize) -> *mut u8;
+ #[rustc_allocator_nounwind]
+ fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
+ #[rustc_allocator_nounwind]
+ fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
+ #[rustc_allocator_nounwind]
+ fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
+}
+
+/// The global memory allocator.
+///
+/// This type implements the [`Allocator`] trait by forwarding calls
+/// to the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// Note: while this type is unstable, the functionality it provides can be
+/// accessed through the [free functions in `alloc`](self#functions).
+#[unstable(feature = "allocator_api", issue = "32838")]
+#[derive(Copy, Clone, Default, Debug)]
+#[cfg(not(test))]
+pub struct Global;
+
+#[cfg(test)]
+pub use std::alloc::Global;
+
+/// Allocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::alloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `alloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::alloc`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc, dealloc, Layout};
+///
+/// unsafe {
+/// let layout = Layout::new::<u16>();
+/// let ptr = alloc(layout);
+///
+/// *(ptr as *mut u16) = 42;
+/// assert_eq!(*(ptr as *mut u16), 42);
+///
+/// dealloc(ptr, layout);
+/// }
+/// ```
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[inline]
+pub unsafe fn alloc(layout: Layout) -> *mut u8 {
+ unsafe { __rust_alloc(layout.size(), layout.align()) }
+}
+
+/// Deallocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `dealloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::dealloc`].
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[inline]
+pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
+ unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
+}
+
+/// Reallocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::realloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `realloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::realloc`].
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[inline]
+pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+ unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
+}
+
+/// Allocate zero-initialized memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::alloc_zeroed`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc_zeroed, dealloc, Layout};
+///
+/// unsafe {
+/// let layout = Layout::new::<u16>();
+/// let ptr = alloc_zeroed(layout);
+///
+/// assert_eq!(*(ptr as *mut u16), 0);
+///
+/// dealloc(ptr, layout);
+/// }
+/// ```
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[inline]
+pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
+ unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
+}
+
+#[cfg(not(test))]
+impl Global {
+ #[inline]
+ fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
+ match layout.size() {
+ 0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
+ // SAFETY: `layout` is non-zero in size,
+ size => unsafe {
+ let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
+ let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+ Ok(NonNull::slice_from_raw_parts(ptr, size))
+ },
+ }
+ }
+
+ // SAFETY: Same as `Allocator::grow`
+ #[inline]
+ unsafe fn grow_impl(
+ &self,
+ ptr: NonNull<u8>,
+ old_layout: Layout,
+ new_layout: Layout,
+ zeroed: bool,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ debug_assert!(
+ new_layout.size() >= old_layout.size(),
+ "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
+ );
+
+ match old_layout.size() {
+ 0 => self.alloc_impl(new_layout, zeroed),
+
+ // SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
+ // as required by safety conditions. Other conditions must be upheld by the caller
+ old_size if old_layout.align() == new_layout.align() => unsafe {
+ let new_size = new_layout.size();
+
+ // `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
+ intrinsics::assume(new_size >= old_layout.size());
+
+ let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
+ let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+ if zeroed {
+ raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
+ }
+ Ok(NonNull::slice_from_raw_parts(ptr, new_size))
+ },
+
+ // SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
+ // both the old and new memory allocation are valid for reads and writes for `old_size`
+ // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
+ // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
+ // for `dealloc` must be upheld by the caller.
+ old_size => unsafe {
+ let new_ptr = self.alloc_impl(new_layout, zeroed)?;
+ ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
+ self.deallocate(ptr, old_layout);
+ Ok(new_ptr)
+ },
+ }
+ }
+}
+
+#[unstable(feature = "allocator_api", issue = "32838")]
+#[cfg(not(test))]
+unsafe impl Allocator for Global {
+ #[inline]
+ fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+ self.alloc_impl(layout, false)
+ }
+
+ #[inline]
+ fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+ self.alloc_impl(layout, true)
+ }
+
+ #[inline]
+ unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+ if layout.size() != 0 {
+ // SAFETY: `layout` is non-zero in size,
+ // other conditions must be upheld by the caller
+ unsafe { dealloc(ptr.as_ptr(), layout) }
+ }
+ }
+
+ #[inline]
+ unsafe fn grow(
+ &self,
+ ptr: NonNull<u8>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ // SAFETY: all conditions must be upheld by the caller
+ unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
+ }
+
+ #[inline]
+ unsafe fn grow_zeroed(
+ &self,
+ ptr: NonNull<u8>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ // SAFETY: all conditions must be upheld by the caller
+ unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
+ }
+
+ #[inline]
+ unsafe fn shrink(
+ &self,
+ ptr: NonNull<u8>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ debug_assert!(
+ new_layout.size() <= old_layout.size(),
+ "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
+ );
+
+ match new_layout.size() {
+ // SAFETY: conditions must be upheld by the caller
+ 0 => unsafe {
+ self.deallocate(ptr, old_layout);
+ Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
+ },
+
+ // SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
+ new_size if old_layout.align() == new_layout.align() => unsafe {
+ // `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
+ intrinsics::assume(new_size <= old_layout.size());
+
+ let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
+ let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+ Ok(NonNull::slice_from_raw_parts(ptr, new_size))
+ },
+
+ // SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
+ // both the old and new memory allocation are valid for reads and writes for `new_size`
+ // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
+ // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
+ // for `dealloc` must be upheld by the caller.
+ new_size => unsafe {
+ let new_ptr = self.allocate(new_layout)?;
+ ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
+ self.deallocate(ptr, old_layout);
+ Ok(new_ptr)
+ },
+ }
+ }
+}
+
+/// The allocator for unique pointers.
+// This function must not unwind. If it does, MIR codegen will fail.
+#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[lang = "exchange_malloc"]
+#[inline]
+unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
+ let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+ match Global.allocate(layout) {
+ Ok(ptr) => ptr.as_mut_ptr(),
+ Err(_) => handle_alloc_error(layout),
+ }
+}
+
+#[cfg_attr(not(test), lang = "box_free")]
+#[inline]
+// This signature has to be the same as `Box`, otherwise an ICE will happen.
+// When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
+// well.
+// For example if `Box` is changed to `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
+// this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
+pub(crate) unsafe fn box_free<T: ?Sized, A: Allocator>(ptr: Unique<T>, alloc: A) {
+ unsafe {
+ let size = size_of_val(ptr.as_ref());
+ let align = min_align_of_val(ptr.as_ref());
+ let layout = Layout::from_size_align_unchecked(size, align);
+ alloc.deallocate(ptr.cast().into(), layout)
+ }
+}
+
+// # Allocation error handler
+
+#[cfg(not(no_global_oom_handling))]
+extern "Rust" {
+ // This is the magic symbol to call the global alloc error handler. rustc generates
+ // it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
+ // default implementations below (`__rdl_oom`) otherwise.
+ #[rustc_allocator_nounwind]
+ fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
+}
+
+/// Abort on memory allocation error or failure.
+///
+/// Callers of memory allocation APIs wishing to abort computation
+/// in response to an allocation error are encouraged to call this function,
+/// rather than directly invoking `panic!` or similar.
+///
+/// The default behavior of this function is to print a message to standard error
+/// and abort the process.
+/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
+///
+/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
+/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[rustc_allocator_nounwind]
+#[cold]
+pub fn handle_alloc_error(layout: Layout) -> ! {
+ unsafe {
+ __rust_alloc_error_handler(layout.size(), layout.align());
+ }
+}
+
+// For alloc test `std::alloc::handle_alloc_error` can be used directly.
+#[cfg(all(not(no_global_oom_handling), test))]
+pub use std::alloc::handle_alloc_error;
+
+#[cfg(all(not(no_global_oom_handling), not(any(target_os = "hermit", test))))]
+#[doc(hidden)]
+#[allow(unused_attributes)]
+#[unstable(feature = "alloc_internals", issue = "none")]
+pub mod __alloc_error_handler {
+ use crate::alloc::Layout;
+
+ // called via generated `__rust_alloc_error_handler`
+
+ // if there is no `#[alloc_error_handler]`
+ #[rustc_std_internal_symbol]
+ pub unsafe extern "C" fn __rdl_oom(size: usize, _align: usize) -> ! {
+ panic!("memory allocation of {} bytes failed", size)
+ }
+
+ // if there is a `#[alloc_error_handler]`
+ #[rustc_std_internal_symbol]
+ pub unsafe extern "C" fn __rg_oom(size: usize, align: usize) -> ! {
+ let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+ extern "Rust" {
+ #[lang = "oom"]
+ fn oom_impl(layout: Layout) -> !;
+ }
+ unsafe { oom_impl(layout) }
+ }
+}
+
+/// Specialize clones into pre-allocated, uninitialized memory.
+/// Used by `Box::clone` and `Rc`/`Arc::make_mut`.
+pub(crate) trait WriteCloneIntoRaw: Sized {
+ unsafe fn write_clone_into_raw(&self, target: *mut Self);
+}
+
+impl<T: Clone> WriteCloneIntoRaw for T {
+ #[inline]
+ default unsafe fn write_clone_into_raw(&self, target: *mut Self) {
+ // Having allocated *first* may allow the optimizer to create
+ // the cloned value in-place, skipping the local and move.
+ unsafe { target.write(self.clone()) };
+ }
+}
+
+impl<T: Copy> WriteCloneIntoRaw for T {
+ #[inline]
+ unsafe fn write_clone_into_raw(&self, target: *mut Self) {
+ // We can always copy in-place, without ever involving a local value.
+ unsafe { target.copy_from_nonoverlapping(self, 1) };
+ }
+}
diff --git a/rust/alloc/borrow.rs b/rust/alloc/borrow.rs
new file mode 100644
index 00000000000..beaf7b330f2
--- /dev/null
+++ b/rust/alloc/borrow.rs
@@ -0,0 +1,493 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A module for working with borrowed data.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::cmp::Ordering;
+use core::hash::{Hash, Hasher};
+use core::ops::Deref;
+#[cfg(not(no_global_oom_handling))]
+use core::ops::{Add, AddAssign};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::borrow::{Borrow, BorrowMut};
+
+use crate::fmt;
+#[cfg(not(no_global_oom_handling))]
+use crate::string::String;
+
+use Cow::*;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
+where
+ B: ToOwned,
+ <B as ToOwned>::Owned: 'a,
+{
+ fn borrow(&self) -> &B {
+ &**self
+ }
+}
+
+/// A generalization of `Clone` to borrowed data.
+///
+/// Some types make it possible to go from borrowed to owned, usually by
+/// implementing the `Clone` trait. But `Clone` works only for going from `&T`
+/// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data
+/// from any borrow of a given type.
+#[cfg_attr(not(test), rustc_diagnostic_item = "ToOwned")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ToOwned {
+ /// The resulting type after obtaining ownership.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ type Owned: Borrow<Self>;
+
+ /// Creates owned data from borrowed data, usually by cloning.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s: &str = "a";
+ /// let ss: String = s.to_owned();
+ ///
+ /// let v: &[i32] = &[1, 2];
+ /// let vv: Vec<i32> = v.to_owned();
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[must_use = "cloning is often expensive and is not expected to have side effects"]
+ fn to_owned(&self) -> Self::Owned;
+
+ /// Uses borrowed data to replace owned data, usually by cloning.
+ ///
+ /// This is borrow-generalized version of `Clone::clone_from`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// # #![feature(toowned_clone_into)]
+ /// let mut s: String = String::new();
+ /// "hello".clone_into(&mut s);
+ ///
+ /// let mut v: Vec<i32> = Vec::new();
+ /// [1, 2][..].clone_into(&mut v);
+ /// ```
+ #[unstable(feature = "toowned_clone_into", reason = "recently added", issue = "41263")]
+ fn clone_into(&self, target: &mut Self::Owned) {
+ *target = self.to_owned();
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> ToOwned for T
+where
+ T: Clone,
+{
+ type Owned = T;
+ fn to_owned(&self) -> T {
+ self.clone()
+ }
+
+ fn clone_into(&self, target: &mut T) {
+ target.clone_from(self);
+ }
+}
+
+/// A clone-on-write smart pointer.
+///
+/// The type `Cow` is a smart pointer providing clone-on-write functionality: it
+/// can enclose and provide immutable access to borrowed data, and clone the
+/// data lazily when mutation or ownership is required. The type is designed to
+/// work with general borrowed data via the `Borrow` trait.
+///
+/// `Cow` implements `Deref`, which means that you can call
+/// non-mutating methods directly on the data it encloses. If mutation
+/// is desired, `to_mut` will obtain a mutable reference to an owned
+/// value, cloning if necessary.
+///
+/// If you need reference-counting pointers, note that
+/// [`Rc::make_mut`][crate::rc::Rc::make_mut] and
+/// [`Arc::make_mut`][crate::sync::Arc::make_mut] can provide clone-on-write
+/// functionality as well.
+///
+/// # Examples
+///
+/// ```
+/// use std::borrow::Cow;
+///
+/// fn abs_all(input: &mut Cow<[i32]>) {
+/// for i in 0..input.len() {
+/// let v = input[i];
+/// if v < 0 {
+/// // Clones into a vector if not already owned.
+/// input.to_mut()[i] = -v;
+/// }
+/// }
+/// }
+///
+/// // No clone occurs because `input` doesn't need to be mutated.
+/// let slice = [0, 1, 2];
+/// let mut input = Cow::from(&slice[..]);
+/// abs_all(&mut input);
+///
+/// // Clone occurs because `input` needs to be mutated.
+/// let slice = [-1, 0, 1];
+/// let mut input = Cow::from(&slice[..]);
+/// abs_all(&mut input);
+///
+/// // No clone occurs because `input` is already owned.
+/// let mut input = Cow::from(vec![-1, 0, 1]);
+/// abs_all(&mut input);
+/// ```
+///
+/// Another example showing how to keep `Cow` in a struct:
+///
+/// ```
+/// use std::borrow::Cow;
+///
+/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
+/// values: Cow<'a, [X]>,
+/// }
+///
+/// impl<'a, X: Clone + 'a> Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
+/// fn new(v: Cow<'a, [X]>) -> Self {
+/// Items { values: v }
+/// }
+/// }
+///
+/// // Creates a container from borrowed values of a slice
+/// let readonly = [1, 2];
+/// let borrowed = Items::new((&readonly[..]).into());
+/// match borrowed {
+/// Items { values: Cow::Borrowed(b) } => println!("borrowed {:?}", b),
+/// _ => panic!("expect borrowed value"),
+/// }
+///
+/// let mut clone_on_write = borrowed;
+/// // Mutates the data from slice into owned vec and pushes a new value on top
+/// clone_on_write.values.to_mut().push(3);
+/// println!("clone_on_write = {:?}", clone_on_write.values);
+///
+/// // The data was mutated. Let check it out.
+/// match clone_on_write {
+/// Items { values: Cow::Owned(_) } => println!("clone_on_write contains owned data"),
+/// _ => panic!("expect owned data"),
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub enum Cow<'a, B: ?Sized + 'a>
+where
+ B: ToOwned,
+{
+ /// Borrowed data.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ Borrowed(#[stable(feature = "rust1", since = "1.0.0")] &'a B),
+
+ /// Owned data.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ Owned(#[stable(feature = "rust1", since = "1.0.0")] <B as ToOwned>::Owned),
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
+ fn clone(&self) -> Self {
+ match *self {
+ Borrowed(b) => Borrowed(b),
+ Owned(ref o) => {
+ let b: &B = o.borrow();
+ Owned(b.to_owned())
+ }
+ }
+ }
+
+ fn clone_from(&mut self, source: &Self) {
+ match (self, source) {
+ (&mut Owned(ref mut dest), &Owned(ref o)) => o.borrow().clone_into(dest),
+ (t, s) => *t = s.clone(),
+ }
+ }
+}
+
+impl<B: ?Sized + ToOwned> Cow<'_, B> {
+ /// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(cow_is_borrowed)]
+ /// use std::borrow::Cow;
+ ///
+ /// let cow = Cow::Borrowed("moo");
+ /// assert!(cow.is_borrowed());
+ ///
+ /// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
+ /// assert!(!bull.is_borrowed());
+ /// ```
+ #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+ #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
+ pub const fn is_borrowed(&self) -> bool {
+ match *self {
+ Borrowed(_) => true,
+ Owned(_) => false,
+ }
+ }
+
+ /// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(cow_is_borrowed)]
+ /// use std::borrow::Cow;
+ ///
+ /// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
+ /// assert!(cow.is_owned());
+ ///
+ /// let bull = Cow::Borrowed("...moo?");
+ /// assert!(!bull.is_owned());
+ /// ```
+ #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+ #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
+ pub const fn is_owned(&self) -> bool {
+ !self.is_borrowed()
+ }
+
+ /// Acquires a mutable reference to the owned form of the data.
+ ///
+ /// Clones the data if it is not already owned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::borrow::Cow;
+ ///
+ /// let mut cow = Cow::Borrowed("foo");
+ /// cow.to_mut().make_ascii_uppercase();
+ ///
+ /// assert_eq!(
+ /// cow,
+ /// Cow::Owned(String::from("FOO")) as Cow<str>
+ /// );
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned {
+ match *self {
+ Borrowed(borrowed) => {
+ *self = Owned(borrowed.to_owned());
+ match *self {
+ Borrowed(..) => unreachable!(),
+ Owned(ref mut owned) => owned,
+ }
+ }
+ Owned(ref mut owned) => owned,
+ }
+ }
+
+ /// Extracts the owned data.
+ ///
+ /// Clones the data if it is not already owned.
+ ///
+ /// # Examples
+ ///
+ /// Calling `into_owned` on a `Cow::Borrowed` clones the underlying data
+ /// and becomes a `Cow::Owned`:
+ ///
+ /// ```
+ /// use std::borrow::Cow;
+ ///
+ /// let s = "Hello world!";
+ /// let cow = Cow::Borrowed(s);
+ ///
+ /// assert_eq!(
+ /// cow.into_owned(),
+ /// String::from(s)
+ /// );
+ /// ```
+ ///
+ /// Calling `into_owned` on a `Cow::Owned` is a no-op:
+ ///
+ /// ```
+ /// use std::borrow::Cow;
+ ///
+ /// let s = "Hello world!";
+ /// let cow: Cow<str> = Cow::Owned(String::from(s));
+ ///
+ /// assert_eq!(
+ /// cow.into_owned(),
+ /// String::from(s)
+ /// );
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn into_owned(self) -> <B as ToOwned>::Owned {
+ match self {
+ Borrowed(borrowed) => borrowed.to_owned(),
+ Owned(owned) => owned,
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized + ToOwned> Deref for Cow<'_, B> {
+ type Target = B;
+
+ fn deref(&self) -> &B {
+ match *self {
+ Borrowed(borrowed) => borrowed,
+ Owned(ref owned) => owned.borrow(),
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Ord for Cow<'_, B>
+where
+ B: Ord + ToOwned,
+{
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ Ord::cmp(&**self, &**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, 'b, B: ?Sized, C: ?Sized> PartialEq<Cow<'b, C>> for Cow<'a, B>
+where
+ B: PartialEq<C> + ToOwned,
+ C: ToOwned,
+{
+ #[inline]
+ fn eq(&self, other: &Cow<'b, C>) -> bool {
+ PartialEq::eq(&**self, &**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> PartialOrd for Cow<'a, B>
+where
+ B: PartialOrd + ToOwned,
+{
+ #[inline]
+ fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering> {
+ PartialOrd::partial_cmp(&**self, &**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> fmt::Debug for Cow<'_, B>
+where
+ B: fmt::Debug + ToOwned<Owned: fmt::Debug>,
+{
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ match *self {
+ Borrowed(ref b) => fmt::Debug::fmt(b, f),
+ Owned(ref o) => fmt::Debug::fmt(o, f),
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> fmt::Display for Cow<'_, B>
+where
+ B: fmt::Display + ToOwned<Owned: fmt::Display>,
+{
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ match *self {
+ Borrowed(ref b) => fmt::Display::fmt(b, f),
+ Owned(ref o) => fmt::Display::fmt(o, f),
+ }
+ }
+}
+
+#[stable(feature = "default", since = "1.11.0")]
+impl<B: ?Sized> Default for Cow<'_, B>
+where
+ B: ToOwned<Owned: Default>,
+{
+ /// Creates an owned Cow<'a, B> with the default value for the contained owned value.
+ fn default() -> Self {
+ Owned(<B as ToOwned>::Owned::default())
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Hash for Cow<'_, B>
+where
+ B: Hash + ToOwned,
+{
+ #[inline]
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ Hash::hash(&**self, state)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
+ fn as_ref(&self) -> &T {
+ self
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> Add<&'a str> for Cow<'a, str> {
+ type Output = Cow<'a, str>;
+
+ #[inline]
+ fn add(mut self, rhs: &'a str) -> Self::Output {
+ self += rhs;
+ self
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> Add<Cow<'a, str>> for Cow<'a, str> {
+ type Output = Cow<'a, str>;
+
+ #[inline]
+ fn add(mut self, rhs: Cow<'a, str>) -> Self::Output {
+ self += rhs;
+ self
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> AddAssign<&'a str> for Cow<'a, str> {
+ fn add_assign(&mut self, rhs: &'a str) {
+ if self.is_empty() {
+ *self = Cow::Borrowed(rhs)
+ } else if !rhs.is_empty() {
+ if let Cow::Borrowed(lhs) = *self {
+ let mut s = String::with_capacity(lhs.len() + rhs.len());
+ s.push_str(lhs);
+ *self = Cow::Owned(s);
+ }
+ self.to_mut().push_str(rhs);
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str> {
+ fn add_assign(&mut self, rhs: Cow<'a, str>) {
+ if self.is_empty() {
+ *self = rhs
+ } else if !rhs.is_empty() {
+ if let Cow::Borrowed(lhs) = *self {
+ let mut s = String::with_capacity(lhs.len() + rhs.len());
+ s.push_str(lhs);
+ *self = Cow::Owned(s);
+ }
+ self.to_mut().push_str(&rhs);
+ }
+ }
+}
diff --git a/rust/alloc/boxed.rs b/rust/alloc/boxed.rs
new file mode 100644
index 00000000000..df6a77eea06
--- /dev/null
+++ b/rust/alloc/boxed.rs
@@ -0,0 +1,1728 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A pointer type for heap allocation.
+//!
+//! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
+//! heap allocation in Rust. Boxes provide ownership for this allocation, and
+//! drop their contents when they go out of scope. Boxes also ensure that they
+//! never allocate more than `isize::MAX` bytes.
+//!
+//! # Examples
+//!
+//! Move a value from the stack to the heap by creating a [`Box`]:
+//!
+//! ```
+//! let val: u8 = 5;
+//! let boxed: Box<u8> = Box::new(val);
+//! ```
+//!
+//! Move a value from a [`Box`] back to the stack by [dereferencing]:
+//!
+//! ```
+//! let boxed: Box<u8> = Box::new(5);
+//! let val: u8 = *boxed;
+//! ```
+//!
+//! Creating a recursive data structure:
+//!
+//! ```
+//! #[derive(Debug)]
+//! enum List<T> {
+//! Cons(T, Box<List<T>>),
+//! Nil,
+//! }
+//!
+//! let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
+//! println!("{:?}", list);
+//! ```
+//!
+//! This will print `Cons(1, Cons(2, Nil))`.
+//!
+//! Recursive structures must be boxed, because if the definition of `Cons`
+//! looked like this:
+//!
+//! ```compile_fail,E0072
+//! # enum List<T> {
+//! Cons(T, List<T>),
+//! # }
+//! ```
+//!
+//! It wouldn't work. This is because the size of a `List` depends on how many
+//! elements are in the list, and so we don't know how much memory to allocate
+//! for a `Cons`. By introducing a [`Box<T>`], which has a defined size, we know how
+//! big `Cons` needs to be.
+//!
+//! # Memory layout
+//!
+//! For non-zero-sized values, a [`Box`] will use the [`Global`] allocator for
+//! its allocation. It is valid to convert both ways between a [`Box`] and a
+//! raw pointer allocated with the [`Global`] allocator, given that the
+//! [`Layout`] used with the allocator is correct for the type. More precisely,
+//! a `value: *mut T` that has been allocated with the [`Global`] allocator
+//! with `Layout::for_value(&*value)` may be converted into a box using
+//! [`Box::<T>::from_raw(value)`]. Conversely, the memory backing a `value: *mut
+//! T` obtained from [`Box::<T>::into_raw`] may be deallocated using the
+//! [`Global`] allocator with [`Layout::for_value(&*value)`].
+//!
+//! For zero-sized values, the `Box` pointer still has to be [valid] for reads
+//! and writes and sufficiently aligned. In particular, casting any aligned
+//! non-zero integer literal to a raw pointer produces a valid pointer, but a
+//! pointer pointing into previously allocated memory that since got freed is
+//! not valid. The recommended way to build a Box to a ZST if `Box::new` cannot
+//! be used is to use [`ptr::NonNull::dangling`].
+//!
+//! So long as `T: Sized`, a `Box<T>` is guaranteed to be represented
+//! as a single pointer and is also ABI-compatible with C pointers
+//! (i.e. the C type `T*`). This means that if you have extern "C"
+//! Rust functions that will be called from C, you can define those
+//! Rust functions using `Box<T>` types, and use `T*` as corresponding
+//! type on the C side. As an example, consider this C header which
+//! declares functions that create and destroy some kind of `Foo`
+//! value:
+//!
+//! ```c
+//! /* C header */
+//!
+//! /* Returns ownership to the caller */
+//! struct Foo* foo_new(void);
+//!
+//! /* Takes ownership from the caller; no-op when invoked with null */
+//! void foo_delete(struct Foo*);
+//! ```
+//!
+//! These two functions might be implemented in Rust as follows. Here, the
+//! `struct Foo*` type from C is translated to `Box<Foo>`, which captures
+//! the ownership constraints. Note also that the nullable argument to
+//! `foo_delete` is represented in Rust as `Option<Box<Foo>>`, since `Box<Foo>`
+//! cannot be null.
+//!
+//! ```
+//! #[repr(C)]
+//! pub struct Foo;
+//!
+//! #[no_mangle]
+//! pub extern "C" fn foo_new() -> Box<Foo> {
+//! Box::new(Foo)
+//! }
+//!
+//! #[no_mangle]
+//! pub extern "C" fn foo_delete(_: Option<Box<Foo>>) {}
+//! ```
+//!
+//! Even though `Box<T>` has the same representation and C ABI as a C pointer,
+//! this does not mean that you can convert an arbitrary `T*` into a `Box<T>`
+//! and expect things to work. `Box<T>` values will always be fully aligned,
+//! non-null pointers. Moreover, the destructor for `Box<T>` will attempt to
+//! free the value with the global allocator. In general, the best practice
+//! is to only use `Box<T>` for pointers that originated from the global
+//! allocator.
+//!
+//! **Important.** At least at present, you should avoid using
+//! `Box<T>` types for functions that are defined in C but invoked
+//! from Rust. In those cases, you should directly mirror the C types
+//! as closely as possible. Using types like `Box<T>` where the C
+//! definition is just using `T*` can lead to undefined behavior, as
+//! described in [rust-lang/unsafe-code-guidelines#198][ucg#198].
+//!
+//! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198
+//! [dereferencing]: core::ops::Deref
+//! [`Box::<T>::from_raw(value)`]: Box::from_raw
+//! [`Global`]: crate::alloc::Global
+//! [`Layout`]: crate::alloc::Layout
+//! [`Layout::for_value(&*value)`]: crate::alloc::Layout::for_value
+//! [valid]: ptr#safety
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::any::Any;
+use core::borrow;
+use core::cmp::Ordering;
+use core::convert::{From, TryFrom};
+use core::fmt;
+use core::future::Future;
+use core::hash::{Hash, Hasher};
+#[cfg(not(no_global_oom_handling))]
+use core::iter::FromIterator;
+use core::iter::{FusedIterator, Iterator};
+use core::marker::{Unpin, Unsize};
+use core::mem;
+use core::ops::{
+ CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver,
+};
+use core::pin::Pin;
+use core::ptr::{self, Unique};
+use core::stream::Stream;
+use core::task::{Context, Poll};
+
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::{handle_alloc_error, WriteCloneIntoRaw};
+use crate::alloc::{AllocError, Allocator, Global, Layout};
+#[cfg(not(no_global_oom_handling))]
+use crate::borrow::Cow;
+#[cfg(not(no_global_oom_handling))]
+use crate::raw_vec::RawVec;
+#[cfg(not(no_global_oom_handling))]
+use crate::str::from_boxed_utf8_unchecked;
+#[cfg(not(no_global_oom_handling))]
+use crate::vec::Vec;
+
+/// A pointer type for heap allocation.
+///
+/// See the [module-level documentation](../../std/boxed/index.html) for more.
+#[lang = "owned_box"]
+#[fundamental]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Box<
+ T: ?Sized,
+ #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+>(Unique<T>, A);
+
+impl<T> Box<T> {
+ /// Allocates memory on the heap and then places `x` into it.
+ ///
+ /// This doesn't actually allocate if `T` is zero-sized.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let five = Box::new(5);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline(always)]
+ #[doc(alias = "alloc")]
+ #[doc(alias = "malloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn new(x: T) -> Self {
+ box x
+ }
+
+ /// Constructs a new box with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let mut five = Box::<u32>::new_uninit();
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// five.as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
+ Self::new_uninit_in(Global)
+ }
+
+ /// Constructs a new `Box` with uninitialized contents, with the memory
+ /// being filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let zero = Box::<u32>::new_zeroed();
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0)
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[doc(alias = "calloc")]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> {
+ Self::new_zeroed_in(Global)
+ }
+
+ /// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then
+ /// `x` will be pinned in memory and unable to be moved.
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "pin", since = "1.33.0")]
+ #[inline(always)]
+ pub fn pin(x: T) -> Pin<Box<T>> {
+ (box x).into()
+ }
+
+ /// Allocates memory on the heap then places `x` into it,
+ /// returning an error if the allocation fails
+ ///
+ /// This doesn't actually allocate if `T` is zero-sized.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// let five = Box::try_new(5)?;
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn try_new(x: T) -> Result<Self, AllocError> {
+ Self::try_new_in(x, Global)
+ }
+
+ /// Constructs a new box with uninitialized contents on the heap,
+ /// returning an error if the allocation fails
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// let mut five = Box::<u32>::try_new_uninit()?;
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// five.as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub fn try_new_uninit() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
+ Box::try_new_uninit_in(Global)
+ }
+
+ /// Constructs a new `Box` with uninitialized contents, with the memory
+ /// being filled with `0` bytes on the heap
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// let zero = Box::<u32>::try_new_zeroed()?;
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub fn try_new_zeroed() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
+ Box::try_new_zeroed_in(Global)
+ }
+}
+
+impl<T, A: Allocator> Box<T, A> {
+ /// Allocates memory in the given allocator then places `x` into it.
+ ///
+ /// This doesn't actually allocate if `T` is zero-sized.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let five = Box::new_in(5, System);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn new_in(x: T, alloc: A) -> Self {
+ let mut boxed = Self::new_uninit_in(alloc);
+ unsafe {
+ boxed.as_mut_ptr().write(x);
+ boxed.assume_init()
+ }
+ }
+
+ /// Allocates memory in the given allocator then places `x` into it,
+ /// returning an error if the allocation fails
+ ///
+ /// This doesn't actually allocate if `T` is zero-sized.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let five = Box::try_new_in(5, System)?;
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> {
+ let mut boxed = Self::try_new_uninit_in(alloc)?;
+ unsafe {
+ boxed.as_mut_ptr().write(x);
+ Ok(boxed.assume_init())
+ }
+ }
+
+ /// Constructs a new box with uninitialized contents in the provided allocator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut five = Box::<u32, _>::new_uninit_in(System);
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// five.as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[cfg(not(no_global_oom_handling))]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> {
+ let layout = Layout::new::<mem::MaybeUninit<T>>();
+ // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
+ // That would make code size bigger.
+ match Box::try_new_uninit_in(alloc) {
+ Ok(m) => m,
+ Err(_) => handle_alloc_error(layout),
+ }
+ }
+
+ /// Constructs a new box with uninitialized contents in the provided allocator,
+ /// returning an error if the allocation fails
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut five = Box::<u32, _>::try_new_uninit_in(System)?;
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// five.as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> {
+ let layout = Layout::new::<mem::MaybeUninit<T>>();
+ let ptr = alloc.allocate(layout)?.cast();
+ unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
+ }
+
+ /// Constructs a new `Box` with uninitialized contents, with the memory
+ /// being filled with `0` bytes in the provided allocator.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let zero = Box::<u32, _>::new_zeroed_in(System);
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0)
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[cfg(not(no_global_oom_handling))]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> {
+ let layout = Layout::new::<mem::MaybeUninit<T>>();
+ // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
+ // That would make code size bigger.
+ match Box::try_new_zeroed_in(alloc) {
+ Ok(m) => m,
+ Err(_) => handle_alloc_error(layout),
+ }
+ }
+
+ /// Constructs a new `Box` with uninitialized contents, with the memory
+ /// being filled with `0` bytes in the provided allocator,
+ /// returning an error if the allocation fails,
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> {
+ let layout = Layout::new::<mem::MaybeUninit<T>>();
+ let ptr = alloc.allocate_zeroed(layout)?.cast();
+ unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
+ }
+
+ /// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement `Unpin`, then
+ /// `x` will be pinned in memory and unable to be moved.
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline(always)]
+ pub fn pin_in(x: T, alloc: A) -> Pin<Self>
+ where
+ A: 'static,
+ {
+ Self::new_in(x, alloc).into()
+ }
+
+ /// Converts a `Box<T>` into a `Box<[T]>`
+ ///
+ /// This conversion does not allocate on the heap and happens in place.
+ #[unstable(feature = "box_into_boxed_slice", issue = "71582")]
+ pub fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
+ let (raw, alloc) = Box::into_raw_with_allocator(boxed);
+ unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) }
+ }
+
+ /// Consumes the `Box`, returning the wrapped value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(box_into_inner)]
+ ///
+ /// let c = Box::new(5);
+ ///
+ /// assert_eq!(Box::into_inner(c), 5);
+ /// ```
+ #[unstable(feature = "box_into_inner", issue = "80437")]
+ #[inline]
+ pub fn into_inner(boxed: Self) -> T {
+ *boxed
+ }
+}
+
+impl<T> Box<[T]> {
+ /// Constructs a new boxed slice with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let mut values = Box::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// values[0].as_mut_ptr().write(1);
+ /// values[1].as_mut_ptr().write(2);
+ /// values[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
+ unsafe { RawVec::with_capacity(len).into_box(len) }
+ }
+
+ /// Constructs a new boxed slice with uninitialized contents, with the memory
+ /// being filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let values = Box::<[u32]>::new_zeroed_slice(3);
+ /// let values = unsafe { values.assume_init() };
+ ///
+ /// assert_eq!(*values, [0, 0, 0])
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
+ unsafe { RawVec::with_capacity_zeroed(len).into_box(len) }
+ }
+}
+
+impl<T, A: Allocator> Box<[T], A> {
+ /// Constructs a new boxed slice with uninitialized contents in the provided allocator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// values[0].as_mut_ptr().write(1);
+ /// values[1].as_mut_ptr().write(2);
+ /// values[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
+ unsafe { RawVec::with_capacity_in(len, alloc).into_box(len) }
+ }
+
+ /// Constructs a new boxed slice with uninitialized contents in the provided allocator,
+ /// with the memory being filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let values = Box::<[u32], _>::new_zeroed_slice_in(3, System);
+ /// let values = unsafe { values.assume_init() };
+ ///
+ /// assert_eq!(*values, [0, 0, 0])
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
+ unsafe { RawVec::with_capacity_zeroed_in(len, alloc).into_box(len) }
+ }
+}
+
+impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
+ /// Converts to `Box<T, A>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the value
+ /// really is in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let mut five = Box::<u32>::new_uninit();
+ ///
+ /// let five: Box<u32> = unsafe {
+ /// // Deferred initialization:
+ /// five.as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Box<T, A> {
+ let (raw, alloc) = Box::into_raw_with_allocator(self);
+ unsafe { Box::from_raw_in(raw as *mut T, alloc) }
+ }
+}
+
+impl<T, A: Allocator> Box<[mem::MaybeUninit<T>], A> {
+ /// Converts to `Box<[T], A>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the values
+ /// really are in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// let mut values = Box::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// values[0].as_mut_ptr().write(1);
+ /// values[1].as_mut_ptr().write(2);
+ /// values[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Box<[T], A> {
+ let (raw, alloc) = Box::into_raw_with_allocator(self);
+ unsafe { Box::from_raw_in(raw as *mut [T], alloc) }
+ }
+}
+
+impl<T: ?Sized> Box<T> {
+ /// Constructs a box from a raw pointer.
+ ///
+ /// After calling this function, the raw pointer is owned by the
+ /// resulting `Box`. Specifically, the `Box` destructor will call
+ /// the destructor of `T` and free the allocated memory. For this
+ /// to be safe, the memory must have been allocated in accordance
+ /// with the [memory layout] used by `Box` .
+ ///
+ /// # Safety
+ ///
+ /// This function is unsafe because improper use may lead to
+ /// memory problems. For example, a double-free may occur if the
+ /// function is called twice on the same raw pointer.
+ ///
+ /// The safety conditions are described in the [memory layout] section.
+ ///
+ /// # Examples
+ ///
+ /// Recreate a `Box` which was previously converted to a raw pointer
+ /// using [`Box::into_raw`]:
+ /// ```
+ /// let x = Box::new(5);
+ /// let ptr = Box::into_raw(x);
+ /// let x = unsafe { Box::from_raw(ptr) };
+ /// ```
+ /// Manually create a `Box` from scratch by using the global allocator:
+ /// ```
+ /// use std::alloc::{alloc, Layout};
+ ///
+ /// unsafe {
+ /// let ptr = alloc(Layout::new::<i32>()) as *mut i32;
+ /// // In general .write is required to avoid attempting to destruct
+ /// // the (uninitialized) previous contents of `ptr`, though for this
+ /// // simple example `*ptr = 5` would have worked as well.
+ /// ptr.write(5);
+ /// let x = Box::from_raw(ptr);
+ /// }
+ /// ```
+ ///
+ /// [memory layout]: self#memory-layout
+ /// [`Layout`]: crate::Layout
+ #[stable(feature = "box_raw", since = "1.4.0")]
+ #[inline]
+ pub unsafe fn from_raw(raw: *mut T) -> Self {
+ unsafe { Self::from_raw_in(raw, Global) }
+ }
+}
+
+impl<T: ?Sized, A: Allocator> Box<T, A> {
+ /// Constructs a box from a raw pointer in the given allocator.
+ ///
+ /// After calling this function, the raw pointer is owned by the
+ /// resulting `Box`. Specifically, the `Box` destructor will call
+ /// the destructor of `T` and free the allocated memory. For this
+ /// to be safe, the memory must have been allocated in accordance
+ /// with the [memory layout] used by `Box` .
+ ///
+ /// # Safety
+ ///
+ /// This function is unsafe because improper use may lead to
+ /// memory problems. For example, a double-free may occur if the
+ /// function is called twice on the same raw pointer.
+ ///
+ ///
+ /// # Examples
+ ///
+ /// Recreate a `Box` which was previously converted to a raw pointer
+ /// using [`Box::into_raw_with_allocator`]:
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let x = Box::new_in(5, System);
+ /// let (ptr, alloc) = Box::into_raw_with_allocator(x);
+ /// let x = unsafe { Box::from_raw_in(ptr, alloc) };
+ /// ```
+ /// Manually create a `Box` from scratch by using the system allocator:
+ /// ```
+ /// #![feature(allocator_api, slice_ptr_get)]
+ ///
+ /// use std::alloc::{Allocator, Layout, System};
+ ///
+ /// unsafe {
+ /// let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
+ /// // In general .write is required to avoid attempting to destruct
+ /// // the (uninitialized) previous contents of `ptr`, though for this
+ /// // simple example `*ptr = 5` would have worked as well.
+ /// ptr.write(5);
+ /// let x = Box::from_raw_in(ptr, System);
+ /// }
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ ///
+ /// [memory layout]: self#memory-layout
+ /// [`Layout`]: crate::Layout
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self {
+ Box(unsafe { Unique::new_unchecked(raw) }, alloc)
+ }
+
+ /// Consumes the `Box`, returning a wrapped raw pointer.
+ ///
+ /// The pointer will be properly aligned and non-null.
+ ///
+ /// After calling this function, the caller is responsible for the
+ /// memory previously managed by the `Box`. In particular, the
+ /// caller should properly destroy `T` and release the memory, taking
+ /// into account the [memory layout] used by `Box`. The easiest way to
+ /// do this is to convert the raw pointer back into a `Box` with the
+ /// [`Box::from_raw`] function, allowing the `Box` destructor to perform
+ /// the cleanup.
+ ///
+ /// Note: this is an associated function, which means that you have
+ /// to call it as `Box::into_raw(b)` instead of `b.into_raw()`. This
+ /// is so that there is no conflict with a method on the inner type.
+ ///
+ /// # Examples
+ /// Converting the raw pointer back into a `Box` with [`Box::from_raw`]
+ /// for automatic cleanup:
+ /// ```
+ /// let x = Box::new(String::from("Hello"));
+ /// let ptr = Box::into_raw(x);
+ /// let x = unsafe { Box::from_raw(ptr) };
+ /// ```
+ /// Manual cleanup by explicitly running the destructor and deallocating
+ /// the memory:
+ /// ```
+ /// use std::alloc::{dealloc, Layout};
+ /// use std::ptr;
+ ///
+ /// let x = Box::new(String::from("Hello"));
+ /// let p = Box::into_raw(x);
+ /// unsafe {
+ /// ptr::drop_in_place(p);
+ /// dealloc(p as *mut u8, Layout::new::<String>());
+ /// }
+ /// ```
+ ///
+ /// [memory layout]: self#memory-layout
+ #[stable(feature = "box_raw", since = "1.4.0")]
+ #[inline]
+ pub fn into_raw(b: Self) -> *mut T {
+ Self::into_raw_with_allocator(b).0
+ }
+
+ /// Consumes the `Box`, returning a wrapped raw pointer and the allocator.
+ ///
+ /// The pointer will be properly aligned and non-null.
+ ///
+ /// After calling this function, the caller is responsible for the
+ /// memory previously managed by the `Box`. In particular, the
+ /// caller should properly destroy `T` and release the memory, taking
+ /// into account the [memory layout] used by `Box`. The easiest way to
+ /// do this is to convert the raw pointer back into a `Box` with the
+ /// [`Box::from_raw_in`] function, allowing the `Box` destructor to perform
+ /// the cleanup.
+ ///
+ /// Note: this is an associated function, which means that you have
+ /// to call it as `Box::into_raw_with_allocator(b)` instead of `b.into_raw_with_allocator()`. This
+ /// is so that there is no conflict with a method on the inner type.
+ ///
+ /// # Examples
+ /// Converting the raw pointer back into a `Box` with [`Box::from_raw_in`]
+ /// for automatic cleanup:
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let x = Box::new_in(String::from("Hello"), System);
+ /// let (ptr, alloc) = Box::into_raw_with_allocator(x);
+ /// let x = unsafe { Box::from_raw_in(ptr, alloc) };
+ /// ```
+ /// Manual cleanup by explicitly running the destructor and deallocating
+ /// the memory:
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::{Allocator, Layout, System};
+ /// use std::ptr::{self, NonNull};
+ ///
+ /// let x = Box::new_in(String::from("Hello"), System);
+ /// let (ptr, alloc) = Box::into_raw_with_allocator(x);
+ /// unsafe {
+ /// ptr::drop_in_place(ptr);
+ /// let non_null = NonNull::new_unchecked(ptr);
+ /// alloc.deallocate(non_null.cast(), Layout::new::<String>());
+ /// }
+ /// ```
+ ///
+ /// [memory layout]: self#memory-layout
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
+ let (leaked, alloc) = Box::into_unique(b);
+ (leaked.as_ptr(), alloc)
+ }
+
+ #[unstable(
+ feature = "ptr_internals",
+ issue = "none",
+ reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead"
+ )]
+ #[inline]
+ #[doc(hidden)]
+ pub fn into_unique(b: Self) -> (Unique<T>, A) {
+ // Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a
+ // raw pointer for the type system. Turning it directly into a raw pointer would not be
+ // recognized as "releasing" the unique pointer to permit aliased raw accesses,
+ // so all raw pointer methods have to go through `Box::leak`. Turning *that* to a raw pointer
+ // behaves correctly.
+ let alloc = unsafe { ptr::read(&b.1) };
+ (Unique::from(Box::leak(b)), alloc)
+ }
+
+ /// Returns a reference to the underlying allocator.
+ ///
+ /// Note: this is an associated function, which means that you have
+ /// to call it as `Box::allocator(&b)` instead of `b.allocator()`. This
+ /// is so that there is no conflict with a method on the inner type.
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn allocator(b: &Self) -> &A {
+ &b.1
+ }
+
+ /// Consumes and leaks the `Box`, returning a mutable reference,
+ /// `&'a mut T`. Note that the type `T` must outlive the chosen lifetime
+ /// `'a`. If the type has only static references, or none at all, then this
+ /// may be chosen to be `'static`.
+ ///
+ /// This function is mainly useful for data that lives for the remainder of
+ /// the program's life. Dropping the returned reference will cause a memory
+ /// leak. If this is not acceptable, the reference should first be wrapped
+ /// with the [`Box::from_raw`] function producing a `Box`. This `Box` can
+ /// then be dropped which will properly destroy `T` and release the
+ /// allocated memory.
+ ///
+ /// Note: this is an associated function, which means that you have
+ /// to call it as `Box::leak(b)` instead of `b.leak()`. This
+ /// is so that there is no conflict with a method on the inner type.
+ ///
+ /// # Examples
+ ///
+ /// Simple usage:
+ ///
+ /// ```
+ /// let x = Box::new(41);
+ /// let static_ref: &'static mut usize = Box::leak(x);
+ /// *static_ref += 1;
+ /// assert_eq!(*static_ref, 42);
+ /// ```
+ ///
+ /// Unsized data:
+ ///
+ /// ```
+ /// let x = vec![1, 2, 3].into_boxed_slice();
+ /// let static_ref = Box::leak(x);
+ /// static_ref[0] = 4;
+ /// assert_eq!(*static_ref, [4, 2, 3]);
+ /// ```
+ #[stable(feature = "box_leak", since = "1.26.0")]
+ #[inline]
+ pub fn leak<'a>(b: Self) -> &'a mut T
+ where
+ A: 'a,
+ {
+ unsafe { &mut *mem::ManuallyDrop::new(b).0.as_ptr() }
+ }
+
+ /// Converts a `Box<T>` into a `Pin<Box<T>>`
+ ///
+ /// This conversion does not allocate on the heap and happens in place.
+ ///
+ /// This is also available via [`From`].
+ #[unstable(feature = "box_into_pin", issue = "62370")]
+ pub fn into_pin(boxed: Self) -> Pin<Self>
+ where
+ A: 'static,
+ {
+ // It's not possible to move or replace the insides of a `Pin<Box<T>>`
+ // when `T: !Unpin`, so it's safe to pin it directly without any
+ // additional requirements.
+ unsafe { Pin::new_unchecked(boxed) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
+ fn drop(&mut self) {
+ // FIXME: Do nothing, drop is currently performed by compiler.
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Default> Default for Box<T> {
+ /// Creates a `Box<T>`, with the `Default` value for T.
+ fn default() -> Self {
+ box T::default()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Default for Box<[T]> {
+ fn default() -> Self {
+ Box::<[T; 0]>::new([])
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "default_box_extra", since = "1.17.0")]
+impl Default for Box<str> {
+ fn default() -> Self {
+ unsafe { from_boxed_utf8_unchecked(Default::default()) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A> {
+ /// Returns a new box with a `clone()` of this box's contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let x = Box::new(5);
+ /// let y = x.clone();
+ ///
+ /// // The value is the same
+ /// assert_eq!(x, y);
+ ///
+ /// // But they are unique objects
+ /// assert_ne!(&*x as *const i32, &*y as *const i32);
+ /// ```
+ #[inline]
+ fn clone(&self) -> Self {
+ // Pre-allocate memory to allow writing the cloned value directly.
+ let mut boxed = Self::new_uninit_in(self.1.clone());
+ unsafe {
+ (**self).write_clone_into_raw(boxed.as_mut_ptr());
+ boxed.assume_init()
+ }
+ }
+
+ /// Copies `source`'s contents into `self` without creating a new allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let x = Box::new(5);
+ /// let mut y = Box::new(10);
+ /// let yp: *const i32 = &*y;
+ ///
+ /// y.clone_from(&x);
+ ///
+ /// // The value is the same
+ /// assert_eq!(x, y);
+ ///
+ /// // And no allocation occurred
+ /// assert_eq!(yp, &*y);
+ /// ```
+ #[inline]
+ fn clone_from(&mut self, source: &Self) {
+ (**self).clone_from(&(**source));
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_slice_clone", since = "1.3.0")]
+impl Clone for Box<str> {
+ fn clone(&self) -> Self {
+ // this makes a copy of the data
+ let buf: Box<[u8]> = self.as_bytes().into();
+ unsafe { from_boxed_utf8_unchecked(buf) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialEq, A: Allocator> PartialEq for Box<T, A> {
+ #[inline]
+ fn eq(&self, other: &Self) -> bool {
+ PartialEq::eq(&**self, &**other)
+ }
+ #[inline]
+ fn ne(&self, other: &Self) -> bool {
+ PartialEq::ne(&**self, &**other)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Box<T, A> {
+ #[inline]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ PartialOrd::partial_cmp(&**self, &**other)
+ }
+ #[inline]
+ fn lt(&self, other: &Self) -> bool {
+ PartialOrd::lt(&**self, &**other)
+ }
+ #[inline]
+ fn le(&self, other: &Self) -> bool {
+ PartialOrd::le(&**self, &**other)
+ }
+ #[inline]
+ fn ge(&self, other: &Self) -> bool {
+ PartialOrd::ge(&**self, &**other)
+ }
+ #[inline]
+ fn gt(&self, other: &Self) -> bool {
+ PartialOrd::gt(&**self, &**other)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A> {
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ Ord::cmp(&**self, &**other)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Hash, A: Allocator> Hash for Box<T, A> {
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ (**self).hash(state);
+ }
+}
+
+#[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
+impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A> {
+ fn finish(&self) -> u64 {
+ (**self).finish()
+ }
+ fn write(&mut self, bytes: &[u8]) {
+ (**self).write(bytes)
+ }
+ fn write_u8(&mut self, i: u8) {
+ (**self).write_u8(i)
+ }
+ fn write_u16(&mut self, i: u16) {
+ (**self).write_u16(i)
+ }
+ fn write_u32(&mut self, i: u32) {
+ (**self).write_u32(i)
+ }
+ fn write_u64(&mut self, i: u64) {
+ (**self).write_u64(i)
+ }
+ fn write_u128(&mut self, i: u128) {
+ (**self).write_u128(i)
+ }
+ fn write_usize(&mut self, i: usize) {
+ (**self).write_usize(i)
+ }
+ fn write_i8(&mut self, i: i8) {
+ (**self).write_i8(i)
+ }
+ fn write_i16(&mut self, i: i16) {
+ (**self).write_i16(i)
+ }
+ fn write_i32(&mut self, i: i32) {
+ (**self).write_i32(i)
+ }
+ fn write_i64(&mut self, i: i64) {
+ (**self).write_i64(i)
+ }
+ fn write_i128(&mut self, i: i128) {
+ (**self).write_i128(i)
+ }
+ fn write_isize(&mut self, i: isize) {
+ (**self).write_isize(i)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_for_ptrs", since = "1.6.0")]
+impl<T> From<T> for Box<T> {
+ /// Converts a `T` into a `Box<T>`
+ ///
+ /// The conversion allocates on the heap and moves `t`
+ /// from the stack into it.
+ ///
+ /// # Examples
+ /// ```rust
+ /// let x = 5;
+ /// let boxed = Box::new(5);
+ ///
+ /// assert_eq!(Box::from(x), boxed);
+ /// ```
+ fn from(t: T) -> Self {
+ Box::new(t)
+ }
+}
+
+#[stable(feature = "pin", since = "1.33.0")]
+impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>>
+where
+ A: 'static,
+{
+ /// Converts a `Box<T>` into a `Pin<Box<T>>`
+ ///
+ /// This conversion does not allocate on the heap and happens in place.
+ fn from(boxed: Box<T, A>) -> Self {
+ Box::into_pin(boxed)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_from_slice", since = "1.17.0")]
+impl<T: Copy> From<&[T]> for Box<[T]> {
+ /// Converts a `&[T]` into a `Box<[T]>`
+ ///
+ /// This conversion allocates on the heap
+ /// and performs a copy of `slice`.
+ ///
+ /// # Examples
+ /// ```rust
+ /// // create a &[u8] which will be used to create a Box<[u8]>
+ /// let slice: &[u8] = &[104, 101, 108, 108, 111];
+ /// let boxed_slice: Box<[u8]> = Box::from(slice);
+ ///
+ /// println!("{:?}", boxed_slice);
+ /// ```
+ fn from(slice: &[T]) -> Box<[T]> {
+ let len = slice.len();
+ let buf = RawVec::with_capacity(len);
+ unsafe {
+ ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
+ buf.into_box(slice.len()).assume_init()
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_from_cow", since = "1.45.0")]
+impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
+ #[inline]
+ fn from(cow: Cow<'_, [T]>) -> Box<[T]> {
+ match cow {
+ Cow::Borrowed(slice) => Box::from(slice),
+ Cow::Owned(slice) => Box::from(slice),
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_from_slice", since = "1.17.0")]
+impl From<&str> for Box<str> {
+ /// Converts a `&str` into a `Box<str>`
+ ///
+ /// This conversion allocates on the heap
+ /// and performs a copy of `s`.
+ ///
+ /// # Examples
+ /// ```rust
+ /// let boxed: Box<str> = Box::from("hello");
+ /// println!("{}", boxed);
+ /// ```
+ #[inline]
+ fn from(s: &str) -> Box<str> {
+ unsafe { from_boxed_utf8_unchecked(Box::from(s.as_bytes())) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_from_cow", since = "1.45.0")]
+impl From<Cow<'_, str>> for Box<str> {
+ #[inline]
+ fn from(cow: Cow<'_, str>) -> Box<str> {
+ match cow {
+ Cow::Borrowed(s) => Box::from(s),
+ Cow::Owned(s) => Box::from(s),
+ }
+ }
+}
+
+#[stable(feature = "boxed_str_conv", since = "1.19.0")]
+impl<A: Allocator> From<Box<str, A>> for Box<[u8], A> {
+ /// Converts a `Box<str>` into a `Box<[u8]>`
+ ///
+ /// This conversion does not allocate on the heap and happens in place.
+ ///
+ /// # Examples
+ /// ```rust
+ /// // create a Box<str> which will be used to create a Box<[u8]>
+ /// let boxed: Box<str> = Box::from("hello");
+ /// let boxed_str: Box<[u8]> = Box::from(boxed);
+ ///
+ /// // create a &[u8] which will be used to create a Box<[u8]>
+ /// let slice: &[u8] = &[104, 101, 108, 108, 111];
+ /// let boxed_slice = Box::from(slice);
+ ///
+ /// assert_eq!(boxed_slice, boxed_str);
+ /// ```
+ #[inline]
+ fn from(s: Box<str, A>) -> Self {
+ let (raw, alloc) = Box::into_raw_with_allocator(s);
+ unsafe { Box::from_raw_in(raw as *mut [u8], alloc) }
+ }
+}
+
+#[stable(feature = "box_from_array", since = "1.45.0")]
+impl<T, const N: usize> From<[T; N]> for Box<[T]> {
+ /// Converts a `[T; N]` into a `Box<[T]>`
+ ///
+ /// This conversion moves the array to newly heap-allocated memory.
+ ///
+ /// # Examples
+ /// ```rust
+ /// let boxed: Box<[u8]> = Box::from([4, 2]);
+ /// println!("{:?}", boxed);
+ /// ```
+ fn from(array: [T; N]) -> Box<[T]> {
+ box array
+ }
+}
+
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
+impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> {
+ type Error = Box<[T]>;
+
+ fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> {
+ if boxed_slice.len() == N {
+ Ok(unsafe { Box::from_raw(Box::into_raw(boxed_slice) as *mut [T; N]) })
+ } else {
+ Err(boxed_slice)
+ }
+ }
+}
+
+impl<A: Allocator> Box<dyn Any, A> {
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ /// Attempt to downcast the box to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::any::Any;
+ ///
+ /// fn print_if_string(value: Box<dyn Any>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Box::new(my_string));
+ /// print_if_string(Box::new(0i8));
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
+ if self.is::<T>() {
+ unsafe {
+ let (raw, alloc): (*mut dyn Any, _) = Box::into_raw_with_allocator(self);
+ Ok(Box::from_raw_in(raw as *mut T, alloc))
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<A: Allocator> Box<dyn Any + Send, A> {
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ /// Attempt to downcast the box to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::any::Any;
+ ///
+ /// fn print_if_string(value: Box<dyn Any + Send>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Box::new(my_string));
+ /// print_if_string(Box::new(0i8));
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
+ if self.is::<T>() {
+ unsafe {
+ let (raw, alloc): (*mut (dyn Any + Send), _) = Box::into_raw_with_allocator(self);
+ Ok(Box::from_raw_in(raw as *mut T, alloc))
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<A: Allocator> Box<dyn Any + Send + Sync, A> {
+ #[inline]
+ #[stable(feature = "box_send_sync_any_downcast", since = "1.51.0")]
+ /// Attempt to downcast the box to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::any::Any;
+ ///
+ /// fn print_if_string(value: Box<dyn Any + Send + Sync>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Box::new(my_string));
+ /// print_if_string(Box::new(0i8));
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
+ if self.is::<T>() {
+ unsafe {
+ let (raw, alloc): (*mut (dyn Any + Send + Sync), _) =
+ Box::into_raw_with_allocator(self);
+ Ok(Box::from_raw_in(raw as *mut T, alloc))
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: fmt::Display + ?Sized, A: Allocator> fmt::Display for Box<T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: fmt::Debug + ?Sized, A: Allocator> fmt::Debug for Box<T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // It's not possible to extract the inner Uniq directly from the Box,
+ // instead we cast it to a *const which aliases the Unique
+ let ptr: *const T = &**self;
+ fmt::Pointer::fmt(&ptr, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized, A: Allocator> Deref for Box<T, A> {
+ type Target = T;
+
+ fn deref(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A> {
+ fn deref_mut(&mut self) -> &mut T {
+ &mut **self
+ }
+}
+
+#[unstable(feature = "receiver_trait", issue = "none")]
+impl<T: ?Sized, A: Allocator> Receiver for Box<T, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> {
+ type Item = I::Item;
+ fn next(&mut self) -> Option<I::Item> {
+ (**self).next()
+ }
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (**self).size_hint()
+ }
+ fn nth(&mut self, n: usize) -> Option<I::Item> {
+ (**self).nth(n)
+ }
+ fn last(self) -> Option<I::Item> {
+ BoxIter::last(self)
+ }
+}
+
+trait BoxIter {
+ type Item;
+ fn last(self) -> Option<Self::Item>;
+}
+
+impl<I: Iterator + ?Sized, A: Allocator> BoxIter for Box<I, A> {
+ type Item = I::Item;
+ default fn last(self) -> Option<I::Item> {
+ #[inline]
+ fn some<T>(_: Option<T>, x: T) -> Option<T> {
+ Some(x)
+ }
+
+ self.fold(None, some)
+ }
+}
+
+/// Specialization for sized `I`s that uses `I`s implementation of `last()`
+/// instead of the default.
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: Iterator, A: Allocator> BoxIter for Box<I, A> {
+ fn last(self) -> Option<I::Item> {
+ (*self).last()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A> {
+ fn next_back(&mut self) -> Option<I::Item> {
+ (**self).next_back()
+ }
+ fn nth_back(&mut self, n: usize) -> Option<I::Item> {
+ (**self).nth_back(n)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A> {
+ fn len(&self) -> usize {
+ (**self).len()
+ }
+ fn is_empty(&self) -> bool {
+ (**self).is_empty()
+ }
+}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {}
+
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
+ type Output = <F as FnOnce<Args>>::Output;
+
+ extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
+ <F as FnOnce<Args>>::call_once(*self, args)
+ }
+}
+
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
+ extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
+ <F as FnMut<Args>>::call_mut(self, args)
+ }
+}
+
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
+ extern "rust-call" fn call(&self, args: Args) -> Self::Output {
+ <F as Fn<Args>>::call(self, args)
+ }
+}
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
+
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global> {}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "boxed_slice_from_iter", since = "1.32.0")]
+impl<I> FromIterator<I> for Box<[I]> {
+ fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
+ iter.into_iter().collect::<Vec<_>>().into_boxed_slice()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_slice_clone", since = "1.3.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A> {
+ fn clone(&self) -> Self {
+ let alloc = Box::allocator(self).clone();
+ self.to_vec_in(alloc).into_boxed_slice()
+ }
+
+ fn clone_from(&mut self, other: &Self) {
+ if self.len() == other.len() {
+ self.clone_from_slice(&other);
+ } else {
+ *self = other.clone();
+ }
+ }
+}
+
+#[stable(feature = "box_borrow", since = "1.1.0")]
+impl<T: ?Sized, A: Allocator> borrow::Borrow<T> for Box<T, A> {
+ fn borrow(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(feature = "box_borrow", since = "1.1.0")]
+impl<T: ?Sized, A: Allocator> borrow::BorrowMut<T> for Box<T, A> {
+ fn borrow_mut(&mut self) -> &mut T {
+ &mut **self
+ }
+}
+
+#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
+impl<T: ?Sized, A: Allocator> AsRef<T> for Box<T, A> {
+ fn as_ref(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
+impl<T: ?Sized, A: Allocator> AsMut<T> for Box<T, A> {
+ fn as_mut(&mut self) -> &mut T {
+ &mut **self
+ }
+}
+
+/* Nota bene
+ *
+ * We could have chosen not to add this impl, and instead have written a
+ * function of Pin<Box<T>> to Pin<T>. Such a function would not be sound,
+ * because Box<T> implements Unpin even when T does not, as a result of
+ * this impl.
+ *
+ * We chose this API instead of the alternative for a few reasons:
+ * - Logically, it is helpful to understand pinning in regard to the
+ * memory region being pointed to. For this reason none of the
+ * standard library pointer types support projecting through a pin
+ * (Box<T> is the only pointer type in std for which this would be
+ * safe.)
+ * - It is in practice very useful to have Box<T> be unconditionally
+ * Unpin because of trait objects, for which the structural auto
+ * trait functionality does not apply (e.g., Box<dyn Foo> would
+ * otherwise not be Unpin).
+ *
+ * Another type with the same semantics as Box but only a conditional
+ * implementation of `Unpin` (where `T: Unpin`) would be valid/safe, and
+ * could have a method to project a Pin<T> from it.
+ */
+#[stable(feature = "pin", since = "1.33.0")]
+impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where A: 'static {}
+
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A>
+where
+ A: 'static,
+{
+ type Yield = G::Yield;
+ type Return = G::Return;
+
+ fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
+ G::resume(Pin::new(&mut *self), arg)
+ }
+}
+
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R>, R, A: Allocator> Generator<R> for Pin<Box<G, A>>
+where
+ A: 'static,
+{
+ type Yield = G::Yield;
+ type Return = G::Return;
+
+ fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
+ G::resume((*self).as_mut(), arg)
+ }
+}
+
+#[stable(feature = "futures_api", since = "1.36.0")]
+impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A>
+where
+ A: 'static,
+{
+ type Output = F::Output;
+
+ fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+ F::poll(Pin::new(&mut *self), cx)
+ }
+}
+
+#[unstable(feature = "async_stream", issue = "79024")]
+impl<S: ?Sized + Stream + Unpin> Stream for Box<S> {
+ type Item = S::Item;
+
+ fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+ Pin::new(&mut **self).poll_next(cx)
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (**self).size_hint()
+ }
+}
diff --git a/rust/alloc/collections/mod.rs b/rust/alloc/collections/mod.rs
new file mode 100644
index 00000000000..2970fe44a21
--- /dev/null
+++ b/rust/alloc/collections/mod.rs
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Collection types.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[cfg(not(no_global_oom_handling))]
+pub mod binary_heap;
+#[cfg(not(no_global_oom_handling))]
+mod btree;
+#[cfg(not(no_global_oom_handling))]
+pub mod linked_list;
+#[cfg(not(no_global_oom_handling))]
+pub mod vec_deque;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod btree_map {
+ //! A map based on a B-Tree.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub use super::btree::map::*;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod btree_set {
+ //! A set based on a B-Tree.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub use super::btree::set::*;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use binary_heap::BinaryHeap;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use btree_map::BTreeMap;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use btree_set::BTreeSet;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use linked_list::LinkedList;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use vec_deque::VecDeque;
+
+use crate::alloc::{Layout, LayoutError};
+use core::fmt::Display;
+
+/// The error type for `try_reserve` methods.
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+pub enum TryReserveError {
+ /// Error due to the computed capacity exceeding the collection's maximum
+ /// (usually `isize::MAX` bytes).
+ CapacityOverflow,
+
+ /// The memory allocator returned an error
+ AllocError {
+ /// The layout of allocation request that failed
+ layout: Layout,
+
+ #[doc(hidden)]
+ #[unstable(
+ feature = "container_error_extra",
+ issue = "none",
+ reason = "\
+ Enable exposing the allocator’s custom error value \
+ if an associated type is added in the future: \
+ https://github.com/rust-lang/wg-allocators/issues/23"
+ )]
+ non_exhaustive: (),
+ },
+}
+
+#[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+impl From<LayoutError> for TryReserveError {
+ #[inline]
+ fn from(_: LayoutError) -> Self {
+ TryReserveError::CapacityOverflow
+ }
+}
+
+#[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+impl Display for TryReserveError {
+ fn fmt(
+ &self,
+ fmt: &mut core::fmt::Formatter<'_>,
+ ) -> core::result::Result<(), core::fmt::Error> {
+ fmt.write_str("memory allocation failed")?;
+ let reason = match &self {
+ TryReserveError::CapacityOverflow => {
+ " because the computed capacity exceeded the collection's maximum"
+ }
+ TryReserveError::AllocError { .. } => " because the memory allocator returned a error",
+ };
+ fmt.write_str(reason)
+ }
+}
+
+/// An intermediate trait for specialization of `Extend`.
+#[doc(hidden)]
+trait SpecExtend<I: IntoIterator> {
+ /// Extends `self` with the contents of the given iterator.
+ fn spec_extend(&mut self, iter: I);
+}
diff --git a/rust/alloc/fmt.rs b/rust/alloc/fmt.rs
new file mode 100644
index 00000000000..9c4e0b2f211
--- /dev/null
+++ b/rust/alloc/fmt.rs
@@ -0,0 +1,587 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Utilities for formatting and printing `String`s.
+//!
+//! This module contains the runtime support for the [`format!`] syntax extension.
+//! This macro is implemented in the compiler to emit calls to this module in
+//! order to format arguments at runtime into strings.
+//!
+//! # Usage
+//!
+//! The [`format!`] macro is intended to be familiar to those coming from C's
+//! `printf`/`fprintf` functions or Python's `str.format` function.
+//!
+//! Some examples of the [`format!`] extension are:
+//!
+//! ```
+//! format!("Hello"); // => "Hello"
+//! format!("Hello, {}!", "world"); // => "Hello, world!"
+//! format!("The number is {}", 1); // => "The number is 1"
+//! format!("{:?}", (3, 4)); // => "(3, 4)"
+//! format!("{value}", value=4); // => "4"
+//! format!("{} {}", 1, 2); // => "1 2"
+//! format!("{:04}", 42); // => "0042" with leading zeros
+//! format!("{:#?}", (100, 200)); // => "(
+//! // 100,
+//! // 200,
+//! // )"
+//! ```
+//!
+//! From these, you can see that the first argument is a format string. It is
+//! required by the compiler for this to be a string literal; it cannot be a
+//! variable passed in (in order to perform validity checking). The compiler
+//! will then parse the format string and determine if the list of arguments
+//! provided is suitable to pass to this format string.
+//!
+//! To convert a single value to a string, use the [`to_string`] method. This
+//! will use the [`Display`] formatting trait.
+//!
+//! ## Positional parameters
+//!
+//! Each formatting argument is allowed to specify which value argument it's
+//! referencing, and if omitted it is assumed to be "the next argument". For
+//! example, the format string `{} {} {}` would take three parameters, and they
+//! would be formatted in the same order as they're given. The format string
+//! `{2} {1} {0}`, however, would format arguments in reverse order.
+//!
+//! Things can get a little tricky once you start intermingling the two types of
+//! positional specifiers. The "next argument" specifier can be thought of as an
+//! iterator over the argument. Each time a "next argument" specifier is seen,
+//! the iterator advances. This leads to behavior like this:
+//!
+//! ```
+//! format!("{1} {} {0} {}", 1, 2); // => "2 1 1 2"
+//! ```
+//!
+//! The internal iterator over the argument has not been advanced by the time
+//! the first `{}` is seen, so it prints the first argument. Then upon reaching
+//! the second `{}`, the iterator has advanced forward to the second argument.
+//! Essentially, parameters that explicitly name their argument do not affect
+//! parameters that do not name an argument in terms of positional specifiers.
+//!
+//! A format string is required to use all of its arguments, otherwise it is a
+//! compile-time error. You may refer to the same argument more than once in the
+//! format string.
+//!
+//! ## Named parameters
+//!
+//! Rust itself does not have a Python-like equivalent of named parameters to a
+//! function, but the [`format!`] macro is a syntax extension that allows it to
+//! leverage named parameters. Named parameters are listed at the end of the
+//! argument list and have the syntax:
+//!
+//! ```text
+//! identifier '=' expression
+//! ```
+//!
+//! For example, the following [`format!`] expressions all use named argument:
+//!
+//! ```
+//! format!("{argument}", argument = "test"); // => "test"
+//! format!("{name} {}", 1, name = 2); // => "2 1"
+//! format!("{a} {c} {b}", a="a", b='b', c=3); // => "a 3 b"
+//! ```
+//!
+//! It is not valid to put positional parameters (those without names) after
+//! arguments that have names. Like with positional parameters, it is not
+//! valid to provide named parameters that are unused by the format string.
+//!
+//! # Formatting Parameters
+//!
+//! Each argument being formatted can be transformed by a number of formatting
+//! parameters (corresponding to `format_spec` in [the syntax](#syntax)). These
+//! parameters affect the string representation of what's being formatted.
+//!
+//! ## Width
+//!
+//! ```
+//! // All of these print "Hello x !"
+//! println!("Hello {:5}!", "x");
+//! println!("Hello {:1$}!", "x", 5);
+//! println!("Hello {1:0$}!", 5, "x");
+//! println!("Hello {:width$}!", "x", width = 5);
+//! ```
+//!
+//! This is a parameter for the "minimum width" that the format should take up.
+//! If the value's string does not fill up this many characters, then the
+//! padding specified by fill/alignment will be used to take up the required
+//! space (see below).
+//!
+//! The value for the width can also be provided as a [`usize`] in the list of
+//! parameters by adding a postfix `$`, indicating that the second argument is
+//! a [`usize`] specifying the width.
+//!
+//! Referring to an argument with the dollar syntax does not affect the "next
+//! argument" counter, so it's usually a good idea to refer to arguments by
+//! position, or use named arguments.
+//!
+//! ## Fill/Alignment
+//!
+//! ```
+//! assert_eq!(format!("Hello {:<5}!", "x"), "Hello x !");
+//! assert_eq!(format!("Hello {:-<5}!", "x"), "Hello x----!");
+//! assert_eq!(format!("Hello {:^5}!", "x"), "Hello x !");
+//! assert_eq!(format!("Hello {:>5}!", "x"), "Hello x!");
+//! ```
+//!
+//! The optional fill character and alignment is provided normally in conjunction with the
+//! [`width`](#width) parameter. It must be defined before `width`, right after the `:`.
+//! This indicates that if the value being formatted is smaller than
+//! `width` some extra characters will be printed around it.
+//! Filling comes in the following variants for different alignments:
+//!
+//! * `[fill]<` - the argument is left-aligned in `width` columns
+//! * `[fill]^` - the argument is center-aligned in `width` columns
+//! * `[fill]>` - the argument is right-aligned in `width` columns
+//!
+//! The default [fill/alignment](#fillalignment) for non-numerics is a space and
+//! left-aligned. The
+//! default for numeric formatters is also a space character but with right-alignment. If
+//! the `0` flag (see below) is specified for numerics, then the implicit fill character is
+//! `0`.
+//!
+//! Note that alignment may not be implemented by some types. In particular, it
+//! is not generally implemented for the `Debug` trait. A good way to ensure
+//! padding is applied is to format your input, then pad this resulting string
+//! to obtain your output:
+//!
+//! ```
+//! println!("Hello {:^15}!", format!("{:?}", Some("hi"))); // => "Hello Some("hi") !"
+//! ```
+//!
+//! ## Sign/`#`/`0`
+//!
+//! ```
+//! assert_eq!(format!("Hello {:+}!", 5), "Hello +5!");
+//! assert_eq!(format!("{:#x}!", 27), "0x1b!");
+//! assert_eq!(format!("Hello {:05}!", 5), "Hello 00005!");
+//! assert_eq!(format!("Hello {:05}!", -5), "Hello -0005!");
+//! assert_eq!(format!("{:#010x}!", 27), "0x0000001b!");
+//! ```
+//!
+//! These are all flags altering the behavior of the formatter.
+//!
+//! * `+` - This is intended for numeric types and indicates that the sign
+//! should always be printed. Positive signs are never printed by
+//! default, and the negative sign is only printed by default for signed values.
+//! This flag indicates that the correct sign (`+` or `-`) should always be printed.
+//! * `-` - Currently not used
+//! * `#` - This flag indicates that the "alternate" form of printing should
+//! be used. The alternate forms are:
+//! * `#?` - pretty-print the [`Debug`] formatting (adds linebreaks and indentation)
+//! * `#x` - precedes the argument with a `0x`
+//! * `#X` - precedes the argument with a `0x`
+//! * `#b` - precedes the argument with a `0b`
+//! * `#o` - precedes the argument with a `0o`
+//! * `0` - This is used to indicate for integer formats that the padding to `width` should
+//! both be done with a `0` character as well as be sign-aware. A format
+//! like `{:08}` would yield `00000001` for the integer `1`, while the
+//! same format would yield `-0000001` for the integer `-1`. Notice that
+//! the negative version has one fewer zero than the positive version.
+//! Note that padding zeros are always placed after the sign (if any)
+//! and before the digits. When used together with the `#` flag, a similar
+//! rule applies: padding zeros are inserted after the prefix but before
+//! the digits. The prefix is included in the total width.
+//!
+//! ## Precision
+//!
+//! For non-numeric types, this can be considered a "maximum width". If the resulting string is
+//! longer than this width, then it is truncated down to this many characters and that truncated
+//! value is emitted with proper `fill`, `alignment` and `width` if those parameters are set.
+//!
+//! For integral types, this is ignored.
+//!
+//! For floating-point types, this indicates how many digits after the decimal point should be
+//! printed.
+//!
+//! There are three possible ways to specify the desired `precision`:
+//!
+//! 1. An integer `.N`:
+//!
+//! the integer `N` itself is the precision.
+//!
+//! 2. An integer or name followed by dollar sign `.N$`:
+//!
+//! use format *argument* `N` (which must be a `usize`) as the precision.
+//!
+//! 3. An asterisk `.*`:
+//!
+//! `.*` means that this `{...}` is associated with *two* format inputs rather than one: the
+//! first input holds the `usize` precision, and the second holds the value to print. Note that
+//! in this case, if one uses the format string `{<arg>:<spec>.*}`, then the `<arg>` part refers
+//! to the *value* to print, and the `precision` must come in the input preceding `<arg>`.
+//!
+//! For example, the following calls all print the same thing `Hello x is 0.01000`:
+//!
+//! ```
+//! // Hello {arg 0 ("x")} is {arg 1 (0.01) with precision specified inline (5)}
+//! println!("Hello {0} is {1:.5}", "x", 0.01);
+//!
+//! // Hello {arg 1 ("x")} is {arg 2 (0.01) with precision specified in arg 0 (5)}
+//! println!("Hello {1} is {2:.0$}", 5, "x", 0.01);
+//!
+//! // Hello {arg 0 ("x")} is {arg 2 (0.01) with precision specified in arg 1 (5)}
+//! println!("Hello {0} is {2:.1$}", "x", 5, 0.01);
+//!
+//! // Hello {next arg ("x")} is {second of next two args (0.01) with precision
+//! // specified in first of next two args (5)}
+//! println!("Hello {} is {:.*}", "x", 5, 0.01);
+//!
+//! // Hello {next arg ("x")} is {arg 2 (0.01) with precision
+//! // specified in its predecessor (5)}
+//! println!("Hello {} is {2:.*}", "x", 5, 0.01);
+//!
+//! // Hello {next arg ("x")} is {arg "number" (0.01) with precision specified
+//! // in arg "prec" (5)}
+//! println!("Hello {} is {number:.prec$}", "x", prec = 5, number = 0.01);
+//! ```
+//!
+//! While these:
+//!
+//! ```
+//! println!("{}, `{name:.*}` has 3 fractional digits", "Hello", 3, name=1234.56);
+//! println!("{}, `{name:.*}` has 3 characters", "Hello", 3, name="1234.56");
+//! println!("{}, `{name:>8.*}` has 3 right-aligned characters", "Hello", 3, name="1234.56");
+//! ```
+//!
+//! print three significantly different things:
+//!
+//! ```text
+//! Hello, `1234.560` has 3 fractional digits
+//! Hello, `123` has 3 characters
+//! Hello, ` 123` has 3 right-aligned characters
+//! ```
+//!
+//! ## Localization
+//!
+//! In some programming languages, the behavior of string formatting functions
+//! depends on the operating system's locale setting. The format functions
+//! provided by Rust's standard library do not have any concept of locale and
+//! will produce the same results on all systems regardless of user
+//! configuration.
+//!
+//! For example, the following code will always print `1.5` even if the system
+//! locale uses a decimal separator other than a dot.
+//!
+//! ```
+//! println!("The value is {}", 1.5);
+//! ```
+//!
+//! # Escaping
+//!
+//! The literal characters `{` and `}` may be included in a string by preceding
+//! them with the same character. For example, the `{` character is escaped with
+//! `{{` and the `}` character is escaped with `}}`.
+//!
+//! ```
+//! assert_eq!(format!("Hello {{}}"), "Hello {}");
+//! assert_eq!(format!("{{ Hello"), "{ Hello");
+//! ```
+//!
+//! # Syntax
+//!
+//! To summarize, here you can find the full grammar of format strings.
+//! The syntax for the formatting language used is drawn from other languages,
+//! so it should not be too alien. Arguments are formatted with Python-like
+//! syntax, meaning that arguments are surrounded by `{}` instead of the C-like
+//! `%`. The actual grammar for the formatting syntax is:
+//!
+//! ```text
+//! format_string := text [ maybe_format text ] *
+//! maybe_format := '{' '{' | '}' '}' | format
+//! format := '{' [ argument ] [ ':' format_spec ] '}'
+//! argument := integer | identifier
+//!
+//! format_spec := [[fill]align][sign]['#']['0'][width]['.' precision]type
+//! fill := character
+//! align := '<' | '^' | '>'
+//! sign := '+' | '-'
+//! width := count
+//! precision := count | '*'
+//! type := '' | '?' | 'x?' | 'X?' | identifier
+//! count := parameter | integer
+//! parameter := argument '$'
+//! ```
+//! In the above grammar, `text` may not contain any `'{'` or `'}'` characters.
+//!
+//! # Formatting traits
+//!
+//! When requesting that an argument be formatted with a particular type, you
+//! are actually requesting that an argument ascribes to a particular trait.
+//! This allows multiple actual types to be formatted via `{:x}` (like [`i8`] as
+//! well as [`isize`]). The current mapping of types to traits is:
+//!
+//! * *nothing* ⇒ [`Display`]
+//! * `?` ⇒ [`Debug`]
+//! * `x?` ⇒ [`Debug`] with lower-case hexadecimal integers
+//! * `X?` ⇒ [`Debug`] with upper-case hexadecimal integers
+//! * `o` ⇒ [`Octal`]
+//! * `x` ⇒ [`LowerHex`]
+//! * `X` ⇒ [`UpperHex`]
+//! * `p` ⇒ [`Pointer`]
+//! * `b` ⇒ [`Binary`]
+//! * `e` ⇒ [`LowerExp`]
+//! * `E` ⇒ [`UpperExp`]
+//!
+//! What this means is that any type of argument which implements the
+//! [`fmt::Binary`][`Binary`] trait can then be formatted with `{:b}`. Implementations
+//! are provided for these traits for a number of primitive types by the
+//! standard library as well. If no format is specified (as in `{}` or `{:6}`),
+//! then the format trait used is the [`Display`] trait.
+//!
+//! When implementing a format trait for your own type, you will have to
+//! implement a method of the signature:
+//!
+//! ```
+//! # #![allow(dead_code)]
+//! # use std::fmt;
+//! # struct Foo; // our custom type
+//! # impl fmt::Display for Foo {
+//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! # write!(f, "testing, testing")
+//! # } }
+//! ```
+//!
+//! Your type will be passed as `self` by-reference, and then the function
+//! should emit output into the `f.buf` stream. It is up to each format trait
+//! implementation to correctly adhere to the requested formatting parameters.
+//! The values of these parameters will be listed in the fields of the
+//! [`Formatter`] struct. In order to help with this, the [`Formatter`] struct also
+//! provides some helper methods.
+//!
+//! Additionally, the return value of this function is [`fmt::Result`] which is a
+//! type alias of [`Result`]`<(), `[`std::fmt::Error`]`>`. Formatting implementations
+//! should ensure that they propagate errors from the [`Formatter`] (e.g., when
+//! calling [`write!`]). However, they should never return errors spuriously. That
+//! is, a formatting implementation must and may only return an error if the
+//! passed-in [`Formatter`] returns an error. This is because, contrary to what
+//! the function signature might suggest, string formatting is an infallible
+//! operation. This function only returns a result because writing to the
+//! underlying stream might fail and it must provide a way to propagate the fact
+//! that an error has occurred back up the stack.
+//!
+//! An example of implementing the formatting traits would look
+//! like:
+//!
+//! ```
+//! use std::fmt;
+//!
+//! #[derive(Debug)]
+//! struct Vector2D {
+//! x: isize,
+//! y: isize,
+//! }
+//!
+//! impl fmt::Display for Vector2D {
+//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! // The `f` value implements the `Write` trait, which is what the
+//! // write! macro is expecting. Note that this formatting ignores the
+//! // various flags provided to format strings.
+//! write!(f, "({}, {})", self.x, self.y)
+//! }
+//! }
+//!
+//! // Different traits allow different forms of output of a type. The meaning
+//! // of this format is to print the magnitude of a vector.
+//! impl fmt::Binary for Vector2D {
+//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! let magnitude = (self.x * self.x + self.y * self.y) as f64;
+//! let magnitude = magnitude.sqrt();
+//!
+//! // Respect the formatting flags by using the helper method
+//! // `pad_integral` on the Formatter object. See the method
+//! // documentation for details, and the function `pad` can be used
+//! // to pad strings.
+//! let decimals = f.precision().unwrap_or(3);
+//! let string = format!("{:.*}", decimals, magnitude);
+//! f.pad_integral(true, "", &string)
+//! }
+//! }
+//!
+//! fn main() {
+//! let myvector = Vector2D { x: 3, y: 4 };
+//!
+//! println!("{}", myvector); // => "(3, 4)"
+//! println!("{:?}", myvector); // => "Vector2D {x: 3, y:4}"
+//! println!("{:10.3b}", myvector); // => " 5.000"
+//! }
+//! ```
+//!
+//! ### `fmt::Display` vs `fmt::Debug`
+//!
+//! These two formatting traits have distinct purposes:
+//!
+//! - [`fmt::Display`][`Display`] implementations assert that the type can be faithfully
+//! represented as a UTF-8 string at all times. It is **not** expected that
+//! all types implement the [`Display`] trait.
+//! - [`fmt::Debug`][`Debug`] implementations should be implemented for **all** public types.
+//! Output will typically represent the internal state as faithfully as possible.
+//! The purpose of the [`Debug`] trait is to facilitate debugging Rust code. In
+//! most cases, using `#[derive(Debug)]` is sufficient and recommended.
+//!
+//! Some examples of the output from both traits:
+//!
+//! ```
+//! assert_eq!(format!("{} {:?}", 3, 4), "3 4");
+//! assert_eq!(format!("{} {:?}", 'a', 'b'), "a 'b'");
+//! assert_eq!(format!("{} {:?}", "foo\n", "bar\n"), "foo\n \"bar\\n\"");
+//! ```
+//!
+//! # Related macros
+//!
+//! There are a number of related macros in the [`format!`] family. The ones that
+//! are currently implemented are:
+//!
+//! ```ignore (only-for-syntax-highlight)
+//! format! // described above
+//! write! // first argument is a &mut io::Write, the destination
+//! writeln! // same as write but appends a newline
+//! print! // the format string is printed to the standard output
+//! println! // same as print but appends a newline
+//! eprint! // the format string is printed to the standard error
+//! eprintln! // same as eprint but appends a newline
+//! format_args! // described below.
+//! ```
+//!
+//! ### `write!`
+//!
+//! This and [`writeln!`] are two macros which are used to emit the format string
+//! to a specified stream. This is used to prevent intermediate allocations of
+//! format strings and instead directly write the output. Under the hood, this
+//! function is actually invoking the [`write_fmt`] function defined on the
+//! [`std::io::Write`] trait. Example usage is:
+//!
+//! ```
+//! # #![allow(unused_must_use)]
+//! use std::io::Write;
+//! let mut w = Vec::new();
+//! write!(&mut w, "Hello {}!", "world");
+//! ```
+//!
+//! ### `print!`
+//!
+//! This and [`println!`] emit their output to stdout. Similarly to the [`write!`]
+//! macro, the goal of these macros is to avoid intermediate allocations when
+//! printing output. Example usage is:
+//!
+//! ```
+//! print!("Hello {}!", "world");
+//! println!("I have a newline {}", "character at the end");
+//! ```
+//! ### `eprint!`
+//!
+//! The [`eprint!`] and [`eprintln!`] macros are identical to
+//! [`print!`] and [`println!`], respectively, except they emit their
+//! output to stderr.
+//!
+//! ### `format_args!`
+//!
+//! This is a curious macro used to safely pass around
+//! an opaque object describing the format string. This object
+//! does not require any heap allocations to create, and it only
+//! references information on the stack. Under the hood, all of
+//! the related macros are implemented in terms of this. First
+//! off, some example usage is:
+//!
+//! ```
+//! # #![allow(unused_must_use)]
+//! use std::fmt;
+//! use std::io::{self, Write};
+//!
+//! let mut some_writer = io::stdout();
+//! write!(&mut some_writer, "{}", format_args!("print with a {}", "macro"));
+//!
+//! fn my_fmt_fn(args: fmt::Arguments) {
+//! write!(&mut io::stdout(), "{}", args);
+//! }
+//! my_fmt_fn(format_args!(", or a {} too", "function"));
+//! ```
+//!
+//! The result of the [`format_args!`] macro is a value of type [`fmt::Arguments`].
+//! This structure can then be passed to the [`write`] and [`format`] functions
+//! inside this module in order to process the format string.
+//! The goal of this macro is to even further prevent intermediate allocations
+//! when dealing with formatting strings.
+//!
+//! For example, a logging library could use the standard formatting syntax, but
+//! it would internally pass around this structure until it has been determined
+//! where output should go to.
+//!
+//! [`fmt::Result`]: Result
+//! [`Result`]: core::result::Result
+//! [`std::fmt::Error`]: Error
+//! [`write!`]: core::write
+//! [`write`]: core::write
+//! [`format!`]: crate::format
+//! [`to_string`]: crate::string::ToString
+//! [`writeln!`]: core::writeln
+//! [`write_fmt`]: ../../std/io/trait.Write.html#method.write_fmt
+//! [`std::io::Write`]: ../../std/io/trait.Write.html
+//! [`print!`]: ../../std/macro.print.html
+//! [`println!`]: ../../std/macro.println.html
+//! [`eprint!`]: ../../std/macro.eprint.html
+//! [`eprintln!`]: ../../std/macro.eprintln.html
+//! [`format_args!`]: core::format_args
+//! [`fmt::Arguments`]: Arguments
+//! [`format`]: crate::format
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[unstable(feature = "fmt_internals", issue = "none")]
+pub use core::fmt::rt;
+#[stable(feature = "fmt_flags_align", since = "1.28.0")]
+pub use core::fmt::Alignment;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::Error;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{write, ArgumentV1, Arguments};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{Binary, Octal};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{Debug, Display};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{Formatter, Result, Write};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{LowerExp, UpperExp};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::fmt::{LowerHex, Pointer, UpperHex};
+
+#[cfg(not(no_global_oom_handling))]
+use crate::string;
+
+/// The `format` function takes an [`Arguments`] struct and returns the resulting
+/// formatted string.
+///
+/// The [`Arguments`] instance can be created with the [`format_args!`] macro.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::fmt;
+///
+/// let s = fmt::format(format_args!("Hello, {}!", "world"));
+/// assert_eq!(s, "Hello, world!");
+/// ```
+///
+/// Please note that using [`format!`] might be preferable.
+/// Example:
+///
+/// ```
+/// let s = format!("Hello, {}!", "world");
+/// assert_eq!(s, "Hello, world!");
+/// ```
+///
+/// [`format_args!`]: core::format_args
+/// [`format!`]: crate::format
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn format(args: Arguments<'_>) -> string::String {
+ let capacity = args.estimated_capacity();
+ let mut output = string::String::with_capacity(capacity);
+ output.write_fmt(args).expect("a formatting trait implementation returned an error");
+ output
+}
diff --git a/rust/alloc/lib.rs b/rust/alloc/lib.rs
new file mode 100644
index 00000000000..f109e7902b2
--- /dev/null
+++ b/rust/alloc/lib.rs
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! # The Rust core allocation and collections library
+//!
+//! This library provides smart pointers and collections for managing
+//! heap-allocated values.
+//!
+//! This library, like libcore, normally doesn’t need to be used directly
+//! since its contents are re-exported in the [`std` crate](../std/index.html).
+//! Crates that use the `#![no_std]` attribute however will typically
+//! not depend on `std`, so they’d use this crate instead.
+//!
+//! ## Boxed values
+//!
+//! The [`Box`] type is a smart pointer type. There can only be one owner of a
+//! [`Box`], and the owner can decide to mutate the contents, which live on the
+//! heap.
+//!
+//! This type can be sent among threads efficiently as the size of a `Box` value
+//! is the same as that of a pointer. Tree-like data structures are often built
+//! with boxes because each node often has only one owner, the parent.
+//!
+//! ## Reference counted pointers
+//!
+//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
+//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
+//! only allows access to `&T`, a shared reference.
+//!
+//! This type is useful when inherited mutability (such as using [`Box`]) is too
+//! constraining for an application, and is often paired with the [`Cell`] or
+//! [`RefCell`] types in order to allow mutation.
+//!
+//! ## Atomically reference counted pointers
+//!
+//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
+//! provides all the same functionality of [`Rc`], except it requires that the
+//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
+//! sendable while [`Rc<T>`][`Rc`] is not.
+//!
+//! This type allows for shared access to the contained data, and is often
+//! paired with synchronization primitives such as mutexes to allow mutation of
+//! shared resources.
+//!
+//! ## Collections
+//!
+//! Implementations of the most common general purpose data structures are
+//! defined in this library. They are re-exported through the
+//! [standard collections library](../std/collections/index.html).
+//!
+//! ## Heap interfaces
+//!
+//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
+//! default global allocator. It is not compatible with the libc allocator API.
+//!
+//! [`Arc`]: sync
+//! [`Box`]: boxed
+//! [`Cell`]: core::cell
+//! [`Rc`]: rc
+//! [`RefCell`]: core::cell
+
+#![allow(unused_attributes)]
+#![stable(feature = "alloc", since = "1.36.0")]
+#![doc(
+ html_playground_url = "https://play.rust-lang.org/",
+ issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
+ test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
+)]
+#![no_std]
+#![needs_allocator]
+#![warn(deprecated_in_future)]
+#![warn(missing_docs)]
+#![warn(missing_debug_implementations)]
+#![allow(explicit_outlives_requirements)]
+#![deny(unsafe_op_in_unsafe_fn)]
+#![feature(rustc_allow_const_fn_unstable)]
+#![cfg_attr(not(test), feature(generator_trait))]
+#![cfg_attr(test, feature(test))]
+#![cfg_attr(test, feature(new_uninit))]
+#![feature(allocator_api)]
+#![feature(array_chunks)]
+#![feature(array_methods)]
+#![feature(array_windows)]
+#![feature(allow_internal_unstable)]
+#![feature(arbitrary_self_types)]
+#![feature(async_stream)]
+#![feature(box_patterns)]
+#![feature(box_syntax)]
+#![feature(cfg_sanitize)]
+#![feature(cfg_target_has_atomic)]
+#![feature(coerce_unsized)]
+#![cfg_attr(not(no_global_oom_handling), feature(const_btree_new))]
+#![feature(const_fn_trait_bound)]
+#![feature(cow_is_borrowed)]
+#![feature(const_cow_is_borrowed)]
+#![feature(destructuring_assignment)]
+#![feature(dispatch_from_dyn)]
+#![feature(core_intrinsics)]
+#![feature(dropck_eyepatch)]
+#![feature(exact_size_is_empty)]
+#![feature(exclusive_range_pattern)]
+#![feature(extend_one)]
+#![feature(fmt_internals)]
+#![feature(fn_traits)]
+#![feature(fundamental)]
+#![feature(inplace_iteration)]
+// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
+// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
+// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
+// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
+#![feature(intra_doc_pointers)]
+#![feature(iter_zip)]
+#![feature(lang_items)]
+#![feature(layout_for_ptr)]
+#![feature(maybe_uninit_ref)]
+#![feature(negative_impls)]
+#![feature(never_type)]
+#![feature(nll)]
+#![feature(nonnull_slice_from_raw_parts)]
+#![feature(auto_traits)]
+#![feature(option_result_unwrap_unchecked)]
+#![feature(pattern)]
+#![feature(ptr_internals)]
+#![feature(rustc_attrs)]
+#![feature(receiver_trait)]
+#![feature(min_specialization)]
+#![feature(set_ptr_value)]
+#![feature(slice_ptr_get)]
+#![feature(slice_ptr_len)]
+#![feature(slice_range)]
+#![feature(staged_api)]
+#![feature(str_internals)]
+#![feature(trusted_len)]
+#![feature(unboxed_closures)]
+#![feature(unicode_internals)]
+#![feature(unsize)]
+#![feature(unsized_fn_params)]
+#![feature(allocator_internals)]
+#![feature(slice_partition_dedup)]
+#![feature(maybe_uninit_extra, maybe_uninit_slice, maybe_uninit_uninit_array)]
+#![feature(alloc_layout_extra)]
+#![feature(trusted_random_access)]
+#![cfg_attr(bootstrap, feature(try_trait))]
+#![cfg_attr(not(bootstrap), feature(try_trait_v2))]
+#![feature(min_type_alias_impl_trait)]
+#![feature(associated_type_bounds)]
+#![feature(slice_group_by)]
+#![feature(decl_macro)]
+#![feature(bindings_after_at)]
+// Allow testing this library
+
+#[cfg(test)]
+#[macro_use]
+extern crate std;
+#[cfg(test)]
+extern crate test;
+
+// Module with internal macros used by other modules (needs to be included before other modules).
+#[macro_use]
+mod macros;
+
+// Heaps provided for low-level allocation strategies
+
+pub mod alloc;
+
+// Primitive types using the heaps above
+
+// Need to conditionally define the mod from `boxed.rs` to avoid
+// duplicating the lang-items when building in test cfg; but also need
+// to allow code to have `use boxed::Box;` declarations.
+#[cfg(not(test))]
+pub mod boxed;
+#[cfg(test)]
+mod boxed {
+ pub use std::boxed::Box;
+}
+pub mod borrow;
+pub mod collections;
+pub mod fmt;
+pub mod prelude;
+pub mod raw_vec;
+pub mod rc;
+pub mod slice;
+pub mod str;
+pub mod string;
+#[cfg(target_has_atomic = "ptr")]
+pub mod sync;
+#[cfg(all(not(no_global_oom_handling), target_has_atomic = "ptr"))]
+pub mod task;
+#[cfg(test)]
+mod tests;
+pub mod vec;
+
+#[doc(hidden)]
+#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
+pub mod __export {
+ pub use core::format_args;
+}
diff --git a/rust/alloc/macros.rs b/rust/alloc/macros.rs
new file mode 100644
index 00000000000..1dea4ec36c3
--- /dev/null
+++ b/rust/alloc/macros.rs
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+/// Creates a [`Vec`] containing the arguments.
+///
+/// `vec!` allows `Vec`s to be defined with the same syntax as array expressions.
+/// There are two forms of this macro:
+///
+/// - Create a [`Vec`] containing a given list of elements:
+///
+/// ```
+/// let v = vec![1, 2, 3];
+/// assert_eq!(v[0], 1);
+/// assert_eq!(v[1], 2);
+/// assert_eq!(v[2], 3);
+/// ```
+///
+/// - Create a [`Vec`] from a given element and size:
+///
+/// ```
+/// let v = vec![1; 3];
+/// assert_eq!(v, [1, 1, 1]);
+/// ```
+///
+/// Note that unlike array expressions this syntax supports all elements
+/// which implement [`Clone`] and the number of elements doesn't have to be
+/// a constant.
+///
+/// This will use `clone` to duplicate an expression, so one should be careful
+/// using this with types having a nonstandard `Clone` implementation. For
+/// example, `vec![Rc::new(1); 5]` will create a vector of five references
+/// to the same boxed integer value, not five references pointing to independently
+/// boxed integers.
+///
+/// Also, note that `vec![expr; 0]` is allowed, and produces an empty vector.
+/// This will still evaluate `expr`, however, and immediately drop the resulting value, so
+/// be mindful of side effects.
+///
+/// [`Vec`]: crate::vec::Vec
+#[cfg(not(test))]
+#[doc(alias = "alloc")]
+#[doc(alias = "malloc")]
+#[macro_export]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[allow_internal_unstable(box_syntax, liballoc_internals)]
+macro_rules! vec {
+ () => (
+ $crate::__rust_force_expr!($crate::vec::Vec::new())
+ );
+ ($elem:expr; $n:expr) => (
+ $crate::__rust_force_expr!($crate::vec::from_elem($elem, $n))
+ );
+ ($($x:expr),+ $(,)?) => (
+ $crate::__rust_force_expr!(<[_]>::into_vec(box [$($x),+]))
+ );
+}
+
+// HACK(japaric): with cfg(test) the inherent `[T]::into_vec` method, which is
+// required for this macro definition, is not available. Instead use the
+// `slice::into_vec` function which is only available with cfg(test)
+// NB see the slice::hack module in slice.rs for more information
+#[cfg(test)]
+macro_rules! vec {
+ () => (
+ $crate::vec::Vec::new()
+ );
+ ($elem:expr; $n:expr) => (
+ $crate::vec::from_elem($elem, $n)
+ );
+ ($($x:expr),*) => (
+ $crate::slice::into_vec(box [$($x),*])
+ );
+ ($($x:expr,)*) => (vec![$($x),*])
+}
+
+/// Creates a `String` using interpolation of runtime expressions.
+///
+/// The first argument `format!` receives is a format string. This must be a string
+/// literal. The power of the formatting string is in the `{}`s contained.
+///
+/// Additional parameters passed to `format!` replace the `{}`s within the
+/// formatting string in the order given unless named or positional parameters
+/// are used; see [`std::fmt`] for more information.
+///
+/// A common use for `format!` is concatenation and interpolation of strings.
+/// The same convention is used with [`print!`] and [`write!`] macros,
+/// depending on the intended destination of the string.
+///
+/// To convert a single value to a string, use the [`to_string`] method. This
+/// will use the [`Display`] formatting trait.
+///
+/// [`std::fmt`]: ../std/fmt/index.html
+/// [`print!`]: ../std/macro.print.html
+/// [`write!`]: core::write
+/// [`to_string`]: crate::string::ToString
+/// [`Display`]: core::fmt::Display
+///
+/// # Panics
+///
+/// `format!` panics if a formatting trait implementation returns an error.
+/// This indicates an incorrect implementation
+/// since `fmt::Write for String` never returns an error itself.
+///
+/// # Examples
+///
+/// ```
+/// format!("test");
+/// format!("hello {}", "world!");
+/// format!("x = {}, y = {y}", 10, y = 30);
+/// ```
+#[macro_export]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "format_macro")]
+macro_rules! format {
+ ($($arg:tt)*) => {{
+ let res = $crate::fmt::format($crate::__export::format_args!($($arg)*));
+ res
+ }}
+}
+
+/// Force AST node to an expression to improve diagnostics in pattern position.
+#[doc(hidden)]
+#[macro_export]
+#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
+macro_rules! __rust_force_expr {
+ ($e:expr) => {
+ $e
+ };
+}
diff --git a/rust/alloc/prelude/mod.rs b/rust/alloc/prelude/mod.rs
new file mode 100644
index 00000000000..a64a1843760
--- /dev/null
+++ b/rust/alloc/prelude/mod.rs
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! The alloc Prelude
+//!
+//! The purpose of this module is to alleviate imports of commonly-used
+//! items of the `alloc` crate by adding a glob import to the top of modules:
+//!
+//! ```
+//! # #![allow(unused_imports)]
+//! #![feature(alloc_prelude)]
+//! extern crate alloc;
+//! use alloc::prelude::v1::*;
+//! ```
+
+#![unstable(feature = "alloc_prelude", issue = "58935")]
+
+pub mod v1;
diff --git a/rust/alloc/prelude/v1.rs b/rust/alloc/prelude/v1.rs
new file mode 100644
index 00000000000..48d75431c0d
--- /dev/null
+++ b/rust/alloc/prelude/v1.rs
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! The first version of the prelude of `alloc` crate.
+//!
+//! See the [module-level documentation](../index.html) for more.
+
+#![unstable(feature = "alloc_prelude", issue = "58935")]
+
+#[unstable(feature = "alloc_prelude", issue = "58935")]
+pub use crate::borrow::ToOwned;
+#[unstable(feature = "alloc_prelude", issue = "58935")]
+pub use crate::boxed::Box;
+#[unstable(feature = "alloc_prelude", issue = "58935")]
+pub use crate::string::{String, ToString};
+#[unstable(feature = "alloc_prelude", issue = "58935")]
+pub use crate::vec::Vec;
diff --git a/rust/alloc/raw_vec.rs b/rust/alloc/raw_vec.rs
new file mode 100644
index 00000000000..629dbd3927d
--- /dev/null
+++ b/rust/alloc/raw_vec.rs
@@ -0,0 +1,612 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#![unstable(feature = "raw_vec_internals", reason = "implementation detail", issue = "none")]
+#![doc(hidden)]
+
+use core::alloc::LayoutError;
+use core::cmp;
+use core::intrinsics;
+use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::ops::Drop;
+use core::ptr::{self, NonNull, Unique};
+use core::slice;
+
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::handle_alloc_error;
+use crate::alloc::{Allocator, Global, Layout};
+use crate::boxed::Box;
+use crate::collections::TryReserveError::{self, *};
+
+#[cfg(test)]
+mod tests;
+
+#[allow(dead_code)]
+enum AllocInit {
+ /// The contents of the new memory are uninitialized.
+ Uninitialized,
+ /// The new memory is guaranteed to be zeroed.
+ Zeroed,
+}
+
+/// A low-level utility for more ergonomically allocating, reallocating, and deallocating
+/// a buffer of memory on the heap without having to worry about all the corner cases
+/// involved. This type is excellent for building your own data structures like Vec and VecDeque.
+/// In particular:
+///
+/// * Produces `Unique::dangling()` on zero-sized types.
+/// * Produces `Unique::dangling()` on zero-length allocations.
+/// * Avoids freeing `Unique::dangling()`.
+/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics).
+/// * Guards against 32-bit systems allocating more than isize::MAX bytes.
+/// * Guards against overflowing your length.
+/// * Calls `handle_alloc_error` for fallible allocations.
+/// * Contains a `ptr::Unique` and thus endows the user with all related benefits.
+/// * Uses the excess returned from the allocator to use the largest available capacity.
+///
+/// This type does not in anyway inspect the memory that it manages. When dropped it *will*
+/// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec`
+/// to handle the actual things *stored* inside of a `RawVec`.
+///
+/// Note that the excess of a zero-sized types is always infinite, so `capacity()` always returns
+/// `usize::MAX`. This means that you need to be careful when round-tripping this type with a
+/// `Box<[T]>`, since `capacity()` won't yield the length.
+#[allow(missing_debug_implementations)]
+pub struct RawVec<T, A: Allocator = Global> {
+ ptr: Unique<T>,
+ cap: usize,
+ alloc: A,
+}
+
+impl<T> RawVec<T, Global> {
+ /// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so
+ /// they cannot call `Self::new()`.
+ ///
+ /// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything
+ /// that would truly const-call something unstable.
+ pub const NEW: Self = Self::new();
+
+ /// Creates the biggest possible `RawVec` (on the system heap)
+ /// without allocating. If `T` has positive size, then this makes a
+ /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
+ /// `RawVec` with capacity `usize::MAX`. Useful for implementing
+ /// delayed allocation.
+ pub const fn new() -> Self {
+ Self::new_in(Global)
+ }
+
+ /// Creates a `RawVec` (on the system heap) with exactly the
+ /// capacity and alignment requirements for a `[T; capacity]`. This is
+ /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is
+ /// zero-sized. Note that if `T` is zero-sized this means you will
+ /// *not* get a `RawVec` with the requested capacity.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the requested capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Aborts
+ ///
+ /// Aborts on OOM.
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn with_capacity(capacity: usize) -> Self {
+ Self::with_capacity_in(capacity, Global)
+ }
+
+ /// Tries to create a `RawVec` (on the system heap) with exactly the
+ /// capacity and alignment requirements for a `[T; capacity]`. This is
+ /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is
+ /// zero-sized. Note that if `T` is zero-sized this means you will
+ /// *not* get a `RawVec` with the requested capacity.
+ #[inline]
+ pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
+ Self::try_with_capacity_in(capacity, Global)
+ }
+
+ /// Like `with_capacity`, but guarantees the buffer is zeroed.
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn with_capacity_zeroed(capacity: usize) -> Self {
+ Self::with_capacity_zeroed_in(capacity, Global)
+ }
+
+ /// Reconstitutes a `RawVec` from a pointer and capacity.
+ ///
+ /// # Safety
+ ///
+ /// The `ptr` must be allocated (on the system heap), and with the given `capacity`.
+ /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit
+ /// systems). ZST vectors may have a capacity up to `usize::MAX`.
+ /// If the `ptr` and `capacity` come from a `RawVec`, then this is guaranteed.
+ #[inline]
+ pub unsafe fn from_raw_parts(ptr: *mut T, capacity: usize) -> Self {
+ unsafe { Self::from_raw_parts_in(ptr, capacity, Global) }
+ }
+}
+
+impl<T, A: Allocator> RawVec<T, A> {
+ // Tiny Vecs are dumb. Skip to:
+ // - 8 if the element size is 1, because any heap allocators is likely
+ // to round up a request of less than 8 bytes to at least 8 bytes.
+ // - 4 if elements are moderate-sized (<= 1 KiB).
+ // - 1 otherwise, to avoid wasting too much space for very short Vecs.
+ const MIN_NON_ZERO_CAP: usize = if mem::size_of::<T>() == 1 {
+ 8
+ } else if mem::size_of::<T>() <= 1024 {
+ 4
+ } else {
+ 1
+ };
+
+ /// Like `new`, but parameterized over the choice of allocator for
+ /// the returned `RawVec`.
+ #[rustc_allow_const_fn_unstable(const_fn)]
+ pub const fn new_in(alloc: A) -> Self {
+ // `cap: 0` means "unallocated". zero-sized types are ignored.
+ Self { ptr: Unique::dangling(), cap: 0, alloc }
+ }
+
+ /// Like `with_capacity`, but parameterized over the choice of
+ /// allocator for the returned `RawVec`.
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
+ Self::allocate_in(capacity, AllocInit::Uninitialized, alloc)
+ }
+
+ /// Like `try_with_capacity`, but parameterized over the choice of
+ /// allocator for the returned `RawVec`.
+ #[inline]
+ pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
+ Self::try_allocate_in(capacity, AllocInit::Uninitialized, alloc)
+ }
+
+ /// Like `with_capacity_zeroed`, but parameterized over the choice
+ /// of allocator for the returned `RawVec`.
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self {
+ Self::allocate_in(capacity, AllocInit::Zeroed, alloc)
+ }
+
+ /// Converts a `Box<[T]>` into a `RawVec<T>`.
+ pub fn from_box(slice: Box<[T], A>) -> Self {
+ unsafe {
+ let (slice, alloc) = Box::into_raw_with_allocator(slice);
+ RawVec::from_raw_parts_in(slice.as_mut_ptr(), slice.len(), alloc)
+ }
+ }
+
+ /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`.
+ ///
+ /// Note that this will correctly reconstitute any `cap` changes
+ /// that may have been performed. (See description of type for details.)
+ ///
+ /// # Safety
+ ///
+ /// * `len` must be greater than or equal to the most recently requested capacity, and
+ /// * `len` must be less than or equal to `self.capacity()`.
+ ///
+ /// Note, that the requested capacity and `self.capacity()` could differ, as
+ /// an allocator could overallocate and return a greater memory block than requested.
+ pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>], A> {
+ // Sanity-check one half of the safety requirement (we cannot check the other half).
+ debug_assert!(
+ len <= self.capacity(),
+ "`len` must be smaller than or equal to `self.capacity()`"
+ );
+
+ let me = ManuallyDrop::new(self);
+ unsafe {
+ let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len);
+ Box::from_raw_in(slice, ptr::read(&me.alloc))
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self {
+ if mem::size_of::<T>() == 0 {
+ Self::new_in(alloc)
+ } else {
+ // We avoid `unwrap_or_else` here because it bloats the amount of
+ // LLVM IR generated.
+ let layout = match Layout::array::<T>(capacity) {
+ Ok(layout) => layout,
+ Err(_) => capacity_overflow(),
+ };
+ match alloc_guard(layout.size()) {
+ Ok(_) => {}
+ Err(_) => capacity_overflow(),
+ }
+ let result = match init {
+ AllocInit::Uninitialized => alloc.allocate(layout),
+ AllocInit::Zeroed => alloc.allocate_zeroed(layout),
+ };
+ let ptr = match result {
+ Ok(ptr) => ptr,
+ Err(_) => handle_alloc_error(layout),
+ };
+
+ Self {
+ ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
+ cap: Self::capacity_from_bytes(ptr.len()),
+ alloc,
+ }
+ }
+ }
+
+ fn try_allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Result<Self, TryReserveError> {
+ if mem::size_of::<T>() == 0 {
+ return Ok(Self::new_in(alloc));
+ }
+
+ let layout = Layout::array::<T>(capacity)?;
+ alloc_guard(layout.size())?;
+ let result = match init {
+ AllocInit::Uninitialized => alloc.allocate(layout),
+ AllocInit::Zeroed => alloc.allocate_zeroed(layout),
+ };
+ let ptr = match result {
+ Ok(ptr) => ptr,
+ Err(_) => return Err(TryReserveError::AllocError { layout, non_exhaustive: () }),
+ };
+
+ Ok(Self {
+ ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
+ cap: Self::capacity_from_bytes(ptr.len()),
+ alloc,
+ })
+ }
+
+ /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
+ ///
+ /// # Safety
+ ///
+ /// The `ptr` must be allocated (via the given allocator `alloc`), and with the given
+ /// `capacity`.
+ /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit
+ /// systems). ZST vectors may have a capacity up to `usize::MAX`.
+ /// If the `ptr` and `capacity` come from a `RawVec` created via `alloc`, then this is
+ /// guaranteed.
+ #[inline]
+ pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self {
+ Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc }
+ }
+
+ /// Gets a raw pointer to the start of the allocation. Note that this is
+ /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
+ /// be careful.
+ #[inline]
+ pub fn ptr(&self) -> *mut T {
+ self.ptr.as_ptr()
+ }
+
+ /// Gets the capacity of the allocation.
+ ///
+ /// This will always be `usize::MAX` if `T` is zero-sized.
+ #[inline(always)]
+ pub fn capacity(&self) -> usize {
+ if mem::size_of::<T>() == 0 { usize::MAX } else { self.cap }
+ }
+
+ /// Returns a shared reference to the allocator backing this `RawVec`.
+ pub fn allocator(&self) -> &A {
+ &self.alloc
+ }
+
+ fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> {
+ if mem::size_of::<T>() == 0 || self.cap == 0 {
+ None
+ } else {
+ // We have an allocated chunk of memory, so we can bypass runtime
+ // checks to get our current layout.
+ unsafe {
+ let align = mem::align_of::<T>();
+ let size = mem::size_of::<T>() * self.cap;
+ let layout = Layout::from_size_align_unchecked(size, align);
+ Some((self.ptr.cast().into(), layout))
+ }
+ }
+ }
+
+ /// Ensures that the buffer contains at least enough space to hold `len +
+ /// additional` elements. If it doesn't already have enough capacity, will
+ /// reallocate enough space plus comfortable slack space to get amortized
+ /// *O*(1) behavior. Will limit this behavior if it would needlessly cause
+ /// itself to panic.
+ ///
+ /// If `len` exceeds `self.capacity()`, this may fail to actually allocate
+ /// the requested space. This is not really unsafe, but the unsafe
+ /// code *you* write that relies on the behavior of this function may break.
+ ///
+ /// This is ideal for implementing a bulk-push operation like `extend`.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Aborts
+ ///
+ /// Aborts on OOM.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![feature(raw_vec_internals)]
+ /// # extern crate alloc;
+ /// # use std::ptr;
+ /// # use alloc::raw_vec::RawVec;
+ /// struct MyVec<T> {
+ /// buf: RawVec<T>,
+ /// len: usize,
+ /// }
+ ///
+ /// impl<T: Clone> MyVec<T> {
+ /// pub fn push_all(&mut self, elems: &[T]) {
+ /// self.buf.reserve(self.len, elems.len());
+ /// // reserve would have aborted or panicked if the len exceeded
+ /// // `isize::MAX` so this is safe to do unchecked now.
+ /// for x in elems {
+ /// unsafe {
+ /// ptr::write(self.buf.ptr().add(self.len), x.clone());
+ /// }
+ /// self.len += 1;
+ /// }
+ /// }
+ /// }
+ /// # fn main() {
+ /// # let mut vector = MyVec { buf: RawVec::new(), len: 0 };
+ /// # vector.push_all(&[1, 3, 5, 7, 9]);
+ /// # }
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn reserve(&mut self, len: usize, additional: usize) {
+ // Callers expect this function to be very cheap when there is already sufficient capacity.
+ // Therefore, we move all the resizing and error-handling logic from grow_amortized and
+ // handle_reserve behind a call, while making sure that the this function is likely to be
+ // inlined as just a comparison and a call if the comparison fails.
+ #[cold]
+ fn do_reserve_and_handle<T, A: Allocator>(
+ slf: &mut RawVec<T, A>,
+ len: usize,
+ additional: usize,
+ ) {
+ handle_reserve(slf.grow_amortized(len, additional));
+ }
+
+ if self.needs_to_grow(len, additional) {
+ do_reserve_and_handle(self, len, additional);
+ }
+ }
+
+ /// The same as `reserve`, but returns on errors instead of panicking or aborting.
+ pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+ if self.needs_to_grow(len, additional) {
+ self.grow_amortized(len, additional)
+ } else {
+ Ok(())
+ }
+ }
+
+ /// Ensures that the buffer contains at least enough space to hold `len +
+ /// additional` elements. If it doesn't already, will reallocate the
+ /// minimum possible amount of memory necessary. Generally this will be
+ /// exactly the amount of memory necessary, but in principle the allocator
+ /// is free to give back more than we asked for.
+ ///
+ /// If `len` exceeds `self.capacity()`, this may fail to actually allocate
+ /// the requested space. This is not really unsafe, but the unsafe code
+ /// *you* write that relies on the behavior of this function may break.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Aborts
+ ///
+ /// Aborts on OOM.
+ #[cfg(not(no_global_oom_handling))]
+ pub fn reserve_exact(&mut self, len: usize, additional: usize) {
+ handle_reserve(self.try_reserve_exact(len, additional));
+ }
+
+ /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting.
+ pub fn try_reserve_exact(
+ &mut self,
+ len: usize,
+ additional: usize,
+ ) -> Result<(), TryReserveError> {
+ if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) }
+ }
+
+ /// Shrinks the allocation down to the specified amount. If the given amount
+ /// is 0, actually completely deallocates.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the given amount is *larger* than the current capacity.
+ ///
+ /// # Aborts
+ ///
+ /// Aborts on OOM.
+ #[cfg(not(no_global_oom_handling))]
+ pub fn shrink_to_fit(&mut self, amount: usize) {
+ handle_reserve(self.shrink(amount));
+ }
+
+ /// Tries to shrink the allocation down to the specified amount. If the given amount
+ /// is 0, actually completely deallocates.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the given amount is *larger* than the current capacity.
+ pub fn try_shrink_to_fit(&mut self, amount: usize) -> Result<(), TryReserveError> {
+ self.shrink(amount)
+ }
+}
+
+impl<T, A: Allocator> RawVec<T, A> {
+ /// Returns if the buffer needs to grow to fulfill the needed extra capacity.
+ /// Mainly used to make inlining reserve-calls possible without inlining `grow`.
+ fn needs_to_grow(&self, len: usize, additional: usize) -> bool {
+ additional > self.capacity().wrapping_sub(len)
+ }
+
+ fn capacity_from_bytes(excess: usize) -> usize {
+ debug_assert_ne!(mem::size_of::<T>(), 0);
+ excess / mem::size_of::<T>()
+ }
+
+ fn set_ptr(&mut self, ptr: NonNull<[u8]>) {
+ self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) };
+ self.cap = Self::capacity_from_bytes(ptr.len());
+ }
+
+ // This method is usually instantiated many times. So we want it to be as
+ // small as possible, to improve compile times. But we also want as much of
+ // its contents to be statically computable as possible, to make the
+ // generated code run faster. Therefore, this method is carefully written
+ // so that all of the code that depends on `T` is within it, while as much
+ // of the code that doesn't depend on `T` as possible is in functions that
+ // are non-generic over `T`.
+ fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+ // This is ensured by the calling contexts.
+ debug_assert!(additional > 0);
+
+ if mem::size_of::<T>() == 0 {
+ // Since we return a capacity of `usize::MAX` when `elem_size` is
+ // 0, getting to here necessarily means the `RawVec` is overfull.
+ return Err(CapacityOverflow);
+ }
+
+ // Nothing we can really do about these checks, sadly.
+ let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
+
+ // This guarantees exponential growth. The doubling cannot overflow
+ // because `cap <= isize::MAX` and the type of `cap` is `usize`.
+ let cap = cmp::max(self.cap * 2, required_cap);
+ let cap = cmp::max(Self::MIN_NON_ZERO_CAP, cap);
+
+ let new_layout = Layout::array::<T>(cap);
+
+ // `finish_grow` is non-generic over `T`.
+ let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
+ self.set_ptr(ptr);
+ Ok(())
+ }
+
+ // The constraints on this method are much the same as those on
+ // `grow_amortized`, but this method is usually instantiated less often so
+ // it's less critical.
+ fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+ if mem::size_of::<T>() == 0 {
+ // Since we return a capacity of `usize::MAX` when the type size is
+ // 0, getting to here necessarily means the `RawVec` is overfull.
+ return Err(CapacityOverflow);
+ }
+
+ let cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
+ let new_layout = Layout::array::<T>(cap);
+
+ // `finish_grow` is non-generic over `T`.
+ let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
+ self.set_ptr(ptr);
+ Ok(())
+ }
+
+ fn shrink(&mut self, amount: usize) -> Result<(), TryReserveError> {
+ assert!(amount <= self.capacity(), "Tried to shrink to a larger capacity");
+
+ let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) };
+ let new_size = amount * mem::size_of::<T>();
+
+ let ptr = unsafe {
+ let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
+ self.alloc.shrink(ptr, layout, new_layout).map_err(|_| TryReserveError::AllocError {
+ layout: new_layout,
+ non_exhaustive: (),
+ })?
+ };
+ self.set_ptr(ptr);
+ Ok(())
+ }
+}
+
+// This function is outside `RawVec` to minimize compile times. See the comment
+// above `RawVec::grow_amortized` for details. (The `A` parameter isn't
+// significant, because the number of different `A` types seen in practice is
+// much smaller than the number of `T` types.)
+#[inline(never)]
+fn finish_grow<A>(
+ new_layout: Result<Layout, LayoutError>,
+ current_memory: Option<(NonNull<u8>, Layout)>,
+ alloc: &mut A,
+) -> Result<NonNull<[u8]>, TryReserveError>
+where
+ A: Allocator,
+{
+ // Check for the error here to minimize the size of `RawVec::grow_*`.
+ let new_layout = new_layout.map_err(|_| CapacityOverflow)?;
+
+ alloc_guard(new_layout.size())?;
+
+ let memory = if let Some((ptr, old_layout)) = current_memory {
+ debug_assert_eq!(old_layout.align(), new_layout.align());
+ unsafe {
+ // The allocator checks for alignment equality
+ intrinsics::assume(old_layout.align() == new_layout.align());
+ alloc.grow(ptr, old_layout, new_layout)
+ }
+ } else {
+ alloc.allocate(new_layout)
+ };
+
+ memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })
+}
+
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawVec<T, A> {
+ /// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
+ fn drop(&mut self) {
+ if let Some((ptr, layout)) = self.current_memory() {
+ unsafe { self.alloc.deallocate(ptr, layout) }
+ }
+ }
+}
+
+// Central function for reserve error handling.
+#[cfg(not(no_global_oom_handling))]
+#[inline]
+fn handle_reserve(result: Result<(), TryReserveError>) {
+ match result {
+ Err(CapacityOverflow) => capacity_overflow(),
+ Err(AllocError { layout, .. }) => handle_alloc_error(layout),
+ Ok(()) => { /* yay */ }
+ }
+}
+
+// We need to guarantee the following:
+// * We don't ever allocate `> isize::MAX` byte-size objects.
+// * We don't overflow `usize::MAX` and actually allocate too little.
+//
+// On 64-bit we just need to check for overflow since trying to allocate
+// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
+// an extra guard for this in case we're running on a platform which can use
+// all 4GB in user-space, e.g., PAE or x32.
+
+#[inline]
+fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
+ if usize::BITS < 64 && alloc_size > isize::MAX as usize {
+ Err(CapacityOverflow)
+ } else {
+ Ok(())
+ }
+}
+
+// One central function responsible for reporting capacity overflows. This'll
+// ensure that the code generation related to these panics is minimal as there's
+// only one location which panics rather than a bunch throughout the module.
+#[cfg(not(no_global_oom_handling))]
+fn capacity_overflow() -> ! {
+ panic!("capacity overflow");
+}
diff --git a/rust/alloc/rc.rs b/rust/alloc/rc.rs
new file mode 100644
index 00000000000..7344cd9a449
--- /dev/null
+++ b/rust/alloc/rc.rs
@@ -0,0 +1,2539 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Single-threaded reference-counting pointers. 'Rc' stands for 'Reference
+//! Counted'.
+//!
+//! The type [`Rc<T>`][`Rc`] provides shared ownership of a value of type `T`,
+//! allocated in the heap. Invoking [`clone`][clone] on [`Rc`] produces a new
+//! pointer to the same allocation in the heap. When the last [`Rc`] pointer to a
+//! given allocation is destroyed, the value stored in that allocation (often
+//! referred to as "inner value") is also dropped.
+//!
+//! Shared references in Rust disallow mutation by default, and [`Rc`]
+//! is no exception: you cannot generally obtain a mutable reference to
+//! something inside an [`Rc`]. If you need mutability, put a [`Cell`]
+//! or [`RefCell`] inside the [`Rc`]; see [an example of mutability
+//! inside an `Rc`][mutability].
+//!
+//! [`Rc`] uses non-atomic reference counting. This means that overhead is very
+//! low, but an [`Rc`] cannot be sent between threads, and consequently [`Rc`]
+//! does not implement [`Send`][send]. As a result, the Rust compiler
+//! will check *at compile time* that you are not sending [`Rc`]s between
+//! threads. If you need multi-threaded, atomic reference counting, use
+//! [`sync::Arc`][arc].
+//!
+//! The [`downgrade`][downgrade] method can be used to create a non-owning
+//! [`Weak`] pointer. A [`Weak`] pointer can be [`upgrade`][upgrade]d
+//! to an [`Rc`], but this will return [`None`] if the value stored in the allocation has
+//! already been dropped. In other words, `Weak` pointers do not keep the value
+//! inside the allocation alive; however, they *do* keep the allocation
+//! (the backing store for the inner value) alive.
+//!
+//! A cycle between [`Rc`] pointers will never be deallocated. For this reason,
+//! [`Weak`] is used to break cycles. For example, a tree could have strong
+//! [`Rc`] pointers from parent nodes to children, and [`Weak`] pointers from
+//! children back to their parents.
+//!
+//! `Rc<T>` automatically dereferences to `T` (via the [`Deref`] trait),
+//! so you can call `T`'s methods on a value of type [`Rc<T>`][`Rc`]. To avoid name
+//! clashes with `T`'s methods, the methods of [`Rc<T>`][`Rc`] itself are associated
+//! functions, called using [fully qualified syntax]:
+//!
+//! ```
+//! use std::rc::Rc;
+//!
+//! let my_rc = Rc::new(());
+//! Rc::downgrade(&my_rc);
+//! ```
+//!
+//! `Rc<T>`'s implementations of traits like `Clone` may also be called using
+//! fully qualified syntax. Some people prefer to use fully qualified syntax,
+//! while others prefer using method-call syntax.
+//!
+//! ```
+//! use std::rc::Rc;
+//!
+//! let rc = Rc::new(());
+//! // Method-call syntax
+//! let rc2 = rc.clone();
+//! // Fully qualified syntax
+//! let rc3 = Rc::clone(&rc);
+//! ```
+//!
+//! [`Weak<T>`][`Weak`] does not auto-dereference to `T`, because the inner value may have
+//! already been dropped.
+//!
+//! # Cloning references
+//!
+//! Creating a new reference to the same allocation as an existing reference counted pointer
+//! is done using the `Clone` trait implemented for [`Rc<T>`][`Rc`] and [`Weak<T>`][`Weak`].
+//!
+//! ```
+//! use std::rc::Rc;
+//!
+//! let foo = Rc::new(vec![1.0, 2.0, 3.0]);
+//! // The two syntaxes below are equivalent.
+//! let a = foo.clone();
+//! let b = Rc::clone(&foo);
+//! // a and b both point to the same memory location as foo.
+//! ```
+//!
+//! The `Rc::clone(&from)` syntax is the most idiomatic because it conveys more explicitly
+//! the meaning of the code. In the example above, this syntax makes it easier to see that
+//! this code is creating a new reference rather than copying the whole content of foo.
+//!
+//! # Examples
+//!
+//! Consider a scenario where a set of `Gadget`s are owned by a given `Owner`.
+//! We want to have our `Gadget`s point to their `Owner`. We can't do this with
+//! unique ownership, because more than one gadget may belong to the same
+//! `Owner`. [`Rc`] allows us to share an `Owner` between multiple `Gadget`s,
+//! and have the `Owner` remain allocated as long as any `Gadget` points at it.
+//!
+//! ```
+//! use std::rc::Rc;
+//!
+//! struct Owner {
+//! name: String,
+//! // ...other fields
+//! }
+//!
+//! struct Gadget {
+//! id: i32,
+//! owner: Rc<Owner>,
+//! // ...other fields
+//! }
+//!
+//! fn main() {
+//! // Create a reference-counted `Owner`.
+//! let gadget_owner: Rc<Owner> = Rc::new(
+//! Owner {
+//! name: "Gadget Man".to_string(),
+//! }
+//! );
+//!
+//! // Create `Gadget`s belonging to `gadget_owner`. Cloning the `Rc<Owner>`
+//! // gives us a new pointer to the same `Owner` allocation, incrementing
+//! // the reference count in the process.
+//! let gadget1 = Gadget {
+//! id: 1,
+//! owner: Rc::clone(&gadget_owner),
+//! };
+//! let gadget2 = Gadget {
+//! id: 2,
+//! owner: Rc::clone(&gadget_owner),
+//! };
+//!
+//! // Dispose of our local variable `gadget_owner`.
+//! drop(gadget_owner);
+//!
+//! // Despite dropping `gadget_owner`, we're still able to print out the name
+//! // of the `Owner` of the `Gadget`s. This is because we've only dropped a
+//! // single `Rc<Owner>`, not the `Owner` it points to. As long as there are
+//! // other `Rc<Owner>` pointing at the same `Owner` allocation, it will remain
+//! // live. The field projection `gadget1.owner.name` works because
+//! // `Rc<Owner>` automatically dereferences to `Owner`.
+//! println!("Gadget {} owned by {}", gadget1.id, gadget1.owner.name);
+//! println!("Gadget {} owned by {}", gadget2.id, gadget2.owner.name);
+//!
+//! // At the end of the function, `gadget1` and `gadget2` are destroyed, and
+//! // with them the last counted references to our `Owner`. Gadget Man now
+//! // gets destroyed as well.
+//! }
+//! ```
+//!
+//! If our requirements change, and we also need to be able to traverse from
+//! `Owner` to `Gadget`, we will run into problems. An [`Rc`] pointer from `Owner`
+//! to `Gadget` introduces a cycle. This means that their
+//! reference counts can never reach 0, and the allocation will never be destroyed:
+//! a memory leak. In order to get around this, we can use [`Weak`]
+//! pointers.
+//!
+//! Rust actually makes it somewhat difficult to produce this loop in the first
+//! place. In order to end up with two values that point at each other, one of
+//! them needs to be mutable. This is difficult because [`Rc`] enforces
+//! memory safety by only giving out shared references to the value it wraps,
+//! and these don't allow direct mutation. We need to wrap the part of the
+//! value we wish to mutate in a [`RefCell`], which provides *interior
+//! mutability*: a method to achieve mutability through a shared reference.
+//! [`RefCell`] enforces Rust's borrowing rules at runtime.
+//!
+//! ```
+//! use std::rc::Rc;
+//! use std::rc::Weak;
+//! use std::cell::RefCell;
+//!
+//! struct Owner {
+//! name: String,
+//! gadgets: RefCell<Vec<Weak<Gadget>>>,
+//! // ...other fields
+//! }
+//!
+//! struct Gadget {
+//! id: i32,
+//! owner: Rc<Owner>,
+//! // ...other fields
+//! }
+//!
+//! fn main() {
+//! // Create a reference-counted `Owner`. Note that we've put the `Owner`'s
+//! // vector of `Gadget`s inside a `RefCell` so that we can mutate it through
+//! // a shared reference.
+//! let gadget_owner: Rc<Owner> = Rc::new(
+//! Owner {
+//! name: "Gadget Man".to_string(),
+//! gadgets: RefCell::new(vec![]),
+//! }
+//! );
+//!
+//! // Create `Gadget`s belonging to `gadget_owner`, as before.
+//! let gadget1 = Rc::new(
+//! Gadget {
+//! id: 1,
+//! owner: Rc::clone(&gadget_owner),
+//! }
+//! );
+//! let gadget2 = Rc::new(
+//! Gadget {
+//! id: 2,
+//! owner: Rc::clone(&gadget_owner),
+//! }
+//! );
+//!
+//! // Add the `Gadget`s to their `Owner`.
+//! {
+//! let mut gadgets = gadget_owner.gadgets.borrow_mut();
+//! gadgets.push(Rc::downgrade(&gadget1));
+//! gadgets.push(Rc::downgrade(&gadget2));
+//!
+//! // `RefCell` dynamic borrow ends here.
+//! }
+//!
+//! // Iterate over our `Gadget`s, printing their details out.
+//! for gadget_weak in gadget_owner.gadgets.borrow().iter() {
+//!
+//! // `gadget_weak` is a `Weak<Gadget>`. Since `Weak` pointers can't
+//! // guarantee the allocation still exists, we need to call
+//! // `upgrade`, which returns an `Option<Rc<Gadget>>`.
+//! //
+//! // In this case we know the allocation still exists, so we simply
+//! // `unwrap` the `Option`. In a more complicated program, you might
+//! // need graceful error handling for a `None` result.
+//!
+//! let gadget = gadget_weak.upgrade().unwrap();
+//! println!("Gadget {} owned by {}", gadget.id, gadget.owner.name);
+//! }
+//!
+//! // At the end of the function, `gadget_owner`, `gadget1`, and `gadget2`
+//! // are destroyed. There are now no strong (`Rc`) pointers to the
+//! // gadgets, so they are destroyed. This zeroes the reference count on
+//! // Gadget Man, so he gets destroyed as well.
+//! }
+//! ```
+//!
+//! [clone]: Clone::clone
+//! [`Cell`]: core::cell::Cell
+//! [`RefCell`]: core::cell::RefCell
+//! [send]: core::marker::Send
+//! [arc]: crate::sync::Arc
+//! [`Deref`]: core::ops::Deref
+//! [downgrade]: Rc::downgrade
+//! [upgrade]: Weak::upgrade
+//! [mutability]: core::cell#introducing-mutability-inside-of-something-immutable
+//! [fully qualified syntax]: https://doc.rust-lang.org/book/ch19-03-advanced-traits.html#fully-qualified-syntax-for-disambiguation-calling-methods-with-the-same-name
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[cfg(not(test))]
+use crate::boxed::Box;
+#[cfg(test)]
+use std::boxed::Box;
+
+use core::any::Any;
+use core::borrow;
+use core::cell::Cell;
+use core::cmp::Ordering;
+use core::convert::{From, TryFrom};
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::intrinsics::abort;
+#[cfg(not(no_global_oom_handling))]
+use core::iter;
+use core::marker::{self, PhantomData, Unpin, Unsize};
+#[cfg(not(no_global_oom_handling))]
+use core::mem::size_of_val;
+use core::mem::{self, align_of_val_raw, forget};
+use core::ops::{CoerceUnsized, Deref, DispatchFromDyn, Receiver};
+#[cfg(not(no_global_oom_handling))]
+use core::pin::Pin;
+use core::ptr::{self, NonNull};
+#[cfg(not(no_global_oom_handling))]
+use core::slice::from_raw_parts_mut;
+
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::handle_alloc_error;
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::{box_free, WriteCloneIntoRaw};
+use crate::alloc::{AllocError, Allocator, Global, Layout};
+use crate::borrow::{Cow, ToOwned};
+#[cfg(not(no_global_oom_handling))]
+use crate::string::String;
+#[cfg(not(no_global_oom_handling))]
+use crate::vec::Vec;
+
+#[cfg(test)]
+mod tests;
+
+// This is repr(C) to future-proof against possible field-reordering, which
+// would interfere with otherwise safe [into|from]_raw() of transmutable
+// inner types.
+#[repr(C)]
+struct RcBox<T: ?Sized> {
+ strong: Cell<usize>,
+ weak: Cell<usize>,
+ value: T,
+}
+
+/// A single-threaded reference-counting pointer. 'Rc' stands for 'Reference
+/// Counted'.
+///
+/// See the [module-level documentation](./index.html) for more details.
+///
+/// The inherent methods of `Rc` are all associated functions, which means
+/// that you have to call them as e.g., [`Rc::get_mut(&mut value)`][get_mut] instead of
+/// `value.get_mut()`. This avoids conflicts with methods of the inner type `T`.
+///
+/// [get_mut]: Rc::get_mut
+#[cfg_attr(not(test), rustc_diagnostic_item = "Rc")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Rc<T: ?Sized> {
+ ptr: NonNull<RcBox<T>>,
+ phantom: PhantomData<RcBox<T>>,
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> !marker::Send for Rc<T> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> !marker::Sync for Rc<T> {}
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Rc<U>> for Rc<T> {}
+
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Rc<U>> for Rc<T> {}
+
+impl<T: ?Sized> Rc<T> {
+ #[inline(always)]
+ fn inner(&self) -> &RcBox<T> {
+ // This unsafety is ok because while this Rc is alive we're guaranteed
+ // that the inner pointer is valid.
+ unsafe { self.ptr.as_ref() }
+ }
+
+ fn from_inner(ptr: NonNull<RcBox<T>>) -> Self {
+ Self { ptr, phantom: PhantomData }
+ }
+
+ unsafe fn from_ptr(ptr: *mut RcBox<T>) -> Self {
+ Self::from_inner(unsafe { NonNull::new_unchecked(ptr) })
+ }
+}
+
+impl<T> Rc<T> {
+ /// Constructs a new `Rc<T>`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn new(value: T) -> Rc<T> {
+ // There is an implicit weak pointer owned by all the strong
+ // pointers, which ensures that the weak destructor never frees
+ // the allocation while the strong destructor is running, even
+ // if the weak pointer is stored inside the strong one.
+ Self::from_inner(
+ Box::leak(box RcBox { strong: Cell::new(1), weak: Cell::new(1), value }).into(),
+ )
+ }
+
+ /// Constructs a new `Rc<T>` using a weak reference to itself. Attempting
+ /// to upgrade the weak reference before this function returns will result
+ /// in a `None` value. However, the weak reference may be cloned freely and
+ /// stored for use at a later time.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(arc_new_cyclic)]
+ /// #![allow(dead_code)]
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// struct Gadget {
+ /// self_weak: Weak<Self>,
+ /// // ... more fields
+ /// }
+ /// impl Gadget {
+ /// pub fn new() -> Rc<Self> {
+ /// Rc::new_cyclic(|self_weak| {
+ /// Gadget { self_weak: self_weak.clone(), /* ... */ }
+ /// })
+ /// }
+ /// }
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "arc_new_cyclic", issue = "75861")]
+ pub fn new_cyclic(data_fn: impl FnOnce(&Weak<T>) -> T) -> Rc<T> {
+ // Construct the inner in the "uninitialized" state with a single
+ // weak reference.
+ let uninit_ptr: NonNull<_> = Box::leak(box RcBox {
+ strong: Cell::new(0),
+ weak: Cell::new(1),
+ value: mem::MaybeUninit::<T>::uninit(),
+ })
+ .into();
+
+ let init_ptr: NonNull<RcBox<T>> = uninit_ptr.cast();
+
+ let weak = Weak { ptr: init_ptr };
+
+ // It's important we don't give up ownership of the weak pointer, or
+ // else the memory might be freed by the time `data_fn` returns. If
+ // we really wanted to pass ownership, we could create an additional
+ // weak pointer for ourselves, but this would result in additional
+ // updates to the weak reference count which might not be necessary
+ // otherwise.
+ let data = data_fn(&weak);
+
+ unsafe {
+ let inner = init_ptr.as_ptr();
+ ptr::write(ptr::addr_of_mut!((*inner).value), data);
+
+ let prev_value = (*inner).strong.get();
+ debug_assert_eq!(prev_value, 0, "No prior strong references should exist");
+ (*inner).strong.set(1);
+ }
+
+ let strong = Rc::from_inner(init_ptr);
+
+ // Strong references should collectively own a shared weak reference,
+ // so don't run the destructor for our old weak reference.
+ mem::forget(weak);
+ strong
+ }
+
+ /// Constructs a new `Rc` with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut five = Rc::<u32>::new_uninit();
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Rc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit() -> Rc<mem::MaybeUninit<T>> {
+ unsafe {
+ Rc::from_ptr(Rc::allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate(layout),
+ |mem| mem as *mut RcBox<mem::MaybeUninit<T>>,
+ ))
+ }
+ }
+
+ /// Constructs a new `Rc` with uninitialized contents, with the memory
+ /// being filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and
+ /// incorrect usage of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let zero = Rc::<u32>::new_zeroed();
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0)
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed() -> Rc<mem::MaybeUninit<T>> {
+ unsafe {
+ Rc::from_ptr(Rc::allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| mem as *mut RcBox<mem::MaybeUninit<T>>,
+ ))
+ }
+ }
+
+ /// Constructs a new `Rc<T>`, returning an error if the allocation fails
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::try_new(5);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ pub fn try_new(value: T) -> Result<Rc<T>, AllocError> {
+ // There is an implicit weak pointer owned by all the strong
+ // pointers, which ensures that the weak destructor never frees
+ // the allocation while the strong destructor is running, even
+ // if the weak pointer is stored inside the strong one.
+ Ok(Self::from_inner(
+ Box::leak(Box::try_new(RcBox { strong: Cell::new(1), weak: Cell::new(1), value })?)
+ .into(),
+ ))
+ }
+
+ /// Constructs a new `Rc` with uninitialized contents, returning an error if the allocation fails
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut five = Rc::<u32>::try_new_uninit()?;
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Rc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_uninit() -> Result<Rc<mem::MaybeUninit<T>>, AllocError> {
+ unsafe {
+ Ok(Rc::from_ptr(Rc::try_allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate(layout),
+ |mem| mem as *mut RcBox<mem::MaybeUninit<T>>,
+ )?))
+ }
+ }
+
+ /// Constructs a new `Rc` with uninitialized contents, with the memory
+ /// being filled with `0` bytes, returning an error if the allocation fails
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and
+ /// incorrect usage of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, new_uninit)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let zero = Rc::<u32>::try_new_zeroed()?;
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ //#[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_zeroed() -> Result<Rc<mem::MaybeUninit<T>>, AllocError> {
+ unsafe {
+ Ok(Rc::from_ptr(Rc::try_allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| mem as *mut RcBox<mem::MaybeUninit<T>>,
+ )?))
+ }
+ }
+ /// Constructs a new `Pin<Rc<T>>`. If `T` does not implement `Unpin`, then
+ /// `value` will be pinned in memory and unable to be moved.
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "pin", since = "1.33.0")]
+ pub fn pin(value: T) -> Pin<Rc<T>> {
+ unsafe { Pin::new_unchecked(Rc::new(value)) }
+ }
+
+ /// Returns the inner value, if the `Rc` has exactly one strong reference.
+ ///
+ /// Otherwise, an [`Err`] is returned with the same `Rc` that was
+ /// passed in.
+ ///
+ /// This will succeed even if there are outstanding weak references.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let x = Rc::new(3);
+ /// assert_eq!(Rc::try_unwrap(x), Ok(3));
+ ///
+ /// let x = Rc::new(4);
+ /// let _y = Rc::clone(&x);
+ /// assert_eq!(*Rc::try_unwrap(x).unwrap_err(), 4);
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn try_unwrap(this: Self) -> Result<T, Self> {
+ if Rc::strong_count(&this) == 1 {
+ unsafe {
+ let val = ptr::read(&*this); // copy the contained object
+
+ // Indicate to Weaks that they can't be promoted by decrementing
+ // the strong count, and then remove the implicit "strong weak"
+ // pointer while also handling drop logic by just crafting a
+ // fake Weak.
+ this.inner().dec_strong();
+ let _weak = Weak { ptr: this.ptr };
+ forget(this);
+ Ok(val)
+ }
+ } else {
+ Err(this)
+ }
+ }
+}
+
+impl<T> Rc<[T]> {
+ /// Constructs a new reference-counted slice with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// Rc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+ /// Rc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+ /// Rc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit_slice(len: usize) -> Rc<[mem::MaybeUninit<T>]> {
+ unsafe { Rc::from_ptr(Rc::allocate_for_slice(len)) }
+ }
+
+ /// Constructs a new reference-counted slice with uninitialized contents, with the memory being
+ /// filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and
+ /// incorrect usage of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let values = Rc::<[u32]>::new_zeroed_slice(3);
+ /// let values = unsafe { values.assume_init() };
+ ///
+ /// assert_eq!(*values, [0, 0, 0])
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed_slice(len: usize) -> Rc<[mem::MaybeUninit<T>]> {
+ unsafe {
+ Rc::from_ptr(Rc::allocate_for_layout(
+ Layout::array::<T>(len).unwrap(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| {
+ ptr::slice_from_raw_parts_mut(mem as *mut T, len)
+ as *mut RcBox<[mem::MaybeUninit<T>]>
+ },
+ ))
+ }
+ }
+}
+
+impl<T> Rc<mem::MaybeUninit<T>> {
+ /// Converts to `Rc<T>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the inner value
+ /// really is in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut five = Rc::<u32>::new_uninit();
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Rc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Rc<T> {
+ Rc::from_inner(mem::ManuallyDrop::new(self).ptr.cast())
+ }
+}
+
+impl<T> Rc<[mem::MaybeUninit<T>]> {
+ /// Converts to `Rc<[T]>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the inner value
+ /// really is in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// Rc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+ /// Rc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+ /// Rc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Rc<[T]> {
+ unsafe { Rc::from_ptr(mem::ManuallyDrop::new(self).ptr.as_ptr() as _) }
+ }
+}
+
+impl<T: ?Sized> Rc<T> {
+ /// Consumes the `Rc`, returning the wrapped pointer.
+ ///
+ /// To avoid a memory leak the pointer must be converted back to an `Rc` using
+ /// [`Rc::from_raw`][from_raw].
+ ///
+ /// [from_raw]: Rc::from_raw
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let x = Rc::new("hello".to_owned());
+ /// let x_ptr = Rc::into_raw(x);
+ /// assert_eq!(unsafe { &*x_ptr }, "hello");
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub fn into_raw(this: Self) -> *const T {
+ let ptr = Self::as_ptr(&this);
+ mem::forget(this);
+ ptr
+ }
+
+ /// Provides a raw pointer to the data.
+ ///
+ /// The counts are not affected in any way and the `Rc` is not consumed. The pointer is valid
+ /// for as long there are strong counts in the `Rc`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let x = Rc::new("hello".to_owned());
+ /// let y = Rc::clone(&x);
+ /// let x_ptr = Rc::as_ptr(&x);
+ /// assert_eq!(x_ptr, Rc::as_ptr(&y));
+ /// assert_eq!(unsafe { &*x_ptr }, "hello");
+ /// ```
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub fn as_ptr(this: &Self) -> *const T {
+ let ptr: *mut RcBox<T> = NonNull::as_ptr(this.ptr);
+
+ // SAFETY: This cannot go through Deref::deref or Rc::inner because
+ // this is required to retain raw/mut provenance such that e.g. `get_mut` can
+ // write through the pointer after the Rc is recovered through `from_raw`.
+ unsafe { ptr::addr_of_mut!((*ptr).value) }
+ }
+
+ /// Constructs an `Rc<T>` from a raw pointer.
+ ///
+ /// The raw pointer must have been previously returned by a call to
+ /// [`Rc<U>::into_raw`][into_raw] where `U` must have the same size
+ /// and alignment as `T`. This is trivially true if `U` is `T`.
+ /// Note that if `U` is not `T` but has the same size and alignment, this is
+ /// basically like transmuting references of different types. See
+ /// [`mem::transmute`][transmute] for more information on what
+ /// restrictions apply in this case.
+ ///
+ /// The user of `from_raw` has to make sure a specific value of `T` is only
+ /// dropped once.
+ ///
+ /// This function is unsafe because improper use may lead to memory unsafety,
+ /// even if the returned `Rc<T>` is never accessed.
+ ///
+ /// [into_raw]: Rc::into_raw
+ /// [transmute]: core::mem::transmute
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let x = Rc::new("hello".to_owned());
+ /// let x_ptr = Rc::into_raw(x);
+ ///
+ /// unsafe {
+ /// // Convert back to an `Rc` to prevent leak.
+ /// let x = Rc::from_raw(x_ptr);
+ /// assert_eq!(&*x, "hello");
+ ///
+ /// // Further calls to `Rc::from_raw(x_ptr)` would be memory-unsafe.
+ /// }
+ ///
+ /// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub unsafe fn from_raw(ptr: *const T) -> Self {
+ let offset = unsafe { data_offset(ptr) };
+
+ // Reverse the offset to find the original RcBox.
+ let rc_ptr =
+ unsafe { (ptr as *mut RcBox<T>).set_ptr_value((ptr as *mut u8).offset(-offset)) };
+
+ unsafe { Self::from_ptr(rc_ptr) }
+ }
+
+ /// Creates a new [`Weak`] pointer to this allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// let weak_five = Rc::downgrade(&five);
+ /// ```
+ #[stable(feature = "rc_weak", since = "1.4.0")]
+ pub fn downgrade(this: &Self) -> Weak<T> {
+ this.inner().inc_weak();
+ // Make sure we do not create a dangling Weak
+ debug_assert!(!is_dangling(this.ptr.as_ptr()));
+ Weak { ptr: this.ptr }
+ }
+
+ /// Gets the number of [`Weak`] pointers to this allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// let _weak_five = Rc::downgrade(&five);
+ ///
+ /// assert_eq!(1, Rc::weak_count(&five));
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_counts", since = "1.15.0")]
+ pub fn weak_count(this: &Self) -> usize {
+ this.inner().weak() - 1
+ }
+
+ /// Gets the number of strong (`Rc`) pointers to this allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// let _also_five = Rc::clone(&five);
+ ///
+ /// assert_eq!(2, Rc::strong_count(&five));
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_counts", since = "1.15.0")]
+ pub fn strong_count(this: &Self) -> usize {
+ this.inner().strong()
+ }
+
+ /// Increments the strong reference count on the `Rc<T>` associated with the
+ /// provided pointer by one.
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have been obtained through `Rc::into_raw`, and the
+ /// associated `Rc` instance must be valid (i.e. the strong count must be at
+ /// least 1) for the duration of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// unsafe {
+ /// let ptr = Rc::into_raw(five);
+ /// Rc::increment_strong_count(ptr);
+ ///
+ /// let five = Rc::from_raw(ptr);
+ /// assert_eq!(2, Rc::strong_count(&five));
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_mutate_strong_count", since = "1.53.0")]
+ pub unsafe fn increment_strong_count(ptr: *const T) {
+ // Retain Rc, but don't touch refcount by wrapping in ManuallyDrop
+ let rc = unsafe { mem::ManuallyDrop::new(Rc::<T>::from_raw(ptr)) };
+ // Now increase refcount, but don't drop new refcount either
+ let _rc_clone: mem::ManuallyDrop<_> = rc.clone();
+ }
+
+ /// Decrements the strong reference count on the `Rc<T>` associated with the
+ /// provided pointer by one.
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have been obtained through `Rc::into_raw`, and the
+ /// associated `Rc` instance must be valid (i.e. the strong count must be at
+ /// least 1) when invoking this method. This method can be used to release
+ /// the final `Rc` and backing storage, but **should not** be called after
+ /// the final `Rc` has been released.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// unsafe {
+ /// let ptr = Rc::into_raw(five);
+ /// Rc::increment_strong_count(ptr);
+ ///
+ /// let five = Rc::from_raw(ptr);
+ /// assert_eq!(2, Rc::strong_count(&five));
+ /// Rc::decrement_strong_count(ptr);
+ /// assert_eq!(1, Rc::strong_count(&five));
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_mutate_strong_count", since = "1.53.0")]
+ pub unsafe fn decrement_strong_count(ptr: *const T) {
+ unsafe { mem::drop(Rc::from_raw(ptr)) };
+ }
+
+ /// Returns `true` if there are no other `Rc` or [`Weak`] pointers to
+ /// this allocation.
+ #[inline]
+ fn is_unique(this: &Self) -> bool {
+ Rc::weak_count(this) == 0 && Rc::strong_count(this) == 1
+ }
+
+ /// Returns a mutable reference into the given `Rc`, if there are
+ /// no other `Rc` or [`Weak`] pointers to the same allocation.
+ ///
+ /// Returns [`None`] otherwise, because it is not safe to
+ /// mutate a shared value.
+ ///
+ /// See also [`make_mut`][make_mut], which will [`clone`][clone]
+ /// the inner value when there are other pointers.
+ ///
+ /// [make_mut]: Rc::make_mut
+ /// [clone]: Clone::clone
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let mut x = Rc::new(3);
+ /// *Rc::get_mut(&mut x).unwrap() = 4;
+ /// assert_eq!(*x, 4);
+ ///
+ /// let _y = Rc::clone(&x);
+ /// assert!(Rc::get_mut(&mut x).is_none());
+ /// ```
+ #[inline]
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn get_mut(this: &mut Self) -> Option<&mut T> {
+ if Rc::is_unique(this) { unsafe { Some(Rc::get_mut_unchecked(this)) } } else { None }
+ }
+
+ /// Returns a mutable reference into the given `Rc`,
+ /// without any check.
+ ///
+ /// See also [`get_mut`], which is safe and does appropriate checks.
+ ///
+ /// [`get_mut`]: Rc::get_mut
+ ///
+ /// # Safety
+ ///
+ /// Any other `Rc` or [`Weak`] pointers to the same allocation must not be dereferenced
+ /// for the duration of the returned borrow.
+ /// This is trivially the case if no such pointers exist,
+ /// for example immediately after `Rc::new`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::rc::Rc;
+ ///
+ /// let mut x = Rc::new(String::new());
+ /// unsafe {
+ /// Rc::get_mut_unchecked(&mut x).push_str("foo")
+ /// }
+ /// assert_eq!(*x, "foo");
+ /// ```
+ #[inline]
+ #[unstable(feature = "get_mut_unchecked", issue = "63292")]
+ pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
+ // We are careful to *not* create a reference covering the "count" fields, as
+ // this would conflict with accesses to the reference counts (e.g. by `Weak`).
+ unsafe { &mut (*this.ptr.as_ptr()).value }
+ }
+
+ #[inline]
+ #[stable(feature = "ptr_eq", since = "1.17.0")]
+ /// Returns `true` if the two `Rc`s point to the same allocation
+ /// (in a vein similar to [`ptr::eq`]).
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// let same_five = Rc::clone(&five);
+ /// let other_five = Rc::new(5);
+ ///
+ /// assert!(Rc::ptr_eq(&five, &same_five));
+ /// assert!(!Rc::ptr_eq(&five, &other_five));
+ /// ```
+ ///
+ /// [`ptr::eq`]: core::ptr::eq
+ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+ this.ptr.as_ptr() == other.ptr.as_ptr()
+ }
+}
+
+impl<T: Clone> Rc<T> {
+ /// Makes a mutable reference into the given `Rc`.
+ ///
+ /// If there are other `Rc` pointers to the same allocation, then `make_mut` will
+ /// [`clone`] the inner value to a new allocation to ensure unique ownership. This is also
+ /// referred to as clone-on-write.
+ ///
+ /// If there are no other `Rc` pointers to this allocation, then [`Weak`]
+ /// pointers to this allocation will be disassociated.
+ ///
+ /// See also [`get_mut`], which will fail rather than cloning.
+ ///
+ /// [`clone`]: Clone::clone
+ /// [`get_mut`]: Rc::get_mut
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let mut data = Rc::new(5);
+ ///
+ /// *Rc::make_mut(&mut data) += 1; // Won't clone anything
+ /// let mut other_data = Rc::clone(&data); // Won't clone inner data
+ /// *Rc::make_mut(&mut data) += 1; // Clones inner data
+ /// *Rc::make_mut(&mut data) += 1; // Won't clone anything
+ /// *Rc::make_mut(&mut other_data) *= 2; // Won't clone anything
+ ///
+ /// // Now `data` and `other_data` point to different allocations.
+ /// assert_eq!(*data, 8);
+ /// assert_eq!(*other_data, 12);
+ /// ```
+ ///
+ /// [`Weak`] pointers will be disassociated:
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let mut data = Rc::new(75);
+ /// let weak = Rc::downgrade(&data);
+ ///
+ /// assert!(75 == *data);
+ /// assert!(75 == *weak.upgrade().unwrap());
+ ///
+ /// *Rc::make_mut(&mut data) += 1;
+ ///
+ /// assert!(76 == *data);
+ /// assert!(weak.upgrade().is_none());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn make_mut(this: &mut Self) -> &mut T {
+ if Rc::strong_count(this) != 1 {
+ // Gotta clone the data, there are other Rcs.
+ // Pre-allocate memory to allow writing the cloned value directly.
+ let mut rc = Self::new_uninit();
+ unsafe {
+ let data = Rc::get_mut_unchecked(&mut rc);
+ (**this).write_clone_into_raw(data.as_mut_ptr());
+ *this = rc.assume_init();
+ }
+ } else if Rc::weak_count(this) != 0 {
+ // Can just steal the data, all that's left is Weaks
+ let mut rc = Self::new_uninit();
+ unsafe {
+ let data = Rc::get_mut_unchecked(&mut rc);
+ data.as_mut_ptr().copy_from_nonoverlapping(&**this, 1);
+
+ this.inner().dec_strong();
+ // Remove implicit strong-weak ref (no need to craft a fake
+ // Weak here -- we know other Weaks can clean up for us)
+ this.inner().dec_weak();
+ ptr::write(this, rc.assume_init());
+ }
+ }
+ // This unsafety is ok because we're guaranteed that the pointer
+ // returned is the *only* pointer that will ever be returned to T. Our
+ // reference count is guaranteed to be 1 at this point, and we required
+ // the `Rc<T>` itself to be `mut`, so we're returning the only possible
+ // reference to the allocation.
+ unsafe { &mut this.ptr.as_mut().value }
+ }
+}
+
+impl Rc<dyn Any> {
+ #[inline]
+ #[stable(feature = "rc_downcast", since = "1.29.0")]
+ /// Attempt to downcast the `Rc<dyn Any>` to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::any::Any;
+ /// use std::rc::Rc;
+ ///
+ /// fn print_if_string(value: Rc<dyn Any>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Rc::new(my_string));
+ /// print_if_string(Rc::new(0i8));
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Rc<T>, Rc<dyn Any>> {
+ if (*self).is::<T>() {
+ let ptr = self.ptr.cast::<RcBox<T>>();
+ forget(self);
+ Ok(Rc::from_inner(ptr))
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<T: ?Sized> Rc<T> {
+ /// Allocates an `RcBox<T>` with sufficient space for
+ /// a possibly-unsized inner value where the value has the layout provided.
+ ///
+ /// The function `mem_to_rcbox` is called with the data pointer
+ /// and must return back a (potentially fat)-pointer for the `RcBox<T>`.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_layout(
+ value_layout: Layout,
+ allocate: impl FnOnce(Layout) -> Result<NonNull<[u8]>, AllocError>,
+ mem_to_rcbox: impl FnOnce(*mut u8) -> *mut RcBox<T>,
+ ) -> *mut RcBox<T> {
+ // Calculate layout using the given value layout.
+ // Previously, layout was calculated on the expression
+ // `&*(ptr as *const RcBox<T>)`, but this created a misaligned
+ // reference (see #54908).
+ let layout = Layout::new::<RcBox<()>>().extend(value_layout).unwrap().0.pad_to_align();
+ unsafe {
+ Rc::try_allocate_for_layout(value_layout, allocate, mem_to_rcbox)
+ .unwrap_or_else(|_| handle_alloc_error(layout))
+ }
+ }
+
+ /// Allocates an `RcBox<T>` with sufficient space for
+ /// a possibly-unsized inner value where the value has the layout provided,
+ /// returning an error if allocation fails.
+ ///
+ /// The function `mem_to_rcbox` is called with the data pointer
+ /// and must return back a (potentially fat)-pointer for the `RcBox<T>`.
+ #[inline]
+ unsafe fn try_allocate_for_layout(
+ value_layout: Layout,
+ allocate: impl FnOnce(Layout) -> Result<NonNull<[u8]>, AllocError>,
+ mem_to_rcbox: impl FnOnce(*mut u8) -> *mut RcBox<T>,
+ ) -> Result<*mut RcBox<T>, AllocError> {
+ // Calculate layout using the given value layout.
+ // Previously, layout was calculated on the expression
+ // `&*(ptr as *const RcBox<T>)`, but this created a misaligned
+ // reference (see #54908).
+ let layout = Layout::new::<RcBox<()>>().extend(value_layout).unwrap().0.pad_to_align();
+
+ // Allocate for the layout.
+ let ptr = allocate(layout)?;
+
+ // Initialize the RcBox
+ let inner = mem_to_rcbox(ptr.as_non_null_ptr().as_ptr());
+ unsafe {
+ debug_assert_eq!(Layout::for_value(&*inner), layout);
+
+ ptr::write(&mut (*inner).strong, Cell::new(1));
+ ptr::write(&mut (*inner).weak, Cell::new(1));
+ }
+
+ Ok(inner)
+ }
+
+ /// Allocates an `RcBox<T>` with sufficient space for an unsized inner value
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_ptr(ptr: *const T) -> *mut RcBox<T> {
+ // Allocate for the `RcBox<T>` using the given value.
+ unsafe {
+ Self::allocate_for_layout(
+ Layout::for_value(&*ptr),
+ |layout| Global.allocate(layout),
+ |mem| (ptr as *mut RcBox<T>).set_ptr_value(mem),
+ )
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ fn from_box(v: Box<T>) -> Rc<T> {
+ unsafe {
+ let (box_unique, alloc) = Box::into_unique(v);
+ let bptr = box_unique.as_ptr();
+
+ let value_size = size_of_val(&*bptr);
+ let ptr = Self::allocate_for_ptr(bptr);
+
+ // Copy value as bytes
+ ptr::copy_nonoverlapping(
+ bptr as *const T as *const u8,
+ &mut (*ptr).value as *mut _ as *mut u8,
+ value_size,
+ );
+
+ // Free the allocation without dropping its contents
+ box_free(box_unique, alloc);
+
+ Self::from_ptr(ptr)
+ }
+ }
+}
+
+impl<T> Rc<[T]> {
+ /// Allocates an `RcBox<[T]>` with the given length.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_slice(len: usize) -> *mut RcBox<[T]> {
+ unsafe {
+ Self::allocate_for_layout(
+ Layout::array::<T>(len).unwrap(),
+ |layout| Global.allocate(layout),
+ |mem| ptr::slice_from_raw_parts_mut(mem as *mut T, len) as *mut RcBox<[T]>,
+ )
+ }
+ }
+
+ /// Copy elements from slice into newly allocated Rc<\[T\]>
+ ///
+ /// Unsafe because the caller must either take ownership or bind `T: Copy`
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn copy_from_slice(v: &[T]) -> Rc<[T]> {
+ unsafe {
+ let ptr = Self::allocate_for_slice(v.len());
+ ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).value as *mut [T] as *mut T, v.len());
+ Self::from_ptr(ptr)
+ }
+ }
+
+ /// Constructs an `Rc<[T]>` from an iterator known to be of a certain size.
+ ///
+ /// Behavior is undefined should the size be wrong.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn from_iter_exact(iter: impl iter::Iterator<Item = T>, len: usize) -> Rc<[T]> {
+ // Panic guard while cloning T elements.
+ // In the event of a panic, elements that have been written
+ // into the new RcBox will be dropped, then the memory freed.
+ struct Guard<T> {
+ mem: NonNull<u8>,
+ elems: *mut T,
+ layout: Layout,
+ n_elems: usize,
+ }
+
+ impl<T> Drop for Guard<T> {
+ fn drop(&mut self) {
+ unsafe {
+ let slice = from_raw_parts_mut(self.elems, self.n_elems);
+ ptr::drop_in_place(slice);
+
+ Global.deallocate(self.mem, self.layout);
+ }
+ }
+ }
+
+ unsafe {
+ let ptr = Self::allocate_for_slice(len);
+
+ let mem = ptr as *mut _ as *mut u8;
+ let layout = Layout::for_value(&*ptr);
+
+ // Pointer to first element
+ let elems = &mut (*ptr).value as *mut [T] as *mut T;
+
+ let mut guard = Guard { mem: NonNull::new_unchecked(mem), elems, layout, n_elems: 0 };
+
+ for (i, item) in iter.enumerate() {
+ ptr::write(elems.add(i), item);
+ guard.n_elems += 1;
+ }
+
+ // All clear. Forget the guard so it doesn't free the new RcBox.
+ forget(guard);
+
+ Self::from_ptr(ptr)
+ }
+ }
+}
+
+/// Specialization trait used for `From<&[T]>`.
+trait RcFromSlice<T> {
+ fn from_slice(slice: &[T]) -> Self;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Clone> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ default fn from_slice(v: &[T]) -> Self {
+ unsafe { Self::from_iter_exact(v.iter().cloned(), v.len()) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Copy> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ fn from_slice(v: &[T]) -> Self {
+ unsafe { Rc::copy_from_slice(v) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Deref for Rc<T> {
+ type Target = T;
+
+ #[inline(always)]
+ fn deref(&self) -> &T {
+ &self.inner().value
+ }
+}
+
+#[unstable(feature = "receiver_trait", issue = "none")]
+impl<T: ?Sized> Receiver for Rc<T> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Rc<T> {
+ /// Drops the `Rc`.
+ ///
+ /// This will decrement the strong reference count. If the strong reference
+ /// count reaches zero then the only other references (if any) are
+ /// [`Weak`], so we `drop` the inner value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// struct Foo;
+ ///
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
+ /// }
+ ///
+ /// let foo = Rc::new(Foo);
+ /// let foo2 = Rc::clone(&foo);
+ ///
+ /// drop(foo); // Doesn't print anything
+ /// drop(foo2); // Prints "dropped!"
+ /// ```
+ fn drop(&mut self) {
+ unsafe {
+ self.inner().dec_strong();
+ if self.inner().strong() == 0 {
+ // destroy the contained object
+ ptr::drop_in_place(Self::get_mut_unchecked(self));
+
+ // remove the implicit "strong weak" pointer now that we've
+ // destroyed the contents.
+ self.inner().dec_weak();
+
+ if self.inner().weak() == 0 {
+ Global.deallocate(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()));
+ }
+ }
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Clone for Rc<T> {
+ /// Makes a clone of the `Rc` pointer.
+ ///
+ /// This creates another pointer to the same allocation, increasing the
+ /// strong reference count.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// let _ = Rc::clone(&five);
+ /// ```
+ #[inline]
+ fn clone(&self) -> Rc<T> {
+ self.inner().inc_strong();
+ Self::from_inner(self.ptr)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Default> Default for Rc<T> {
+ /// Creates a new `Rc<T>`, with the `Default` value for `T`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let x: Rc<i32> = Default::default();
+ /// assert_eq!(*x, 0);
+ /// ```
+ #[inline]
+ fn default() -> Rc<T> {
+ Rc::new(Default::default())
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+trait RcEqIdent<T: ?Sized + PartialEq> {
+ fn eq(&self, other: &Rc<T>) -> bool;
+ fn ne(&self, other: &Rc<T>) -> bool;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialEq> RcEqIdent<T> for Rc<T> {
+ #[inline]
+ default fn eq(&self, other: &Rc<T>) -> bool {
+ **self == **other
+ }
+
+ #[inline]
+ default fn ne(&self, other: &Rc<T>) -> bool {
+ **self != **other
+ }
+}
+
+// Hack to allow specializing on `Eq` even though `Eq` has a method.
+#[rustc_unsafe_specialization_marker]
+pub(crate) trait MarkerEq: PartialEq<Self> {}
+
+impl<T: Eq> MarkerEq for T {}
+
+/// We're doing this specialization here, and not as a more general optimization on `&T`, because it
+/// would otherwise add a cost to all equality checks on refs. We assume that `Rc`s are used to
+/// store large values, that are slow to clone, but also heavy to check for equality, causing this
+/// cost to pay off more easily. It's also more likely to have two `Rc` clones, that point to
+/// the same value, than two `&T`s.
+///
+/// We can only do this when `T: Eq` as a `PartialEq` might be deliberately irreflexive.
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + MarkerEq> RcEqIdent<T> for Rc<T> {
+ #[inline]
+ fn eq(&self, other: &Rc<T>) -> bool {
+ Rc::ptr_eq(self, other) || **self == **other
+ }
+
+ #[inline]
+ fn ne(&self, other: &Rc<T>) -> bool {
+ !Rc::ptr_eq(self, other) && **self != **other
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialEq> PartialEq for Rc<T> {
+ /// Equality for two `Rc`s.
+ ///
+ /// Two `Rc`s are equal if their inner values are equal, even if they are
+ /// stored in different allocation.
+ ///
+ /// If `T` also implements `Eq` (implying reflexivity of equality),
+ /// two `Rc`s that point to the same allocation are
+ /// always equal.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five == Rc::new(5));
+ /// ```
+ #[inline]
+ fn eq(&self, other: &Rc<T>) -> bool {
+ RcEqIdent::eq(self, other)
+ }
+
+ /// Inequality for two `Rc`s.
+ ///
+ /// Two `Rc`s are unequal if their inner values are unequal.
+ ///
+ /// If `T` also implements `Eq` (implying reflexivity of equality),
+ /// two `Rc`s that point to the same allocation are
+ /// never unequal.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five != Rc::new(6));
+ /// ```
+ #[inline]
+ fn ne(&self, other: &Rc<T>) -> bool {
+ RcEqIdent::ne(self, other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Eq> Eq for Rc<T> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialOrd> PartialOrd for Rc<T> {
+ /// Partial comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `partial_cmp()` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ /// use std::cmp::Ordering;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert_eq!(Some(Ordering::Less), five.partial_cmp(&Rc::new(6)));
+ /// ```
+ #[inline(always)]
+ fn partial_cmp(&self, other: &Rc<T>) -> Option<Ordering> {
+ (**self).partial_cmp(&**other)
+ }
+
+ /// Less-than comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `<` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five < Rc::new(6));
+ /// ```
+ #[inline(always)]
+ fn lt(&self, other: &Rc<T>) -> bool {
+ **self < **other
+ }
+
+ /// 'Less than or equal to' comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `<=` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five <= Rc::new(5));
+ /// ```
+ #[inline(always)]
+ fn le(&self, other: &Rc<T>) -> bool {
+ **self <= **other
+ }
+
+ /// Greater-than comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `>` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five > Rc::new(4));
+ /// ```
+ #[inline(always)]
+ fn gt(&self, other: &Rc<T>) -> bool {
+ **self > **other
+ }
+
+ /// 'Greater than or equal to' comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `>=` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert!(five >= Rc::new(5));
+ /// ```
+ #[inline(always)]
+ fn ge(&self, other: &Rc<T>) -> bool {
+ **self >= **other
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Ord> Ord for Rc<T> {
+ /// Comparison for two `Rc`s.
+ ///
+ /// The two are compared by calling `cmp()` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ /// use std::cmp::Ordering;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// assert_eq!(Ordering::Less, five.cmp(&Rc::new(6)));
+ /// ```
+ #[inline]
+ fn cmp(&self, other: &Rc<T>) -> Ordering {
+ (**self).cmp(&**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Hash> Hash for Rc<T> {
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ (**self).hash(state);
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + fmt::Display> fmt::Display for Rc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Rc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> fmt::Pointer for Rc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&(&**self as *const T), f)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_for_ptrs", since = "1.6.0")]
+impl<T> From<T> for Rc<T> {
+ /// Converts a generic type `T` into a `Rc<T>`
+ ///
+ /// The conversion allocates on the heap and moves `t`
+ /// from the stack into it.
+ ///
+ /// # Example
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// let x = 5;
+ /// let rc = Rc::new(5);
+ ///
+ /// assert_eq!(Rc::from(x), rc);
+ /// ```
+ fn from(t: T) -> Self {
+ Rc::new(t)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: Clone> From<&[T]> for Rc<[T]> {
+ /// Allocate a reference-counted slice and fill it by cloning `v`'s items.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::rc::Rc;
+ /// let original: &[i32] = &[1, 2, 3];
+ /// let shared: Rc<[i32]> = Rc::from(original);
+ /// assert_eq!(&[1, 2, 3], &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: &[T]) -> Rc<[T]> {
+ <Self as RcFromSlice<T>>::from_slice(v)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<&str> for Rc<str> {
+ /// Allocate a reference-counted string slice and copy `v` into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::rc::Rc;
+ /// let shared: Rc<str> = Rc::from("statue");
+ /// assert_eq!("statue", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: &str) -> Rc<str> {
+ let rc = Rc::<[u8]>::from(v.as_bytes());
+ unsafe { Rc::from_raw(Rc::into_raw(rc) as *const str) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<String> for Rc<str> {
+ /// Allocate a reference-counted string slice and copy `v` into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::rc::Rc;
+ /// let original: String = "statue".to_owned();
+ /// let shared: Rc<str> = Rc::from(original);
+ /// assert_eq!("statue", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: String) -> Rc<str> {
+ Rc::from(&v[..])
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: ?Sized> From<Box<T>> for Rc<T> {
+ /// Move a boxed object to a new, reference counted, allocation.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::rc::Rc;
+ /// let original: Box<i32> = Box::new(1);
+ /// let shared: Rc<i32> = Rc::from(original);
+ /// assert_eq!(1, *shared);
+ /// ```
+ #[inline]
+ fn from(v: Box<T>) -> Rc<T> {
+ Rc::from_box(v)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T> From<Vec<T>> for Rc<[T]> {
+ /// Allocate a reference-counted slice and move `v`'s items into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::rc::Rc;
+ /// let original: Box<Vec<i32>> = Box::new(vec![1, 2, 3]);
+ /// let shared: Rc<Vec<i32>> = Rc::from(original);
+ /// assert_eq!(vec![1, 2, 3], *shared);
+ /// ```
+ #[inline]
+ fn from(mut v: Vec<T>) -> Rc<[T]> {
+ unsafe {
+ let rc = Rc::copy_from_slice(&v);
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ rc
+ }
+ }
+}
+
+#[stable(feature = "shared_from_cow", since = "1.45.0")]
+impl<'a, B> From<Cow<'a, B>> for Rc<B>
+where
+ B: ToOwned + ?Sized,
+ Rc<B>: From<&'a B> + From<B::Owned>,
+{
+ /// Create a reference-counted pointer from
+ /// a clone-on-write pointer by copying its content.
+ ///
+ /// # Example
+ ///
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// # use std::borrow::Cow;
+ /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+ /// let shared: Rc<str> = Rc::from(cow);
+ /// assert_eq!("eggplant", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(cow: Cow<'a, B>) -> Rc<B> {
+ match cow {
+ Cow::Borrowed(s) => Rc::from(s),
+ Cow::Owned(s) => Rc::from(s),
+ }
+ }
+}
+
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
+impl<T, const N: usize> TryFrom<Rc<[T]>> for Rc<[T; N]> {
+ type Error = Rc<[T]>;
+
+ fn try_from(boxed_slice: Rc<[T]>) -> Result<Self, Self::Error> {
+ if boxed_slice.len() == N {
+ Ok(unsafe { Rc::from_raw(Rc::into_raw(boxed_slice) as *mut [T; N]) })
+ } else {
+ Err(boxed_slice)
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_iter", since = "1.37.0")]
+impl<T> iter::FromIterator<T> for Rc<[T]> {
+ /// Takes each element in the `Iterator` and collects it into an `Rc<[T]>`.
+ ///
+ /// # Performance characteristics
+ ///
+ /// ## The general case
+ ///
+ /// In the general case, collecting into `Rc<[T]>` is done by first
+ /// collecting into a `Vec<T>`. That is, when writing the following:
+ ///
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// let evens: Rc<[u8]> = (0..10).filter(|&x| x % 2 == 0).collect();
+ /// # assert_eq!(&*evens, &[0, 2, 4, 6, 8]);
+ /// ```
+ ///
+ /// this behaves as if we wrote:
+ ///
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// let evens: Rc<[u8]> = (0..10).filter(|&x| x % 2 == 0)
+ /// .collect::<Vec<_>>() // The first set of allocations happens here.
+ /// .into(); // A second allocation for `Rc<[T]>` happens here.
+ /// # assert_eq!(&*evens, &[0, 2, 4, 6, 8]);
+ /// ```
+ ///
+ /// This will allocate as many times as needed for constructing the `Vec<T>`
+ /// and then it will allocate once for turning the `Vec<T>` into the `Rc<[T]>`.
+ ///
+ /// ## Iterators of known length
+ ///
+ /// When your `Iterator` implements `TrustedLen` and is of an exact size,
+ /// a single allocation will be made for the `Rc<[T]>`. For example:
+ ///
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// let evens: Rc<[u8]> = (0..10).collect(); // Just a single allocation happens here.
+ /// # assert_eq!(&*evens, &*(0..10).collect::<Vec<_>>());
+ /// ```
+ fn from_iter<I: iter::IntoIterator<Item = T>>(iter: I) -> Self {
+ ToRcSlice::to_rc_slice(iter.into_iter())
+ }
+}
+
+/// Specialization trait used for collecting into `Rc<[T]>`.
+#[cfg(not(no_global_oom_handling))]
+trait ToRcSlice<T>: Iterator<Item = T> + Sized {
+ fn to_rc_slice(self) -> Rc<[T]>;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I: Iterator<Item = T>> ToRcSlice<T> for I {
+ default fn to_rc_slice(self) -> Rc<[T]> {
+ self.collect::<Vec<T>>().into()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I: iter::TrustedLen<Item = T>> ToRcSlice<T> for I {
+ fn to_rc_slice(self) -> Rc<[T]> {
+ // This is the case for a `TrustedLen` iterator.
+ let (low, high) = self.size_hint();
+ if let Some(high) = high {
+ debug_assert_eq!(
+ low,
+ high,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+
+ unsafe {
+ // SAFETY: We need to ensure that the iterator has an exact length and we have.
+ Rc::from_iter_exact(self, low)
+ }
+ } else {
+ // TrustedLen contract guarantees that `upper_bound == `None` implies an iterator
+ // length exceeding `usize::MAX`.
+ // The default implementation would collect into a vec which would panic.
+ // Thus we panic here immediately without invoking `Vec` code.
+ panic!("capacity overflow");
+ }
+ }
+}
+
+/// `Weak` is a version of [`Rc`] that holds a non-owning reference to the
+/// managed allocation. The allocation is accessed by calling [`upgrade`] on the `Weak`
+/// pointer, which returns an [`Option`]`<`[`Rc`]`<T>>`.
+///
+/// Since a `Weak` reference does not count towards ownership, it will not
+/// prevent the value stored in the allocation from being dropped, and `Weak` itself makes no
+/// guarantees about the value still being present. Thus it may return [`None`]
+/// when [`upgrade`]d. Note however that a `Weak` reference *does* prevent the allocation
+/// itself (the backing store) from being deallocated.
+///
+/// A `Weak` pointer is useful for keeping a temporary reference to the allocation
+/// managed by [`Rc`] without preventing its inner value from being dropped. It is also used to
+/// prevent circular references between [`Rc`] pointers, since mutual owning references
+/// would never allow either [`Rc`] to be dropped. For example, a tree could
+/// have strong [`Rc`] pointers from parent nodes to children, and `Weak`
+/// pointers from children back to their parents.
+///
+/// The typical way to obtain a `Weak` pointer is to call [`Rc::downgrade`].
+///
+/// [`upgrade`]: Weak::upgrade
+#[stable(feature = "rc_weak", since = "1.4.0")]
+pub struct Weak<T: ?Sized> {
+ // This is a `NonNull` to allow optimizing the size of this type in enums,
+ // but it is not necessarily a valid pointer.
+ // `Weak::new` sets this to `usize::MAX` so that it doesn’t need
+ // to allocate space on the heap. That's not a value a real pointer
+ // will ever have because RcBox has alignment at least 2.
+ // This is only possible when `T: Sized`; unsized `T` never dangle.
+ ptr: NonNull<RcBox<T>>,
+}
+
+#[stable(feature = "rc_weak", since = "1.4.0")]
+impl<T: ?Sized> !marker::Send for Weak<T> {}
+#[stable(feature = "rc_weak", since = "1.4.0")]
+impl<T: ?Sized> !marker::Sync for Weak<T> {}
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Weak<U>> for Weak<T> {}
+
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Weak<U>> for Weak<T> {}
+
+impl<T> Weak<T> {
+ /// Constructs a new `Weak<T>`, without allocating any memory.
+ /// Calling [`upgrade`] on the return value always gives [`None`].
+ ///
+ /// [`upgrade`]: Weak::upgrade
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Weak;
+ ///
+ /// let empty: Weak<i64> = Weak::new();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ #[stable(feature = "downgraded_weak", since = "1.10.0")]
+ pub fn new() -> Weak<T> {
+ Weak { ptr: NonNull::new(usize::MAX as *mut RcBox<T>).expect("MAX is not 0") }
+ }
+}
+
+pub(crate) fn is_dangling<T: ?Sized>(ptr: *mut T) -> bool {
+ let address = ptr as *mut () as usize;
+ address == usize::MAX
+}
+
+/// Helper type to allow accessing the reference counts without
+/// making any assertions about the data field.
+struct WeakInner<'a> {
+ weak: &'a Cell<usize>,
+ strong: &'a Cell<usize>,
+}
+
+impl<T: ?Sized> Weak<T> {
+ /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
+ ///
+ /// The pointer is valid only if there are some strong references. The pointer may be dangling,
+ /// unaligned or even [`null`] otherwise.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ /// use std::ptr;
+ ///
+ /// let strong = Rc::new("hello".to_owned());
+ /// let weak = Rc::downgrade(&strong);
+ /// // Both point to the same object
+ /// assert!(ptr::eq(&*strong, weak.as_ptr()));
+ /// // The strong here keeps it alive, so we can still access the object.
+ /// assert_eq!("hello", unsafe { &*weak.as_ptr() });
+ ///
+ /// drop(strong);
+ /// // But not any more. We can do weak.as_ptr(), but accessing the pointer would lead to
+ /// // undefined behaviour.
+ /// // assert_eq!("hello", unsafe { &*weak.as_ptr() });
+ /// ```
+ ///
+ /// [`null`]: core::ptr::null
+ #[stable(feature = "rc_as_ptr", since = "1.45.0")]
+ pub fn as_ptr(&self) -> *const T {
+ let ptr: *mut RcBox<T> = NonNull::as_ptr(self.ptr);
+
+ if is_dangling(ptr) {
+ // If the pointer is dangling, we return the sentinel directly. This cannot be
+ // a valid payload address, as the payload is at least as aligned as RcBox (usize).
+ ptr as *const T
+ } else {
+ // SAFETY: if is_dangling returns false, then the pointer is dereferencable.
+ // The payload may be dropped at this point, and we have to maintain provenance,
+ // so use raw pointer manipulation.
+ unsafe { ptr::addr_of_mut!((*ptr).value) }
+ }
+ }
+
+ /// Consumes the `Weak<T>` and turns it into a raw pointer.
+ ///
+ /// This converts the weak pointer into a raw pointer, while still preserving the ownership of
+ /// one weak reference (the weak count is not modified by this operation). It can be turned
+ /// back into the `Weak<T>` with [`from_raw`].
+ ///
+ /// The same restrictions of accessing the target of the pointer as with
+ /// [`as_ptr`] apply.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// let strong = Rc::new("hello".to_owned());
+ /// let weak = Rc::downgrade(&strong);
+ /// let raw = weak.into_raw();
+ ///
+ /// assert_eq!(1, Rc::weak_count(&strong));
+ /// assert_eq!("hello", unsafe { &*raw });
+ ///
+ /// drop(unsafe { Weak::from_raw(raw) });
+ /// assert_eq!(0, Rc::weak_count(&strong));
+ /// ```
+ ///
+ /// [`from_raw`]: Weak::from_raw
+ /// [`as_ptr`]: Weak::as_ptr
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub fn into_raw(self) -> *const T {
+ let result = self.as_ptr();
+ mem::forget(self);
+ result
+ }
+
+ /// Converts a raw pointer previously created by [`into_raw`] back into `Weak<T>`.
+ ///
+ /// This can be used to safely get a strong reference (by calling [`upgrade`]
+ /// later) or to deallocate the weak count by dropping the `Weak<T>`.
+ ///
+ /// It takes ownership of one weak reference (with the exception of pointers created by [`new`],
+ /// as these don't own anything; the method still works on them).
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have originated from the [`into_raw`] and must still own its potential
+ /// weak reference.
+ ///
+ /// It is allowed for the strong count to be 0 at the time of calling this. Nevertheless, this
+ /// takes ownership of one weak reference currently represented as a raw pointer (the weak
+ /// count is not modified by this operation) and therefore it must be paired with a previous
+ /// call to [`into_raw`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// let strong = Rc::new("hello".to_owned());
+ ///
+ /// let raw_1 = Rc::downgrade(&strong).into_raw();
+ /// let raw_2 = Rc::downgrade(&strong).into_raw();
+ ///
+ /// assert_eq!(2, Rc::weak_count(&strong));
+ ///
+ /// assert_eq!("hello", &*unsafe { Weak::from_raw(raw_1) }.upgrade().unwrap());
+ /// assert_eq!(1, Rc::weak_count(&strong));
+ ///
+ /// drop(strong);
+ ///
+ /// // Decrement the last weak count.
+ /// assert!(unsafe { Weak::from_raw(raw_2) }.upgrade().is_none());
+ /// ```
+ ///
+ /// [`into_raw`]: Weak::into_raw
+ /// [`upgrade`]: Weak::upgrade
+ /// [`new`]: Weak::new
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub unsafe fn from_raw(ptr: *const T) -> Self {
+ // See Weak::as_ptr for context on how the input pointer is derived.
+
+ let ptr = if is_dangling(ptr as *mut T) {
+ // This is a dangling Weak.
+ ptr as *mut RcBox<T>
+ } else {
+ // Otherwise, we're guaranteed the pointer came from a nondangling Weak.
+ // SAFETY: data_offset is safe to call, as ptr references a real (potentially dropped) T.
+ let offset = unsafe { data_offset(ptr) };
+ // Thus, we reverse the offset to get the whole RcBox.
+ // SAFETY: the pointer originated from a Weak, so this offset is safe.
+ unsafe { (ptr as *mut RcBox<T>).set_ptr_value((ptr as *mut u8).offset(-offset)) }
+ };
+
+ // SAFETY: we now have recovered the original Weak pointer, so can create the Weak.
+ Weak { ptr: unsafe { NonNull::new_unchecked(ptr) } }
+ }
+
+ /// Attempts to upgrade the `Weak` pointer to an [`Rc`], delaying
+ /// dropping of the inner value if successful.
+ ///
+ /// Returns [`None`] if the inner value has since been dropped.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// let weak_five = Rc::downgrade(&five);
+ ///
+ /// let strong_five: Option<Rc<_>> = weak_five.upgrade();
+ /// assert!(strong_five.is_some());
+ ///
+ /// // Destroy all strong pointers.
+ /// drop(strong_five);
+ /// drop(five);
+ ///
+ /// assert!(weak_five.upgrade().is_none());
+ /// ```
+ #[stable(feature = "rc_weak", since = "1.4.0")]
+ pub fn upgrade(&self) -> Option<Rc<T>> {
+ let inner = self.inner()?;
+ if inner.strong() == 0 {
+ None
+ } else {
+ inner.inc_strong();
+ Some(Rc::from_inner(self.ptr))
+ }
+ }
+
+ /// Gets the number of strong (`Rc`) pointers pointing to this allocation.
+ ///
+ /// If `self` was created using [`Weak::new`], this will return 0.
+ #[stable(feature = "weak_counts", since = "1.41.0")]
+ pub fn strong_count(&self) -> usize {
+ if let Some(inner) = self.inner() { inner.strong() } else { 0 }
+ }
+
+ /// Gets the number of `Weak` pointers pointing to this allocation.
+ ///
+ /// If no strong pointers remain, this will return zero.
+ #[stable(feature = "weak_counts", since = "1.41.0")]
+ pub fn weak_count(&self) -> usize {
+ self.inner()
+ .map(|inner| {
+ if inner.strong() > 0 {
+ inner.weak() - 1 // subtract the implicit weak ptr
+ } else {
+ 0
+ }
+ })
+ .unwrap_or(0)
+ }
+
+ /// Returns `None` when the pointer is dangling and there is no allocated `RcBox`,
+ /// (i.e., when this `Weak` was created by `Weak::new`).
+ #[inline]
+ fn inner(&self) -> Option<WeakInner<'_>> {
+ if is_dangling(self.ptr.as_ptr()) {
+ None
+ } else {
+ // We are careful to *not* create a reference covering the "data" field, as
+ // the field may be mutated concurrently (for example, if the last `Rc`
+ // is dropped, the data field will be dropped in-place).
+ Some(unsafe {
+ let ptr = self.ptr.as_ptr();
+ WeakInner { strong: &(*ptr).strong, weak: &(*ptr).weak }
+ })
+ }
+ }
+
+ /// Returns `true` if the two `Weak`s point to the same allocation (similar to
+ /// [`ptr::eq`]), or if both don't point to any allocation
+ /// (because they were created with `Weak::new()`).
+ ///
+ /// # Notes
+ ///
+ /// Since this compares pointers it means that `Weak::new()` will equal each
+ /// other, even though they don't point to any allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let first_rc = Rc::new(5);
+ /// let first = Rc::downgrade(&first_rc);
+ /// let second = Rc::downgrade(&first_rc);
+ ///
+ /// assert!(first.ptr_eq(&second));
+ ///
+ /// let third_rc = Rc::new(5);
+ /// let third = Rc::downgrade(&third_rc);
+ ///
+ /// assert!(!first.ptr_eq(&third));
+ /// ```
+ ///
+ /// Comparing `Weak::new`.
+ ///
+ /// ```
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// let first = Weak::new();
+ /// let second = Weak::new();
+ /// assert!(first.ptr_eq(&second));
+ ///
+ /// let third_rc = Rc::new(());
+ /// let third = Rc::downgrade(&third_rc);
+ /// assert!(!first.ptr_eq(&third));
+ /// ```
+ ///
+ /// [`ptr::eq`]: core::ptr::eq
+ #[inline]
+ #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
+ pub fn ptr_eq(&self, other: &Self) -> bool {
+ self.ptr.as_ptr() == other.ptr.as_ptr()
+ }
+}
+
+#[stable(feature = "rc_weak", since = "1.4.0")]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
+ /// Drops the `Weak` pointer.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// struct Foo;
+ ///
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
+ /// }
+ ///
+ /// let foo = Rc::new(Foo);
+ /// let weak_foo = Rc::downgrade(&foo);
+ /// let other_weak_foo = Weak::clone(&weak_foo);
+ ///
+ /// drop(weak_foo); // Doesn't print anything
+ /// drop(foo); // Prints "dropped!"
+ ///
+ /// assert!(other_weak_foo.upgrade().is_none());
+ /// ```
+ fn drop(&mut self) {
+ let inner = if let Some(inner) = self.inner() { inner } else { return };
+
+ inner.dec_weak();
+ // the weak count starts at 1, and will only go to zero if all
+ // the strong pointers have disappeared.
+ if inner.weak() == 0 {
+ unsafe {
+ Global.deallocate(self.ptr.cast(), Layout::for_value_raw(self.ptr.as_ptr()));
+ }
+ }
+ }
+}
+
+#[stable(feature = "rc_weak", since = "1.4.0")]
+impl<T: ?Sized> Clone for Weak<T> {
+ /// Makes a clone of the `Weak` pointer that points to the same allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::{Rc, Weak};
+ ///
+ /// let weak_five = Rc::downgrade(&Rc::new(5));
+ ///
+ /// let _ = Weak::clone(&weak_five);
+ /// ```
+ #[inline]
+ fn clone(&self) -> Weak<T> {
+ if let Some(inner) = self.inner() {
+ inner.inc_weak()
+ }
+ Weak { ptr: self.ptr }
+ }
+}
+
+#[stable(feature = "rc_weak", since = "1.4.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "(Weak)")
+ }
+}
+
+#[stable(feature = "downgraded_weak", since = "1.10.0")]
+impl<T> Default for Weak<T> {
+ /// Constructs a new `Weak<T>`, without allocating any memory.
+ /// Calling [`upgrade`] on the return value always gives [`None`].
+ ///
+ /// [`None`]: Option
+ /// [`upgrade`]: Weak::upgrade
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Weak;
+ ///
+ /// let empty: Weak<i64> = Default::default();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ fn default() -> Weak<T> {
+ Weak::new()
+ }
+}
+
+// NOTE: We checked_add here to deal with mem::forget safely. In particular
+// if you mem::forget Rcs (or Weaks), the ref-count can overflow, and then
+// you can free the allocation while outstanding Rcs (or Weaks) exist.
+// We abort because this is such a degenerate scenario that we don't care about
+// what happens -- no real program should ever experience this.
+//
+// This should have negligible overhead since you don't actually need to
+// clone these much in Rust thanks to ownership and move-semantics.
+
+#[doc(hidden)]
+trait RcInnerPtr {
+ fn weak_ref(&self) -> &Cell<usize>;
+ fn strong_ref(&self) -> &Cell<usize>;
+
+ #[inline]
+ fn strong(&self) -> usize {
+ self.strong_ref().get()
+ }
+
+ #[inline]
+ fn inc_strong(&self) {
+ let strong = self.strong();
+
+ // We want to abort on overflow instead of dropping the value.
+ // The reference count will never be zero when this is called;
+ // nevertheless, we insert an abort here to hint LLVM at
+ // an otherwise missed optimization.
+ if strong == 0 || strong == usize::MAX {
+ abort();
+ }
+ self.strong_ref().set(strong + 1);
+ }
+
+ #[inline]
+ fn dec_strong(&self) {
+ self.strong_ref().set(self.strong() - 1);
+ }
+
+ #[inline]
+ fn weak(&self) -> usize {
+ self.weak_ref().get()
+ }
+
+ #[inline]
+ fn inc_weak(&self) {
+ let weak = self.weak();
+
+ // We want to abort on overflow instead of dropping the value.
+ // The reference count will never be zero when this is called;
+ // nevertheless, we insert an abort here to hint LLVM at
+ // an otherwise missed optimization.
+ if weak == 0 || weak == usize::MAX {
+ abort();
+ }
+ self.weak_ref().set(weak + 1);
+ }
+
+ #[inline]
+ fn dec_weak(&self) {
+ self.weak_ref().set(self.weak() - 1);
+ }
+}
+
+impl<T: ?Sized> RcInnerPtr for RcBox<T> {
+ #[inline(always)]
+ fn weak_ref(&self) -> &Cell<usize> {
+ &self.weak
+ }
+
+ #[inline(always)]
+ fn strong_ref(&self) -> &Cell<usize> {
+ &self.strong
+ }
+}
+
+impl<'a> RcInnerPtr for WeakInner<'a> {
+ #[inline(always)]
+ fn weak_ref(&self) -> &Cell<usize> {
+ self.weak
+ }
+
+ #[inline(always)]
+ fn strong_ref(&self) -> &Cell<usize> {
+ self.strong
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> borrow::Borrow<T> for Rc<T> {
+ fn borrow(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
+impl<T: ?Sized> AsRef<T> for Rc<T> {
+ fn as_ref(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(feature = "pin", since = "1.33.0")]
+impl<T: ?Sized> Unpin for Rc<T> {}
+
+/// Get the offset within an `RcBox` for the payload behind a pointer.
+///
+/// # Safety
+///
+/// The pointer must point to (and have valid metadata for) a previously
+/// valid instance of T, but the T is allowed to be dropped.
+unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> isize {
+ // Align the unsized value to the end of the RcBox.
+ // Because RcBox is repr(C), it will always be the last field in memory.
+ // SAFETY: since the only unsized types possible are slices, trait objects,
+ // and extern types, the input safety requirement is currently enough to
+ // satisfy the requirements of align_of_val_raw; this is an implementation
+ // detail of the language that may not be relied upon outside of std.
+ unsafe { data_offset_align(align_of_val_raw(ptr)) }
+}
+
+#[inline]
+fn data_offset_align(align: usize) -> isize {
+ let layout = Layout::new::<RcBox<()>>();
+ (layout.size() + layout.padding_needed_for(align)) as isize
+}
diff --git a/rust/alloc/slice.rs b/rust/alloc/slice.rs
new file mode 100644
index 00000000000..455d1be60c1
--- /dev/null
+++ b/rust/alloc/slice.rs
@@ -0,0 +1,1271 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A dynamically-sized view into a contiguous sequence, `[T]`.
+//!
+//! *[See also the slice primitive type](slice).*
+//!
+//! Slices are a view into a block of memory represented as a pointer and a
+//! length.
+//!
+//! ```
+//! // slicing a Vec
+//! let vec = vec![1, 2, 3];
+//! let int_slice = &vec[..];
+//! // coercing an array to a slice
+//! let str_slice: &[&str] = &["one", "two", "three"];
+//! ```
+//!
+//! Slices are either mutable or shared. The shared slice type is `&[T]`,
+//! while the mutable slice type is `&mut [T]`, where `T` represents the element
+//! type. For example, you can mutate the block of memory that a mutable slice
+//! points to:
+//!
+//! ```
+//! let x = &mut [1, 2, 3];
+//! x[1] = 7;
+//! assert_eq!(x, &[1, 7, 3]);
+//! ```
+//!
+//! Here are some of the things this module contains:
+//!
+//! ## Structs
+//!
+//! There are several structs that are useful for slices, such as [`Iter`], which
+//! represents iteration over a slice.
+//!
+//! ## Trait Implementations
+//!
+//! There are several implementations of common traits for slices. Some examples
+//! include:
+//!
+//! * [`Clone`]
+//! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].
+//! * [`Hash`] - for slices whose element type is [`Hash`].
+//!
+//! ## Iteration
+//!
+//! The slices implement `IntoIterator`. The iterator yields references to the
+//! slice elements.
+//!
+//! ```
+//! let numbers = &[0, 1, 2];
+//! for n in numbers {
+//! println!("{} is a number!", n);
+//! }
+//! ```
+//!
+//! The mutable slice yields mutable references to the elements:
+//!
+//! ```
+//! let mut scores = [7, 8, 9];
+//! for score in &mut scores[..] {
+//! *score += 1;
+//! }
+//! ```
+//!
+//! This iterator yields mutable references to the slice's elements, so while
+//! the element type of the slice is `i32`, the element type of the iterator is
+//! `&mut i32`.
+//!
+//! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
+//! iterators.
+//! * Further methods that return iterators are [`.split`], [`.splitn`],
+//! [`.chunks`], [`.windows`] and more.
+//!
+//! [`Hash`]: core::hash::Hash
+//! [`.iter`]: slice::iter
+//! [`.iter_mut`]: slice::iter_mut
+//! [`.split`]: slice::split
+//! [`.splitn`]: slice::splitn
+//! [`.chunks`]: slice::chunks
+//! [`.windows`]: slice::windows
+#![stable(feature = "rust1", since = "1.0.0")]
+// Many of the usings in this module are only used in the test configuration.
+// It's cleaner to just turn off the unused_imports warning than to fix them.
+#![cfg_attr(test, allow(unused_imports, dead_code))]
+
+use core::borrow::{Borrow, BorrowMut};
+#[cfg(not(no_global_oom_handling))]
+use core::cmp::Ordering::{self, Less};
+#[cfg(not(no_global_oom_handling))]
+use core::mem;
+#[cfg(not(no_global_oom_handling))]
+use core::mem::size_of;
+#[cfg(not(no_global_oom_handling))]
+use core::ptr;
+
+use crate::alloc::Allocator;
+use crate::alloc::Global;
+#[cfg(not(no_global_oom_handling))]
+use crate::borrow::ToOwned;
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::vec::Vec;
+
+#[unstable(feature = "slice_range", issue = "76393")]
+pub use core::slice::range;
+#[unstable(feature = "array_chunks", issue = "74985")]
+pub use core::slice::ArrayChunks;
+#[unstable(feature = "array_chunks", issue = "74985")]
+pub use core::slice::ArrayChunksMut;
+#[unstable(feature = "array_windows", issue = "75027")]
+pub use core::slice::ArrayWindows;
+#[stable(feature = "slice_get_slice", since = "1.28.0")]
+pub use core::slice::SliceIndex;
+#[stable(feature = "from_ref", since = "1.28.0")]
+pub use core::slice::{from_mut, from_ref};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::slice::{from_raw_parts, from_raw_parts_mut};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::slice::{Chunks, Windows};
+#[stable(feature = "chunks_exact", since = "1.31.0")]
+pub use core::slice::{ChunksExact, ChunksExactMut};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::slice::{ChunksMut, Split, SplitMut};
+#[unstable(feature = "slice_group_by", issue = "80552")]
+pub use core::slice::{GroupBy, GroupByMut};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::slice::{Iter, IterMut};
+#[stable(feature = "rchunks", since = "1.31.0")]
+pub use core::slice::{RChunks, RChunksExact, RChunksExactMut, RChunksMut};
+#[stable(feature = "slice_rsplit", since = "1.27.0")]
+pub use core::slice::{RSplit, RSplitMut};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::slice::{RSplitN, RSplitNMut, SplitN, SplitNMut};
+
+////////////////////////////////////////////////////////////////////////////////
+// Basic slice extension methods
+////////////////////////////////////////////////////////////////////////////////
+
+// HACK(japaric) needed for the implementation of `vec!` macro during testing
+// N.B., see the `hack` module in this file for more details.
+#[cfg(test)]
+pub use hack::into_vec;
+
+// HACK(japaric) needed for the implementation of `Vec::clone` during testing
+// N.B., see the `hack` module in this file for more details.
+#[cfg(test)]
+pub use hack::to_vec;
+
+// HACK(japaric): With cfg(test) `impl [T]` is not available, these three
+// functions are actually methods that are in `impl [T]` but not in
+// `core::slice::SliceExt` - we need to supply these functions for the
+// `test_permutations` test
+mod hack {
+ use core::alloc::Allocator;
+
+ use crate::boxed::Box;
+ use crate::collections::TryReserveError;
+ use crate::vec::Vec;
+
+ // We shouldn't add inline attribute to this since this is used in
+ // `vec!` macro mostly and causes perf regression. See #71204 for
+ // discussion and perf results.
+ pub fn into_vec<T, A: Allocator>(b: Box<[T], A>) -> Vec<T, A> {
+ unsafe {
+ let len = b.len();
+ let (b, alloc) = Box::into_raw_with_allocator(b);
+ Vec::from_raw_parts_in(b as *mut T, len, len, alloc)
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub fn to_vec<T: ConvertVec, A: Allocator>(s: &[T], alloc: A) -> Vec<T, A> {
+ T::to_vec(s, alloc)
+ }
+
+ #[inline]
+ pub fn try_to_vec<T: TryConvertVec, A: Allocator>(s: &[T], alloc: A) -> Result<Vec<T, A>, TryReserveError> {
+ T::try_to_vec(s, alloc)
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ pub trait ConvertVec {
+ fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A>
+ where
+ Self: Sized;
+ }
+
+ pub trait TryConvertVec {
+ fn try_to_vec<A: Allocator>(s: &[Self], alloc: A) -> Result<Vec<Self, A>, TryReserveError>
+ where
+ Self: Sized;
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ impl<T: Clone> ConvertVec for T {
+ #[inline]
+ default fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> {
+ struct DropGuard<'a, T, A: Allocator> {
+ vec: &'a mut Vec<T, A>,
+ num_init: usize,
+ }
+ impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> {
+ #[inline]
+ fn drop(&mut self) {
+ // SAFETY:
+ // items were marked initialized in the loop below
+ unsafe {
+ self.vec.set_len(self.num_init);
+ }
+ }
+ }
+ let mut vec = Vec::with_capacity_in(s.len(), alloc);
+ let mut guard = DropGuard { vec: &mut vec, num_init: 0 };
+ let slots = guard.vec.spare_capacity_mut();
+ // .take(slots.len()) is necessary for LLVM to remove bounds checks
+ // and has better codegen than zip.
+ for (i, b) in s.iter().enumerate().take(slots.len()) {
+ guard.num_init = i;
+ slots[i].write(b.clone());
+ }
+ core::mem::forget(guard);
+ // SAFETY:
+ // the vec was allocated and initialized above to at least this length.
+ unsafe {
+ vec.set_len(s.len());
+ }
+ vec
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ impl<T: Copy> ConvertVec for T {
+ #[inline]
+ fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> {
+ let mut v = Vec::with_capacity_in(s.len(), alloc);
+ // SAFETY:
+ // allocated above with the capacity of `s`, and initialize to `s.len()` in
+ // ptr::copy_to_non_overlapping below.
+ unsafe {
+ s.as_ptr().copy_to_nonoverlapping(v.as_mut_ptr(), s.len());
+ v.set_len(s.len());
+ }
+ v
+ }
+ }
+
+ impl<T: Clone> TryConvertVec for T {
+ #[inline]
+ default fn try_to_vec<A: Allocator>(s: &[Self], alloc: A) -> Result<Vec<Self, A>, TryReserveError> {
+ struct DropGuard<'a, T, A: Allocator> {
+ vec: &'a mut Vec<T, A>,
+ num_init: usize,
+ }
+ impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> {
+ #[inline]
+ fn drop(&mut self) {
+ // SAFETY:
+ // items were marked initialized in the loop below
+ unsafe {
+ self.vec.set_len(self.num_init);
+ }
+ }
+ }
+ let mut vec = Vec::try_with_capacity_in(s.len(), alloc)?;
+ let mut guard = DropGuard { vec: &mut vec, num_init: 0 };
+ let slots = guard.vec.spare_capacity_mut();
+ // .take(slots.len()) is necessary for LLVM to remove bounds checks
+ // and has better codegen than zip.
+ for (i, b) in s.iter().enumerate().take(slots.len()) {
+ guard.num_init = i;
+ slots[i].write(b.clone());
+ }
+ core::mem::forget(guard);
+ // SAFETY:
+ // the vec was allocated and initialized above to at least this length.
+ unsafe {
+ vec.set_len(s.len());
+ }
+ Ok(vec)
+ }
+ }
+}
+
+#[lang = "slice_alloc"]
+#[cfg(not(test))]
+impl<T> [T] {
+ /// Sorts the slice.
+ ///
+ /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*)) worst-case.
+ ///
+ /// When applicable, unstable sorting is preferred because it is generally faster than stable
+ /// sorting and it doesn't allocate auxiliary memory.
+ /// See [`sort_unstable`](slice::sort_unstable).
+ ///
+ /// # Current implementation
+ ///
+ /// The current algorithm is an adaptive, iterative merge sort inspired by
+ /// [timsort](https://en.wikipedia.org/wiki/Timsort).
+ /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
+ /// two or more sorted sequences concatenated one after another.
+ ///
+ /// Also, it allocates temporary storage half the size of `self`, but for short slices a
+ /// non-allocating insertion sort is used instead.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = [-5, 4, 1, -3, 2];
+ ///
+ /// v.sort();
+ /// assert!(v == [-5, -3, 1, 2, 4]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn sort(&mut self)
+ where
+ T: Ord,
+ {
+ merge_sort(self, |a, b| a.lt(b));
+ }
+
+ /// Sorts the slice with a comparator function.
+ ///
+ /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*)) worst-case.
+ ///
+ /// The comparator function must define a total ordering for the elements in the slice. If
+ /// the ordering is not total, the order of the elements is unspecified. An order is a
+ /// total order if it is (for all `a`, `b` and `c`):
+ ///
+ /// * total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true, and
+ /// * transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.
+ ///
+ /// For example, while [`f64`] doesn't implement [`Ord`] because `NaN != NaN`, we can use
+ /// `partial_cmp` as our sort function when we know the slice doesn't contain a `NaN`.
+ ///
+ /// ```
+ /// let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0];
+ /// floats.sort_by(|a, b| a.partial_cmp(b).unwrap());
+ /// assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]);
+ /// ```
+ ///
+ /// When applicable, unstable sorting is preferred because it is generally faster than stable
+ /// sorting and it doesn't allocate auxiliary memory.
+ /// See [`sort_unstable_by`](slice::sort_unstable_by).
+ ///
+ /// # Current implementation
+ ///
+ /// The current algorithm is an adaptive, iterative merge sort inspired by
+ /// [timsort](https://en.wikipedia.org/wiki/Timsort).
+ /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
+ /// two or more sorted sequences concatenated one after another.
+ ///
+ /// Also, it allocates temporary storage half the size of `self`, but for short slices a
+ /// non-allocating insertion sort is used instead.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = [5, 4, 1, 3, 2];
+ /// v.sort_by(|a, b| a.cmp(b));
+ /// assert!(v == [1, 2, 3, 4, 5]);
+ ///
+ /// // reverse sorting
+ /// v.sort_by(|a, b| b.cmp(a));
+ /// assert!(v == [5, 4, 3, 2, 1]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn sort_by<F>(&mut self, mut compare: F)
+ where
+ F: FnMut(&T, &T) -> Ordering,
+ {
+ merge_sort(self, |a, b| compare(a, b) == Less);
+ }
+
+ /// Sorts the slice with a key extraction function.
+ ///
+ /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* \* log(*n*))
+ /// worst-case, where the key function is *O*(*m*).
+ ///
+ /// For expensive key functions (e.g. functions that are not simple property accesses or
+ /// basic operations), [`sort_by_cached_key`](slice::sort_by_cached_key) is likely to be
+ /// significantly faster, as it does not recompute element keys.
+ ///
+ /// When applicable, unstable sorting is preferred because it is generally faster than stable
+ /// sorting and it doesn't allocate auxiliary memory.
+ /// See [`sort_unstable_by_key`](slice::sort_unstable_by_key).
+ ///
+ /// # Current implementation
+ ///
+ /// The current algorithm is an adaptive, iterative merge sort inspired by
+ /// [timsort](https://en.wikipedia.org/wiki/Timsort).
+ /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
+ /// two or more sorted sequences concatenated one after another.
+ ///
+ /// Also, it allocates temporary storage half the size of `self`, but for short slices a
+ /// non-allocating insertion sort is used instead.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = [-5i32, 4, 1, -3, 2];
+ ///
+ /// v.sort_by_key(|k| k.abs());
+ /// assert!(v == [1, 2, -3, 4, -5]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "slice_sort_by_key", since = "1.7.0")]
+ #[inline]
+ pub fn sort_by_key<K, F>(&mut self, mut f: F)
+ where
+ F: FnMut(&T) -> K,
+ K: Ord,
+ {
+ merge_sort(self, |a, b| f(a).lt(&f(b)));
+ }
+
+ /// Sorts the slice with a key extraction function.
+ ///
+ /// During sorting, the key function is called only once per element.
+ ///
+ /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* + *n* \* log(*n*))
+ /// worst-case, where the key function is *O*(*m*).
+ ///
+ /// For simple key functions (e.g., functions that are property accesses or
+ /// basic operations), [`sort_by_key`](slice::sort_by_key) is likely to be
+ /// faster.
+ ///
+ /// # Current implementation
+ ///
+ /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
+ /// which combines the fast average case of randomized quicksort with the fast worst case of
+ /// heapsort, while achieving linear time on slices with certain patterns. It uses some
+ /// randomization to avoid degenerate cases, but with a fixed seed to always provide
+ /// deterministic behavior.
+ ///
+ /// In the worst case, the algorithm allocates temporary storage in a `Vec<(K, usize)>` the
+ /// length of the slice.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = [-5i32, 4, 32, -3, 2];
+ ///
+ /// v.sort_by_cached_key(|k| k.to_string());
+ /// assert!(v == [-3, -5, 2, 32, 4]);
+ /// ```
+ ///
+ /// [pdqsort]: https://github.com/orlp/pdqsort
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "slice_sort_by_cached_key", since = "1.34.0")]
+ #[inline]
+ pub fn sort_by_cached_key<K, F>(&mut self, f: F)
+ where
+ F: FnMut(&T) -> K,
+ K: Ord,
+ {
+ // Helper macro for indexing our vector by the smallest possible type, to reduce allocation.
+ macro_rules! sort_by_key {
+ ($t:ty, $slice:ident, $f:ident) => {{
+ let mut indices: Vec<_> =
+ $slice.iter().map($f).enumerate().map(|(i, k)| (k, i as $t)).collect();
+ // The elements of `indices` are unique, as they are indexed, so any sort will be
+ // stable with respect to the original slice. We use `sort_unstable` here because
+ // it requires less memory allocation.
+ indices.sort_unstable();
+ for i in 0..$slice.len() {
+ let mut index = indices[i].1;
+ while (index as usize) < i {
+ index = indices[index as usize].1;
+ }
+ indices[i].1 = index;
+ $slice.swap(i, index as usize);
+ }
+ }};
+ }
+
+ let sz_u8 = mem::size_of::<(K, u8)>();
+ let sz_u16 = mem::size_of::<(K, u16)>();
+ let sz_u32 = mem::size_of::<(K, u32)>();
+ let sz_usize = mem::size_of::<(K, usize)>();
+
+ let len = self.len();
+ if len < 2 {
+ return;
+ }
+ if sz_u8 < sz_u16 && len <= (u8::MAX as usize) {
+ return sort_by_key!(u8, self, f);
+ }
+ if sz_u16 < sz_u32 && len <= (u16::MAX as usize) {
+ return sort_by_key!(u16, self, f);
+ }
+ if sz_u32 < sz_usize && len <= (u32::MAX as usize) {
+ return sort_by_key!(u32, self, f);
+ }
+ sort_by_key!(usize, self, f)
+ }
+
+ /// Copies `self` into a new `Vec`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let s = [10, 40, 30];
+ /// let x = s.to_vec();
+ /// // Here, `s` and `x` can be modified independently.
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[rustc_conversion_suggestion]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn to_vec(&self) -> Vec<T>
+ where
+ T: Clone,
+ {
+ self.to_vec_in(Global)
+ }
+
+ /// Tries to copy `self` into a new `Vec`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let s = [10, 40, 30];
+ /// let x = s.try_to_vec().unwrap();
+ /// // Here, `s` and `x` can be modified independently.
+ /// ```
+ #[inline]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_to_vec(&self) -> Result<Vec<T>, TryReserveError>
+ where
+ T: Clone,
+ {
+ self.try_to_vec_in(Global)
+ }
+
+ /// Copies `self` into a new `Vec` with an allocator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let s = [10, 40, 30];
+ /// let x = s.to_vec_in(System);
+ /// // Here, `s` and `x` can be modified independently.
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ pub fn to_vec_in<A: Allocator>(&self, alloc: A) -> Vec<T, A>
+ where
+ T: Clone,
+ {
+ // N.B., see the `hack` module in this file for more details.
+ hack::to_vec(self, alloc)
+ }
+
+ /// Tries to copy `self` into a new `Vec` with an allocator.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let s = [10, 40, 30];
+ /// let x = s.try_to_vec_in(System).unwrap();
+ /// // Here, `s` and `x` can be modified independently.
+ /// ```
+ #[inline]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_to_vec_in<A: Allocator>(&self, alloc: A) -> Result<Vec<T, A>, TryReserveError>
+ where
+ T: Clone,
+ {
+ // N.B., see the `hack` module in this file for more details.
+ hack::try_to_vec(self, alloc)
+ }
+
+ /// Converts `self` into a vector without clones or allocation.
+ ///
+ /// The resulting vector can be converted back into a box via
+ /// `Vec<T>`'s `into_boxed_slice` method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let s: Box<[i32]> = Box::new([10, 40, 30]);
+ /// let x = s.into_vec();
+ /// // `s` cannot be used anymore because it has been converted into `x`.
+ ///
+ /// assert_eq!(x, vec![10, 40, 30]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn into_vec<A: Allocator>(self: Box<Self, A>) -> Vec<T, A> {
+ // N.B., see the `hack` module in this file for more details.
+ hack::into_vec(self)
+ }
+
+ /// Creates a vector by repeating a slice `n` times.
+ ///
+ /// # Panics
+ ///
+ /// This function will panic if the capacity would overflow.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);
+ /// ```
+ ///
+ /// A panic upon overflow:
+ ///
+ /// ```should_panic
+ /// // this will panic at runtime
+ /// b"0123456789abcdef".repeat(usize::MAX);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "repeat_generic_slice", since = "1.40.0")]
+ pub fn repeat(&self, n: usize) -> Vec<T>
+ where
+ T: Copy,
+ {
+ if n == 0 {
+ return Vec::new();
+ }
+
+ // If `n` is larger than zero, it can be split as
+ // `n = 2^expn + rem (2^expn > rem, expn >= 0, rem >= 0)`.
+ // `2^expn` is the number represented by the leftmost '1' bit of `n`,
+ // and `rem` is the remaining part of `n`.
+
+ // Using `Vec` to access `set_len()`.
+ let capacity = self.len().checked_mul(n).expect("capacity overflow");
+ let mut buf = Vec::with_capacity(capacity);
+
+ // `2^expn` repetition is done by doubling `buf` `expn`-times.
+ buf.extend(self);
+ {
+ let mut m = n >> 1;
+ // If `m > 0`, there are remaining bits up to the leftmost '1'.
+ while m > 0 {
+ // `buf.extend(buf)`:
+ unsafe {
+ ptr::copy_nonoverlapping(
+ buf.as_ptr(),
+ (buf.as_mut_ptr() as *mut T).add(buf.len()),
+ buf.len(),
+ );
+ // `buf` has capacity of `self.len() * n`.
+ let buf_len = buf.len();
+ buf.set_len(buf_len * 2);
+ }
+
+ m >>= 1;
+ }
+ }
+
+ // `rem` (`= n - 2^expn`) repetition is done by copying
+ // first `rem` repetitions from `buf` itself.
+ let rem_len = capacity - buf.len(); // `self.len() * rem`
+ if rem_len > 0 {
+ // `buf.extend(buf[0 .. rem_len])`:
+ unsafe {
+ // This is non-overlapping since `2^expn > rem`.
+ ptr::copy_nonoverlapping(
+ buf.as_ptr(),
+ (buf.as_mut_ptr() as *mut T).add(buf.len()),
+ rem_len,
+ );
+ // `buf.len() + rem_len` equals to `buf.capacity()` (`= self.len() * n`).
+ buf.set_len(capacity);
+ }
+ }
+ buf
+ }
+
+ /// Flattens a slice of `T` into a single value `Self::Output`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(["hello", "world"].concat(), "helloworld");
+ /// assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn concat<Item: ?Sized>(&self) -> <Self as Concat<Item>>::Output
+ where
+ Self: Concat<Item>,
+ {
+ Concat::concat(self)
+ }
+
+ /// Flattens a slice of `T` into a single value `Self::Output`, placing a
+ /// given separator between each.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(["hello", "world"].join(" "), "hello world");
+ /// assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);
+ /// assert_eq!([[1, 2], [3, 4]].join(&[0, 0][..]), [1, 2, 0, 0, 3, 4]);
+ /// ```
+ #[stable(feature = "rename_connect_to_join", since = "1.3.0")]
+ pub fn join<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output
+ where
+ Self: Join<Separator>,
+ {
+ Join::join(self, sep)
+ }
+
+ /// Flattens a slice of `T` into a single value `Self::Output`, placing a
+ /// given separator between each.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![allow(deprecated)]
+ /// assert_eq!(["hello", "world"].connect(" "), "hello world");
+ /// assert_eq!([[1, 2], [3, 4]].connect(&0), [1, 2, 0, 3, 4]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")]
+ pub fn connect<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output
+ where
+ Self: Join<Separator>,
+ {
+ Join::join(self, sep)
+ }
+}
+
+#[lang = "slice_u8_alloc"]
+#[cfg(not(test))]
+impl [u8] {
+ /// Returns a vector containing a copy of this slice where each byte
+ /// is mapped to its ASCII upper case equivalent.
+ ///
+ /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+ /// but non-ASCII letters are unchanged.
+ ///
+ /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+ ///
+ /// [`make_ascii_uppercase`]: slice::make_ascii_uppercase
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+ #[inline]
+ pub fn to_ascii_uppercase(&self) -> Vec<u8> {
+ let mut me = self.to_vec();
+ me.make_ascii_uppercase();
+ me
+ }
+
+ /// Returns a vector containing a copy of this slice where each byte
+ /// is mapped to its ASCII lower case equivalent.
+ ///
+ /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+ /// but non-ASCII letters are unchanged.
+ ///
+ /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+ ///
+ /// [`make_ascii_lowercase`]: slice::make_ascii_lowercase
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+ #[inline]
+ pub fn to_ascii_lowercase(&self) -> Vec<u8> {
+ let mut me = self.to_vec();
+ me.make_ascii_lowercase();
+ me
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Extension traits for slices over specific kinds of data
+////////////////////////////////////////////////////////////////////////////////
+
+/// Helper trait for [`[T]::concat`](slice::concat).
+///
+/// Note: the `Item` type parameter is not used in this trait,
+/// but it allows impls to be more generic.
+/// Without it, we get this error:
+///
+/// ```error
+/// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica
+/// --> src/liballoc/slice.rs:608:6
+/// |
+/// 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] {
+/// | ^ unconstrained type parameter
+/// ```
+///
+/// This is because there could exist `V` types with multiple `Borrow<[_]>` impls,
+/// such that multiple `T` types would apply:
+///
+/// ```
+/// # #[allow(dead_code)]
+/// pub struct Foo(Vec<u32>, Vec<String>);
+///
+/// impl std::borrow::Borrow<[u32]> for Foo {
+/// fn borrow(&self) -> &[u32] { &self.0 }
+/// }
+///
+/// impl std::borrow::Borrow<[String]> for Foo {
+/// fn borrow(&self) -> &[String] { &self.1 }
+/// }
+/// ```
+#[unstable(feature = "slice_concat_trait", issue = "27747")]
+pub trait Concat<Item: ?Sized> {
+ #[unstable(feature = "slice_concat_trait", issue = "27747")]
+ /// The resulting type after concatenation
+ type Output;
+
+ /// Implementation of [`[T]::concat`](slice::concat)
+ #[unstable(feature = "slice_concat_trait", issue = "27747")]
+ fn concat(slice: &Self) -> Self::Output;
+}
+
+/// Helper trait for [`[T]::join`](slice::join)
+#[unstable(feature = "slice_concat_trait", issue = "27747")]
+pub trait Join<Separator> {
+ #[unstable(feature = "slice_concat_trait", issue = "27747")]
+ /// The resulting type after concatenation
+ type Output;
+
+ /// Implementation of [`[T]::join`](slice::join)
+ #[unstable(feature = "slice_concat_trait", issue = "27747")]
+ fn join(slice: &Self, sep: Separator) -> Self::Output;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "slice_concat_ext", issue = "27747")]
+impl<T: Clone, V: Borrow<[T]>> Concat<T> for [V] {
+ type Output = Vec<T>;
+
+ fn concat(slice: &Self) -> Vec<T> {
+ let size = slice.iter().map(|slice| slice.borrow().len()).sum();
+ let mut result = Vec::with_capacity(size);
+ for v in slice {
+ result.extend_from_slice(v.borrow())
+ }
+ result
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "slice_concat_ext", issue = "27747")]
+impl<T: Clone, V: Borrow<[T]>> Join<&T> for [V] {
+ type Output = Vec<T>;
+
+ fn join(slice: &Self, sep: &T) -> Vec<T> {
+ let mut iter = slice.iter();
+ let first = match iter.next() {
+ Some(first) => first,
+ None => return vec![],
+ };
+ let size = slice.iter().map(|v| v.borrow().len()).sum::<usize>() + slice.len() - 1;
+ let mut result = Vec::with_capacity(size);
+ result.extend_from_slice(first.borrow());
+
+ for v in iter {
+ result.push(sep.clone());
+ result.extend_from_slice(v.borrow())
+ }
+ result
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "slice_concat_ext", issue = "27747")]
+impl<T: Clone, V: Borrow<[T]>> Join<&[T]> for [V] {
+ type Output = Vec<T>;
+
+ fn join(slice: &Self, sep: &[T]) -> Vec<T> {
+ let mut iter = slice.iter();
+ let first = match iter.next() {
+ Some(first) => first,
+ None => return vec![],
+ };
+ let size =
+ slice.iter().map(|v| v.borrow().len()).sum::<usize>() + sep.len() * (slice.len() - 1);
+ let mut result = Vec::with_capacity(size);
+ result.extend_from_slice(first.borrow());
+
+ for v in iter {
+ result.extend_from_slice(sep);
+ result.extend_from_slice(v.borrow())
+ }
+ result
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Standard trait implementations for slices
+////////////////////////////////////////////////////////////////////////////////
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Borrow<[T]> for Vec<T> {
+ fn borrow(&self) -> &[T] {
+ &self[..]
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> BorrowMut<[T]> for Vec<T> {
+ fn borrow_mut(&mut self) -> &mut [T] {
+ &mut self[..]
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone> ToOwned for [T] {
+ type Owned = Vec<T>;
+ #[cfg(not(test))]
+ fn to_owned(&self) -> Vec<T> {
+ self.to_vec()
+ }
+
+ #[cfg(test)]
+ fn to_owned(&self) -> Vec<T> {
+ hack::to_vec(self, Global)
+ }
+
+ fn clone_into(&self, target: &mut Vec<T>) {
+ // drop anything in target that will not be overwritten
+ target.truncate(self.len());
+
+ // target.len <= self.len due to the truncate above, so the
+ // slices here are always in-bounds.
+ let (init, tail) = self.split_at(target.len());
+
+ // reuse the contained values' allocations/resources.
+ target.clone_from_slice(init);
+ target.extend_from_slice(tail);
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Sorting
+////////////////////////////////////////////////////////////////////////////////
+
+/// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted.
+///
+/// This is the integral subroutine of insertion sort.
+#[cfg(not(no_global_oom_handling))]
+fn insert_head<T, F>(v: &mut [T], is_less: &mut F)
+where
+ F: FnMut(&T, &T) -> bool,
+{
+ if v.len() >= 2 && is_less(&v[1], &v[0]) {
+ unsafe {
+ // There are three ways to implement insertion here:
+ //
+ // 1. Swap adjacent elements until the first one gets to its final destination.
+ // However, this way we copy data around more than is necessary. If elements are big
+ // structures (costly to copy), this method will be slow.
+ //
+ // 2. Iterate until the right place for the first element is found. Then shift the
+ // elements succeeding it to make room for it and finally place it into the
+ // remaining hole. This is a good method.
+ //
+ // 3. Copy the first element into a temporary variable. Iterate until the right place
+ // for it is found. As we go along, copy every traversed element into the slot
+ // preceding it. Finally, copy data from the temporary variable into the remaining
+ // hole. This method is very good. Benchmarks demonstrated slightly better
+ // performance than with the 2nd method.
+ //
+ // All methods were benchmarked, and the 3rd showed best results. So we chose that one.
+ let mut tmp = mem::ManuallyDrop::new(ptr::read(&v[0]));
+
+ // Intermediate state of the insertion process is always tracked by `hole`, which
+ // serves two purposes:
+ // 1. Protects integrity of `v` from panics in `is_less`.
+ // 2. Fills the remaining hole in `v` in the end.
+ //
+ // Panic safety:
+ //
+ // If `is_less` panics at any point during the process, `hole` will get dropped and
+ // fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it
+ // initially held exactly once.
+ let mut hole = InsertionHole { src: &mut *tmp, dest: &mut v[1] };
+ ptr::copy_nonoverlapping(&v[1], &mut v[0], 1);
+
+ for i in 2..v.len() {
+ if !is_less(&v[i], &*tmp) {
+ break;
+ }
+ ptr::copy_nonoverlapping(&v[i], &mut v[i - 1], 1);
+ hole.dest = &mut v[i];
+ }
+ // `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`.
+ }
+ }
+
+ // When dropped, copies from `src` into `dest`.
+ struct InsertionHole<T> {
+ src: *mut T,
+ dest: *mut T,
+ }
+
+ impl<T> Drop for InsertionHole<T> {
+ fn drop(&mut self) {
+ unsafe {
+ ptr::copy_nonoverlapping(self.src, self.dest, 1);
+ }
+ }
+ }
+}
+
+/// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and
+/// stores the result into `v[..]`.
+///
+/// # Safety
+///
+/// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough
+/// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type.
+#[cfg(not(no_global_oom_handling))]
+unsafe fn merge<T, F>(v: &mut [T], mid: usize, buf: *mut T, is_less: &mut F)
+where
+ F: FnMut(&T, &T) -> bool,
+{
+ let len = v.len();
+ let v = v.as_mut_ptr();
+ let (v_mid, v_end) = unsafe { (v.add(mid), v.add(len)) };
+
+ // The merge process first copies the shorter run into `buf`. Then it traces the newly copied
+ // run and the longer run forwards (or backwards), comparing their next unconsumed elements and
+ // copying the lesser (or greater) one into `v`.
+ //
+ // As soon as the shorter run is fully consumed, the process is done. If the longer run gets
+ // consumed first, then we must copy whatever is left of the shorter run into the remaining
+ // hole in `v`.
+ //
+ // Intermediate state of the process is always tracked by `hole`, which serves two purposes:
+ // 1. Protects integrity of `v` from panics in `is_less`.
+ // 2. Fills the remaining hole in `v` if the longer run gets consumed first.
+ //
+ // Panic safety:
+ //
+ // If `is_less` panics at any point during the process, `hole` will get dropped and fill the
+ // hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every
+ // object it initially held exactly once.
+ let mut hole;
+
+ if mid <= len - mid {
+ // The left run is shorter.
+ unsafe {
+ ptr::copy_nonoverlapping(v, buf, mid);
+ hole = MergeHole { start: buf, end: buf.add(mid), dest: v };
+ }
+
+ // Initially, these pointers point to the beginnings of their arrays.
+ let left = &mut hole.start;
+ let mut right = v_mid;
+ let out = &mut hole.dest;
+
+ while *left < hole.end && right < v_end {
+ // Consume the lesser side.
+ // If equal, prefer the left run to maintain stability.
+ unsafe {
+ let to_copy = if is_less(&*right, &**left) {
+ get_and_increment(&mut right)
+ } else {
+ get_and_increment(left)
+ };
+ ptr::copy_nonoverlapping(to_copy, get_and_increment(out), 1);
+ }
+ }
+ } else {
+ // The right run is shorter.
+ unsafe {
+ ptr::copy_nonoverlapping(v_mid, buf, len - mid);
+ hole = MergeHole { start: buf, end: buf.add(len - mid), dest: v_mid };
+ }
+
+ // Initially, these pointers point past the ends of their arrays.
+ let left = &mut hole.dest;
+ let right = &mut hole.end;
+ let mut out = v_end;
+
+ while v < *left && buf < *right {
+ // Consume the greater side.
+ // If equal, prefer the right run to maintain stability.
+ unsafe {
+ let to_copy = if is_less(&*right.offset(-1), &*left.offset(-1)) {
+ decrement_and_get(left)
+ } else {
+ decrement_and_get(right)
+ };
+ ptr::copy_nonoverlapping(to_copy, decrement_and_get(&mut out), 1);
+ }
+ }
+ }
+ // Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of
+ // it will now be copied into the hole in `v`.
+
+ unsafe fn get_and_increment<T>(ptr: &mut *mut T) -> *mut T {
+ let old = *ptr;
+ *ptr = unsafe { ptr.offset(1) };
+ old
+ }
+
+ unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T {
+ *ptr = unsafe { ptr.offset(-1) };
+ *ptr
+ }
+
+ // When dropped, copies the range `start..end` into `dest..`.
+ struct MergeHole<T> {
+ start: *mut T,
+ end: *mut T,
+ dest: *mut T,
+ }
+
+ impl<T> Drop for MergeHole<T> {
+ fn drop(&mut self) {
+ // `T` is not a zero-sized type, so it's okay to divide by its size.
+ let len = (self.end as usize - self.start as usize) / mem::size_of::<T>();
+ unsafe {
+ ptr::copy_nonoverlapping(self.start, self.dest, len);
+ }
+ }
+ }
+}
+
+/// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail
+/// [here](http://svn.python.org/projects/python/trunk/Objects/listsort.txt).
+///
+/// The algorithm identifies strictly descending and non-descending subsequences, which are called
+/// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed
+/// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are
+/// satisfied:
+///
+/// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`
+/// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`
+///
+/// The invariants ensure that the total running time is *O*(*n* \* log(*n*)) worst-case.
+#[cfg(not(no_global_oom_handling))]
+fn merge_sort<T, F>(v: &mut [T], mut is_less: F)
+where
+ F: FnMut(&T, &T) -> bool,
+{
+ // Slices of up to this length get sorted using insertion sort.
+ const MAX_INSERTION: usize = 20;
+ // Very short runs are extended using insertion sort to span at least this many elements.
+ const MIN_RUN: usize = 10;
+
+ // Sorting has no meaningful behavior on zero-sized types.
+ if size_of::<T>() == 0 {
+ return;
+ }
+
+ let len = v.len();
+
+ // Short arrays get sorted in-place via insertion sort to avoid allocations.
+ if len <= MAX_INSERTION {
+ if len >= 2 {
+ for i in (0..len - 1).rev() {
+ insert_head(&mut v[i..], &mut is_less);
+ }
+ }
+ return;
+ }
+
+ // Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it
+ // shallow copies of the contents of `v` without risking the dtors running on copies if
+ // `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run,
+ // which will always have length at most `len / 2`.
+ let mut buf = Vec::with_capacity(len / 2);
+
+ // In order to identify natural runs in `v`, we traverse it backwards. That might seem like a
+ // strange decision, but consider the fact that merges more often go in the opposite direction
+ // (forwards). According to benchmarks, merging forwards is slightly faster than merging
+ // backwards. To conclude, identifying runs by traversing backwards improves performance.
+ let mut runs = vec![];
+ let mut end = len;
+ while end > 0 {
+ // Find the next natural run, and reverse it if it's strictly descending.
+ let mut start = end - 1;
+ if start > 0 {
+ start -= 1;
+ unsafe {
+ if is_less(v.get_unchecked(start + 1), v.get_unchecked(start)) {
+ while start > 0 && is_less(v.get_unchecked(start), v.get_unchecked(start - 1)) {
+ start -= 1;
+ }
+ v[start..end].reverse();
+ } else {
+ while start > 0 && !is_less(v.get_unchecked(start), v.get_unchecked(start - 1))
+ {
+ start -= 1;
+ }
+ }
+ }
+ }
+
+ // Insert some more elements into the run if it's too short. Insertion sort is faster than
+ // merge sort on short sequences, so this significantly improves performance.
+ while start > 0 && end - start < MIN_RUN {
+ start -= 1;
+ insert_head(&mut v[start..end], &mut is_less);
+ }
+
+ // Push this run onto the stack.
+ runs.push(Run { start, len: end - start });
+ end = start;
+
+ // Merge some pairs of adjacent runs to satisfy the invariants.
+ while let Some(r) = collapse(&runs) {
+ let left = runs[r + 1];
+ let right = runs[r];
+ unsafe {
+ merge(
+ &mut v[left.start..right.start + right.len],
+ left.len,
+ buf.as_mut_ptr(),
+ &mut is_less,
+ );
+ }
+ runs[r] = Run { start: left.start, len: left.len + right.len };
+ runs.remove(r + 1);
+ }
+ }
+
+ // Finally, exactly one run must remain in the stack.
+ debug_assert!(runs.len() == 1 && runs[0].start == 0 && runs[0].len == len);
+
+ // Examines the stack of runs and identifies the next pair of runs to merge. More specifically,
+ // if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the
+ // algorithm should continue building a new run instead, `None` is returned.
+ //
+ // TimSort is infamous for its buggy implementations, as described here:
+ // http://envisage-project.eu/timsort-specification-and-verification/
+ //
+ // The gist of the story is: we must enforce the invariants on the top four runs on the stack.
+ // Enforcing them on just top three is not sufficient to ensure that the invariants will still
+ // hold for *all* runs in the stack.
+ //
+ // This function correctly checks invariants for the top four runs. Additionally, if the top
+ // run starts at index 0, it will always demand a merge operation until the stack is fully
+ // collapsed, in order to complete the sort.
+ #[inline]
+ fn collapse(runs: &[Run]) -> Option<usize> {
+ let n = runs.len();
+ if n >= 2
+ && (runs[n - 1].start == 0
+ || runs[n - 2].len <= runs[n - 1].len
+ || (n >= 3 && runs[n - 3].len <= runs[n - 2].len + runs[n - 1].len)
+ || (n >= 4 && runs[n - 4].len <= runs[n - 3].len + runs[n - 2].len))
+ {
+ if n >= 3 && runs[n - 3].len < runs[n - 1].len { Some(n - 3) } else { Some(n - 2) }
+ } else {
+ None
+ }
+ }
+
+ #[derive(Clone, Copy)]
+ struct Run {
+ start: usize,
+ len: usize,
+ }
+}
diff --git a/rust/alloc/str.rs b/rust/alloc/str.rs
new file mode 100644
index 00000000000..ed31405fa1c
--- /dev/null
+++ b/rust/alloc/str.rs
@@ -0,0 +1,614 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Unicode string slices.
+//!
+//! *[See also the `str` primitive type](str).*
+//!
+//! The `&str` type is one of the two main string types, the other being `String`.
+//! Unlike its `String` counterpart, its contents are borrowed.
+//!
+//! # Basic Usage
+//!
+//! A basic string declaration of `&str` type:
+//!
+//! ```
+//! let hello_world = "Hello, World!";
+//! ```
+//!
+//! Here we have declared a string literal, also known as a string slice.
+//! String literals have a static lifetime, which means the string `hello_world`
+//! is guaranteed to be valid for the duration of the entire program.
+//! We can explicitly specify `hello_world`'s lifetime as well:
+//!
+//! ```
+//! let hello_world: &'static str = "Hello, world!";
+//! ```
+
+#![stable(feature = "rust1", since = "1.0.0")]
+// Many of the usings in this module are only used in the test configuration.
+// It's cleaner to just turn off the unused_imports warning than to fix them.
+#![allow(unused_imports)]
+
+use core::borrow::{Borrow, BorrowMut};
+use core::iter::FusedIterator;
+use core::mem;
+use core::ptr;
+use core::str::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
+use core::unicode::conversions;
+
+use crate::borrow::ToOwned;
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::slice::{Concat, Join, SliceIndex};
+use crate::string::String;
+use crate::vec::Vec;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::pattern;
+#[stable(feature = "encode_utf16", since = "1.8.0")]
+pub use core::str::EncodeUtf16;
+#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
+pub use core::str::SplitAsciiWhitespace;
+#[stable(feature = "split_inclusive", since = "1.53.0")]
+pub use core::str::SplitInclusive;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::SplitWhitespace;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{from_utf8, from_utf8_mut, Bytes, CharIndices, Chars};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{from_utf8_unchecked, from_utf8_unchecked_mut, ParseBoolError};
+#[stable(feature = "str_escape", since = "1.34.0")]
+pub use core::str::{EscapeDebug, EscapeDefault, EscapeUnicode};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{FromStr, Utf8Error};
+#[allow(deprecated)]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{Lines, LinesAny};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{MatchIndices, RMatchIndices};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{Matches, RMatches};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{RSplit, Split};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{RSplitN, SplitN};
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::str::{RSplitTerminator, SplitTerminator};
+
+/// Note: `str` in `Concat<str>` is not meaningful here.
+/// This type parameter of the trait only exists to enable another impl.
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "slice_concat_ext", issue = "27747")]
+impl<S: Borrow<str>> Concat<str> for [S] {
+ type Output = String;
+
+ fn concat(slice: &Self) -> String {
+ Join::join(slice, "")
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "slice_concat_ext", issue = "27747")]
+impl<S: Borrow<str>> Join<&str> for [S] {
+ type Output = String;
+
+ fn join(slice: &Self, sep: &str) -> String {
+ unsafe { String::from_utf8_unchecked(join_generic_copy(slice, sep.as_bytes())) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+macro_rules! specialize_for_lengths {
+ ($separator:expr, $target:expr, $iter:expr; $($num:expr),*) => {{
+ let mut target = $target;
+ let iter = $iter;
+ let sep_bytes = $separator;
+ match $separator.len() {
+ $(
+ // loops with hardcoded sizes run much faster
+ // specialize the cases with small separator lengths
+ $num => {
+ for s in iter {
+ copy_slice_and_advance!(target, sep_bytes);
+ let content_bytes = s.borrow().as_ref();
+ copy_slice_and_advance!(target, content_bytes);
+ }
+ },
+ )*
+ _ => {
+ // arbitrary non-zero size fallback
+ for s in iter {
+ copy_slice_and_advance!(target, sep_bytes);
+ let content_bytes = s.borrow().as_ref();
+ copy_slice_and_advance!(target, content_bytes);
+ }
+ }
+ }
+ target
+ }}
+}
+
+#[cfg(not(no_global_oom_handling))]
+macro_rules! copy_slice_and_advance {
+ ($target:expr, $bytes:expr) => {
+ let len = $bytes.len();
+ let (head, tail) = { $target }.split_at_mut(len);
+ head.copy_from_slice($bytes);
+ $target = tail;
+ };
+}
+
+// Optimized join implementation that works for both Vec<T> (T: Copy) and String's inner vec
+// Currently (2018-05-13) there is a bug with type inference and specialization (see issue #36262)
+// For this reason SliceConcat<T> is not specialized for T: Copy and SliceConcat<str> is the
+// only user of this function. It is left in place for the time when that is fixed.
+//
+// the bounds for String-join are S: Borrow<str> and for Vec-join Borrow<[T]>
+// [T] and str both impl AsRef<[T]> for some T
+// => s.borrow().as_ref() and we always have slices
+#[cfg(not(no_global_oom_handling))]
+fn join_generic_copy<B, T, S>(slice: &[S], sep: &[T]) -> Vec<T>
+where
+ T: Copy,
+ B: AsRef<[T]> + ?Sized,
+ S: Borrow<B>,
+{
+ let sep_len = sep.len();
+ let mut iter = slice.iter();
+
+ // the first slice is the only one without a separator preceding it
+ let first = match iter.next() {
+ Some(first) => first,
+ None => return vec![],
+ };
+
+ // compute the exact total length of the joined Vec
+ // if the `len` calculation overflows, we'll panic
+ // we would have run out of memory anyway and the rest of the function requires
+ // the entire Vec pre-allocated for safety
+ let reserved_len = sep_len
+ .checked_mul(iter.len())
+ .and_then(|n| {
+ slice.iter().map(|s| s.borrow().as_ref().len()).try_fold(n, usize::checked_add)
+ })
+ .expect("attempt to join into collection with len > usize::MAX");
+
+ // prepare an uninitialized buffer
+ let mut result = Vec::with_capacity(reserved_len);
+ debug_assert!(result.capacity() >= reserved_len);
+
+ result.extend_from_slice(first.borrow().as_ref());
+
+ unsafe {
+ let pos = result.len();
+ let target = result.get_unchecked_mut(pos..reserved_len);
+
+ // copy separator and slices over without bounds checks
+ // generate loops with hardcoded offsets for small separators
+ // massive improvements possible (~ x2)
+ let remain = specialize_for_lengths!(sep, target, iter; 0, 1, 2, 3, 4);
+
+ // A weird borrow implementation may return different
+ // slices for the length calculation and the actual copy.
+ // Make sure we don't expose uninitialized bytes to the caller.
+ let result_len = reserved_len - remain.len();
+ result.set_len(result_len);
+ }
+ result
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Borrow<str> for String {
+ #[inline]
+ fn borrow(&self) -> &str {
+ &self[..]
+ }
+}
+
+#[stable(feature = "string_borrow_mut", since = "1.36.0")]
+impl BorrowMut<str> for String {
+ #[inline]
+ fn borrow_mut(&mut self) -> &mut str {
+ &mut self[..]
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ToOwned for str {
+ type Owned = String;
+ #[inline]
+ fn to_owned(&self) -> String {
+ unsafe { String::from_utf8_unchecked(self.as_bytes().to_owned()) }
+ }
+
+ fn clone_into(&self, target: &mut String) {
+ let mut b = mem::take(target).into_bytes();
+ self.as_bytes().clone_into(&mut b);
+ *target = unsafe { String::from_utf8_unchecked(b) }
+ }
+}
+
+/// Methods for string slices.
+#[lang = "str_alloc"]
+#[cfg(not(test))]
+impl str {
+ /// Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = "this is a string";
+ /// let boxed_str = s.to_owned().into_boxed_str();
+ /// let boxed_bytes = boxed_str.into_boxed_bytes();
+ /// assert_eq!(*boxed_bytes, *s.as_bytes());
+ /// ```
+ #[stable(feature = "str_box_extras", since = "1.20.0")]
+ #[inline]
+ pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> {
+ self.into()
+ }
+
+ /// Replaces all matches of a pattern with another string.
+ ///
+ /// `replace` creates a new [`String`], and copies the data from this string slice into it.
+ /// While doing so, it attempts to find matches of a pattern. If it finds any, it
+ /// replaces them with the replacement string slice.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = "this is old";
+ ///
+ /// assert_eq!("this is new", s.replace("old", "new"));
+ /// ```
+ ///
+ /// When the pattern doesn't match:
+ ///
+ /// ```
+ /// let s = "this is old";
+ /// assert_eq!(s, s.replace("cookie monster", "little lamb"));
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[must_use = "this returns the replaced string as a new allocation, \
+ without modifying the original"]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String {
+ let mut result = String::new();
+ let mut last_end = 0;
+ for (start, part) in self.match_indices(from) {
+ result.push_str(unsafe { self.get_unchecked(last_end..start) });
+ result.push_str(to);
+ last_end = start + part.len();
+ }
+ result.push_str(unsafe { self.get_unchecked(last_end..self.len()) });
+ result
+ }
+
+ /// Replaces first N matches of a pattern with another string.
+ ///
+ /// `replacen` creates a new [`String`], and copies the data from this string slice into it.
+ /// While doing so, it attempts to find matches of a pattern. If it finds any, it
+ /// replaces them with the replacement string slice at most `count` times.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = "foo foo 123 foo";
+ /// assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
+ /// assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
+ /// assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));
+ /// ```
+ ///
+ /// When the pattern doesn't match:
+ ///
+ /// ```
+ /// let s = "this is old";
+ /// assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[must_use = "this returns the replaced string as a new allocation, \
+ without modifying the original"]
+ #[stable(feature = "str_replacen", since = "1.16.0")]
+ pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String {
+ // Hope to reduce the times of re-allocation
+ let mut result = String::with_capacity(32);
+ let mut last_end = 0;
+ for (start, part) in self.match_indices(pat).take(count) {
+ result.push_str(unsafe { self.get_unchecked(last_end..start) });
+ result.push_str(to);
+ last_end = start + part.len();
+ }
+ result.push_str(unsafe { self.get_unchecked(last_end..self.len()) });
+ result
+ }
+
+ /// Returns the lowercase equivalent of this string slice, as a new [`String`].
+ ///
+ /// 'Lowercase' is defined according to the terms of the Unicode Derived Core Property
+ /// `Lowercase`.
+ ///
+ /// Since some characters can expand into multiple characters when changing
+ /// the case, this function returns a [`String`] instead of modifying the
+ /// parameter in-place.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = "HELLO";
+ ///
+ /// assert_eq!("hello", s.to_lowercase());
+ /// ```
+ ///
+ /// A tricky example, with sigma:
+ ///
+ /// ```
+ /// let sigma = "Σ";
+ ///
+ /// assert_eq!("σ", sigma.to_lowercase());
+ ///
+ /// // but at the end of a word, it's ς, not σ:
+ /// let odysseus = "ὈΔΥΣΣΕΎΣ";
+ ///
+ /// assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());
+ /// ```
+ ///
+ /// Languages without case are not changed:
+ ///
+ /// ```
+ /// let new_year = "农历新年";
+ ///
+ /// assert_eq!(new_year, new_year.to_lowercase());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
+ pub fn to_lowercase(&self) -> String {
+ let mut s = String::with_capacity(self.len());
+ for (i, c) in self[..].char_indices() {
+ if c == 'Σ' {
+ // Σ maps to σ, except at the end of a word where it maps to ς.
+ // This is the only conditional (contextual) but language-independent mapping
+ // in `SpecialCasing.txt`,
+ // so hard-code it rather than have a generic "condition" mechanism.
+ // See https://github.com/rust-lang/rust/issues/26035
+ map_uppercase_sigma(self, i, &mut s)
+ } else {
+ match conversions::to_lower(c) {
+ [a, '\0', _] => s.push(a),
+ [a, b, '\0'] => {
+ s.push(a);
+ s.push(b);
+ }
+ [a, b, c] => {
+ s.push(a);
+ s.push(b);
+ s.push(c);
+ }
+ }
+ }
+ }
+ return s;
+
+ fn map_uppercase_sigma(from: &str, i: usize, to: &mut String) {
+ // See http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
+ // for the definition of `Final_Sigma`.
+ debug_assert!('Σ'.len_utf8() == 2);
+ let is_word_final = case_ignoreable_then_cased(from[..i].chars().rev())
+ && !case_ignoreable_then_cased(from[i + 2..].chars());
+ to.push_str(if is_word_final { "ς" } else { "σ" });
+ }
+
+ fn case_ignoreable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool {
+ use core::unicode::{Case_Ignorable, Cased};
+ match iter.skip_while(|&c| Case_Ignorable(c)).next() {
+ Some(c) => Cased(c),
+ None => false,
+ }
+ }
+ }
+
+ /// Returns the uppercase equivalent of this string slice, as a new [`String`].
+ ///
+ /// 'Uppercase' is defined according to the terms of the Unicode Derived Core Property
+ /// `Uppercase`.
+ ///
+ /// Since some characters can expand into multiple characters when changing
+ /// the case, this function returns a [`String`] instead of modifying the
+ /// parameter in-place.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = "hello";
+ ///
+ /// assert_eq!("HELLO", s.to_uppercase());
+ /// ```
+ ///
+ /// Scripts without case are not changed:
+ ///
+ /// ```
+ /// let new_year = "农历新年";
+ ///
+ /// assert_eq!(new_year, new_year.to_uppercase());
+ /// ```
+ ///
+ /// One character can become multiple:
+ /// ```
+ /// let s = "tschüß";
+ ///
+ /// assert_eq!("TSCHÜSS", s.to_uppercase());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
+ pub fn to_uppercase(&self) -> String {
+ let mut s = String::with_capacity(self.len());
+ for c in self[..].chars() {
+ match conversions::to_upper(c) {
+ [a, '\0', _] => s.push(a),
+ [a, b, '\0'] => {
+ s.push(a);
+ s.push(b);
+ }
+ [a, b, c] => {
+ s.push(a);
+ s.push(b);
+ s.push(c);
+ }
+ }
+ }
+ s
+ }
+
+ /// Converts a [`Box<str>`] into a [`String`] without copying or allocating.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let string = String::from("birthday gift");
+ /// let boxed_str = string.clone().into_boxed_str();
+ ///
+ /// assert_eq!(boxed_str.into_string(), string);
+ /// ```
+ #[stable(feature = "box_str", since = "1.4.0")]
+ #[inline]
+ pub fn into_string(self: Box<str>) -> String {
+ let slice = Box::<[u8]>::from(self);
+ unsafe { String::from_utf8_unchecked(slice.into_vec()) }
+ }
+
+ /// Creates a new [`String`] by repeating a string `n` times.
+ ///
+ /// # Panics
+ ///
+ /// This function will panic if the capacity would overflow.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
+ /// ```
+ ///
+ /// A panic upon overflow:
+ ///
+ /// ```should_panic
+ /// // this will panic at runtime
+ /// "0123456789abcdef".repeat(usize::MAX);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "repeat_str", since = "1.16.0")]
+ pub fn repeat(&self, n: usize) -> String {
+ unsafe { String::from_utf8_unchecked(self.as_bytes().repeat(n)) }
+ }
+
+ /// Returns a copy of this string where each character is mapped to its
+ /// ASCII upper case equivalent.
+ ///
+ /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+ /// but non-ASCII letters are unchanged.
+ ///
+ /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+ ///
+ /// To uppercase ASCII characters in addition to non-ASCII characters, use
+ /// [`to_uppercase`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let s = "Grüße, Jürgen ❤";
+ ///
+ /// assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());
+ /// ```
+ ///
+ /// [`make_ascii_uppercase`]: str::make_ascii_uppercase
+ /// [`to_uppercase`]: #method.to_uppercase
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+ #[inline]
+ pub fn to_ascii_uppercase(&self) -> String {
+ let mut bytes = self.as_bytes().to_vec();
+ bytes.make_ascii_uppercase();
+ // make_ascii_uppercase() preserves the UTF-8 invariant.
+ unsafe { String::from_utf8_unchecked(bytes) }
+ }
+
+ /// Returns a copy of this string where each character is mapped to its
+ /// ASCII lower case equivalent.
+ ///
+ /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+ /// but non-ASCII letters are unchanged.
+ ///
+ /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+ ///
+ /// To lowercase ASCII characters in addition to non-ASCII characters, use
+ /// [`to_lowercase`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let s = "Grüße, Jürgen ❤";
+ ///
+ /// assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());
+ /// ```
+ ///
+ /// [`make_ascii_lowercase`]: str::make_ascii_lowercase
+ /// [`to_lowercase`]: #method.to_lowercase
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+ #[inline]
+ pub fn to_ascii_lowercase(&self) -> String {
+ let mut bytes = self.as_bytes().to_vec();
+ bytes.make_ascii_lowercase();
+ // make_ascii_lowercase() preserves the UTF-8 invariant.
+ unsafe { String::from_utf8_unchecked(bytes) }
+ }
+
+ /// Tries to create a `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s: &str = "a";
+ /// let ss: String = s.try_to_owned().unwrap();
+ /// ```
+ #[inline]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_to_owned(&self) -> Result<String, TryReserveError> {
+ unsafe { Ok(String::from_utf8_unchecked(self.as_bytes().try_to_vec()?)) }
+ }
+}
+
+/// Converts a boxed slice of bytes to a boxed string slice without checking
+/// that the string contains valid UTF-8.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let smile_utf8 = Box::new([226, 152, 186]);
+/// let smile = unsafe { std::str::from_boxed_utf8_unchecked(smile_utf8) };
+///
+/// assert_eq!("☺", &*smile);
+/// ```
+#[stable(feature = "str_box_extras", since = "1.20.0")]
+#[inline]
+pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
+ unsafe { Box::from_raw(Box::into_raw(v) as *mut str) }
+}
diff --git a/rust/alloc/string.rs b/rust/alloc/string.rs
new file mode 100644
index 00000000000..55293c3041e
--- /dev/null
+++ b/rust/alloc/string.rs
@@ -0,0 +1,2847 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A UTF-8–encoded, growable string.
+//!
+//! This module contains the [`String`] type, the [`ToString`] trait for
+//! converting to strings, and several error types that may result from
+//! working with [`String`]s.
+//!
+//! # Examples
+//!
+//! There are multiple ways to create a new [`String`] from a string literal:
+//!
+//! ```
+//! let s = "Hello".to_string();
+//!
+//! let s = String::from("world");
+//! let s: String = "also this".into();
+//! ```
+//!
+//! You can create a new [`String`] from an existing one by concatenating with
+//! `+`:
+//!
+//! ```
+//! let s = "Hello".to_string();
+//!
+//! let message = s + " world!";
+//! ```
+//!
+//! If you have a vector of valid UTF-8 bytes, you can make a [`String`] out of
+//! it. You can do the reverse too.
+//!
+//! ```
+//! let sparkle_heart = vec![240, 159, 146, 150];
+//!
+//! // We know these bytes are valid, so we'll use `unwrap()`.
+//! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+//!
+//! assert_eq!("💖", sparkle_heart);
+//!
+//! let bytes = sparkle_heart.into_bytes();
+//!
+//! assert_eq!(bytes, [240, 159, 146, 150]);
+//! ```
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[cfg(not(no_global_oom_handling))]
+use core::char::{decode_utf16, REPLACEMENT_CHARACTER};
+use core::fmt;
+use core::hash;
+#[cfg(not(no_global_oom_handling))]
+use core::iter::{from_fn, FromIterator};
+use core::iter::FusedIterator;
+#[cfg(not(no_global_oom_handling))]
+use core::ops::Add;
+#[cfg(not(no_global_oom_handling))]
+use core::ops::AddAssign;
+#[cfg(not(no_global_oom_handling))]
+use core::ops::Bound::{Excluded, Included, Unbounded};
+use core::ops::{self, Index, IndexMut, Range, RangeBounds};
+use core::ptr;
+use core::slice;
+#[cfg(not(no_global_oom_handling))]
+use core::str::lossy;
+use core::str::pattern::Pattern;
+
+#[cfg(not(no_global_oom_handling))]
+use crate::borrow::{Cow, ToOwned};
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::str::{self, Chars, Utf8Error};
+#[cfg(not(no_global_oom_handling))]
+use crate::str::{from_boxed_utf8_unchecked, FromStr};
+use crate::vec::Vec;
+
+/// A UTF-8–encoded, growable string.
+///
+/// The `String` type is the most common string type that has ownership over the
+/// contents of the string. It has a close relationship with its borrowed
+/// counterpart, the primitive [`str`].
+///
+/// # Examples
+///
+/// You can create a `String` from [a literal string][`str`] with [`String::from`]:
+///
+/// [`String::from`]: From::from
+///
+/// ```
+/// let hello = String::from("Hello, world!");
+/// ```
+///
+/// You can append a [`char`] to a `String` with the [`push`] method, and
+/// append a [`&str`] with the [`push_str`] method:
+///
+/// ```
+/// let mut hello = String::from("Hello, ");
+///
+/// hello.push('w');
+/// hello.push_str("orld!");
+/// ```
+///
+/// [`push`]: String::push
+/// [`push_str`]: String::push_str
+///
+/// If you have a vector of UTF-8 bytes, you can create a `String` from it with
+/// the [`from_utf8`] method:
+///
+/// ```
+/// // some bytes, in a vector
+/// let sparkle_heart = vec![240, 159, 146, 150];
+///
+/// // We know these bytes are valid, so we'll use `unwrap()`.
+/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+///
+/// assert_eq!("💖", sparkle_heart);
+/// ```
+///
+/// [`from_utf8`]: String::from_utf8
+///
+/// # UTF-8
+///
+/// `String`s are always valid UTF-8. This has a few implications, the first of
+/// which is that if you need a non-UTF-8 string, consider [`OsString`]. It is
+/// similar, but without the UTF-8 constraint. The second implication is that
+/// you cannot index into a `String`:
+///
+/// ```compile_fail,E0277
+/// let s = "hello";
+///
+/// println!("The first letter of s is {}", s[0]); // ERROR!!!
+/// ```
+///
+/// [`OsString`]: ../../std/ffi/struct.OsString.html
+///
+/// Indexing is intended to be a constant-time operation, but UTF-8 encoding
+/// does not allow us to do this. Furthermore, it's not clear what sort of
+/// thing the index should return: a byte, a codepoint, or a grapheme cluster.
+/// The [`bytes`] and [`chars`] methods return iterators over the first
+/// two, respectively.
+///
+/// [`bytes`]: str::bytes
+/// [`chars`]: str::chars
+///
+/// # Deref
+///
+/// `String`s implement [`Deref`]`<Target=str>`, and so inherit all of [`str`]'s
+/// methods. In addition, this means that you can pass a `String` to a
+/// function which takes a [`&str`] by using an ampersand (`&`):
+///
+/// ```
+/// fn takes_str(s: &str) { }
+///
+/// let s = String::from("Hello");
+///
+/// takes_str(&s);
+/// ```
+///
+/// This will create a [`&str`] from the `String` and pass it in. This
+/// conversion is very inexpensive, and so generally, functions will accept
+/// [`&str`]s as arguments unless they need a `String` for some specific
+/// reason.
+///
+/// In certain cases Rust doesn't have enough information to make this
+/// conversion, known as [`Deref`] coercion. In the following example a string
+/// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function
+/// `example_func` takes anything that implements the trait. In this case Rust
+/// would need to make two implicit conversions, which Rust doesn't have the
+/// means to do. For that reason, the following example will not compile.
+///
+/// ```compile_fail,E0277
+/// trait TraitExample {}
+///
+/// impl<'a> TraitExample for &'a str {}
+///
+/// fn example_func<A: TraitExample>(example_arg: A) {}
+///
+/// let example_string = String::from("example_string");
+/// example_func(&example_string);
+/// ```
+///
+/// There are two options that would work instead. The first would be to
+/// change the line `example_func(&example_string);` to
+/// `example_func(example_string.as_str());`, using the method [`as_str()`]
+/// to explicitly extract the string slice containing the string. The second
+/// way changes `example_func(&example_string);` to
+/// `example_func(&*example_string);`. In this case we are dereferencing a
+/// `String` to a [`str`][`&str`], then referencing the [`str`][`&str`] back to
+/// [`&str`]. The second way is more idiomatic, however both work to do the
+/// conversion explicitly rather than relying on the implicit conversion.
+///
+/// # Representation
+///
+/// A `String` is made up of three components: a pointer to some bytes, a
+/// length, and a capacity. The pointer points to an internal buffer `String`
+/// uses to store its data. The length is the number of bytes currently stored
+/// in the buffer, and the capacity is the size of the buffer in bytes. As such,
+/// the length will always be less than or equal to the capacity.
+///
+/// This buffer is always stored on the heap.
+///
+/// You can look at these with the [`as_ptr`], [`len`], and [`capacity`]
+/// methods:
+///
+/// ```
+/// use std::mem;
+///
+/// let story = String::from("Once upon a time...");
+///
+// FIXME Update this when vec_into_raw_parts is stabilized
+/// // Prevent automatically dropping the String's data
+/// let mut story = mem::ManuallyDrop::new(story);
+///
+/// let ptr = story.as_mut_ptr();
+/// let len = story.len();
+/// let capacity = story.capacity();
+///
+/// // story has nineteen bytes
+/// assert_eq!(19, len);
+///
+/// // We can re-build a String out of ptr, len, and capacity. This is all
+/// // unsafe because we are responsible for making sure the components are
+/// // valid:
+/// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ;
+///
+/// assert_eq!(String::from("Once upon a time..."), s);
+/// ```
+///
+/// [`as_ptr`]: str::as_ptr
+/// [`len`]: String::len
+/// [`capacity`]: String::capacity
+///
+/// If a `String` has enough capacity, adding elements to it will not
+/// re-allocate. For example, consider this program:
+///
+/// ```
+/// let mut s = String::new();
+///
+/// println!("{}", s.capacity());
+///
+/// for _ in 0..5 {
+/// s.push_str("hello");
+/// println!("{}", s.capacity());
+/// }
+/// ```
+///
+/// This will output the following:
+///
+/// ```text
+/// 0
+/// 5
+/// 10
+/// 20
+/// 20
+/// 40
+/// ```
+///
+/// At first, we have no memory allocated at all, but as we append to the
+/// string, it increases its capacity appropriately. If we instead use the
+/// [`with_capacity`] method to allocate the correct capacity initially:
+///
+/// ```
+/// let mut s = String::with_capacity(25);
+///
+/// println!("{}", s.capacity());
+///
+/// for _ in 0..5 {
+/// s.push_str("hello");
+/// println!("{}", s.capacity());
+/// }
+/// ```
+///
+/// [`with_capacity`]: String::with_capacity
+///
+/// We end up with a different output:
+///
+/// ```text
+/// 25
+/// 25
+/// 25
+/// 25
+/// 25
+/// 25
+/// ```
+///
+/// Here, there's no need to allocate more memory inside the loop.
+///
+/// [`str`]: prim@str
+/// [`&str`]: prim@str
+/// [`Deref`]: core::ops::Deref
+/// [`as_str()`]: String::as_str
+#[derive(PartialOrd, Eq, Ord)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "string_type")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct String {
+ vec: Vec<u8>,
+}
+
+/// A possible error value when converting a `String` from a UTF-8 byte vector.
+///
+/// This type is the error type for the [`from_utf8`] method on [`String`]. It
+/// is designed in such a way to carefully avoid reallocations: the
+/// [`into_bytes`] method will give back the byte vector that was used in the
+/// conversion attempt.
+///
+/// [`from_utf8`]: String::from_utf8
+/// [`into_bytes`]: FromUtf8Error::into_bytes
+///
+/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
+/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
+/// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error`
+/// through the [`utf8_error`] method.
+///
+/// [`Utf8Error`]: core::str::Utf8Error
+/// [`std::str`]: core::str
+/// [`&str`]: prim@str
+/// [`utf8_error`]: Self::utf8_error
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // some invalid bytes, in a vector
+/// let bytes = vec![0, 159];
+///
+/// let value = String::from_utf8(bytes);
+///
+/// assert!(value.is_err());
+/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(no_global_oom_handling), derive(Clone))]
+#[derive(Debug, PartialEq, Eq)]
+pub struct FromUtf8Error {
+ bytes: Vec<u8>,
+ error: Utf8Error,
+}
+
+/// A possible error value when converting a `String` from a UTF-16 byte slice.
+///
+/// This type is the error type for the [`from_utf16`] method on [`String`].
+///
+/// [`from_utf16`]: String::from_utf16
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // 𝄞mu<invalid>ic
+/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+/// 0xD800, 0x0069, 0x0063];
+///
+/// assert!(String::from_utf16(v).is_err());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Debug)]
+pub struct FromUtf16Error(());
+
+impl String {
+ /// Creates a new empty `String`.
+ ///
+ /// Given that the `String` is empty, this will not allocate any initial
+ /// buffer. While that means that this initial operation is very
+ /// inexpensive, it may cause excessive allocation later when you add
+ /// data. If you have an idea of how much data the `String` will hold,
+ /// consider the [`with_capacity`] method to prevent excessive
+ /// re-allocation.
+ ///
+ /// [`with_capacity`]: String::with_capacity
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::new();
+ /// ```
+ #[inline]
+ #[rustc_const_stable(feature = "const_string_new", since = "1.39.0")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub const fn new() -> String {
+ String { vec: Vec::new() }
+ }
+
+ /// Creates a new empty `String` with a particular capacity.
+ ///
+ /// `String`s have an internal buffer to hold their data. The capacity is
+ /// the length of that buffer, and can be queried with the [`capacity`]
+ /// method. This method creates an empty `String`, but one with an initial
+ /// buffer that can hold `capacity` bytes. This is useful when you may be
+ /// appending a bunch of data to the `String`, reducing the number of
+ /// reallocations it needs to do.
+ ///
+ /// [`capacity`]: String::capacity
+ ///
+ /// If the given capacity is `0`, no allocation will occur, and this method
+ /// is identical to the [`new`] method.
+ ///
+ /// [`new`]: String::new
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::with_capacity(10);
+ ///
+ /// // The String contains no chars, even though it has capacity for more
+ /// assert_eq!(s.len(), 0);
+ ///
+ /// // These are all done without reallocating...
+ /// let cap = s.capacity();
+ /// for _ in 0..10 {
+ /// s.push('a');
+ /// }
+ ///
+ /// assert_eq!(s.capacity(), cap);
+ ///
+ /// // ...but this may make the string reallocate
+ /// s.push('a');
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[doc(alias = "alloc")]
+ #[doc(alias = "malloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn with_capacity(capacity: usize) -> String {
+ String { vec: Vec::with_capacity(capacity) }
+ }
+
+ // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
+ // required for this method definition, is not available. Since we don't
+ // require this method for testing purposes, I'll just stub it
+ // NB see the slice::hack module in slice.rs for more information
+ #[inline]
+ #[cfg(test)]
+ pub fn from_str(_: &str) -> String {
+ panic!("not available with cfg(test)");
+ }
+
+ /// Converts a vector of bytes to a `String`.
+ ///
+ /// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes
+ /// ([`Vec<u8>`]) is made of bytes, so this function converts between the
+ /// two. Not all byte slices are valid `String`s, however: `String`
+ /// requires that it is valid UTF-8. `from_utf8()` checks to ensure that
+ /// the bytes are valid UTF-8, and then does the conversion.
+ ///
+ /// If you are sure that the byte slice is valid UTF-8, and you don't want
+ /// to incur the overhead of the validity check, there is an unsafe version
+ /// of this function, [`from_utf8_unchecked`], which has the same behavior
+ /// but skips the check.
+ ///
+ /// This method will take care to not copy the vector, for efficiency's
+ /// sake.
+ ///
+ /// If you need a [`&str`] instead of a `String`, consider
+ /// [`str::from_utf8`].
+ ///
+ /// The inverse of this method is [`into_bytes`].
+ ///
+ /// # Errors
+ ///
+ /// Returns [`Err`] if the slice is not UTF-8 with a description as to why the
+ /// provided bytes are not UTF-8. The vector you moved in is also included.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some bytes, in a vector
+ /// let sparkle_heart = vec![240, 159, 146, 150];
+ ///
+ /// // We know these bytes are valid, so we'll use `unwrap()`.
+ /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+ ///
+ /// assert_eq!("💖", sparkle_heart);
+ /// ```
+ ///
+ /// Incorrect bytes:
+ ///
+ /// ```
+ /// // some invalid bytes, in a vector
+ /// let sparkle_heart = vec![0, 159, 146, 150];
+ ///
+ /// assert!(String::from_utf8(sparkle_heart).is_err());
+ /// ```
+ ///
+ /// See the docs for [`FromUtf8Error`] for more details on what you can do
+ /// with this error.
+ ///
+ /// [`from_utf8_unchecked`]: String::from_utf8_unchecked
+ /// [`Vec<u8>`]: crate::vec::Vec
+ /// [`&str`]: prim@str
+ /// [`into_bytes`]: String::into_bytes
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> {
+ match str::from_utf8(&vec) {
+ Ok(..) => Ok(String { vec }),
+ Err(e) => Err(FromUtf8Error { bytes: vec, error: e }),
+ }
+ }
+
+ /// Converts a slice of bytes to a string, including invalid characters.
+ ///
+ /// Strings are made of bytes ([`u8`]), and a slice of bytes
+ /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts
+ /// between the two. Not all byte slices are valid strings, however: strings
+ /// are required to be valid UTF-8. During this conversion,
+ /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with
+ /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: �
+ ///
+ /// [byteslice]: prim@slice
+ /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
+ ///
+ /// If you are sure that the byte slice is valid UTF-8, and you don't want
+ /// to incur the overhead of the conversion, there is an unsafe version
+ /// of this function, [`from_utf8_unchecked`], which has the same behavior
+ /// but skips the checks.
+ ///
+ /// [`from_utf8_unchecked`]: String::from_utf8_unchecked
+ ///
+ /// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid
+ /// UTF-8, then we need to insert the replacement characters, which will
+ /// change the size of the string, and hence, require a `String`. But if
+ /// it's already valid UTF-8, we don't need a new allocation. This return
+ /// type allows us to handle both cases.
+ ///
+ /// [`Cow<'a, str>`]: crate::borrow::Cow
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some bytes, in a vector
+ /// let sparkle_heart = vec![240, 159, 146, 150];
+ ///
+ /// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);
+ ///
+ /// assert_eq!("💖", sparkle_heart);
+ /// ```
+ ///
+ /// Incorrect bytes:
+ ///
+ /// ```
+ /// // some invalid bytes
+ /// let input = b"Hello \xF0\x90\x80World";
+ /// let output = String::from_utf8_lossy(input);
+ ///
+ /// assert_eq!("Hello �World", output);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> {
+ let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks();
+
+ let (first_valid, first_broken) = if let Some(chunk) = iter.next() {
+ let lossy::Utf8LossyChunk { valid, broken } = chunk;
+ if valid.len() == v.len() {
+ debug_assert!(broken.is_empty());
+ return Cow::Borrowed(valid);
+ }
+ (valid, broken)
+ } else {
+ return Cow::Borrowed("");
+ };
+
+ const REPLACEMENT: &str = "\u{FFFD}";
+
+ let mut res = String::with_capacity(v.len());
+ res.push_str(first_valid);
+ if !first_broken.is_empty() {
+ res.push_str(REPLACEMENT);
+ }
+
+ for lossy::Utf8LossyChunk { valid, broken } in iter {
+ res.push_str(valid);
+ if !broken.is_empty() {
+ res.push_str(REPLACEMENT);
+ }
+ }
+
+ Cow::Owned(res)
+ }
+
+ /// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`]
+ /// if `v` contains any invalid data.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // 𝄞music
+ /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+ /// 0x0073, 0x0069, 0x0063];
+ /// assert_eq!(String::from("𝄞music"),
+ /// String::from_utf16(v).unwrap());
+ ///
+ /// // 𝄞mu<invalid>ic
+ /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+ /// 0xD800, 0x0069, 0x0063];
+ /// assert!(String::from_utf16(v).is_err());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> {
+ // This isn't done via collect::<Result<_, _>>() for performance reasons.
+ // FIXME: the function can be simplified again when #48994 is closed.
+ let mut ret = String::with_capacity(v.len());
+ for c in decode_utf16(v.iter().cloned()) {
+ if let Ok(c) = c {
+ ret.push(c);
+ } else {
+ return Err(FromUtf16Error(()));
+ }
+ }
+ Ok(ret)
+ }
+
+ /// Decode a UTF-16–encoded slice `v` into a `String`, replacing
+ /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
+ ///
+ /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
+ /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8
+ /// conversion requires a memory allocation.
+ ///
+ /// [`from_utf8_lossy`]: String::from_utf8_lossy
+ /// [`Cow<'a, str>`]: crate::borrow::Cow
+ /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // 𝄞mus<invalid>ic<invalid>
+ /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+ /// 0x0073, 0xDD1E, 0x0069, 0x0063,
+ /// 0xD834];
+ ///
+ /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
+ /// String::from_utf16_lossy(v));
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn from_utf16_lossy(v: &[u16]) -> String {
+ decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect()
+ }
+
+ /// Decomposes a `String` into its raw components.
+ ///
+ /// Returns the raw pointer to the underlying data, the length of
+ /// the string (in bytes), and the allocated capacity of the data
+ /// (in bytes). These are the same arguments in the same order as
+ /// the arguments to [`from_raw_parts`].
+ ///
+ /// After calling this function, the caller is responsible for the
+ /// memory previously managed by the `String`. The only way to do
+ /// this is to convert the raw pointer, length, and capacity back
+ /// into a `String` with the [`from_raw_parts`] function, allowing
+ /// the destructor to perform the cleanup.
+ ///
+ /// [`from_raw_parts`]: String::from_raw_parts
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(vec_into_raw_parts)]
+ /// let s = String::from("hello");
+ ///
+ /// let (ptr, len, cap) = s.into_raw_parts();
+ ///
+ /// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) };
+ /// assert_eq!(rebuilt, "hello");
+ /// ```
+ #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
+ pub fn into_raw_parts(self) -> (*mut u8, usize, usize) {
+ self.vec.into_raw_parts()
+ }
+
+ /// Creates a new `String` from a length, capacity, and pointer.
+ ///
+ /// # Safety
+ ///
+ /// This is highly unsafe, due to the number of invariants that aren't
+ /// checked:
+ ///
+ /// * The memory at `buf` needs to have been previously allocated by the
+ /// same allocator the standard library uses, with a required alignment of exactly 1.
+ /// * `length` needs to be less than or equal to `capacity`.
+ /// * `capacity` needs to be the correct value.
+ /// * The first `length` bytes at `buf` need to be valid UTF-8.
+ ///
+ /// Violating these may cause problems like corrupting the allocator's
+ /// internal data structures.
+ ///
+ /// The ownership of `buf` is effectively transferred to the
+ /// `String` which may then deallocate, reallocate or change the
+ /// contents of memory pointed to by the pointer at will. Ensure
+ /// that nothing else uses the pointer after calling this
+ /// function.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// use std::mem;
+ ///
+ /// unsafe {
+ /// let s = String::from("hello");
+ ///
+ // FIXME Update this when vec_into_raw_parts is stabilized
+ /// // Prevent automatically dropping the String's data
+ /// let mut s = mem::ManuallyDrop::new(s);
+ ///
+ /// let ptr = s.as_mut_ptr();
+ /// let len = s.len();
+ /// let capacity = s.capacity();
+ ///
+ /// let s = String::from_raw_parts(ptr, len, capacity);
+ ///
+ /// assert_eq!(String::from("hello"), s);
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String {
+ unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } }
+ }
+
+ /// Converts a vector of bytes to a `String` without checking that the
+ /// string contains valid UTF-8.
+ ///
+ /// See the safe version, [`from_utf8`], for more details.
+ ///
+ /// [`from_utf8`]: String::from_utf8
+ ///
+ /// # Safety
+ ///
+ /// This function is unsafe because it does not check that the bytes passed
+ /// to it are valid UTF-8. If this constraint is violated, it may cause
+ /// memory unsafety issues with future users of the `String`, as the rest of
+ /// the standard library assumes that `String`s are valid UTF-8.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some bytes, in a vector
+ /// let sparkle_heart = vec![240, 159, 146, 150];
+ ///
+ /// let sparkle_heart = unsafe {
+ /// String::from_utf8_unchecked(sparkle_heart)
+ /// };
+ ///
+ /// assert_eq!("💖", sparkle_heart);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String {
+ String { vec: bytes }
+ }
+
+ /// Converts a `String` into a byte vector.
+ ///
+ /// This consumes the `String`, so we do not need to copy its contents.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::from("hello");
+ /// let bytes = s.into_bytes();
+ ///
+ /// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn into_bytes(self) -> Vec<u8> {
+ self.vec
+ }
+
+ /// Extracts a string slice containing the entire `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::from("foo");
+ ///
+ /// assert_eq!("foo", s.as_str());
+ /// ```
+ #[inline]
+ #[stable(feature = "string_as_str", since = "1.7.0")]
+ pub fn as_str(&self) -> &str {
+ self
+ }
+
+ /// Converts a `String` into a mutable string slice.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foobar");
+ /// let s_mut_str = s.as_mut_str();
+ ///
+ /// s_mut_str.make_ascii_uppercase();
+ ///
+ /// assert_eq!("FOOBAR", s_mut_str);
+ /// ```
+ #[inline]
+ #[stable(feature = "string_as_str", since = "1.7.0")]
+ pub fn as_mut_str(&mut self) -> &mut str {
+ self
+ }
+
+ /// Appends a given string slice onto the end of this `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foo");
+ ///
+ /// s.push_str("bar");
+ ///
+ /// assert_eq!("foobar", s);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn push_str(&mut self, string: &str) {
+ self.vec.extend_from_slice(string.as_bytes())
+ }
+
+ /// Copies elements from `src` range to the end of the string.
+ ///
+ /// ## Panics
+ ///
+ /// Panics if the starting point or end point do not lie on a [`char`]
+ /// boundary, or if they're out of bounds.
+ ///
+ /// ## Examples
+ ///
+ /// ```
+ /// #![feature(string_extend_from_within)]
+ /// let mut string = String::from("abcde");
+ ///
+ /// string.extend_from_within(2..);
+ /// assert_eq!(string, "abcdecde");
+ ///
+ /// string.extend_from_within(..2);
+ /// assert_eq!(string, "abcdecdeab");
+ ///
+ /// string.extend_from_within(4..8);
+ /// assert_eq!(string, "abcdecdeabecde");
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "string_extend_from_within", issue = "none")]
+ pub fn extend_from_within<R>(&mut self, src: R)
+ where
+ R: RangeBounds<usize>,
+ {
+ let src @ Range { start, end } = slice::range(src, ..self.len());
+
+ assert!(self.is_char_boundary(start));
+ assert!(self.is_char_boundary(end));
+
+ self.vec.extend_from_within(src);
+ }
+
+ /// Returns this `String`'s capacity, in bytes.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::with_capacity(10);
+ ///
+ /// assert!(s.capacity() >= 10);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn capacity(&self) -> usize {
+ self.vec.capacity()
+ }
+
+ /// Ensures that this `String`'s capacity is at least `additional` bytes
+ /// larger than its length.
+ ///
+ /// The capacity may be increased by more than `additional` bytes if it
+ /// chooses, to prevent frequent reallocations.
+ ///
+ /// If you do not want this "at least" behavior, see the [`reserve_exact`]
+ /// method.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity overflows [`usize`].
+ ///
+ /// [`reserve_exact`]: String::reserve_exact
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::new();
+ ///
+ /// s.reserve(10);
+ ///
+ /// assert!(s.capacity() >= 10);
+ /// ```
+ ///
+ /// This may not actually increase the capacity:
+ ///
+ /// ```
+ /// let mut s = String::with_capacity(10);
+ /// s.push('a');
+ /// s.push('b');
+ ///
+ /// // s now has a length of 2 and a capacity of 10
+ /// assert_eq!(2, s.len());
+ /// assert_eq!(10, s.capacity());
+ ///
+ /// // Since we already have an extra 8 capacity, calling this...
+ /// s.reserve(8);
+ ///
+ /// // ... doesn't actually increase.
+ /// assert_eq!(10, s.capacity());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn reserve(&mut self, additional: usize) {
+ self.vec.reserve(additional)
+ }
+
+ /// Ensures that this `String`'s capacity is `additional` bytes
+ /// larger than its length.
+ ///
+ /// Consider using the [`reserve`] method unless you absolutely know
+ /// better than the allocator.
+ ///
+ /// [`reserve`]: String::reserve
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity overflows `usize`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::new();
+ ///
+ /// s.reserve_exact(10);
+ ///
+ /// assert!(s.capacity() >= 10);
+ /// ```
+ ///
+ /// This may not actually increase the capacity:
+ ///
+ /// ```
+ /// let mut s = String::with_capacity(10);
+ /// s.push('a');
+ /// s.push('b');
+ ///
+ /// // s now has a length of 2 and a capacity of 10
+ /// assert_eq!(2, s.len());
+ /// assert_eq!(10, s.capacity());
+ ///
+ /// // Since we already have an extra 8 capacity, calling this...
+ /// s.reserve_exact(8);
+ ///
+ /// // ... doesn't actually increase.
+ /// assert_eq!(10, s.capacity());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn reserve_exact(&mut self, additional: usize) {
+ self.vec.reserve_exact(additional)
+ }
+
+ /// Tries to reserve capacity for at least `additional` more elements to be inserted
+ /// in the given `String`. The collection may reserve more space to avoid
+ /// frequent reallocations. After calling `reserve`, capacity will be
+ /// greater than or equal to `self.len() + additional`. Does nothing if
+ /// capacity is already sufficient.
+ ///
+ /// # Errors
+ ///
+ /// If the capacity overflows, or the allocator reports a failure, then an error
+ /// is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(try_reserve)]
+ /// use std::collections::TryReserveError;
+ ///
+ /// fn process_data(data: &str) -> Result<String, TryReserveError> {
+ /// let mut output = String::new();
+ ///
+ /// // Pre-reserve the memory, exiting if we can't
+ /// output.try_reserve(data.len())?;
+ ///
+ /// // Now we know this can't OOM in the middle of our complex work
+ /// output.push_str(data);
+ ///
+ /// Ok(output)
+ /// }
+ /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
+ /// ```
+ #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+ pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
+ self.vec.try_reserve(additional)
+ }
+
+ /// Tries to reserve the minimum capacity for exactly `additional` more elements to
+ /// be inserted in the given `String`. After calling `reserve_exact`,
+ /// capacity will be greater than or equal to `self.len() + additional`.
+ /// Does nothing if the capacity is already sufficient.
+ ///
+ /// Note that the allocator may give the collection more space than it
+ /// requests. Therefore, capacity can not be relied upon to be precisely
+ /// minimal. Prefer `reserve` if future insertions are expected.
+ ///
+ /// # Errors
+ ///
+ /// If the capacity overflows, or the allocator reports a failure, then an error
+ /// is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(try_reserve)]
+ /// use std::collections::TryReserveError;
+ ///
+ /// fn process_data(data: &str) -> Result<String, TryReserveError> {
+ /// let mut output = String::new();
+ ///
+ /// // Pre-reserve the memory, exiting if we can't
+ /// output.try_reserve(data.len())?;
+ ///
+ /// // Now we know this can't OOM in the middle of our complex work
+ /// output.push_str(data);
+ ///
+ /// Ok(output)
+ /// }
+ /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?");
+ /// ```
+ #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+ pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
+ self.vec.try_reserve_exact(additional)
+ }
+
+ /// Shrinks the capacity of this `String` to match its length.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foo");
+ ///
+ /// s.reserve(100);
+ /// assert!(s.capacity() >= 100);
+ ///
+ /// s.shrink_to_fit();
+ /// assert_eq!(3, s.capacity());
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn shrink_to_fit(&mut self) {
+ self.vec.shrink_to_fit()
+ }
+
+ /// Shrinks the capacity of this `String` with a lower bound.
+ ///
+ /// The capacity will remain at least as large as both the length
+ /// and the supplied value.
+ ///
+ /// If the current capacity is less than the lower limit, this is a no-op.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(shrink_to)]
+ /// let mut s = String::from("foo");
+ ///
+ /// s.reserve(100);
+ /// assert!(s.capacity() >= 100);
+ ///
+ /// s.shrink_to(10);
+ /// assert!(s.capacity() >= 10);
+ /// s.shrink_to(0);
+ /// assert!(s.capacity() >= 3);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")]
+ pub fn shrink_to(&mut self, min_capacity: usize) {
+ self.vec.shrink_to(min_capacity)
+ }
+
+ /// Appends the given [`char`] to the end of this `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("abc");
+ ///
+ /// s.push('1');
+ /// s.push('2');
+ /// s.push('3');
+ ///
+ /// assert_eq!("abc123", s);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn push(&mut self, ch: char) {
+ match ch.len_utf8() {
+ 1 => self.vec.push(ch as u8),
+ _ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()),
+ }
+ }
+
+ /// Returns a byte slice of this `String`'s contents.
+ ///
+ /// The inverse of this method is [`from_utf8`].
+ ///
+ /// [`from_utf8`]: String::from_utf8
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::from("hello");
+ ///
+ /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn as_bytes(&self) -> &[u8] {
+ &self.vec
+ }
+
+ /// Shortens this `String` to the specified length.
+ ///
+ /// If `new_len` is greater than the string's current length, this has no
+ /// effect.
+ ///
+ /// Note that this method has no effect on the allocated capacity
+ /// of the string
+ ///
+ /// # Panics
+ ///
+ /// Panics if `new_len` does not lie on a [`char`] boundary.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("hello");
+ ///
+ /// s.truncate(2);
+ ///
+ /// assert_eq!("he", s);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn truncate(&mut self, new_len: usize) {
+ if new_len <= self.len() {
+ assert!(self.is_char_boundary(new_len));
+ self.vec.truncate(new_len)
+ }
+ }
+
+ /// Removes the last character from the string buffer and returns it.
+ ///
+ /// Returns [`None`] if this `String` is empty.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foo");
+ ///
+ /// assert_eq!(s.pop(), Some('o'));
+ /// assert_eq!(s.pop(), Some('o'));
+ /// assert_eq!(s.pop(), Some('f'));
+ ///
+ /// assert_eq!(s.pop(), None);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn pop(&mut self) -> Option<char> {
+ let ch = self.chars().rev().next()?;
+ let newlen = self.len() - ch.len_utf8();
+ unsafe {
+ self.vec.set_len(newlen);
+ }
+ Some(ch)
+ }
+
+ /// Removes a [`char`] from this `String` at a byte position and returns it.
+ ///
+ /// This is an *O*(*n*) operation, as it requires copying every element in the
+ /// buffer.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `idx` is larger than or equal to the `String`'s length,
+ /// or if it does not lie on a [`char`] boundary.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foo");
+ ///
+ /// assert_eq!(s.remove(0), 'f');
+ /// assert_eq!(s.remove(1), 'o');
+ /// assert_eq!(s.remove(0), 'o');
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn remove(&mut self, idx: usize) -> char {
+ let ch = match self[idx..].chars().next() {
+ Some(ch) => ch,
+ None => panic!("cannot remove a char from the end of a string"),
+ };
+
+ let next = idx + ch.len_utf8();
+ let len = self.len();
+ unsafe {
+ ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next);
+ self.vec.set_len(len - (next - idx));
+ }
+ ch
+ }
+
+ /// Remove all matches of pattern `pat` in the `String`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(string_remove_matches)]
+ /// let mut s = String::from("Trees are not green, the sky is not blue.");
+ /// s.remove_matches("not ");
+ /// assert_eq!("Trees are green, the sky is blue.", s);
+ /// ```
+ ///
+ /// Matches will be detected and removed iteratively, so in cases where
+ /// patterns overlap, only the first pattern will be removed:
+ ///
+ /// ```
+ /// #![feature(string_remove_matches)]
+ /// let mut s = String::from("banana");
+ /// s.remove_matches("ana");
+ /// assert_eq!("bna", s);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")]
+ pub fn remove_matches<'a, P>(&'a mut self, pat: P)
+ where
+ P: for<'x> Pattern<'x>,
+ {
+ use core::str::pattern::Searcher;
+
+ let rejections = {
+ let mut searcher = pat.into_searcher(self);
+ // Per Searcher::next:
+ //
+ // A Match result needs to contain the whole matched pattern,
+ // however Reject results may be split up into arbitrary many
+ // adjacent fragments. Both ranges may have zero length.
+ //
+ // In practice the implementation of Searcher::next_match tends to
+ // be more efficient, so we use it here and do some work to invert
+ // matches into rejections since that's what we want to copy below.
+ let mut front = 0;
+ let rejections: Vec<_> = from_fn(|| {
+ let (start, end) = searcher.next_match()?;
+ let prev_front = front;
+ front = end;
+ Some((prev_front, start))
+ })
+ .collect();
+ rejections.into_iter().chain(core::iter::once((front, self.len())))
+ };
+
+ let mut len = 0;
+ let ptr = self.vec.as_mut_ptr();
+
+ for (start, end) in rejections {
+ let count = end - start;
+ if start != len {
+ // SAFETY: per Searcher::next:
+ //
+ // The stream of Match and Reject values up to a Done will
+ // contain index ranges that are adjacent, non-overlapping,
+ // covering the whole haystack, and laying on utf8
+ // boundaries.
+ unsafe {
+ ptr::copy(ptr.add(start), ptr.add(len), count);
+ }
+ }
+ len += count;
+ }
+
+ unsafe {
+ self.vec.set_len(len);
+ }
+ }
+
+ /// Retains only the characters specified by the predicate.
+ ///
+ /// In other words, remove all characters `c` such that `f(c)` returns `false`.
+ /// This method operates in place, visiting each character exactly once in the
+ /// original order, and preserves the order of the retained characters.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut s = String::from("f_o_ob_ar");
+ ///
+ /// s.retain(|c| c != '_');
+ ///
+ /// assert_eq!(s, "foobar");
+ /// ```
+ ///
+ /// The exact order may be useful for tracking external state, like an index.
+ ///
+ /// ```
+ /// let mut s = String::from("abcde");
+ /// let keep = [false, true, true, false, true];
+ /// let mut i = 0;
+ /// s.retain(|_| (keep[i], i += 1).0);
+ /// assert_eq!(s, "bce");
+ /// ```
+ #[inline]
+ #[stable(feature = "string_retain", since = "1.26.0")]
+ pub fn retain<F>(&mut self, mut f: F)
+ where
+ F: FnMut(char) -> bool,
+ {
+ struct SetLenOnDrop<'a> {
+ s: &'a mut String,
+ idx: usize,
+ del_bytes: usize,
+ }
+
+ impl<'a> Drop for SetLenOnDrop<'a> {
+ fn drop(&mut self) {
+ let new_len = self.idx - self.del_bytes;
+ debug_assert!(new_len <= self.s.len());
+ unsafe { self.s.vec.set_len(new_len) };
+ }
+ }
+
+ let len = self.len();
+ let mut guard = SetLenOnDrop { s: self, idx: 0, del_bytes: 0 };
+
+ while guard.idx < len {
+ let ch = unsafe { guard.s.get_unchecked(guard.idx..len).chars().next().unwrap() };
+ let ch_len = ch.len_utf8();
+
+ if !f(ch) {
+ guard.del_bytes += ch_len;
+ } else if guard.del_bytes > 0 {
+ unsafe {
+ ptr::copy(
+ guard.s.vec.as_ptr().add(guard.idx),
+ guard.s.vec.as_mut_ptr().add(guard.idx - guard.del_bytes),
+ ch_len,
+ );
+ }
+ }
+
+ // Point idx to the next char
+ guard.idx += ch_len;
+ }
+
+ drop(guard);
+ }
+
+ /// Inserts a character into this `String` at a byte position.
+ ///
+ /// This is an *O*(*n*) operation as it requires copying every element in the
+ /// buffer.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `idx` is larger than the `String`'s length, or if it does not
+ /// lie on a [`char`] boundary.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::with_capacity(3);
+ ///
+ /// s.insert(0, 'f');
+ /// s.insert(1, 'o');
+ /// s.insert(2, 'o');
+ ///
+ /// assert_eq!("foo", s);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn insert(&mut self, idx: usize, ch: char) {
+ assert!(self.is_char_boundary(idx));
+ let mut bits = [0; 4];
+ let bits = ch.encode_utf8(&mut bits).as_bytes();
+
+ unsafe {
+ self.insert_bytes(idx, bits);
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) {
+ let len = self.len();
+ let amt = bytes.len();
+ self.vec.reserve(amt);
+
+ unsafe {
+ ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx);
+ ptr::copy(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt);
+ self.vec.set_len(len + amt);
+ }
+ }
+
+ /// Inserts a string slice into this `String` at a byte position.
+ ///
+ /// This is an *O*(*n*) operation as it requires copying every element in the
+ /// buffer.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `idx` is larger than the `String`'s length, or if it does not
+ /// lie on a [`char`] boundary.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("bar");
+ ///
+ /// s.insert_str(0, "foo");
+ ///
+ /// assert_eq!("foobar", s);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "insert_str", since = "1.16.0")]
+ pub fn insert_str(&mut self, idx: usize, string: &str) {
+ assert!(self.is_char_boundary(idx));
+
+ unsafe {
+ self.insert_bytes(idx, string.as_bytes());
+ }
+ }
+
+ /// Returns a mutable reference to the contents of this `String`.
+ ///
+ /// # Safety
+ ///
+ /// This function is unsafe because it does not check that the bytes passed
+ /// to it are valid UTF-8. If this constraint is violated, it may cause
+ /// memory unsafety issues with future users of the `String`, as the rest of
+ /// the standard library assumes that `String`s are valid UTF-8.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("hello");
+ ///
+ /// unsafe {
+ /// let vec = s.as_mut_vec();
+ /// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);
+ ///
+ /// vec.reverse();
+ /// }
+ /// assert_eq!(s, "olleh");
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> {
+ &mut self.vec
+ }
+
+ /// Returns the length of this `String`, in bytes, not [`char`]s or
+ /// graphemes. In other words, it may not be what a human considers the
+ /// length of the string.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = String::from("foo");
+ /// assert_eq!(a.len(), 3);
+ ///
+ /// let fancy_f = String::from("ƒoo");
+ /// assert_eq!(fancy_f.len(), 4);
+ /// assert_eq!(fancy_f.chars().count(), 3);
+ /// ```
+ #[doc(alias = "length")]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn len(&self) -> usize {
+ self.vec.len()
+ }
+
+ /// Returns `true` if this `String` has a length of zero, and `false` otherwise.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut v = String::new();
+ /// assert!(v.is_empty());
+ ///
+ /// v.push('a');
+ /// assert!(!v.is_empty());
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn is_empty(&self) -> bool {
+ self.len() == 0
+ }
+
+ /// Splits the string into two at the given byte index.
+ ///
+ /// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and
+ /// the returned `String` contains bytes `[at, len)`. `at` must be on the
+ /// boundary of a UTF-8 code point.
+ ///
+ /// Note that the capacity of `self` does not change.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last
+ /// code point of the string.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # fn main() {
+ /// let mut hello = String::from("Hello, World!");
+ /// let world = hello.split_off(7);
+ /// assert_eq!(hello, "Hello, ");
+ /// assert_eq!(world, "World!");
+ /// # }
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "string_split_off", since = "1.16.0")]
+ #[must_use = "use `.truncate()` if you don't need the other half"]
+ pub fn split_off(&mut self, at: usize) -> String {
+ assert!(self.is_char_boundary(at));
+ let other = self.vec.split_off(at);
+ unsafe { String::from_utf8_unchecked(other) }
+ }
+
+ /// Truncates this `String`, removing all contents.
+ ///
+ /// While this means the `String` will have a length of zero, it does not
+ /// touch its capacity.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("foo");
+ ///
+ /// s.clear();
+ ///
+ /// assert!(s.is_empty());
+ /// assert_eq!(0, s.len());
+ /// assert_eq!(3, s.capacity());
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn clear(&mut self) {
+ self.vec.clear()
+ }
+
+ /// Creates a draining iterator that removes the specified range in the `String`
+ /// and yields the removed `chars`.
+ ///
+ /// Note: The element range is removed even if the iterator is not
+ /// consumed until the end.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the starting point or end point do not lie on a [`char`]
+ /// boundary, or if they're out of bounds.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("α is alpha, β is beta");
+ /// let beta_offset = s.find('β').unwrap_or(s.len());
+ ///
+ /// // Remove the range up until the β from the string
+ /// let t: String = s.drain(..beta_offset).collect();
+ /// assert_eq!(t, "α is alpha, ");
+ /// assert_eq!(s, "β is beta");
+ ///
+ /// // A full range clears the string
+ /// s.drain(..);
+ /// assert_eq!(s, "");
+ /// ```
+ #[stable(feature = "drain", since = "1.6.0")]
+ pub fn drain<R>(&mut self, range: R) -> Drain<'_>
+ where
+ R: RangeBounds<usize>,
+ {
+ // Memory safety
+ //
+ // The String version of Drain does not have the memory safety issues
+ // of the vector version. The data is just plain bytes.
+ // Because the range removal happens in Drop, if the Drain iterator is leaked,
+ // the removal will not happen.
+ let Range { start, end } = slice::range(range, ..self.len());
+ assert!(self.is_char_boundary(start));
+ assert!(self.is_char_boundary(end));
+
+ // Take out two simultaneous borrows. The &mut String won't be accessed
+ // until iteration is over, in Drop.
+ let self_ptr = self as *mut _;
+ // SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks.
+ let chars_iter = unsafe { self.get_unchecked(start..end) }.chars();
+
+ Drain { start, end, iter: chars_iter, string: self_ptr }
+ }
+
+ /// Removes the specified range in the string,
+ /// and replaces it with the given string.
+ /// The given string doesn't need to be the same length as the range.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the starting point or end point do not lie on a [`char`]
+ /// boundary, or if they're out of bounds.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = String::from("α is alpha, β is beta");
+ /// let beta_offset = s.find('β').unwrap_or(s.len());
+ ///
+ /// // Replace the range up until the β from the string
+ /// s.replace_range(..beta_offset, "Α is capital alpha; ");
+ /// assert_eq!(s, "Α is capital alpha; β is beta");
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "splice", since = "1.27.0")]
+ pub fn replace_range<R>(&mut self, range: R, replace_with: &str)
+ where
+ R: RangeBounds<usize>,
+ {
+ // Memory safety
+ //
+ // Replace_range does not have the memory safety issues of a vector Splice.
+ // of the vector version. The data is just plain bytes.
+
+ // WARNING: Inlining this variable would be unsound (#81138)
+ let start = range.start_bound();
+ match start {
+ Included(&n) => assert!(self.is_char_boundary(n)),
+ Excluded(&n) => assert!(self.is_char_boundary(n + 1)),
+ Unbounded => {}
+ };
+ // WARNING: Inlining this variable would be unsound (#81138)
+ let end = range.end_bound();
+ match end {
+ Included(&n) => assert!(self.is_char_boundary(n + 1)),
+ Excluded(&n) => assert!(self.is_char_boundary(n)),
+ Unbounded => {}
+ };
+
+ // Using `range` again would be unsound (#81138)
+ // We assume the bounds reported by `range` remain the same, but
+ // an adversarial implementation could change between calls
+ unsafe { self.as_mut_vec() }.splice((start, end), replace_with.bytes());
+ }
+
+ /// Converts this `String` into a [`Box`]`<`[`str`]`>`.
+ ///
+ /// This will drop any excess capacity.
+ ///
+ /// [`str`]: prim@str
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s = String::from("hello");
+ ///
+ /// let b = s.into_boxed_str();
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "box_str", since = "1.4.0")]
+ #[inline]
+ pub fn into_boxed_str(self) -> Box<str> {
+ let slice = self.vec.into_boxed_slice();
+ unsafe { from_boxed_utf8_unchecked(slice) }
+ }
+}
+
+impl FromUtf8Error {
+ /// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some invalid bytes, in a vector
+ /// let bytes = vec![0, 159];
+ ///
+ /// let value = String::from_utf8(bytes);
+ ///
+ /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes());
+ /// ```
+ #[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")]
+ pub fn as_bytes(&self) -> &[u8] {
+ &self.bytes[..]
+ }
+
+ /// Returns the bytes that were attempted to convert to a `String`.
+ ///
+ /// This method is carefully constructed to avoid allocation. It will
+ /// consume the error, moving out the bytes, so that a copy of the bytes
+ /// does not need to be made.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some invalid bytes, in a vector
+ /// let bytes = vec![0, 159];
+ ///
+ /// let value = String::from_utf8(bytes);
+ ///
+ /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn into_bytes(self) -> Vec<u8> {
+ self.bytes
+ }
+
+ /// Fetch a `Utf8Error` to get more details about the conversion failure.
+ ///
+ /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
+ /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
+ /// an analogue to `FromUtf8Error`. See its documentation for more details
+ /// on using it.
+ ///
+ /// [`std::str`]: core::str
+ /// [`&str`]: prim@str
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // some invalid bytes, in a vector
+ /// let bytes = vec![0, 159];
+ ///
+ /// let error = String::from_utf8(bytes).unwrap_err().utf8_error();
+ ///
+ /// // the first byte is invalid here
+ /// assert_eq!(1, error.valid_up_to());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn utf8_error(&self) -> Utf8Error {
+ self.error
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for FromUtf8Error {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&self.error, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for FromUtf16Error {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt("invalid utf-16: lone surrogate found", f)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Clone for String {
+ fn clone(&self) -> Self {
+ String { vec: self.vec.clone() }
+ }
+
+ fn clone_from(&mut self, source: &Self) {
+ self.vec.clone_from(&source.vec);
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl FromIterator<char> for String {
+ fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String {
+ let mut buf = String::new();
+ buf.extend(iter);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "string_from_iter_by_ref", since = "1.17.0")]
+impl<'a> FromIterator<&'a char> for String {
+ fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String {
+ let mut buf = String::new();
+ buf.extend(iter);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> FromIterator<&'a str> for String {
+ fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String {
+ let mut buf = String::new();
+ buf.extend(iter);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "extend_string", since = "1.4.0")]
+impl FromIterator<String> for String {
+ fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
+ let mut iterator = iter.into_iter();
+
+ // Because we're iterating over `String`s, we can avoid at least
+ // one allocation by getting the first string from the iterator
+ // and appending to it all the subsequent strings.
+ match iterator.next() {
+ None => String::new(),
+ Some(mut buf) => {
+ buf.extend(iterator);
+ buf
+ }
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_str2", since = "1.45.0")]
+impl FromIterator<Box<str>> for String {
+ fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String {
+ let mut buf = String::new();
+ buf.extend(iter);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "herd_cows", since = "1.19.0")]
+impl<'a> FromIterator<Cow<'a, str>> for String {
+ fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String {
+ let mut iterator = iter.into_iter();
+
+ // Because we're iterating over CoWs, we can (potentially) avoid at least
+ // one allocation by getting the first item and appending to it all the
+ // subsequent items.
+ match iterator.next() {
+ None => String::new(),
+ Some(cow) => {
+ let mut buf = cow.into_owned();
+ buf.extend(iterator);
+ buf
+ }
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Extend<char> for String {
+ fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) {
+ let iterator = iter.into_iter();
+ let (lower_bound, _) = iterator.size_hint();
+ self.reserve(lower_bound);
+ iterator.for_each(move |c| self.push(c));
+ }
+
+ #[inline]
+ fn extend_one(&mut self, c: char) {
+ self.push(c);
+ }
+
+ #[inline]
+ fn extend_reserve(&mut self, additional: usize) {
+ self.reserve(additional);
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "extend_ref", since = "1.2.0")]
+impl<'a> Extend<&'a char> for String {
+ fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) {
+ self.extend(iter.into_iter().cloned());
+ }
+
+ #[inline]
+ fn extend_one(&mut self, &c: &'a char) {
+ self.push(c);
+ }
+
+ #[inline]
+ fn extend_reserve(&mut self, additional: usize) {
+ self.reserve(additional);
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> Extend<&'a str> for String {
+ fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
+ iter.into_iter().for_each(move |s| self.push_str(s));
+ }
+
+ #[inline]
+ fn extend_one(&mut self, s: &'a str) {
+ self.push_str(s);
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_str2", since = "1.45.0")]
+impl Extend<Box<str>> for String {
+ fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I) {
+ iter.into_iter().for_each(move |s| self.push_str(&s));
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "extend_string", since = "1.4.0")]
+impl Extend<String> for String {
+ fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
+ iter.into_iter().for_each(move |s| self.push_str(&s));
+ }
+
+ #[inline]
+ fn extend_one(&mut self, s: String) {
+ self.push_str(&s);
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "herd_cows", since = "1.19.0")]
+impl<'a> Extend<Cow<'a, str>> for String {
+ fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) {
+ iter.into_iter().for_each(move |s| self.push_str(&s));
+ }
+
+ #[inline]
+ fn extend_one(&mut self, s: Cow<'a, str>) {
+ self.push_str(&s);
+ }
+}
+
+/// A convenience impl that delegates to the impl for `&str`.
+///
+/// # Examples
+///
+/// ```
+/// assert_eq!(String::from("Hello world").find("world"), Some(6));
+/// ```
+#[unstable(
+ feature = "pattern",
+ reason = "API not fully fleshed out and ready to be stabilized",
+ issue = "27721"
+)]
+impl<'a, 'b> Pattern<'a> for &'b String {
+ type Searcher = <&'b str as Pattern<'a>>::Searcher;
+
+ fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
+ self[..].into_searcher(haystack)
+ }
+
+ #[inline]
+ fn is_contained_in(self, haystack: &'a str) -> bool {
+ self[..].is_contained_in(haystack)
+ }
+
+ #[inline]
+ fn is_prefix_of(self, haystack: &'a str) -> bool {
+ self[..].is_prefix_of(haystack)
+ }
+
+ #[inline]
+ fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> {
+ self[..].strip_prefix_of(haystack)
+ }
+
+ #[inline]
+ fn is_suffix_of(self, haystack: &'a str) -> bool {
+ self[..].is_suffix_of(haystack)
+ }
+
+ #[inline]
+ fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> {
+ self[..].strip_suffix_of(haystack)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl PartialEq for String {
+ #[inline]
+ fn eq(&self, other: &String) -> bool {
+ PartialEq::eq(&self[..], &other[..])
+ }
+ #[inline]
+ fn ne(&self, other: &String) -> bool {
+ PartialEq::ne(&self[..], &other[..])
+ }
+}
+
+macro_rules! impl_eq {
+ ($lhs:ty, $rhs: ty) => {
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[allow(unused_lifetimes)]
+ impl<'a, 'b> PartialEq<$rhs> for $lhs {
+ #[inline]
+ fn eq(&self, other: &$rhs) -> bool {
+ PartialEq::eq(&self[..], &other[..])
+ }
+ #[inline]
+ fn ne(&self, other: &$rhs) -> bool {
+ PartialEq::ne(&self[..], &other[..])
+ }
+ }
+
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[allow(unused_lifetimes)]
+ impl<'a, 'b> PartialEq<$lhs> for $rhs {
+ #[inline]
+ fn eq(&self, other: &$lhs) -> bool {
+ PartialEq::eq(&self[..], &other[..])
+ }
+ #[inline]
+ fn ne(&self, other: &$lhs) -> bool {
+ PartialEq::ne(&self[..], &other[..])
+ }
+ }
+ };
+}
+
+impl_eq! { String, str }
+impl_eq! { String, &'a str }
+#[cfg(not(no_global_oom_handling))]
+impl_eq! { Cow<'a, str>, str }
+#[cfg(not(no_global_oom_handling))]
+impl_eq! { Cow<'a, str>, &'b str }
+#[cfg(not(no_global_oom_handling))]
+impl_eq! { Cow<'a, str>, String }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Default for String {
+ /// Creates an empty `String`.
+ #[inline]
+ fn default() -> String {
+ String::new()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for String {
+ #[inline]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for String {
+ #[inline]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl hash::Hash for String {
+ #[inline]
+ fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
+ (**self).hash(hasher)
+ }
+}
+
+/// Implements the `+` operator for concatenating two strings.
+///
+/// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if
+/// necessary). This is done to avoid allocating a new `String` and copying the entire contents on
+/// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by
+/// repeated concatenation.
+///
+/// The string on the right-hand side is only borrowed; its contents are copied into the returned
+/// `String`.
+///
+/// # Examples
+///
+/// Concatenating two `String`s takes the first by value and borrows the second:
+///
+/// ```
+/// let a = String::from("hello");
+/// let b = String::from(" world");
+/// let c = a + &b;
+/// // `a` is moved and can no longer be used here.
+/// ```
+///
+/// If you want to keep using the first `String`, you can clone it and append to the clone instead:
+///
+/// ```
+/// let a = String::from("hello");
+/// let b = String::from(" world");
+/// let c = a.clone() + &b;
+/// // `a` is still valid here.
+/// ```
+///
+/// Concatenating `&str` slices can be done by converting the first to a `String`:
+///
+/// ```
+/// let a = "hello";
+/// let b = " world";
+/// let c = a.to_string() + b;
+/// ```
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Add<&str> for String {
+ type Output = String;
+
+ #[inline]
+ fn add(mut self, other: &str) -> String {
+ self.push_str(other);
+ self
+ }
+}
+
+/// Implements the `+=` operator for appending to a `String`.
+///
+/// This has the same behavior as the [`push_str`][String::push_str] method.
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "stringaddassign", since = "1.12.0")]
+impl AddAssign<&str> for String {
+ #[inline]
+ fn add_assign(&mut self, other: &str) {
+ self.push_str(other);
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::Range<usize>> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, index: ops::Range<usize>) -> &str {
+ &self[..][index]
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeTo<usize>> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, index: ops::RangeTo<usize>) -> &str {
+ &self[..][index]
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeFrom<usize>> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, index: ops::RangeFrom<usize>) -> &str {
+ &self[..][index]
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeFull> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, _index: ops::RangeFull) -> &str {
+ unsafe { str::from_utf8_unchecked(&self.vec) }
+ }
+}
+#[stable(feature = "inclusive_range", since = "1.26.0")]
+impl ops::Index<ops::RangeInclusive<usize>> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, index: ops::RangeInclusive<usize>) -> &str {
+ Index::index(&**self, index)
+ }
+}
+#[stable(feature = "inclusive_range", since = "1.26.0")]
+impl ops::Index<ops::RangeToInclusive<usize>> for String {
+ type Output = str;
+
+ #[inline]
+ fn index(&self, index: ops::RangeToInclusive<usize>) -> &str {
+ Index::index(&**self, index)
+ }
+}
+
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::Range<usize>> for String {
+ #[inline]
+ fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str {
+ &mut self[..][index]
+ }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeTo<usize>> for String {
+ #[inline]
+ fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str {
+ &mut self[..][index]
+ }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeFrom<usize>> for String {
+ #[inline]
+ fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str {
+ &mut self[..][index]
+ }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeFull> for String {
+ #[inline]
+ fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str {
+ unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
+ }
+}
+#[stable(feature = "inclusive_range", since = "1.26.0")]
+impl ops::IndexMut<ops::RangeInclusive<usize>> for String {
+ #[inline]
+ fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str {
+ IndexMut::index_mut(&mut **self, index)
+ }
+}
+#[stable(feature = "inclusive_range", since = "1.26.0")]
+impl ops::IndexMut<ops::RangeToInclusive<usize>> for String {
+ #[inline]
+ fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str {
+ IndexMut::index_mut(&mut **self, index)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Deref for String {
+ type Target = str;
+
+ #[inline]
+ fn deref(&self) -> &str {
+ unsafe { str::from_utf8_unchecked(&self.vec) }
+ }
+}
+
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::DerefMut for String {
+ #[inline]
+ fn deref_mut(&mut self) -> &mut str {
+ unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
+ }
+}
+
+/// A type alias for [`Infallible`].
+///
+/// This alias exists for backwards compatibility, and may be eventually deprecated.
+///
+/// [`Infallible`]: core::convert::Infallible
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+pub type ParseError = core::convert::Infallible;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl FromStr for String {
+ type Err = core::convert::Infallible;
+ #[inline]
+ fn from_str(s: &str) -> Result<String, Self::Err> {
+ Ok(String::from(s))
+ }
+}
+
+/// A trait for converting a value to a `String`.
+///
+/// This trait is automatically implemented for any type which implements the
+/// [`Display`] trait. As such, `ToString` shouldn't be implemented directly:
+/// [`Display`] should be implemented instead, and you get the `ToString`
+/// implementation for free.
+///
+/// [`Display`]: fmt::Display
+#[cfg_attr(not(test), rustc_diagnostic_item = "ToString")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ToString {
+ /// Converts the given value to a `String`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let i = 5;
+ /// let five = String::from("5");
+ ///
+ /// assert_eq!(five, i.to_string());
+ /// ```
+ #[rustc_conversion_suggestion]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn to_string(&self) -> String;
+}
+
+/// # Panics
+///
+/// In this implementation, the `to_string` method panics
+/// if the `Display` implementation returns an error.
+/// This indicates an incorrect `Display` implementation
+/// since `fmt::Write for String` never returns an error itself.
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: fmt::Display + ?Sized> ToString for T {
+ // A common guideline is to not inline generic functions. However,
+ // removing `#[inline]` from this method causes non-negligible regressions.
+ // See <https://github.com/rust-lang/rust/pull/74852>, the last attempt
+ // to try to remove it.
+ #[inline]
+ default fn to_string(&self) -> String {
+ let mut buf = String::new();
+ let mut formatter = core::fmt::Formatter::new(&mut buf);
+ // Bypass format_args!() to avoid write_str with zero-length strs
+ fmt::Display::fmt(self, &mut formatter)
+ .expect("a Display implementation returned an error unexpectedly");
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "char_to_string_specialization", since = "1.46.0")]
+impl ToString for char {
+ #[inline]
+ fn to_string(&self) -> String {
+ String::from(self.encode_utf8(&mut [0; 4]))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "u8_to_string_specialization", since = "1.54.0")]
+impl ToString for u8 {
+ #[inline]
+ fn to_string(&self) -> String {
+ let mut buf = String::with_capacity(3);
+ let mut n = *self;
+ if n >= 10 {
+ if n >= 100 {
+ buf.push((b'0' + n / 100) as char);
+ n %= 100;
+ }
+ buf.push((b'0' + n / 10) as char);
+ n %= 10;
+ }
+ buf.push((b'0' + n) as char);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "i8_to_string_specialization", since = "1.54.0")]
+impl ToString for i8 {
+ #[inline]
+ fn to_string(&self) -> String {
+ let mut buf = String::with_capacity(4);
+ if self.is_negative() {
+ buf.push('-');
+ }
+ let mut n = self.unsigned_abs();
+ if n >= 10 {
+ if n >= 100 {
+ buf.push('1');
+ n -= 100;
+ }
+ buf.push((b'0' + n / 10) as char);
+ n %= 10;
+ }
+ buf.push((b'0' + n) as char);
+ buf
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
+impl ToString for str {
+ #[inline]
+ fn to_string(&self) -> String {
+ String::from(self)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")]
+impl ToString for Cow<'_, str> {
+ #[inline]
+ fn to_string(&self) -> String {
+ self[..].to_owned()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "string_to_string_specialization", since = "1.17.0")]
+impl ToString for String {
+ #[inline]
+ fn to_string(&self) -> String {
+ self.to_owned()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl AsRef<str> for String {
+ #[inline]
+ fn as_ref(&self) -> &str {
+ self
+ }
+}
+
+#[stable(feature = "string_as_mut", since = "1.43.0")]
+impl AsMut<str> for String {
+ #[inline]
+ fn as_mut(&mut self) -> &mut str {
+ self
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl AsRef<[u8]> for String {
+ #[inline]
+ fn as_ref(&self) -> &[u8] {
+ self.as_bytes()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl From<&str> for String {
+ /// Converts a `&str` into a [`String`].
+ ///
+ /// The result is allocated on the heap.
+ #[inline]
+ fn from(s: &str) -> String {
+ s.to_owned()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_mut_str_for_string", since = "1.44.0")]
+impl From<&mut str> for String {
+ /// Converts a `&mut str` into a [`String`].
+ ///
+ /// The result is allocated on the heap.
+ #[inline]
+ fn from(s: &mut str) -> String {
+ s.to_owned()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_ref_string", since = "1.35.0")]
+impl From<&String> for String {
+ /// Converts a `&String` into a [`String`].
+ ///
+ /// This clones `s` and returns the clone.
+ #[inline]
+ fn from(s: &String) -> String {
+ s.clone()
+ }
+}
+
+// note: test pulls in libstd, which causes errors here
+#[cfg(not(test))]
+#[stable(feature = "string_from_box", since = "1.18.0")]
+impl From<Box<str>> for String {
+ /// Converts the given boxed `str` slice to a [`String`].
+ /// It is notable that the `str` slice is owned.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s1: String = String::from("hello world");
+ /// let s2: Box<str> = s1.into_boxed_str();
+ /// let s3: String = String::from(s2);
+ ///
+ /// assert_eq!("hello world", s3)
+ /// ```
+ fn from(s: Box<str>) -> String {
+ s.into_string()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "box_from_str", since = "1.20.0")]
+impl From<String> for Box<str> {
+ /// Converts the given [`String`] to a boxed `str` slice that is owned.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s1: String = String::from("hello world");
+ /// let s2: Box<str> = Box::from(s1);
+ /// let s3: String = String::from(s2);
+ ///
+ /// assert_eq!("hello world", s3)
+ /// ```
+ fn from(s: String) -> Box<str> {
+ s.into_boxed_str()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "string_from_cow_str", since = "1.14.0")]
+impl<'a> From<Cow<'a, str>> for String {
+ /// Converts a clone-on-write string to an owned
+ /// instance of [`String`].
+ ///
+ /// This extracts the owned string,
+ /// clones the string if it is not already owned.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::borrow::Cow;
+ /// // If the string is not owned...
+ /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+ /// // It will allocate on the heap and copy the string.
+ /// let owned: String = String::from(cow);
+ /// assert_eq!(&owned[..], "eggplant");
+ /// ```
+ fn from(s: Cow<'a, str>) -> String {
+ s.into_owned()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<&'a str> for Cow<'a, str> {
+ /// Converts a string slice into a [`Borrowed`] variant.
+ /// No heap allocation is performed, and the string
+ /// is not copied.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::borrow::Cow;
+ /// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));
+ /// ```
+ ///
+ /// [`Borrowed`]: crate::borrow::Cow::Borrowed
+ #[inline]
+ fn from(s: &'a str) -> Cow<'a, str> {
+ Cow::Borrowed(s)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<String> for Cow<'a, str> {
+ /// Converts a [`String`] into an [`Owned`] variant.
+ /// No heap allocation is performed, and the string
+ /// is not copied.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::borrow::Cow;
+ /// let s = "eggplant".to_string();
+ /// let s2 = "eggplant".to_string();
+ /// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2));
+ /// ```
+ ///
+ /// [`Owned`]: crate::borrow::Cow::Owned
+ #[inline]
+ fn from(s: String) -> Cow<'a, str> {
+ Cow::Owned(s)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_from_string_ref", since = "1.28.0")]
+impl<'a> From<&'a String> for Cow<'a, str> {
+ /// Converts a [`String`] reference into a [`Borrowed`] variant.
+ /// No heap allocation is performed, and the string
+ /// is not copied.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::borrow::Cow;
+ /// let s = "eggplant".to_string();
+ /// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant"));
+ /// ```
+ ///
+ /// [`Borrowed`]: crate::borrow::Cow::Borrowed
+ #[inline]
+ fn from(s: &'a String) -> Cow<'a, str> {
+ Cow::Borrowed(s.as_str())
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a> FromIterator<char> for Cow<'a, str> {
+ fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> {
+ Cow::Owned(FromIterator::from_iter(it))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> {
+ fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> {
+ Cow::Owned(FromIterator::from_iter(it))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a> FromIterator<String> for Cow<'a, str> {
+ fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> {
+ Cow::Owned(FromIterator::from_iter(it))
+ }
+}
+
+#[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
+impl From<String> for Vec<u8> {
+ /// Converts the given [`String`] to a vector [`Vec`] that holds values of type [`u8`].
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s1 = String::from("hello world");
+ /// let v1 = Vec::from(s1);
+ ///
+ /// for b in v1 {
+ /// println!("{}", b);
+ /// }
+ /// ```
+ fn from(string: String) -> Vec<u8> {
+ string.into_bytes()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Write for String {
+ #[inline]
+ fn write_str(&mut self, s: &str) -> fmt::Result {
+ self.push_str(s);
+ Ok(())
+ }
+
+ #[inline]
+ fn write_char(&mut self, c: char) -> fmt::Result {
+ self.push(c);
+ Ok(())
+ }
+}
+
+/// A draining iterator for `String`.
+///
+/// This struct is created by the [`drain`] method on [`String`]. See its
+/// documentation for more.
+///
+/// [`drain`]: String::drain
+#[stable(feature = "drain", since = "1.6.0")]
+pub struct Drain<'a> {
+ /// Will be used as &'a mut String in the destructor
+ string: *mut String,
+ /// Start of part to remove
+ start: usize,
+ /// End of part to remove
+ end: usize,
+ /// Current remaining range to remove
+ iter: Chars<'a>,
+}
+
+#[stable(feature = "collection_debug", since = "1.17.0")]
+impl fmt::Debug for Drain<'_> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_tuple("Drain").field(&self.as_str()).finish()
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl Sync for Drain<'_> {}
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl Send for Drain<'_> {}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl Drop for Drain<'_> {
+ fn drop(&mut self) {
+ unsafe {
+ // Use Vec::drain. "Reaffirm" the bounds checks to avoid
+ // panic code being inserted again.
+ let self_vec = (*self.string).as_mut_vec();
+ if self.start <= self.end && self.end <= self_vec.len() {
+ self_vec.drain(self.start..self.end);
+ }
+ }
+ }
+}
+
+impl<'a> Drain<'a> {
+ /// Returns the remaining (sub)string of this iterator as a slice.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(string_drain_as_str)]
+ /// let mut s = String::from("abc");
+ /// let mut drain = s.drain(..);
+ /// assert_eq!(drain.as_str(), "abc");
+ /// let _ = drain.next().unwrap();
+ /// assert_eq!(drain.as_str(), "bc");
+ /// ```
+ #[unstable(feature = "string_drain_as_str", issue = "76905")] // Note: uncomment AsRef impls below when stabilizing.
+ pub fn as_str(&self) -> &str {
+ self.iter.as_str()
+ }
+}
+
+// Uncomment when stabilizing `string_drain_as_str`.
+// #[unstable(feature = "string_drain_as_str", issue = "76905")]
+// impl<'a> AsRef<str> for Drain<'a> {
+// fn as_ref(&self) -> &str {
+// self.as_str()
+// }
+// }
+//
+// #[unstable(feature = "string_drain_as_str", issue = "76905")]
+// impl<'a> AsRef<[u8]> for Drain<'a> {
+// fn as_ref(&self) -> &[u8] {
+// self.as_str().as_bytes()
+// }
+// }
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl Iterator for Drain<'_> {
+ type Item = char;
+
+ #[inline]
+ fn next(&mut self) -> Option<char> {
+ self.iter.next()
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.iter.size_hint()
+ }
+
+ #[inline]
+ fn last(mut self) -> Option<char> {
+ self.next_back()
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl DoubleEndedIterator for Drain<'_> {
+ #[inline]
+ fn next_back(&mut self) -> Option<char> {
+ self.iter.next_back()
+ }
+}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl FusedIterator for Drain<'_> {}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_char_for_string", since = "1.46.0")]
+impl From<char> for String {
+ /// Allocates an owned [`String`] from a single character.
+ ///
+ /// # Example
+ /// ```rust
+ /// let c: char = 'a';
+ /// let s: String = String::from(c);
+ /// assert_eq!("a", &s[..]);
+ /// ```
+ #[inline]
+ fn from(c: char) -> Self {
+ c.to_string()
+ }
+}
diff --git a/rust/alloc/sync.rs b/rust/alloc/sync.rs
new file mode 100644
index 00000000000..1f4e446806c
--- /dev/null
+++ b/rust/alloc/sync.rs
@@ -0,0 +1,2631 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+//! Thread-safe reference-counting pointers.
+//!
+//! See the [`Arc<T>`][Arc] documentation for more details.
+
+use core::any::Any;
+use core::borrow;
+use core::cmp::Ordering;
+use core::convert::{From, TryFrom};
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::hint;
+use core::intrinsics::abort;
+#[cfg(not(no_global_oom_handling))]
+use core::iter;
+use core::marker::{PhantomData, Unpin, Unsize};
+#[cfg(not(no_global_oom_handling))]
+use core::mem::size_of_val;
+use core::mem::{self, align_of_val_raw};
+use core::ops::{CoerceUnsized, Deref, DispatchFromDyn, Receiver};
+#[cfg(not(no_global_oom_handling))]
+use core::pin::Pin;
+use core::ptr::{self, NonNull};
+#[cfg(not(no_global_oom_handling))]
+use core::slice::from_raw_parts_mut;
+use core::sync::atomic;
+use core::sync::atomic::Ordering::{Acquire, Relaxed, Release, SeqCst};
+
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::handle_alloc_error;
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::{box_free, WriteCloneIntoRaw};
+use crate::alloc::{AllocError, Allocator, Global, Layout};
+use crate::borrow::{Cow, ToOwned};
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::rc::is_dangling;
+#[cfg(not(no_global_oom_handling))]
+use crate::string::String;
+use crate::vec::Vec;
+
+#[cfg(test)]
+mod tests;
+
+/// A soft limit on the amount of references that may be made to an `Arc`.
+///
+/// Going above this limit will abort your program (although not
+/// necessarily) at _exactly_ `MAX_REFCOUNT + 1` references.
+const MAX_REFCOUNT: usize = (isize::MAX) as usize;
+
+#[cfg(not(sanitize = "thread"))]
+macro_rules! acquire {
+ ($x:expr) => {
+ atomic::fence(Acquire)
+ };
+}
+
+// ThreadSanitizer does not support memory fences. To avoid false positive
+// reports in Arc / Weak implementation use atomic loads for synchronization
+// instead.
+#[cfg(sanitize = "thread")]
+macro_rules! acquire {
+ ($x:expr) => {
+ $x.load(Acquire)
+ };
+}
+
+/// A thread-safe reference-counting pointer. 'Arc' stands for 'Atomically
+/// Reference Counted'.
+///
+/// The type `Arc<T>` provides shared ownership of a value of type `T`,
+/// allocated in the heap. Invoking [`clone`][clone] on `Arc` produces
+/// a new `Arc` instance, which points to the same allocation on the heap as the
+/// source `Arc`, while increasing a reference count. When the last `Arc`
+/// pointer to a given allocation is destroyed, the value stored in that allocation (often
+/// referred to as "inner value") is also dropped.
+///
+/// Shared references in Rust disallow mutation by default, and `Arc` is no
+/// exception: you cannot generally obtain a mutable reference to something
+/// inside an `Arc`. If you need to mutate through an `Arc`, use
+/// [`Mutex`][mutex], [`RwLock`][rwlock], or one of the [`Atomic`][atomic]
+/// types.
+///
+/// ## Thread Safety
+///
+/// Unlike [`Rc<T>`], `Arc<T>` uses atomic operations for its reference
+/// counting. This means that it is thread-safe. The disadvantage is that
+/// atomic operations are more expensive than ordinary memory accesses. If you
+/// are not sharing reference-counted allocations between threads, consider using
+/// [`Rc<T>`] for lower overhead. [`Rc<T>`] is a safe default, because the
+/// compiler will catch any attempt to send an [`Rc<T>`] between threads.
+/// However, a library might choose `Arc<T>` in order to give library consumers
+/// more flexibility.
+///
+/// `Arc<T>` will implement [`Send`] and [`Sync`] as long as the `T` implements
+/// [`Send`] and [`Sync`]. Why can't you put a non-thread-safe type `T` in an
+/// `Arc<T>` to make it thread-safe? This may be a bit counter-intuitive at
+/// first: after all, isn't the point of `Arc<T>` thread safety? The key is
+/// this: `Arc<T>` makes it thread safe to have multiple ownership of the same
+/// data, but it doesn't add thread safety to its data. Consider
+/// `Arc<`[`RefCell<T>`]`>`. [`RefCell<T>`] isn't [`Sync`], and if `Arc<T>` was always
+/// [`Send`], `Arc<`[`RefCell<T>`]`>` would be as well. But then we'd have a problem:
+/// [`RefCell<T>`] is not thread safe; it keeps track of the borrowing count using
+/// non-atomic operations.
+///
+/// In the end, this means that you may need to pair `Arc<T>` with some sort of
+/// [`std::sync`] type, usually [`Mutex<T>`][mutex].
+///
+/// ## Breaking cycles with `Weak`
+///
+/// The [`downgrade`][downgrade] method can be used to create a non-owning
+/// [`Weak`] pointer. A [`Weak`] pointer can be [`upgrade`][upgrade]d
+/// to an `Arc`, but this will return [`None`] if the value stored in the allocation has
+/// already been dropped. In other words, `Weak` pointers do not keep the value
+/// inside the allocation alive; however, they *do* keep the allocation
+/// (the backing store for the value) alive.
+///
+/// A cycle between `Arc` pointers will never be deallocated. For this reason,
+/// [`Weak`] is used to break cycles. For example, a tree could have
+/// strong `Arc` pointers from parent nodes to children, and [`Weak`]
+/// pointers from children back to their parents.
+///
+/// # Cloning references
+///
+/// Creating a new reference from an existing reference-counted pointer is done using the
+/// `Clone` trait implemented for [`Arc<T>`][Arc] and [`Weak<T>`][Weak].
+///
+/// ```
+/// use std::sync::Arc;
+/// let foo = Arc::new(vec![1.0, 2.0, 3.0]);
+/// // The two syntaxes below are equivalent.
+/// let a = foo.clone();
+/// let b = Arc::clone(&foo);
+/// // a, b, and foo are all Arcs that point to the same memory location
+/// ```
+///
+/// ## `Deref` behavior
+///
+/// `Arc<T>` automatically dereferences to `T` (via the [`Deref`][deref] trait),
+/// so you can call `T`'s methods on a value of type `Arc<T>`. To avoid name
+/// clashes with `T`'s methods, the methods of `Arc<T>` itself are associated
+/// functions, called using [fully qualified syntax]:
+///
+/// ```
+/// use std::sync::Arc;
+///
+/// let my_arc = Arc::new(());
+/// Arc::downgrade(&my_arc);
+/// ```
+///
+/// `Arc<T>`'s implementations of traits like `Clone` may also be called using
+/// fully qualified syntax. Some people prefer to use fully qualified syntax,
+/// while others prefer using method-call syntax.
+///
+/// ```
+/// use std::sync::Arc;
+///
+/// let arc = Arc::new(());
+/// // Method-call syntax
+/// let arc2 = arc.clone();
+/// // Fully qualified syntax
+/// let arc3 = Arc::clone(&arc);
+/// ```
+///
+/// [`Weak<T>`][Weak] does not auto-dereference to `T`, because the inner value may have
+/// already been dropped.
+///
+/// [`Rc<T>`]: crate::rc::Rc
+/// [clone]: Clone::clone
+/// [mutex]: ../../std/sync/struct.Mutex.html
+/// [rwlock]: ../../std/sync/struct.RwLock.html
+/// [atomic]: core::sync::atomic
+/// [`Send`]: core::marker::Send
+/// [`Sync`]: core::marker::Sync
+/// [deref]: core::ops::Deref
+/// [downgrade]: Arc::downgrade
+/// [upgrade]: Weak::upgrade
+/// [`RefCell<T>`]: core::cell::RefCell
+/// [`std::sync`]: ../../std/sync/index.html
+/// [`Arc::clone(&from)`]: Arc::clone
+/// [fully qualified syntax]: https://doc.rust-lang.org/book/ch19-03-advanced-traits.html#fully-qualified-syntax-for-disambiguation-calling-methods-with-the-same-name
+///
+/// # Examples
+///
+/// Sharing some immutable data between threads:
+///
+// Note that we **do not** run these tests here. The windows builders get super
+// unhappy if a thread outlives the main thread and then exits at the same time
+// (something deadlocks) so we just avoid this entirely by not running these
+// tests.
+/// ```no_run
+/// use std::sync::Arc;
+/// use std::thread;
+///
+/// let five = Arc::new(5);
+///
+/// for _ in 0..10 {
+/// let five = Arc::clone(&five);
+///
+/// thread::spawn(move || {
+/// println!("{:?}", five);
+/// });
+/// }
+/// ```
+///
+/// Sharing a mutable [`AtomicUsize`]:
+///
+/// [`AtomicUsize`]: core::sync::atomic::AtomicUsize
+///
+/// ```no_run
+/// use std::sync::Arc;
+/// use std::sync::atomic::{AtomicUsize, Ordering};
+/// use std::thread;
+///
+/// let val = Arc::new(AtomicUsize::new(5));
+///
+/// for _ in 0..10 {
+/// let val = Arc::clone(&val);
+///
+/// thread::spawn(move || {
+/// let v = val.fetch_add(1, Ordering::SeqCst);
+/// println!("{:?}", v);
+/// });
+/// }
+/// ```
+///
+/// See the [`rc` documentation][rc_examples] for more examples of reference
+/// counting in general.
+///
+/// [rc_examples]: crate::rc#examples
+#[cfg_attr(not(test), rustc_diagnostic_item = "Arc")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Arc<T: ?Sized> {
+ ptr: NonNull<ArcInner<T>>,
+ phantom: PhantomData<ArcInner<T>>,
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> {}
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}
+
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Arc<U>> for Arc<T> {}
+
+impl<T: ?Sized> Arc<T> {
+ fn from_inner(ptr: NonNull<ArcInner<T>>) -> Self {
+ Self { ptr, phantom: PhantomData }
+ }
+
+ unsafe fn from_ptr(ptr: *mut ArcInner<T>) -> Self {
+ unsafe { Self::from_inner(NonNull::new_unchecked(ptr)) }
+ }
+}
+
+/// `Weak` is a version of [`Arc`] that holds a non-owning reference to the
+/// managed allocation. The allocation is accessed by calling [`upgrade`] on the `Weak`
+/// pointer, which returns an [`Option`]`<`[`Arc`]`<T>>`.
+///
+/// Since a `Weak` reference does not count towards ownership, it will not
+/// prevent the value stored in the allocation from being dropped, and `Weak` itself makes no
+/// guarantees about the value still being present. Thus it may return [`None`]
+/// when [`upgrade`]d. Note however that a `Weak` reference *does* prevent the allocation
+/// itself (the backing store) from being deallocated.
+///
+/// A `Weak` pointer is useful for keeping a temporary reference to the allocation
+/// managed by [`Arc`] without preventing its inner value from being dropped. It is also used to
+/// prevent circular references between [`Arc`] pointers, since mutual owning references
+/// would never allow either [`Arc`] to be dropped. For example, a tree could
+/// have strong [`Arc`] pointers from parent nodes to children, and `Weak`
+/// pointers from children back to their parents.
+///
+/// The typical way to obtain a `Weak` pointer is to call [`Arc::downgrade`].
+///
+/// [`upgrade`]: Weak::upgrade
+#[stable(feature = "arc_weak", since = "1.4.0")]
+pub struct Weak<T: ?Sized> {
+ // This is a `NonNull` to allow optimizing the size of this type in enums,
+ // but it is not necessarily a valid pointer.
+ // `Weak::new` sets this to `usize::MAX` so that it doesn’t need
+ // to allocate space on the heap. That's not a value a real pointer
+ // will ever have because RcBox has alignment at least 2.
+ // This is only possible when `T: Sized`; unsized `T` never dangle.
+ ptr: NonNull<ArcInner<T>>,
+}
+
+#[stable(feature = "arc_weak", since = "1.4.0")]
+unsafe impl<T: ?Sized + Sync + Send> Send for Weak<T> {}
+#[stable(feature = "arc_weak", since = "1.4.0")]
+unsafe impl<T: ?Sized + Sync + Send> Sync for Weak<T> {}
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Weak<U>> for Weak<T> {}
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Weak<U>> for Weak<T> {}
+
+#[stable(feature = "arc_weak", since = "1.4.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "(Weak)")
+ }
+}
+
+// This is repr(C) to future-proof against possible field-reordering, which
+// would interfere with otherwise safe [into|from]_raw() of transmutable
+// inner types.
+#[repr(C)]
+struct ArcInner<T: ?Sized> {
+ strong: atomic::AtomicUsize,
+
+ // the value usize::MAX acts as a sentinel for temporarily "locking" the
+ // ability to upgrade weak pointers or downgrade strong ones; this is used
+ // to avoid races in `make_mut` and `get_mut`.
+ weak: atomic::AtomicUsize,
+
+ data: T,
+}
+
+unsafe impl<T: ?Sized + Sync + Send> Send for ArcInner<T> {}
+unsafe impl<T: ?Sized + Sync + Send> Sync for ArcInner<T> {}
+
+impl<T> Arc<T> {
+ /// Constructs a new `Arc<T>`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn new(data: T) -> Arc<T> {
+ // Start the weak pointer count as 1 which is the weak pointer that's
+ // held by all the strong pointers (kinda), see std/rc.rs for more info
+ let x: Box<_> = box ArcInner {
+ strong: atomic::AtomicUsize::new(1),
+ weak: atomic::AtomicUsize::new(1),
+ data,
+ };
+ Self::from_inner(Box::leak(x).into())
+ }
+
+ /// Constructs a new `Arc<T>` using a weak reference to itself. Attempting
+ /// to upgrade the weak reference before this function returns will result
+ /// in a `None` value. However, the weak reference may be cloned freely and
+ /// stored for use at a later time.
+ ///
+ /// # Examples
+ /// ```
+ /// #![feature(arc_new_cyclic)]
+ /// #![allow(dead_code)]
+ ///
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// struct Foo {
+ /// me: Weak<Foo>,
+ /// }
+ ///
+ /// let foo = Arc::new_cyclic(|me| Foo {
+ /// me: me.clone(),
+ /// });
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[unstable(feature = "arc_new_cyclic", issue = "75861")]
+ pub fn new_cyclic(data_fn: impl FnOnce(&Weak<T>) -> T) -> Arc<T> {
+ // Construct the inner in the "uninitialized" state with a single
+ // weak reference.
+ let uninit_ptr: NonNull<_> = Box::leak(box ArcInner {
+ strong: atomic::AtomicUsize::new(0),
+ weak: atomic::AtomicUsize::new(1),
+ data: mem::MaybeUninit::<T>::uninit(),
+ })
+ .into();
+ let init_ptr: NonNull<ArcInner<T>> = uninit_ptr.cast();
+
+ let weak = Weak { ptr: init_ptr };
+
+ // It's important we don't give up ownership of the weak pointer, or
+ // else the memory might be freed by the time `data_fn` returns. If
+ // we really wanted to pass ownership, we could create an additional
+ // weak pointer for ourselves, but this would result in additional
+ // updates to the weak reference count which might not be necessary
+ // otherwise.
+ let data = data_fn(&weak);
+
+ // Now we can properly initialize the inner value and turn our weak
+ // reference into a strong reference.
+ unsafe {
+ let inner = init_ptr.as_ptr();
+ ptr::write(ptr::addr_of_mut!((*inner).data), data);
+
+ // The above write to the data field must be visible to any threads which
+ // observe a non-zero strong count. Therefore we need at least "Release" ordering
+ // in order to synchronize with the `compare_exchange_weak` in `Weak::upgrade`.
+ //
+ // "Acquire" ordering is not required. When considering the possible behaviours
+ // of `data_fn` we only need to look at what it could do with a reference to a
+ // non-upgradeable `Weak`:
+ // - It can *clone* the `Weak`, increasing the weak reference count.
+ // - It can drop those clones, decreasing the weak reference count (but never to zero).
+ //
+ // These side effects do not impact us in any way, and no other side effects are
+ // possible with safe code alone.
+ let prev_value = (*inner).strong.fetch_add(1, Release);
+ debug_assert_eq!(prev_value, 0, "No prior strong references should exist");
+ }
+
+ let strong = Arc::from_inner(init_ptr);
+
+ // Strong references should collectively own a shared weak reference,
+ // so don't run the destructor for our old weak reference.
+ mem::forget(weak);
+ strong
+ }
+
+ /// Constructs a new `Arc` with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut five = Arc::<u32>::new_uninit();
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit() -> Arc<mem::MaybeUninit<T>> {
+ unsafe {
+ Arc::from_ptr(Arc::allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate(layout),
+ |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
+ ))
+ }
+ }
+
+ /// Constructs a new `Arc` with uninitialized contents, with the memory
+ /// being filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let zero = Arc::<u32>::new_zeroed();
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0)
+ /// ```
+ ///
+ /// [zeroed]: ../../std/mem/union.MaybeUninit.html#method.zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed() -> Arc<mem::MaybeUninit<T>> {
+ unsafe {
+ Arc::from_ptr(Arc::allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
+ ))
+ }
+ }
+
+ /// Constructs a new `Pin<Arc<T>>`. If `T` does not implement `Unpin`, then
+ /// `data` will be pinned in memory and unable to be moved.
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "pin", since = "1.33.0")]
+ pub fn pin(data: T) -> Pin<Arc<T>> {
+ unsafe { Pin::new_unchecked(Arc::new(data)) }
+ }
+
+ /// Constructs a new `Arc<T>`, returning an error if allocation fails.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::try_new(5)?;
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn try_new(data: T) -> Result<Arc<T>, AllocError> {
+ // Start the weak pointer count as 1 which is the weak pointer that's
+ // held by all the strong pointers (kinda), see std/rc.rs for more info
+ let x: Box<_> = Box::try_new(ArcInner {
+ strong: atomic::AtomicUsize::new(1),
+ weak: atomic::AtomicUsize::new(1),
+ data,
+ })?;
+ Ok(Self::from_inner(Box::leak(x).into()))
+ }
+
+ /// Constructs a new `Arc` with uninitialized contents, returning an error
+ /// if allocation fails.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit, allocator_api)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut five = Arc::<u32>::try_new_uninit()?;
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_uninit() -> Result<Arc<mem::MaybeUninit<T>>, AllocError> {
+ unsafe {
+ Ok(Arc::from_ptr(Arc::try_allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate(layout),
+ |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
+ )?))
+ }
+ }
+
+ /// Constructs a new `Arc` with uninitialized contents, with the memory
+ /// being filled with `0` bytes, returning an error if allocation fails.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
+ /// of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit, allocator_api)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let zero = Arc::<u32>::try_new_zeroed()?;
+ /// let zero = unsafe { zero.assume_init() };
+ ///
+ /// assert_eq!(*zero, 0);
+ /// # Ok::<(), std::alloc::AllocError>(())
+ /// ```
+ ///
+ /// [zeroed]: mem::MaybeUninit::zeroed
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn try_new_zeroed() -> Result<Arc<mem::MaybeUninit<T>>, AllocError> {
+ unsafe {
+ Ok(Arc::from_ptr(Arc::try_allocate_for_layout(
+ Layout::new::<T>(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
+ )?))
+ }
+ }
+ /// Returns the inner value, if the `Arc` has exactly one strong reference.
+ ///
+ /// Otherwise, an [`Err`] is returned with the same `Arc` that was
+ /// passed in.
+ ///
+ /// This will succeed even if there are outstanding weak references.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let x = Arc::new(3);
+ /// assert_eq!(Arc::try_unwrap(x), Ok(3));
+ ///
+ /// let x = Arc::new(4);
+ /// let _y = Arc::clone(&x);
+ /// assert_eq!(*Arc::try_unwrap(x).unwrap_err(), 4);
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_unique", since = "1.4.0")]
+ pub fn try_unwrap(this: Self) -> Result<T, Self> {
+ if this.inner().strong.compare_exchange(1, 0, Relaxed, Relaxed).is_err() {
+ return Err(this);
+ }
+
+ acquire!(this.inner().strong);
+
+ unsafe {
+ let elem = ptr::read(&this.ptr.as_ref().data);
+
+ // Make a weak pointer to clean up the implicit strong-weak reference
+ let _weak = Weak { ptr: this.ptr };
+ mem::forget(this);
+
+ Ok(elem)
+ }
+ }
+}
+
+impl<T> Arc<[T]> {
+ /// Constructs a new atomically reference-counted slice with uninitialized contents.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+ /// Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+ /// Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_uninit_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
+ unsafe { Arc::from_ptr(Arc::allocate_for_slice(len)) }
+ }
+
+ /// Constructs a new atomically reference-counted slice with uninitialized contents, with the memory being
+ /// filled with `0` bytes.
+ ///
+ /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and
+ /// incorrect usage of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let values = Arc::<[u32]>::new_zeroed_slice(3);
+ /// let values = unsafe { values.assume_init() };
+ ///
+ /// assert_eq!(*values, [0, 0, 0])
+ /// ```
+ ///
+ /// [zeroed]: ../../std/mem/union.MaybeUninit.html#method.zeroed
+ #[cfg(not(no_global_oom_handling))]
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ pub fn new_zeroed_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
+ unsafe {
+ Arc::from_ptr(Arc::allocate_for_layout(
+ Layout::array::<T>(len).unwrap(),
+ |layout| Global.allocate_zeroed(layout),
+ |mem| {
+ ptr::slice_from_raw_parts_mut(mem as *mut T, len)
+ as *mut ArcInner<[mem::MaybeUninit<T>]>
+ },
+ ))
+ }
+ }
+}
+
+impl<T> Arc<mem::MaybeUninit<T>> {
+ /// Converts to `Arc<T>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the inner value
+ /// really is in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut five = Arc::<u32>::new_uninit();
+ ///
+ /// let five = unsafe {
+ /// // Deferred initialization:
+ /// Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
+ ///
+ /// five.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*five, 5)
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Arc<T> {
+ Arc::from_inner(mem::ManuallyDrop::new(self).ptr.cast())
+ }
+}
+
+impl<T> Arc<[mem::MaybeUninit<T>]> {
+ /// Converts to `Arc<[T]>`.
+ ///
+ /// # Safety
+ ///
+ /// As with [`MaybeUninit::assume_init`],
+ /// it is up to the caller to guarantee that the inner value
+ /// really is in an initialized state.
+ /// Calling this when the content is not yet fully initialized
+ /// causes immediate undefined behavior.
+ ///
+ /// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(new_uninit)]
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
+ ///
+ /// let values = unsafe {
+ /// // Deferred initialization:
+ /// Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
+ /// Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
+ /// Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
+ ///
+ /// values.assume_init()
+ /// };
+ ///
+ /// assert_eq!(*values, [1, 2, 3])
+ /// ```
+ #[unstable(feature = "new_uninit", issue = "63291")]
+ #[inline]
+ pub unsafe fn assume_init(self) -> Arc<[T]> {
+ unsafe { Arc::from_ptr(mem::ManuallyDrop::new(self).ptr.as_ptr() as _) }
+ }
+}
+
+impl<T: ?Sized> Arc<T> {
+ /// Consumes the `Arc`, returning the wrapped pointer.
+ ///
+ /// To avoid a memory leak the pointer must be converted back to an `Arc` using
+ /// [`Arc::from_raw`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let x = Arc::new("hello".to_owned());
+ /// let x_ptr = Arc::into_raw(x);
+ /// assert_eq!(unsafe { &*x_ptr }, "hello");
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub fn into_raw(this: Self) -> *const T {
+ let ptr = Self::as_ptr(&this);
+ mem::forget(this);
+ ptr
+ }
+
+ /// Provides a raw pointer to the data.
+ ///
+ /// The counts are not affected in any way and the `Arc` is not consumed. The pointer is valid for
+ /// as long as there are strong counts in the `Arc`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let x = Arc::new("hello".to_owned());
+ /// let y = Arc::clone(&x);
+ /// let x_ptr = Arc::as_ptr(&x);
+ /// assert_eq!(x_ptr, Arc::as_ptr(&y));
+ /// assert_eq!(unsafe { &*x_ptr }, "hello");
+ /// ```
+ #[stable(feature = "rc_as_ptr", since = "1.45.0")]
+ pub fn as_ptr(this: &Self) -> *const T {
+ let ptr: *mut ArcInner<T> = NonNull::as_ptr(this.ptr);
+
+ // SAFETY: This cannot go through Deref::deref or RcBoxPtr::inner because
+ // this is required to retain raw/mut provenance such that e.g. `get_mut` can
+ // write through the pointer after the Rc is recovered through `from_raw`.
+ unsafe { ptr::addr_of_mut!((*ptr).data) }
+ }
+
+ /// Constructs an `Arc<T>` from a raw pointer.
+ ///
+ /// The raw pointer must have been previously returned by a call to
+ /// [`Arc<U>::into_raw`][into_raw] where `U` must have the same size and
+ /// alignment as `T`. This is trivially true if `U` is `T`.
+ /// Note that if `U` is not `T` but has the same size and alignment, this is
+ /// basically like transmuting references of different types. See
+ /// [`mem::transmute`][transmute] for more information on what
+ /// restrictions apply in this case.
+ ///
+ /// The user of `from_raw` has to make sure a specific value of `T` is only
+ /// dropped once.
+ ///
+ /// This function is unsafe because improper use may lead to memory unsafety,
+ /// even if the returned `Arc<T>` is never accessed.
+ ///
+ /// [into_raw]: Arc::into_raw
+ /// [transmute]: core::mem::transmute
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let x = Arc::new("hello".to_owned());
+ /// let x_ptr = Arc::into_raw(x);
+ ///
+ /// unsafe {
+ /// // Convert back to an `Arc` to prevent leak.
+ /// let x = Arc::from_raw(x_ptr);
+ /// assert_eq!(&*x, "hello");
+ ///
+ /// // Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
+ /// }
+ ///
+ /// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub unsafe fn from_raw(ptr: *const T) -> Self {
+ unsafe {
+ let offset = data_offset(ptr);
+
+ // Reverse the offset to find the original ArcInner.
+ let arc_ptr = (ptr as *mut ArcInner<T>).set_ptr_value((ptr as *mut u8).offset(-offset));
+
+ Self::from_ptr(arc_ptr)
+ }
+ }
+
+ /// Creates a new [`Weak`] pointer to this allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// let weak_five = Arc::downgrade(&five);
+ /// ```
+ #[stable(feature = "arc_weak", since = "1.4.0")]
+ pub fn downgrade(this: &Self) -> Weak<T> {
+ // This Relaxed is OK because we're checking the value in the CAS
+ // below.
+ let mut cur = this.inner().weak.load(Relaxed);
+
+ loop {
+ // check if the weak counter is currently "locked"; if so, spin.
+ if cur == usize::MAX {
+ hint::spin_loop();
+ cur = this.inner().weak.load(Relaxed);
+ continue;
+ }
+
+ // NOTE: this code currently ignores the possibility of overflow
+ // into usize::MAX; in general both Rc and Arc need to be adjusted
+ // to deal with overflow.
+
+ // Unlike with Clone(), we need this to be an Acquire read to
+ // synchronize with the write coming from `is_unique`, so that the
+ // events prior to that write happen before this read.
+ match this.inner().weak.compare_exchange_weak(cur, cur + 1, Acquire, Relaxed) {
+ Ok(_) => {
+ // Make sure we do not create a dangling Weak
+ debug_assert!(!is_dangling(this.ptr.as_ptr()));
+ return Weak { ptr: this.ptr };
+ }
+ Err(old) => cur = old,
+ }
+ }
+ }
+
+ /// Gets the number of [`Weak`] pointers to this allocation.
+ ///
+ /// # Safety
+ ///
+ /// This method by itself is safe, but using it correctly requires extra care.
+ /// Another thread can change the weak count at any time,
+ /// including potentially between calling this method and acting on the result.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ /// let _weak_five = Arc::downgrade(&five);
+ ///
+ /// // This assertion is deterministic because we haven't shared
+ /// // the `Arc` or `Weak` between threads.
+ /// assert_eq!(1, Arc::weak_count(&five));
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_counts", since = "1.15.0")]
+ pub fn weak_count(this: &Self) -> usize {
+ let cnt = this.inner().weak.load(SeqCst);
+ // If the weak count is currently locked, the value of the
+ // count was 0 just before taking the lock.
+ if cnt == usize::MAX { 0 } else { cnt - 1 }
+ }
+
+ /// Gets the number of strong (`Arc`) pointers to this allocation.
+ ///
+ /// # Safety
+ ///
+ /// This method by itself is safe, but using it correctly requires extra care.
+ /// Another thread can change the strong count at any time,
+ /// including potentially between calling this method and acting on the result.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ /// let _also_five = Arc::clone(&five);
+ ///
+ /// // This assertion is deterministic because we haven't shared
+ /// // the `Arc` between threads.
+ /// assert_eq!(2, Arc::strong_count(&five));
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_counts", since = "1.15.0")]
+ pub fn strong_count(this: &Self) -> usize {
+ this.inner().strong.load(SeqCst)
+ }
+
+ /// Increments the strong reference count on the `Arc<T>` associated with the
+ /// provided pointer by one.
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have been obtained through `Arc::into_raw`, and the
+ /// associated `Arc` instance must be valid (i.e. the strong count must be at
+ /// least 1) for the duration of this method.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// unsafe {
+ /// let ptr = Arc::into_raw(five);
+ /// Arc::increment_strong_count(ptr);
+ ///
+ /// // This assertion is deterministic because we haven't shared
+ /// // the `Arc` between threads.
+ /// let five = Arc::from_raw(ptr);
+ /// assert_eq!(2, Arc::strong_count(&five));
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_mutate_strong_count", since = "1.51.0")]
+ pub unsafe fn increment_strong_count(ptr: *const T) {
+ // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
+ let arc = unsafe { mem::ManuallyDrop::new(Arc::<T>::from_raw(ptr)) };
+ // Now increase refcount, but don't drop new refcount either
+ let _arc_clone: mem::ManuallyDrop<_> = arc.clone();
+ }
+
+ /// Decrements the strong reference count on the `Arc<T>` associated with the
+ /// provided pointer by one.
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have been obtained through `Arc::into_raw`, and the
+ /// associated `Arc` instance must be valid (i.e. the strong count must be at
+ /// least 1) when invoking this method. This method can be used to release the final
+ /// `Arc` and backing storage, but **should not** be called after the final `Arc` has been
+ /// released.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// unsafe {
+ /// let ptr = Arc::into_raw(five);
+ /// Arc::increment_strong_count(ptr);
+ ///
+ /// // Those assertions are deterministic because we haven't shared
+ /// // the `Arc` between threads.
+ /// let five = Arc::from_raw(ptr);
+ /// assert_eq!(2, Arc::strong_count(&five));
+ /// Arc::decrement_strong_count(ptr);
+ /// assert_eq!(1, Arc::strong_count(&five));
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_mutate_strong_count", since = "1.51.0")]
+ pub unsafe fn decrement_strong_count(ptr: *const T) {
+ unsafe { mem::drop(Arc::from_raw(ptr)) };
+ }
+
+ #[inline]
+ fn inner(&self) -> &ArcInner<T> {
+ // This unsafety is ok because while this arc is alive we're guaranteed
+ // that the inner pointer is valid. Furthermore, we know that the
+ // `ArcInner` structure itself is `Sync` because the inner data is
+ // `Sync` as well, so we're ok loaning out an immutable pointer to these
+ // contents.
+ unsafe { self.ptr.as_ref() }
+ }
+
+ // Non-inlined part of `drop`.
+ #[inline(never)]
+ unsafe fn drop_slow(&mut self) {
+ // Destroy the data at this time, even though we may not free the box
+ // allocation itself (there may still be weak pointers lying around).
+ unsafe { ptr::drop_in_place(Self::get_mut_unchecked(self)) };
+
+ // Drop the weak ref collectively held by all strong references
+ drop(Weak { ptr: self.ptr });
+ }
+
+ #[inline]
+ #[stable(feature = "ptr_eq", since = "1.17.0")]
+ /// Returns `true` if the two `Arc`s point to the same allocation
+ /// (in a vein similar to [`ptr::eq`]).
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ /// let same_five = Arc::clone(&five);
+ /// let other_five = Arc::new(5);
+ ///
+ /// assert!(Arc::ptr_eq(&five, &same_five));
+ /// assert!(!Arc::ptr_eq(&five, &other_five));
+ /// ```
+ ///
+ /// [`ptr::eq`]: core::ptr::eq
+ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+ this.ptr.as_ptr() == other.ptr.as_ptr()
+ }
+}
+
+impl<T: ?Sized> Arc<T> {
+ /// Allocates an `ArcInner<T>` with sufficient space for
+ /// a possibly-unsized inner value where the value has the layout provided.
+ ///
+ /// The function `mem_to_arcinner` is called with the data pointer
+ /// and must return back a (potentially fat)-pointer for the `ArcInner<T>`.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_layout(
+ value_layout: Layout,
+ allocate: impl FnOnce(Layout) -> Result<NonNull<[u8]>, AllocError>,
+ mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>,
+ ) -> *mut ArcInner<T> {
+ // Calculate layout using the given value layout.
+ // Previously, layout was calculated on the expression
+ // `&*(ptr as *const ArcInner<T>)`, but this created a misaligned
+ // reference (see #54908).
+ let layout = Layout::new::<ArcInner<()>>().extend(value_layout).unwrap().0.pad_to_align();
+ unsafe {
+ Arc::try_allocate_for_layout(value_layout, allocate, mem_to_arcinner)
+ .unwrap_or_else(|_| handle_alloc_error(layout))
+ }
+ }
+
+ /// Allocates an `ArcInner<T>` with sufficient space for
+ /// a possibly-unsized inner value where the value has the layout provided,
+ /// returning an error if allocation fails.
+ ///
+ /// The function `mem_to_arcinner` is called with the data pointer
+ /// and must return back a (potentially fat)-pointer for the `ArcInner<T>`.
+ unsafe fn try_allocate_for_layout(
+ value_layout: Layout,
+ allocate: impl FnOnce(Layout) -> Result<NonNull<[u8]>, AllocError>,
+ mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>,
+ ) -> Result<*mut ArcInner<T>, AllocError> {
+ // Calculate layout using the given value layout.
+ // Previously, layout was calculated on the expression
+ // `&*(ptr as *const ArcInner<T>)`, but this created a misaligned
+ // reference (see #54908).
+ let layout = Layout::new::<ArcInner<()>>().extend(value_layout).unwrap().0.pad_to_align();
+
+ let ptr = allocate(layout)?;
+
+ // Initialize the ArcInner
+ let inner = mem_to_arcinner(ptr.as_non_null_ptr().as_ptr());
+ debug_assert_eq!(unsafe { Layout::for_value(&*inner) }, layout);
+
+ unsafe {
+ ptr::write(&mut (*inner).strong, atomic::AtomicUsize::new(1));
+ ptr::write(&mut (*inner).weak, atomic::AtomicUsize::new(1));
+ }
+
+ Ok(inner)
+ }
+
+ /// Allocates an `ArcInner<T>` with sufficient space for an unsized inner value.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_ptr(ptr: *const T) -> *mut ArcInner<T> {
+ // Allocate for the `ArcInner<T>` using the given value.
+ unsafe {
+ Self::allocate_for_layout(
+ Layout::for_value(&*ptr),
+ |layout| Global.allocate(layout),
+ |mem| (ptr as *mut ArcInner<T>).set_ptr_value(mem) as *mut ArcInner<T>,
+ )
+ }
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ fn from_box(v: Box<T>) -> Arc<T> {
+ unsafe {
+ let (box_unique, alloc) = Box::into_unique(v);
+ let bptr = box_unique.as_ptr();
+
+ let value_size = size_of_val(&*bptr);
+ let ptr = Self::allocate_for_ptr(bptr);
+
+ // Copy value as bytes
+ ptr::copy_nonoverlapping(
+ bptr as *const T as *const u8,
+ &mut (*ptr).data as *mut _ as *mut u8,
+ value_size,
+ );
+
+ // Free the allocation without dropping its contents
+ box_free(box_unique, alloc);
+
+ Self::from_ptr(ptr)
+ }
+ }
+}
+
+impl<T> Arc<[T]> {
+ /// Allocates an `ArcInner<[T]>` with the given length.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn allocate_for_slice(len: usize) -> *mut ArcInner<[T]> {
+ unsafe {
+ Self::allocate_for_layout(
+ Layout::array::<T>(len).unwrap(),
+ |layout| Global.allocate(layout),
+ |mem| ptr::slice_from_raw_parts_mut(mem as *mut T, len) as *mut ArcInner<[T]>,
+ )
+ }
+ }
+
+ /// Tries to allocate an `ArcInner<[T]>` with the given length.
+ unsafe fn try_allocate_for_slice(len: usize) -> Result<*mut ArcInner<[T]>, TryReserveError> {
+ unsafe {
+ let layout = Layout::array::<T>(len)?;
+ Self::try_allocate_for_layout(
+ layout,
+ |l| Global.allocate(l),
+ |mem| ptr::slice_from_raw_parts_mut(mem as *mut T, len) as *mut ArcInner<[T]>,
+ ).map_err(|_| TryReserveError::AllocError { layout, non_exhaustive: () })
+ }
+ }
+
+ /// Copy elements from slice into newly allocated Arc<\[T\]>
+ ///
+ /// Unsafe because the caller must either take ownership or bind `T: Copy`.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn copy_from_slice(v: &[T]) -> Arc<[T]> {
+ unsafe {
+ let ptr = Self::allocate_for_slice(v.len());
+
+ ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).data as *mut [T] as *mut T, v.len());
+
+ Self::from_ptr(ptr)
+ }
+ }
+
+ /// Tries to copy elements from slice into newly allocated Arc<\[T\]>
+ ///
+ /// Unsafe because the caller must either take ownership or bind `T: Copy`.
+ unsafe fn try_copy_from_slice(v: &[T]) -> Result<Arc<[T]>, TryReserveError> {
+ unsafe {
+ let ptr = Self::try_allocate_for_slice(v.len())?;
+
+ ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).data as *mut [T] as *mut T, v.len());
+
+ Ok(Self::from_ptr(ptr))
+ }
+ }
+
+ /// Constructs an `Arc<[T]>` from an iterator known to be of a certain size.
+ ///
+ /// Behavior is undefined should the size be wrong.
+ #[cfg(not(no_global_oom_handling))]
+ unsafe fn from_iter_exact(iter: impl iter::Iterator<Item = T>, len: usize) -> Arc<[T]> {
+ // Panic guard while cloning T elements.
+ // In the event of a panic, elements that have been written
+ // into the new ArcInner will be dropped, then the memory freed.
+ struct Guard<T> {
+ mem: NonNull<u8>,
+ elems: *mut T,
+ layout: Layout,
+ n_elems: usize,
+ }
+
+ impl<T> Drop for Guard<T> {
+ fn drop(&mut self) {
+ unsafe {
+ let slice = from_raw_parts_mut(self.elems, self.n_elems);
+ ptr::drop_in_place(slice);
+
+ Global.deallocate(self.mem, self.layout);
+ }
+ }
+ }
+
+ unsafe {
+ let ptr = Self::allocate_for_slice(len);
+
+ let mem = ptr as *mut _ as *mut u8;
+ let layout = Layout::for_value(&*ptr);
+
+ // Pointer to first element
+ let elems = &mut (*ptr).data as *mut [T] as *mut T;
+
+ let mut guard = Guard { mem: NonNull::new_unchecked(mem), elems, layout, n_elems: 0 };
+
+ for (i, item) in iter.enumerate() {
+ ptr::write(elems.add(i), item);
+ guard.n_elems += 1;
+ }
+
+ // All clear. Forget the guard so it doesn't free the new ArcInner.
+ mem::forget(guard);
+
+ Self::from_ptr(ptr)
+ }
+ }
+}
+
+/// Specialization trait used for `From<&[T]>`.
+#[cfg(not(no_global_oom_handling))]
+trait ArcFromSlice<T> {
+ fn from_slice(slice: &[T]) -> Self;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Clone> ArcFromSlice<T> for Arc<[T]> {
+ #[inline]
+ default fn from_slice(v: &[T]) -> Self {
+ unsafe { Self::from_iter_exact(v.iter().cloned(), v.len()) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Copy> ArcFromSlice<T> for Arc<[T]> {
+ #[inline]
+ fn from_slice(v: &[T]) -> Self {
+ unsafe { Arc::copy_from_slice(v) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Clone for Arc<T> {
+ /// Makes a clone of the `Arc` pointer.
+ ///
+ /// This creates another pointer to the same allocation, increasing the
+ /// strong reference count.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// let _ = Arc::clone(&five);
+ /// ```
+ #[inline]
+ fn clone(&self) -> Arc<T> {
+ // Using a relaxed ordering is alright here, as knowledge of the
+ // original reference prevents other threads from erroneously deleting
+ // the object.
+ //
+ // As explained in the [Boost documentation][1], Increasing the
+ // reference counter can always be done with memory_order_relaxed: New
+ // references to an object can only be formed from an existing
+ // reference, and passing an existing reference from one thread to
+ // another must already provide any required synchronization.
+ //
+ // [1]: (http://www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
+ let old_size = self.inner().strong.fetch_add(1, Relaxed);
+
+ // However we need to guard against massive refcounts in case someone
+ // is `mem::forget`ing Arcs. If we don't do this the count can overflow
+ // and users will use-after free. We racily saturate to `isize::MAX` on
+ // the assumption that there aren't ~2 billion threads incrementing
+ // the reference count at once. This branch will never be taken in
+ // any realistic program.
+ //
+ // We abort because such a program is incredibly degenerate, and we
+ // don't care to support it.
+ if old_size > MAX_REFCOUNT {
+ abort();
+ }
+
+ Self::from_inner(self.ptr)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Deref for Arc<T> {
+ type Target = T;
+
+ #[inline]
+ fn deref(&self) -> &T {
+ &self.inner().data
+ }
+}
+
+#[unstable(feature = "receiver_trait", issue = "none")]
+impl<T: ?Sized> Receiver for Arc<T> {}
+
+impl<T: Clone> Arc<T> {
+ /// Makes a mutable reference into the given `Arc`.
+ ///
+ /// If there are other `Arc` or [`Weak`] pointers to the same allocation,
+ /// then `make_mut` will create a new allocation and invoke [`clone`][clone] on the inner value
+ /// to ensure unique ownership. This is also referred to as clone-on-write.
+ ///
+ /// Note that this differs from the behavior of [`Rc::make_mut`] which disassociates
+ /// any remaining `Weak` pointers.
+ ///
+ /// See also [`get_mut`][get_mut], which will fail rather than cloning.
+ ///
+ /// [clone]: Clone::clone
+ /// [get_mut]: Arc::get_mut
+ /// [`Rc::make_mut`]: super::rc::Rc::make_mut
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let mut data = Arc::new(5);
+ ///
+ /// *Arc::make_mut(&mut data) += 1; // Won't clone anything
+ /// let mut other_data = Arc::clone(&data); // Won't clone inner data
+ /// *Arc::make_mut(&mut data) += 1; // Clones inner data
+ /// *Arc::make_mut(&mut data) += 1; // Won't clone anything
+ /// *Arc::make_mut(&mut other_data) *= 2; // Won't clone anything
+ ///
+ /// // Now `data` and `other_data` point to different allocations.
+ /// assert_eq!(*data, 8);
+ /// assert_eq!(*other_data, 12);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "arc_unique", since = "1.4.0")]
+ pub fn make_mut(this: &mut Self) -> &mut T {
+ // Note that we hold both a strong reference and a weak reference.
+ // Thus, releasing our strong reference only will not, by itself, cause
+ // the memory to be deallocated.
+ //
+ // Use Acquire to ensure that we see any writes to `weak` that happen
+ // before release writes (i.e., decrements) to `strong`. Since we hold a
+ // weak count, there's no chance the ArcInner itself could be
+ // deallocated.
+ if this.inner().strong.compare_exchange(1, 0, Acquire, Relaxed).is_err() {
+ // Another strong pointer exists, so we must clone.
+ // Pre-allocate memory to allow writing the cloned value directly.
+ let mut arc = Self::new_uninit();
+ unsafe {
+ let data = Arc::get_mut_unchecked(&mut arc);
+ (**this).write_clone_into_raw(data.as_mut_ptr());
+ *this = arc.assume_init();
+ }
+ } else if this.inner().weak.load(Relaxed) != 1 {
+ // Relaxed suffices in the above because this is fundamentally an
+ // optimization: we are always racing with weak pointers being
+ // dropped. Worst case, we end up allocated a new Arc unnecessarily.
+
+ // We removed the last strong ref, but there are additional weak
+ // refs remaining. We'll move the contents to a new Arc, and
+ // invalidate the other weak refs.
+
+ // Note that it is not possible for the read of `weak` to yield
+ // usize::MAX (i.e., locked), since the weak count can only be
+ // locked by a thread with a strong reference.
+
+ // Materialize our own implicit weak pointer, so that it can clean
+ // up the ArcInner as needed.
+ let _weak = Weak { ptr: this.ptr };
+
+ // Can just steal the data, all that's left is Weaks
+ let mut arc = Self::new_uninit();
+ unsafe {
+ let data = Arc::get_mut_unchecked(&mut arc);
+ data.as_mut_ptr().copy_from_nonoverlapping(&**this, 1);
+ ptr::write(this, arc.assume_init());
+ }
+ } else {
+ // We were the sole reference of either kind; bump back up the
+ // strong ref count.
+ this.inner().strong.store(1, Release);
+ }
+
+ // As with `get_mut()`, the unsafety is ok because our reference was
+ // either unique to begin with, or became one upon cloning the contents.
+ unsafe { Self::get_mut_unchecked(this) }
+ }
+}
+
+impl<T: ?Sized> Arc<T> {
+ /// Returns a mutable reference into the given `Arc`, if there are
+ /// no other `Arc` or [`Weak`] pointers to the same allocation.
+ ///
+ /// Returns [`None`] otherwise, because it is not safe to
+ /// mutate a shared value.
+ ///
+ /// See also [`make_mut`][make_mut], which will [`clone`][clone]
+ /// the inner value when there are other pointers.
+ ///
+ /// [make_mut]: Arc::make_mut
+ /// [clone]: Clone::clone
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let mut x = Arc::new(3);
+ /// *Arc::get_mut(&mut x).unwrap() = 4;
+ /// assert_eq!(*x, 4);
+ ///
+ /// let _y = Arc::clone(&x);
+ /// assert!(Arc::get_mut(&mut x).is_none());
+ /// ```
+ #[inline]
+ #[stable(feature = "arc_unique", since = "1.4.0")]
+ pub fn get_mut(this: &mut Self) -> Option<&mut T> {
+ if this.is_unique() {
+ // This unsafety is ok because we're guaranteed that the pointer
+ // returned is the *only* pointer that will ever be returned to T. Our
+ // reference count is guaranteed to be 1 at this point, and we required
+ // the Arc itself to be `mut`, so we're returning the only possible
+ // reference to the inner data.
+ unsafe { Some(Arc::get_mut_unchecked(this)) }
+ } else {
+ None
+ }
+ }
+
+ /// Returns a mutable reference into the given `Arc`,
+ /// without any check.
+ ///
+ /// See also [`get_mut`], which is safe and does appropriate checks.
+ ///
+ /// [`get_mut`]: Arc::get_mut
+ ///
+ /// # Safety
+ ///
+ /// Any other `Arc` or [`Weak`] pointers to the same allocation must not be dereferenced
+ /// for the duration of the returned borrow.
+ /// This is trivially the case if no such pointers exist,
+ /// for example immediately after `Arc::new`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(get_mut_unchecked)]
+ ///
+ /// use std::sync::Arc;
+ ///
+ /// let mut x = Arc::new(String::new());
+ /// unsafe {
+ /// Arc::get_mut_unchecked(&mut x).push_str("foo")
+ /// }
+ /// assert_eq!(*x, "foo");
+ /// ```
+ #[inline]
+ #[unstable(feature = "get_mut_unchecked", issue = "63292")]
+ pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
+ // We are careful to *not* create a reference covering the "count" fields, as
+ // this would alias with concurrent access to the reference counts (e.g. by `Weak`).
+ unsafe { &mut (*this.ptr.as_ptr()).data }
+ }
+
+ /// Determine whether this is the unique reference (including weak refs) to
+ /// the underlying data.
+ ///
+ /// Note that this requires locking the weak ref count.
+ fn is_unique(&mut self) -> bool {
+ // lock the weak pointer count if we appear to be the sole weak pointer
+ // holder.
+ //
+ // The acquire label here ensures a happens-before relationship with any
+ // writes to `strong` (in particular in `Weak::upgrade`) prior to decrements
+ // of the `weak` count (via `Weak::drop`, which uses release). If the upgraded
+ // weak ref was never dropped, the CAS here will fail so we do not care to synchronize.
+ if self.inner().weak.compare_exchange(1, usize::MAX, Acquire, Relaxed).is_ok() {
+ // This needs to be an `Acquire` to synchronize with the decrement of the `strong`
+ // counter in `drop` -- the only access that happens when any but the last reference
+ // is being dropped.
+ let unique = self.inner().strong.load(Acquire) == 1;
+
+ // The release write here synchronizes with a read in `downgrade`,
+ // effectively preventing the above read of `strong` from happening
+ // after the write.
+ self.inner().weak.store(1, Release); // release the lock
+ unique
+ } else {
+ false
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Arc<T> {
+ /// Drops the `Arc`.
+ ///
+ /// This will decrement the strong reference count. If the strong reference
+ /// count reaches zero then the only other references (if any) are
+ /// [`Weak`], so we `drop` the inner value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// struct Foo;
+ ///
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
+ /// }
+ ///
+ /// let foo = Arc::new(Foo);
+ /// let foo2 = Arc::clone(&foo);
+ ///
+ /// drop(foo); // Doesn't print anything
+ /// drop(foo2); // Prints "dropped!"
+ /// ```
+ #[inline]
+ fn drop(&mut self) {
+ // Because `fetch_sub` is already atomic, we do not need to synchronize
+ // with other threads unless we are going to delete the object. This
+ // same logic applies to the below `fetch_sub` to the `weak` count.
+ if self.inner().strong.fetch_sub(1, Release) != 1 {
+ return;
+ }
+
+ // This fence is needed to prevent reordering of use of the data and
+ // deletion of the data. Because it is marked `Release`, the decreasing
+ // of the reference count synchronizes with this `Acquire` fence. This
+ // means that use of the data happens before decreasing the reference
+ // count, which happens before this fence, which happens before the
+ // deletion of the data.
+ //
+ // As explained in the [Boost documentation][1],
+ //
+ // > It is important to enforce any possible access to the object in one
+ // > thread (through an existing reference) to *happen before* deleting
+ // > the object in a different thread. This is achieved by a "release"
+ // > operation after dropping a reference (any access to the object
+ // > through this reference must obviously happened before), and an
+ // > "acquire" operation before deleting the object.
+ //
+ // In particular, while the contents of an Arc are usually immutable, it's
+ // possible to have interior writes to something like a Mutex<T>. Since a
+ // Mutex is not acquired when it is deleted, we can't rely on its
+ // synchronization logic to make writes in thread A visible to a destructor
+ // running in thread B.
+ //
+ // Also note that the Acquire fence here could probably be replaced with an
+ // Acquire load, which could improve performance in highly-contended
+ // situations. See [2].
+ //
+ // [1]: (http://www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
+ // [2]: (https://github.com/rust-lang/rust/pull/41714)
+ acquire!(self.inner().strong);
+
+ unsafe {
+ self.drop_slow();
+ }
+ }
+}
+
+impl Arc<dyn Any + Send + Sync> {
+ #[inline]
+ #[stable(feature = "rc_downcast", since = "1.29.0")]
+ /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::any::Any;
+ /// use std::sync::Arc;
+ ///
+ /// fn print_if_string(value: Arc<dyn Any + Send + Sync>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Arc::new(my_string));
+ /// print_if_string(Arc::new(0i8));
+ /// ```
+ pub fn downcast<T>(self) -> Result<Arc<T>, Self>
+ where
+ T: Any + Send + Sync + 'static,
+ {
+ if (*self).is::<T>() {
+ let ptr = self.ptr.cast::<ArcInner<T>>();
+ mem::forget(self);
+ Ok(Arc::from_inner(ptr))
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<T> Weak<T> {
+ /// Constructs a new `Weak<T>`, without allocating any memory.
+ /// Calling [`upgrade`] on the return value always gives [`None`].
+ ///
+ /// [`upgrade`]: Weak::upgrade
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Weak;
+ ///
+ /// let empty: Weak<i64> = Weak::new();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ #[stable(feature = "downgraded_weak", since = "1.10.0")]
+ pub fn new() -> Weak<T> {
+ Weak { ptr: NonNull::new(usize::MAX as *mut ArcInner<T>).expect("MAX is not 0") }
+ }
+}
+
+/// Helper type to allow accessing the reference counts without
+/// making any assertions about the data field.
+struct WeakInner<'a> {
+ weak: &'a atomic::AtomicUsize,
+ strong: &'a atomic::AtomicUsize,
+}
+
+impl<T: ?Sized> Weak<T> {
+ /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
+ ///
+ /// The pointer is valid only if there are some strong references. The pointer may be dangling,
+ /// unaligned or even [`null`] otherwise.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ /// use std::ptr;
+ ///
+ /// let strong = Arc::new("hello".to_owned());
+ /// let weak = Arc::downgrade(&strong);
+ /// // Both point to the same object
+ /// assert!(ptr::eq(&*strong, weak.as_ptr()));
+ /// // The strong here keeps it alive, so we can still access the object.
+ /// assert_eq!("hello", unsafe { &*weak.as_ptr() });
+ ///
+ /// drop(strong);
+ /// // But not any more. We can do weak.as_ptr(), but accessing the pointer would lead to
+ /// // undefined behaviour.
+ /// // assert_eq!("hello", unsafe { &*weak.as_ptr() });
+ /// ```
+ ///
+ /// [`null`]: core::ptr::null
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub fn as_ptr(&self) -> *const T {
+ let ptr: *mut ArcInner<T> = NonNull::as_ptr(self.ptr);
+
+ if is_dangling(ptr) {
+ // If the pointer is dangling, we return the sentinel directly. This cannot be
+ // a valid payload address, as the payload is at least as aligned as ArcInner (usize).
+ ptr as *const T
+ } else {
+ // SAFETY: if is_dangling returns false, then the pointer is dereferencable.
+ // The payload may be dropped at this point, and we have to maintain provenance,
+ // so use raw pointer manipulation.
+ unsafe { ptr::addr_of_mut!((*ptr).data) }
+ }
+ }
+
+ /// Consumes the `Weak<T>` and turns it into a raw pointer.
+ ///
+ /// This converts the weak pointer into a raw pointer, while still preserving the ownership of
+ /// one weak reference (the weak count is not modified by this operation). It can be turned
+ /// back into the `Weak<T>` with [`from_raw`].
+ ///
+ /// The same restrictions of accessing the target of the pointer as with
+ /// [`as_ptr`] apply.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// let strong = Arc::new("hello".to_owned());
+ /// let weak = Arc::downgrade(&strong);
+ /// let raw = weak.into_raw();
+ ///
+ /// assert_eq!(1, Arc::weak_count(&strong));
+ /// assert_eq!("hello", unsafe { &*raw });
+ ///
+ /// drop(unsafe { Weak::from_raw(raw) });
+ /// assert_eq!(0, Arc::weak_count(&strong));
+ /// ```
+ ///
+ /// [`from_raw`]: Weak::from_raw
+ /// [`as_ptr`]: Weak::as_ptr
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub fn into_raw(self) -> *const T {
+ let result = self.as_ptr();
+ mem::forget(self);
+ result
+ }
+
+ /// Converts a raw pointer previously created by [`into_raw`] back into `Weak<T>`.
+ ///
+ /// This can be used to safely get a strong reference (by calling [`upgrade`]
+ /// later) or to deallocate the weak count by dropping the `Weak<T>`.
+ ///
+ /// It takes ownership of one weak reference (with the exception of pointers created by [`new`],
+ /// as these don't own anything; the method still works on them).
+ ///
+ /// # Safety
+ ///
+ /// The pointer must have originated from the [`into_raw`] and must still own its potential
+ /// weak reference.
+ ///
+ /// It is allowed for the strong count to be 0 at the time of calling this. Nevertheless, this
+ /// takes ownership of one weak reference currently represented as a raw pointer (the weak
+ /// count is not modified by this operation) and therefore it must be paired with a previous
+ /// call to [`into_raw`].
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// let strong = Arc::new("hello".to_owned());
+ ///
+ /// let raw_1 = Arc::downgrade(&strong).into_raw();
+ /// let raw_2 = Arc::downgrade(&strong).into_raw();
+ ///
+ /// assert_eq!(2, Arc::weak_count(&strong));
+ ///
+ /// assert_eq!("hello", &*unsafe { Weak::from_raw(raw_1) }.upgrade().unwrap());
+ /// assert_eq!(1, Arc::weak_count(&strong));
+ ///
+ /// drop(strong);
+ ///
+ /// // Decrement the last weak count.
+ /// assert!(unsafe { Weak::from_raw(raw_2) }.upgrade().is_none());
+ /// ```
+ ///
+ /// [`new`]: Weak::new
+ /// [`into_raw`]: Weak::into_raw
+ /// [`upgrade`]: Weak::upgrade
+ /// [`forget`]: std::mem::forget
+ #[stable(feature = "weak_into_raw", since = "1.45.0")]
+ pub unsafe fn from_raw(ptr: *const T) -> Self {
+ // See Weak::as_ptr for context on how the input pointer is derived.
+
+ let ptr = if is_dangling(ptr as *mut T) {
+ // This is a dangling Weak.
+ ptr as *mut ArcInner<T>
+ } else {
+ // Otherwise, we're guaranteed the pointer came from a nondangling Weak.
+ // SAFETY: data_offset is safe to call, as ptr references a real (potentially dropped) T.
+ let offset = unsafe { data_offset(ptr) };
+ // Thus, we reverse the offset to get the whole RcBox.
+ // SAFETY: the pointer originated from a Weak, so this offset is safe.
+ unsafe { (ptr as *mut ArcInner<T>).set_ptr_value((ptr as *mut u8).offset(-offset)) }
+ };
+
+ // SAFETY: we now have recovered the original Weak pointer, so can create the Weak.
+ Weak { ptr: unsafe { NonNull::new_unchecked(ptr) } }
+ }
+}
+
+impl<T: ?Sized> Weak<T> {
+ /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying
+ /// dropping of the inner value if successful.
+ ///
+ /// Returns [`None`] if the inner value has since been dropped.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// let weak_five = Arc::downgrade(&five);
+ ///
+ /// let strong_five: Option<Arc<_>> = weak_five.upgrade();
+ /// assert!(strong_five.is_some());
+ ///
+ /// // Destroy all strong pointers.
+ /// drop(strong_five);
+ /// drop(five);
+ ///
+ /// assert!(weak_five.upgrade().is_none());
+ /// ```
+ #[stable(feature = "arc_weak", since = "1.4.0")]
+ pub fn upgrade(&self) -> Option<Arc<T>> {
+ // We use a CAS loop to increment the strong count instead of a
+ // fetch_add as this function should never take the reference count
+ // from zero to one.
+ let inner = self.inner()?;
+
+ // Relaxed load because any write of 0 that we can observe
+ // leaves the field in a permanently zero state (so a
+ // "stale" read of 0 is fine), and any other value is
+ // confirmed via the CAS below.
+ let mut n = inner.strong.load(Relaxed);
+
+ loop {
+ if n == 0 {
+ return None;
+ }
+
+ // See comments in `Arc::clone` for why we do this (for `mem::forget`).
+ if n > MAX_REFCOUNT {
+ abort();
+ }
+
+ // Relaxed is fine for the failure case because we don't have any expectations about the new state.
+ // Acquire is necessary for the success case to synchronise with `Arc::new_cyclic`, when the inner
+ // value can be initialized after `Weak` references have already been created. In that case, we
+ // expect to observe the fully initialized value.
+ match inner.strong.compare_exchange_weak(n, n + 1, Acquire, Relaxed) {
+ Ok(_) => return Some(Arc::from_inner(self.ptr)), // null checked above
+ Err(old) => n = old,
+ }
+ }
+ }
+
+ /// Gets the number of strong (`Arc`) pointers pointing to this allocation.
+ ///
+ /// If `self` was created using [`Weak::new`], this will return 0.
+ #[stable(feature = "weak_counts", since = "1.41.0")]
+ pub fn strong_count(&self) -> usize {
+ if let Some(inner) = self.inner() { inner.strong.load(SeqCst) } else { 0 }
+ }
+
+ /// Gets an approximation of the number of `Weak` pointers pointing to this
+ /// allocation.
+ ///
+ /// If `self` was created using [`Weak::new`], or if there are no remaining
+ /// strong pointers, this will return 0.
+ ///
+ /// # Accuracy
+ ///
+ /// Due to implementation details, the returned value can be off by 1 in
+ /// either direction when other threads are manipulating any `Arc`s or
+ /// `Weak`s pointing to the same allocation.
+ #[stable(feature = "weak_counts", since = "1.41.0")]
+ pub fn weak_count(&self) -> usize {
+ self.inner()
+ .map(|inner| {
+ let weak = inner.weak.load(SeqCst);
+ let strong = inner.strong.load(SeqCst);
+ if strong == 0 {
+ 0
+ } else {
+ // Since we observed that there was at least one strong pointer
+ // after reading the weak count, we know that the implicit weak
+ // reference (present whenever any strong references are alive)
+ // was still around when we observed the weak count, and can
+ // therefore safely subtract it.
+ weak - 1
+ }
+ })
+ .unwrap_or(0)
+ }
+
+ /// Returns `None` when the pointer is dangling and there is no allocated `ArcInner`,
+ /// (i.e., when this `Weak` was created by `Weak::new`).
+ #[inline]
+ fn inner(&self) -> Option<WeakInner<'_>> {
+ if is_dangling(self.ptr.as_ptr()) {
+ None
+ } else {
+ // We are careful to *not* create a reference covering the "data" field, as
+ // the field may be mutated concurrently (for example, if the last `Arc`
+ // is dropped, the data field will be dropped in-place).
+ Some(unsafe {
+ let ptr = self.ptr.as_ptr();
+ WeakInner { strong: &(*ptr).strong, weak: &(*ptr).weak }
+ })
+ }
+ }
+
+ /// Returns `true` if the two `Weak`s point to the same allocation (similar to
+ /// [`ptr::eq`]), or if both don't point to any allocation
+ /// (because they were created with `Weak::new()`).
+ ///
+ /// # Notes
+ ///
+ /// Since this compares pointers it means that `Weak::new()` will equal each
+ /// other, even though they don't point to any allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let first_rc = Arc::new(5);
+ /// let first = Arc::downgrade(&first_rc);
+ /// let second = Arc::downgrade(&first_rc);
+ ///
+ /// assert!(first.ptr_eq(&second));
+ ///
+ /// let third_rc = Arc::new(5);
+ /// let third = Arc::downgrade(&third_rc);
+ ///
+ /// assert!(!first.ptr_eq(&third));
+ /// ```
+ ///
+ /// Comparing `Weak::new`.
+ ///
+ /// ```
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// let first = Weak::new();
+ /// let second = Weak::new();
+ /// assert!(first.ptr_eq(&second));
+ ///
+ /// let third_rc = Arc::new(());
+ /// let third = Arc::downgrade(&third_rc);
+ /// assert!(!first.ptr_eq(&third));
+ /// ```
+ ///
+ /// [`ptr::eq`]: core::ptr::eq
+ #[inline]
+ #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
+ pub fn ptr_eq(&self, other: &Self) -> bool {
+ self.ptr.as_ptr() == other.ptr.as_ptr()
+ }
+}
+
+#[stable(feature = "arc_weak", since = "1.4.0")]
+impl<T: ?Sized> Clone for Weak<T> {
+ /// Makes a clone of the `Weak` pointer that points to the same allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// let weak_five = Arc::downgrade(&Arc::new(5));
+ ///
+ /// let _ = Weak::clone(&weak_five);
+ /// ```
+ #[inline]
+ fn clone(&self) -> Weak<T> {
+ let inner = if let Some(inner) = self.inner() {
+ inner
+ } else {
+ return Weak { ptr: self.ptr };
+ };
+ // See comments in Arc::clone() for why this is relaxed. This can use a
+ // fetch_add (ignoring the lock) because the weak count is only locked
+ // where are *no other* weak pointers in existence. (So we can't be
+ // running this code in that case).
+ let old_size = inner.weak.fetch_add(1, Relaxed);
+
+ // See comments in Arc::clone() for why we do this (for mem::forget).
+ if old_size > MAX_REFCOUNT {
+ abort();
+ }
+
+ Weak { ptr: self.ptr }
+ }
+}
+
+#[stable(feature = "downgraded_weak", since = "1.10.0")]
+impl<T> Default for Weak<T> {
+ /// Constructs a new `Weak<T>`, without allocating memory.
+ /// Calling [`upgrade`] on the return value always
+ /// gives [`None`].
+ ///
+ /// [`upgrade`]: Weak::upgrade
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Weak;
+ ///
+ /// let empty: Weak<i64> = Default::default();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ fn default() -> Weak<T> {
+ Weak::new()
+ }
+}
+
+#[stable(feature = "arc_weak", since = "1.4.0")]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
+ /// Drops the `Weak` pointer.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::{Arc, Weak};
+ ///
+ /// struct Foo;
+ ///
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
+ /// }
+ ///
+ /// let foo = Arc::new(Foo);
+ /// let weak_foo = Arc::downgrade(&foo);
+ /// let other_weak_foo = Weak::clone(&weak_foo);
+ ///
+ /// drop(weak_foo); // Doesn't print anything
+ /// drop(foo); // Prints "dropped!"
+ ///
+ /// assert!(other_weak_foo.upgrade().is_none());
+ /// ```
+ fn drop(&mut self) {
+ // If we find out that we were the last weak pointer, then its time to
+ // deallocate the data entirely. See the discussion in Arc::drop() about
+ // the memory orderings
+ //
+ // It's not necessary to check for the locked state here, because the
+ // weak count can only be locked if there was precisely one weak ref,
+ // meaning that drop could only subsequently run ON that remaining weak
+ // ref, which can only happen after the lock is released.
+ let inner = if let Some(inner) = self.inner() { inner } else { return };
+
+ if inner.weak.fetch_sub(1, Release) == 1 {
+ acquire!(inner.weak);
+ unsafe { Global.deallocate(self.ptr.cast(), Layout::for_value_raw(self.ptr.as_ptr())) }
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+trait ArcEqIdent<T: ?Sized + PartialEq> {
+ fn eq(&self, other: &Arc<T>) -> bool;
+ fn ne(&self, other: &Arc<T>) -> bool;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialEq> ArcEqIdent<T> for Arc<T> {
+ #[inline]
+ default fn eq(&self, other: &Arc<T>) -> bool {
+ **self == **other
+ }
+ #[inline]
+ default fn ne(&self, other: &Arc<T>) -> bool {
+ **self != **other
+ }
+}
+
+/// We're doing this specialization here, and not as a more general optimization on `&T`, because it
+/// would otherwise add a cost to all equality checks on refs. We assume that `Arc`s are used to
+/// store large values, that are slow to clone, but also heavy to check for equality, causing this
+/// cost to pay off more easily. It's also more likely to have two `Arc` clones, that point to
+/// the same value, than two `&T`s.
+///
+/// We can only do this when `T: Eq` as a `PartialEq` might be deliberately irreflexive.
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + crate::rc::MarkerEq> ArcEqIdent<T> for Arc<T> {
+ #[inline]
+ fn eq(&self, other: &Arc<T>) -> bool {
+ Arc::ptr_eq(self, other) || **self == **other
+ }
+
+ #[inline]
+ fn ne(&self, other: &Arc<T>) -> bool {
+ !Arc::ptr_eq(self, other) && **self != **other
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialEq> PartialEq for Arc<T> {
+ /// Equality for two `Arc`s.
+ ///
+ /// Two `Arc`s are equal if their inner values are equal, even if they are
+ /// stored in different allocation.
+ ///
+ /// If `T` also implements `Eq` (implying reflexivity of equality),
+ /// two `Arc`s that point to the same allocation are always equal.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five == Arc::new(5));
+ /// ```
+ #[inline]
+ fn eq(&self, other: &Arc<T>) -> bool {
+ ArcEqIdent::eq(self, other)
+ }
+
+ /// Inequality for two `Arc`s.
+ ///
+ /// Two `Arc`s are unequal if their inner values are unequal.
+ ///
+ /// If `T` also implements `Eq` (implying reflexivity of equality),
+ /// two `Arc`s that point to the same value are never unequal.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five != Arc::new(6));
+ /// ```
+ #[inline]
+ fn ne(&self, other: &Arc<T>) -> bool {
+ ArcEqIdent::ne(self, other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + PartialOrd> PartialOrd for Arc<T> {
+ /// Partial comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `partial_cmp()` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ /// use std::cmp::Ordering;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert_eq!(Some(Ordering::Less), five.partial_cmp(&Arc::new(6)));
+ /// ```
+ fn partial_cmp(&self, other: &Arc<T>) -> Option<Ordering> {
+ (**self).partial_cmp(&**other)
+ }
+
+ /// Less-than comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `<` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five < Arc::new(6));
+ /// ```
+ fn lt(&self, other: &Arc<T>) -> bool {
+ *(*self) < *(*other)
+ }
+
+ /// 'Less than or equal to' comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `<=` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five <= Arc::new(5));
+ /// ```
+ fn le(&self, other: &Arc<T>) -> bool {
+ *(*self) <= *(*other)
+ }
+
+ /// Greater-than comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `>` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five > Arc::new(4));
+ /// ```
+ fn gt(&self, other: &Arc<T>) -> bool {
+ *(*self) > *(*other)
+ }
+
+ /// 'Greater than or equal to' comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `>=` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert!(five >= Arc::new(5));
+ /// ```
+ fn ge(&self, other: &Arc<T>) -> bool {
+ *(*self) >= *(*other)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Ord> Ord for Arc<T> {
+ /// Comparison for two `Arc`s.
+ ///
+ /// The two are compared by calling `cmp()` on their inner values.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ /// use std::cmp::Ordering;
+ ///
+ /// let five = Arc::new(5);
+ ///
+ /// assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));
+ /// ```
+ fn cmp(&self, other: &Arc<T>) -> Ordering {
+ (**self).cmp(&**other)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Eq> Eq for Arc<T> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + fmt::Display> fmt::Display for Arc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Arc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> fmt::Pointer for Arc<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&(&**self as *const T), f)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Default> Default for Arc<T> {
+ /// Creates a new `Arc<T>`, with the `Default` value for `T`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::Arc;
+ ///
+ /// let x: Arc<i32> = Default::default();
+ /// assert_eq!(*x, 0);
+ /// ```
+ fn default() -> Arc<T> {
+ Arc::new(Default::default())
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Hash> Hash for Arc<T> {
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ (**self).hash(state)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "from_for_ptrs", since = "1.6.0")]
+impl<T> From<T> for Arc<T> {
+ fn from(t: T) -> Self {
+ Arc::new(t)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: Clone> From<&[T]> for Arc<[T]> {
+ /// Allocate a reference-counted slice and fill it by cloning `v`'s items.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let original: &[i32] = &[1, 2, 3];
+ /// let shared: Arc<[i32]> = Arc::from(original);
+ /// assert_eq!(&[1, 2, 3], &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: &[T]) -> Arc<[T]> {
+ <Self as ArcFromSlice<T>>::from_slice(v)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<&str> for Arc<str> {
+ /// Allocate a reference-counted `str` and copy `v` into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let shared: Arc<str> = Arc::from("eggplant");
+ /// assert_eq!("eggplant", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: &str) -> Arc<str> {
+ let arc = Arc::<[u8]>::from(v.as_bytes());
+ unsafe { Arc::from_raw(Arc::into_raw(arc) as *const str) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<String> for Arc<str> {
+ /// Allocate a reference-counted `str` and copy `v` into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let unique: String = "eggplant".to_owned();
+ /// let shared: Arc<str> = Arc::from(unique);
+ /// assert_eq!("eggplant", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: String) -> Arc<str> {
+ Arc::from(&v[..])
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: ?Sized> From<Box<T>> for Arc<T> {
+ /// Move a boxed object to a new, reference-counted allocation.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let unique: Box<str> = Box::from("eggplant");
+ /// let shared: Arc<str> = Arc::from(unique);
+ /// assert_eq!("eggplant", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(v: Box<T>) -> Arc<T> {
+ Arc::from_box(v)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T> From<Vec<T>> for Arc<[T]> {
+ /// Allocate a reference-counted slice and move `v`'s items into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let unique: Vec<i32> = vec![1, 2, 3];
+ /// let shared: Arc<[i32]> = Arc::from(unique);
+ /// assert_eq!(&[1, 2, 3], &shared[..]);
+ /// ```
+ #[inline]
+ fn from(mut v: Vec<T>) -> Arc<[T]> {
+ unsafe {
+ let arc = Arc::copy_from_slice(&v);
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ arc
+ }
+ }
+}
+
+// Avoid `error: specializing impl repeats parameter` implementing `TryFrom`.
+impl<T> Arc<[T]> {
+ /// Tries to allocate a reference-counted slice and move `v`'s items into it.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use std::sync::Arc;
+ /// let unique: Vec<i32> = vec![1, 2, 3];
+ /// let shared: Arc<[i32]> = Arc::try_from(unique).unwrap();
+ /// assert_eq!(&[1, 2, 3], &shared[..]);
+ /// ```
+ #[stable(feature = "kernel", since = "1.0.0")]
+ #[inline]
+ pub fn try_from_vec(mut v: Vec<T>) -> Result<Self, TryReserveError> {
+ unsafe {
+ let arc = Arc::try_copy_from_slice(&v)?;
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ Ok(arc)
+ }
+ }
+}
+
+#[stable(feature = "shared_from_cow", since = "1.45.0")]
+impl<'a, B> From<Cow<'a, B>> for Arc<B>
+where
+ B: ToOwned + ?Sized,
+ Arc<B>: From<&'a B> + From<B::Owned>,
+{
+ /// Create an atomically reference-counted pointer from
+ /// a clone-on-write pointer by copying its content.
+ ///
+ /// # Example
+ ///
+ /// ```rust
+ /// # use std::sync::Arc;
+ /// # use std::borrow::Cow;
+ /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+ /// let shared: Arc<str> = Arc::from(cow);
+ /// assert_eq!("eggplant", &shared[..]);
+ /// ```
+ #[inline]
+ fn from(cow: Cow<'a, B>) -> Arc<B> {
+ match cow {
+ Cow::Borrowed(s) => Arc::from(s),
+ Cow::Owned(s) => Arc::from(s),
+ }
+ }
+}
+
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
+impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]> {
+ type Error = Arc<[T]>;
+
+ fn try_from(boxed_slice: Arc<[T]>) -> Result<Self, Self::Error> {
+ if boxed_slice.len() == N {
+ Ok(unsafe { Arc::from_raw(Arc::into_raw(boxed_slice) as *mut [T; N]) })
+ } else {
+ Err(boxed_slice)
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "shared_from_iter", since = "1.37.0")]
+impl<T> iter::FromIterator<T> for Arc<[T]> {
+ /// Takes each element in the `Iterator` and collects it into an `Arc<[T]>`.
+ ///
+ /// # Performance characteristics
+ ///
+ /// ## The general case
+ ///
+ /// In the general case, collecting into `Arc<[T]>` is done by first
+ /// collecting into a `Vec<T>`. That is, when writing the following:
+ ///
+ /// ```rust
+ /// # use std::sync::Arc;
+ /// let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0).collect();
+ /// # assert_eq!(&*evens, &[0, 2, 4, 6, 8]);
+ /// ```
+ ///
+ /// this behaves as if we wrote:
+ ///
+ /// ```rust
+ /// # use std::sync::Arc;
+ /// let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0)
+ /// .collect::<Vec<_>>() // The first set of allocations happens here.
+ /// .into(); // A second allocation for `Arc<[T]>` happens here.
+ /// # assert_eq!(&*evens, &[0, 2, 4, 6, 8]);
+ /// ```
+ ///
+ /// This will allocate as many times as needed for constructing the `Vec<T>`
+ /// and then it will allocate once for turning the `Vec<T>` into the `Arc<[T]>`.
+ ///
+ /// ## Iterators of known length
+ ///
+ /// When your `Iterator` implements `TrustedLen` and is of an exact size,
+ /// a single allocation will be made for the `Arc<[T]>`. For example:
+ ///
+ /// ```rust
+ /// # use std::sync::Arc;
+ /// let evens: Arc<[u8]> = (0..10).collect(); // Just a single allocation happens here.
+ /// # assert_eq!(&*evens, &*(0..10).collect::<Vec<_>>());
+ /// ```
+ fn from_iter<I: iter::IntoIterator<Item = T>>(iter: I) -> Self {
+ ToArcSlice::to_arc_slice(iter.into_iter())
+ }
+}
+
+/// Specialization trait used for collecting into `Arc<[T]>`.
+trait ToArcSlice<T>: Iterator<Item = T> + Sized {
+ fn to_arc_slice(self) -> Arc<[T]>;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I: Iterator<Item = T>> ToArcSlice<T> for I {
+ default fn to_arc_slice(self) -> Arc<[T]> {
+ self.collect::<Vec<T>>().into()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I: iter::TrustedLen<Item = T>> ToArcSlice<T> for I {
+ fn to_arc_slice(self) -> Arc<[T]> {
+ // This is the case for a `TrustedLen` iterator.
+ let (low, high) = self.size_hint();
+ if let Some(high) = high {
+ debug_assert_eq!(
+ low,
+ high,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+
+ unsafe {
+ // SAFETY: We need to ensure that the iterator has an exact length and we have.
+ Arc::from_iter_exact(self, low)
+ }
+ } else {
+ // TrustedLen contract guarantees that `upper_bound == `None` implies an iterator
+ // length exceeding `usize::MAX`.
+ // The default implementation would collect into a vec which would panic.
+ // Thus we panic here immediately without invoking `Vec` code.
+ panic!("capacity overflow");
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> borrow::Borrow<T> for Arc<T> {
+ fn borrow(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
+impl<T: ?Sized> AsRef<T> for Arc<T> {
+ fn as_ref(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(feature = "pin", since = "1.33.0")]
+impl<T: ?Sized> Unpin for Arc<T> {}
+
+/// Get the offset within an `ArcInner` for the payload behind a pointer.
+///
+/// # Safety
+///
+/// The pointer must point to (and have valid metadata for) a previously
+/// valid instance of T, but the T is allowed to be dropped.
+unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> isize {
+ // Align the unsized value to the end of the ArcInner.
+ // Because RcBox is repr(C), it will always be the last field in memory.
+ // SAFETY: since the only unsized types possible are slices, trait objects,
+ // and extern types, the input safety requirement is currently enough to
+ // satisfy the requirements of align_of_val_raw; this is an implementation
+ // detail of the language that may not be relied upon outside of std.
+ unsafe { data_offset_align(align_of_val_raw(ptr)) }
+}
+
+#[inline]
+fn data_offset_align(align: usize) -> isize {
+ let layout = Layout::new::<ArcInner<()>>();
+ (layout.size() + layout.padding_needed_for(align)) as isize
+}
diff --git a/rust/alloc/vec/drain.rs b/rust/alloc/vec/drain.rs
new file mode 100644
index 00000000000..65f7e32e95f
--- /dev/null
+++ b/rust/alloc/vec/drain.rs
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::{Allocator, Global};
+use core::fmt;
+use core::iter::{FusedIterator, TrustedLen};
+use core::mem::{self};
+use core::ptr::{self, NonNull};
+use core::slice::{self};
+
+use super::Vec;
+
+/// A draining iterator for `Vec<T>`.
+///
+/// This `struct` is created by [`Vec::drain`].
+/// See its documentation for more.
+///
+/// # Example
+///
+/// ```
+/// let mut v = vec![0, 1, 2];
+/// let iter: std::vec::Drain<_> = v.drain(..);
+/// ```
+#[stable(feature = "drain", since = "1.6.0")]
+pub struct Drain<
+ 'a,
+ T: 'a,
+ #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
+> {
+ /// Index of tail to preserve
+ pub(super) tail_start: usize,
+ /// Length of tail
+ pub(super) tail_len: usize,
+ /// Current remaining range to remove
+ pub(super) iter: slice::Iter<'a, T>,
+ pub(super) vec: NonNull<Vec<T, A>>,
+}
+
+#[stable(feature = "collection_debug", since = "1.17.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_tuple("Drain").field(&self.iter.as_slice()).finish()
+ }
+}
+
+impl<'a, T, A: Allocator> Drain<'a, T, A> {
+ /// Returns the remaining items of this iterator as a slice.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec!['a', 'b', 'c'];
+ /// let mut drain = vec.drain(..);
+ /// assert_eq!(drain.as_slice(), &['a', 'b', 'c']);
+ /// let _ = drain.next().unwrap();
+ /// assert_eq!(drain.as_slice(), &['b', 'c']);
+ /// ```
+ #[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
+ pub fn as_slice(&self) -> &[T] {
+ self.iter.as_slice()
+ }
+
+ /// Returns a reference to the underlying allocator.
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn allocator(&self) -> &A {
+ unsafe { self.vec.as_ref().allocator() }
+ }
+}
+
+#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
+impl<'a, T, A: Allocator> AsRef<[T]> for Drain<'a, T, A> {
+ fn as_ref(&self) -> &[T] {
+ self.as_slice()
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<T: Sync, A: Sync + Allocator> Sync for Drain<'_, T, A> {}
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<T: Send, A: Send + Allocator> Send for Drain<'_, T, A> {}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
+ type Item = T;
+
+ #[inline]
+ fn next(&mut self) -> Option<T> {
+ self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.iter.size_hint()
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> {
+ #[inline]
+ fn next_back(&mut self) -> Option<T> {
+ self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> Drop for Drain<'_, T, A> {
+ fn drop(&mut self) {
+ /// Continues dropping the remaining elements in the `Drain`, then moves back the
+ /// un-`Drain`ed elements to restore the original `Vec`.
+ struct DropGuard<'r, 'a, T, A: Allocator>(&'r mut Drain<'a, T, A>);
+
+ impl<'r, 'a, T, A: Allocator> Drop for DropGuard<'r, 'a, T, A> {
+ fn drop(&mut self) {
+ // Continue the same loop we have below. If the loop already finished, this does
+ // nothing.
+ self.0.for_each(drop);
+
+ if self.0.tail_len > 0 {
+ unsafe {
+ let source_vec = self.0.vec.as_mut();
+ // memmove back untouched tail, update to new length
+ let start = source_vec.len();
+ let tail = self.0.tail_start;
+ if tail != start {
+ let src = source_vec.as_ptr().add(tail);
+ let dst = source_vec.as_mut_ptr().add(start);
+ ptr::copy(src, dst, self.0.tail_len);
+ }
+ source_vec.set_len(start + self.0.tail_len);
+ }
+ }
+ }
+ }
+
+ // exhaust self first
+ while let Some(item) = self.next() {
+ let guard = DropGuard(self);
+ drop(item);
+ mem::forget(guard);
+ }
+
+ // Drop a `DropGuard` to move back the non-drained tail of `self`.
+ DropGuard(self);
+ }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
+ fn is_empty(&self) -> bool {
+ self.iter.is_empty()
+ }
+}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}
diff --git a/rust/alloc/vec/drain_filter.rs b/rust/alloc/vec/drain_filter.rs
new file mode 100644
index 00000000000..b04fce04162
--- /dev/null
+++ b/rust/alloc/vec/drain_filter.rs
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::{Allocator, Global};
+use core::ptr::{self};
+use core::slice::{self};
+
+use super::Vec;
+
+/// An iterator which uses a closure to determine if an element should be removed.
+///
+/// This struct is created by [`Vec::drain_filter`].
+/// See its documentation for more.
+///
+/// # Example
+///
+/// ```
+/// #![feature(drain_filter)]
+///
+/// let mut v = vec![0, 1, 2];
+/// let iter: std::vec::DrainFilter<_, _> = v.drain_filter(|x| *x % 2 == 0);
+/// ```
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[derive(Debug)]
+pub struct DrainFilter<
+ 'a,
+ T,
+ F,
+ #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> where
+ F: FnMut(&mut T) -> bool,
+{
+ pub(super) vec: &'a mut Vec<T, A>,
+ /// The index of the item that will be inspected by the next call to `next`.
+ pub(super) idx: usize,
+ /// The number of items that have been drained (removed) thus far.
+ pub(super) del: usize,
+ /// The original length of `vec` prior to draining.
+ pub(super) old_len: usize,
+ /// The filter test predicate.
+ pub(super) pred: F,
+ /// A flag that indicates a panic has occurred in the filter test predicate.
+ /// This is used as a hint in the drop implementation to prevent consumption
+ /// of the remainder of the `DrainFilter`. Any unprocessed items will be
+ /// backshifted in the `vec`, but no further items will be dropped or
+ /// tested by the filter predicate.
+ pub(super) panic_flag: bool,
+}
+
+impl<T, F, A: Allocator> DrainFilter<'_, T, F, A>
+where
+ F: FnMut(&mut T) -> bool,
+{
+ /// Returns a reference to the underlying allocator.
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn allocator(&self) -> &A {
+ self.vec.allocator()
+ }
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
+where
+ F: FnMut(&mut T) -> bool,
+{
+ type Item = T;
+
+ fn next(&mut self) -> Option<T> {
+ unsafe {
+ while self.idx < self.old_len {
+ let i = self.idx;
+ let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
+ self.panic_flag = true;
+ let drained = (self.pred)(&mut v[i]);
+ self.panic_flag = false;
+ // Update the index *after* the predicate is called. If the index
+ // is updated prior and the predicate panics, the element at this
+ // index would be leaked.
+ self.idx += 1;
+ if drained {
+ self.del += 1;
+ return Some(ptr::read(&v[i]));
+ } else if self.del > 0 {
+ let del = self.del;
+ let src: *const T = &v[i];
+ let dst: *mut T = &mut v[i - del];
+ ptr::copy_nonoverlapping(src, dst, 1);
+ }
+ }
+ None
+ }
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (0, Some(self.old_len - self.idx))
+ }
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<T, F, A: Allocator> Drop for DrainFilter<'_, T, F, A>
+where
+ F: FnMut(&mut T) -> bool,
+{
+ fn drop(&mut self) {
+ struct BackshiftOnDrop<'a, 'b, T, F, A: Allocator>
+ where
+ F: FnMut(&mut T) -> bool,
+ {
+ drain: &'b mut DrainFilter<'a, T, F, A>,
+ }
+
+ impl<'a, 'b, T, F, A: Allocator> Drop for BackshiftOnDrop<'a, 'b, T, F, A>
+ where
+ F: FnMut(&mut T) -> bool,
+ {
+ fn drop(&mut self) {
+ unsafe {
+ if self.drain.idx < self.drain.old_len && self.drain.del > 0 {
+ // This is a pretty messed up state, and there isn't really an
+ // obviously right thing to do. We don't want to keep trying
+ // to execute `pred`, so we just backshift all the unprocessed
+ // elements and tell the vec that they still exist. The backshift
+ // is required to prevent a double-drop of the last successfully
+ // drained item prior to a panic in the predicate.
+ let ptr = self.drain.vec.as_mut_ptr();
+ let src = ptr.add(self.drain.idx);
+ let dst = src.sub(self.drain.del);
+ let tail_len = self.drain.old_len - self.drain.idx;
+ src.copy_to(dst, tail_len);
+ }
+ self.drain.vec.set_len(self.drain.old_len - self.drain.del);
+ }
+ }
+ }
+
+ let backshift = BackshiftOnDrop { drain: self };
+
+ // Attempt to consume any remaining elements if the filter predicate
+ // has not yet panicked. We'll backshift any remaining elements
+ // whether we've already panicked or if the consumption here panics.
+ if !backshift.drain.panic_flag {
+ backshift.drain.for_each(drop);
+ }
+ }
+}
diff --git a/rust/alloc/vec/into_iter.rs b/rust/alloc/vec/into_iter.rs
new file mode 100644
index 00000000000..86a167aad10
--- /dev/null
+++ b/rust/alloc/vec/into_iter.rs
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::{Allocator, Global};
+use crate::raw_vec::RawVec;
+use core::fmt;
+use core::intrinsics::arith_offset;
+use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccess};
+use core::marker::PhantomData;
+use core::mem::{self};
+use core::ptr::{self, NonNull};
+use core::slice::{self};
+
+/// An iterator that moves out of a vector.
+///
+/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
+/// (provided by the [`IntoIterator`] trait).
+///
+/// # Example
+///
+/// ```
+/// let v = vec![0, 1, 2];
+/// let iter: std::vec::IntoIter<_> = v.into_iter();
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct IntoIter<
+ T,
+ #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
+ pub(super) buf: NonNull<T>,
+ pub(super) phantom: PhantomData<T>,
+ pub(super) cap: usize,
+ pub(super) alloc: A,
+ pub(super) ptr: *const T,
+ pub(super) end: *const T,
+}
+
+#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
+ }
+}
+
+impl<T, A: Allocator> IntoIter<T, A> {
+ /// Returns the remaining items of this iterator as a slice.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let vec = vec!['a', 'b', 'c'];
+ /// let mut into_iter = vec.into_iter();
+ /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+ /// let _ = into_iter.next().unwrap();
+ /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
+ /// ```
+ #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+ pub fn as_slice(&self) -> &[T] {
+ unsafe { slice::from_raw_parts(self.ptr, self.len()) }
+ }
+
+ /// Returns the remaining items of this iterator as a mutable slice.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let vec = vec!['a', 'b', 'c'];
+ /// let mut into_iter = vec.into_iter();
+ /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+ /// into_iter.as_mut_slice()[2] = 'z';
+ /// assert_eq!(into_iter.next().unwrap(), 'a');
+ /// assert_eq!(into_iter.next().unwrap(), 'b');
+ /// assert_eq!(into_iter.next().unwrap(), 'z');
+ /// ```
+ #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+ pub fn as_mut_slice(&mut self) -> &mut [T] {
+ unsafe { &mut *self.as_raw_mut_slice() }
+ }
+
+ /// Returns a reference to the underlying allocator.
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn allocator(&self) -> &A {
+ &self.alloc
+ }
+
+ fn as_raw_mut_slice(&mut self) -> *mut [T] {
+ ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
+ }
+
+ /// Drops remaining elements and relinquishes the backing allocation.
+ ///
+ /// This is roughly equivalent to the following, but more efficient
+ ///
+ /// ```
+ /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
+ /// (&mut into_iter).for_each(core::mem::drop);
+ /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ pub(super) fn forget_allocation_drop_remaining(&mut self) {
+ let remaining = self.as_raw_mut_slice();
+
+ // overwrite the individual fields instead of creating a new
+ // struct and then overwriting &mut self.
+ // this creates less assembly
+ self.cap = 0;
+ self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
+ self.ptr = self.buf.as_ptr();
+ self.end = self.buf.as_ptr();
+
+ unsafe {
+ ptr::drop_in_place(remaining);
+ }
+ }
+}
+
+#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
+impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
+ fn as_ref(&self) -> &[T] {
+ self.as_slice()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Sync, A: Allocator> Sync for IntoIter<T, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> Iterator for IntoIter<T, A> {
+ type Item = T;
+
+ #[inline]
+ fn next(&mut self) -> Option<T> {
+ if self.ptr as *const _ == self.end {
+ None
+ } else if mem::size_of::<T>() == 0 {
+ // purposefully don't use 'ptr.offset' because for
+ // vectors with 0-size elements this would return the
+ // same pointer.
+ self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+
+ // Make up a value of this ZST.
+ Some(unsafe { mem::zeroed() })
+ } else {
+ let old = self.ptr;
+ self.ptr = unsafe { self.ptr.offset(1) };
+
+ Some(unsafe { ptr::read(old) })
+ }
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ let exact = if mem::size_of::<T>() == 0 {
+ (self.end as usize).wrapping_sub(self.ptr as usize)
+ } else {
+ unsafe { self.end.offset_from(self.ptr) as usize }
+ };
+ (exact, Some(exact))
+ }
+
+ #[inline]
+ fn count(self) -> usize {
+ self.len()
+ }
+
+ unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
+ where
+ Self: TrustedRandomAccess,
+ {
+ // SAFETY: the caller must guarantee that `i` is in bounds of the
+ // `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
+ // is guaranteed to pointer to an element of the `Vec<T>` and
+ // thus guaranteed to be valid to dereference.
+ //
+ // Also note the implementation of `Self: TrustedRandomAccess` requires
+ // that `T: Copy` so reading elements from the buffer doesn't invalidate
+ // them for `Drop`.
+ unsafe {
+ if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
+ #[inline]
+ fn next_back(&mut self) -> Option<T> {
+ if self.end == self.ptr {
+ None
+ } else if mem::size_of::<T>() == 0 {
+ // See above for why 'ptr.offset' isn't used
+ self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+
+ // Make up a value of this ZST.
+ Some(unsafe { mem::zeroed() })
+ } else {
+ self.end = unsafe { self.end.offset(-1) };
+
+ Some(unsafe { ptr::read(self.end) })
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
+ fn is_empty(&self) -> bool {
+ self.ptr == self.end
+ }
+}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
+
+#[doc(hidden)]
+#[unstable(issue = "none", feature = "std_internals")]
+// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
+// and thus we can't implement drop-handling
+unsafe impl<T, A: Allocator> TrustedRandomAccess for IntoIter<T, A>
+where
+ T: Copy,
+{
+ const MAY_HAVE_SIDE_EFFECT: bool = false;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
+ #[cfg(not(test))]
+ fn clone(&self) -> Self {
+ self.as_slice().to_vec_in(self.alloc.clone()).into_iter()
+ }
+ #[cfg(test)]
+ fn clone(&self) -> Self {
+ crate::slice::to_vec(self.as_slice(), self.alloc.clone()).into_iter()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
+ fn drop(&mut self) {
+ struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
+
+ impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
+ fn drop(&mut self) {
+ unsafe {
+ // `IntoIter::alloc` is not used anymore after this
+ let alloc = ptr::read(&self.0.alloc);
+ // RawVec handles deallocation
+ let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
+ }
+ }
+ }
+
+ let guard = DropGuard(self);
+ // destroy the remaining elements
+ unsafe {
+ ptr::drop_in_place(guard.0.as_raw_mut_slice());
+ }
+ // now `guard` will be dropped and do the rest
+ }
+}
+
+#[unstable(issue = "none", feature = "inplace_iteration")]
+#[doc(hidden)]
+unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
+
+#[unstable(issue = "none", feature = "inplace_iteration")]
+#[doc(hidden)]
+unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
+ type Source = Self;
+
+ #[inline]
+ unsafe fn as_inner(&mut self) -> &mut Self::Source {
+ self
+ }
+}
+
+// internal helper trait for in-place iteration specialization.
+#[rustc_specialization_trait]
+pub(crate) trait AsIntoIter {
+ type Item;
+ fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item>;
+}
+
+impl<T> AsIntoIter for IntoIter<T> {
+ type Item = T;
+
+ fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
+ self
+ }
+}
diff --git a/rust/alloc/vec/is_zero.rs b/rust/alloc/vec/is_zero.rs
new file mode 100644
index 00000000000..40e1e667c9f
--- /dev/null
+++ b/rust/alloc/vec/is_zero.rs
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::boxed::Box;
+
+#[rustc_specialization_trait]
+pub(super) unsafe trait IsZero {
+ /// Whether this value is zero
+ fn is_zero(&self) -> bool;
+}
+
+macro_rules! impl_is_zero {
+ ($t:ty, $is_zero:expr) => {
+ unsafe impl IsZero for $t {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ $is_zero(*self)
+ }
+ }
+ };
+}
+
+impl_is_zero!(i16, |x| x == 0);
+impl_is_zero!(i32, |x| x == 0);
+impl_is_zero!(i64, |x| x == 0);
+impl_is_zero!(i128, |x| x == 0);
+impl_is_zero!(isize, |x| x == 0);
+
+impl_is_zero!(u16, |x| x == 0);
+impl_is_zero!(u32, |x| x == 0);
+impl_is_zero!(u64, |x| x == 0);
+impl_is_zero!(u128, |x| x == 0);
+impl_is_zero!(usize, |x| x == 0);
+
+impl_is_zero!(bool, |x| x == false);
+impl_is_zero!(char, |x| x == '\0');
+
+impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
+impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
+
+unsafe impl<T> IsZero for *const T {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ (*self).is_null()
+ }
+}
+
+unsafe impl<T> IsZero for *mut T {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ (*self).is_null()
+ }
+}
+
+// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
+// For fat pointers, the bytes that would be the pointer metadata in the `Some`
+// variant are padding in the `None` variant, so ignoring them and
+// zero-initializing instead is ok.
+// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of
+// `SpecFromElem`.
+
+unsafe impl<T: ?Sized> IsZero for Option<&T> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ self.is_none()
+ }
+}
+
+unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ self.is_none()
+ }
+}
+
+// `Option<num::NonZeroU32>` and similar have a representation guarantee that
+// they're the same size as the corresponding `u32` type, as well as a guarantee
+// that transmuting between `NonZeroU32` and `Option<num::NonZeroU32>` works.
+// While the documentation officially makes it UB to transmute from `None`,
+// we're the standard library so we can make extra inferences, and we know that
+// the only niche available to represent `None` is the one that's all zeros.
+
+macro_rules! impl_is_zero_option_of_nonzero {
+ ($($t:ident,)+) => {$(
+ unsafe impl IsZero for Option<core::num::$t> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ self.is_none()
+ }
+ }
+ )+};
+}
+
+impl_is_zero_option_of_nonzero!(
+ NonZeroU8,
+ NonZeroU16,
+ NonZeroU32,
+ NonZeroU64,
+ NonZeroU128,
+ NonZeroI8,
+ NonZeroI16,
+ NonZeroI32,
+ NonZeroI64,
+ NonZeroI128,
+ NonZeroUsize,
+ NonZeroIsize,
+);
diff --git a/rust/alloc/vec/mod.rs b/rust/alloc/vec/mod.rs
new file mode 100644
index 00000000000..2abffb93e49
--- /dev/null
+++ b/rust/alloc/vec/mod.rs
@@ -0,0 +1,3255 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A contiguous growable array type with heap-allocated contents, written
+//! `Vec<T>`.
+//!
+//! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and
+//! `O(1)` pop (from the end).
+//!
+//! Vectors ensure they never allocate more than `isize::MAX` bytes.
+//!
+//! # Examples
+//!
+//! You can explicitly create a [`Vec`] with [`Vec::new`]:
+//!
+//! ```
+//! let v: Vec<i32> = Vec::new();
+//! ```
+//!
+//! ...or by using the [`vec!`] macro:
+//!
+//! ```
+//! let v: Vec<i32> = vec![];
+//!
+//! let v = vec![1, 2, 3, 4, 5];
+//!
+//! let v = vec![0; 10]; // ten zeroes
+//! ```
+//!
+//! You can [`push`] values onto the end of a vector (which will grow the vector
+//! as needed):
+//!
+//! ```
+//! let mut v = vec![1, 2];
+//!
+//! v.push(3);
+//! ```
+//!
+//! Popping values works in much the same way:
+//!
+//! ```
+//! let mut v = vec![1, 2];
+//!
+//! let two = v.pop();
+//! ```
+//!
+//! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits):
+//!
+//! ```
+//! let mut v = vec![1, 2, 3];
+//! let three = v[2];
+//! v[1] = v[1] + 5;
+//! ```
+//!
+//! [`push`]: Vec::push
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[cfg(not(no_global_oom_handling))]
+use core::cmp;
+use core::cmp::Ordering;
+use core::convert::TryFrom;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::intrinsics::{arith_offset, assume};
+use core::iter;
+#[cfg(not(no_global_oom_handling))]
+use core::iter::FromIterator;
+use core::marker::PhantomData;
+use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::ops::{self, Index, IndexMut, Range, RangeBounds};
+use core::ptr::{self, NonNull};
+use core::slice::{self, SliceIndex};
+
+use crate::alloc::{Allocator, Global};
+use crate::borrow::{Cow, ToOwned};
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::raw_vec::RawVec;
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+pub use self::drain_filter::DrainFilter;
+
+mod drain_filter;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "vec_splice", since = "1.21.0")]
+pub use self::splice::Splice;
+
+#[cfg(not(no_global_oom_handling))]
+mod splice;
+
+#[stable(feature = "drain", since = "1.6.0")]
+pub use self::drain::Drain;
+
+mod drain;
+
+#[cfg(not(no_global_oom_handling))]
+mod cow;
+
+#[cfg(not(no_global_oom_handling))]
+pub(crate) use self::into_iter::AsIntoIter;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::into_iter::IntoIter;
+
+mod into_iter;
+
+#[cfg(not(no_global_oom_handling))]
+use self::is_zero::IsZero;
+
+mod is_zero;
+
+#[cfg(not(no_global_oom_handling))]
+mod source_iter_marker;
+
+mod partial_eq;
+
+#[cfg(not(no_global_oom_handling))]
+use self::spec_from_elem::SpecFromElem;
+
+#[cfg(not(no_global_oom_handling))]
+mod spec_from_elem;
+
+use self::set_len_on_drop::SetLenOnDrop;
+
+mod set_len_on_drop;
+
+#[cfg(not(no_global_oom_handling))]
+use self::in_place_drop::InPlaceDrop;
+
+#[cfg(not(no_global_oom_handling))]
+mod in_place_drop;
+
+#[cfg(not(no_global_oom_handling))]
+use self::spec_from_iter_nested::SpecFromIterNested;
+
+#[cfg(not(no_global_oom_handling))]
+mod spec_from_iter_nested;
+
+#[cfg(not(no_global_oom_handling))]
+use self::spec_from_iter::SpecFromIter;
+
+#[cfg(not(no_global_oom_handling))]
+mod spec_from_iter;
+
+#[cfg(not(no_global_oom_handling))]
+use self::spec_extend::SpecExtend;
+
+use self::spec_extend::TrySpecExtend;
+
+mod spec_extend;
+
+/// A contiguous growable array type, written as `Vec<T>` and pronounced 'vector'.
+///
+/// # Examples
+///
+/// ```
+/// let mut vec = Vec::new();
+/// vec.push(1);
+/// vec.push(2);
+///
+/// assert_eq!(vec.len(), 2);
+/// assert_eq!(vec[0], 1);
+///
+/// assert_eq!(vec.pop(), Some(2));
+/// assert_eq!(vec.len(), 1);
+///
+/// vec[0] = 7;
+/// assert_eq!(vec[0], 7);
+///
+/// vec.extend([1, 2, 3].iter().copied());
+///
+/// for x in &vec {
+/// println!("{}", x);
+/// }
+/// assert_eq!(vec, [7, 1, 2, 3]);
+/// ```
+///
+/// The [`vec!`] macro is provided to make initialization more convenient:
+///
+/// ```
+/// let mut vec = vec![1, 2, 3];
+/// vec.push(4);
+/// assert_eq!(vec, [1, 2, 3, 4]);
+/// ```
+///
+/// It can also initialize each element of a `Vec<T>` with a given value.
+/// This may be more efficient than performing allocation and initialization
+/// in separate steps, especially when initializing a vector of zeros:
+///
+/// ```
+/// let vec = vec![0; 5];
+/// assert_eq!(vec, [0, 0, 0, 0, 0]);
+///
+/// // The following is equivalent, but potentially slower:
+/// let mut vec = Vec::with_capacity(5);
+/// vec.resize(5, 0);
+/// assert_eq!(vec, [0, 0, 0, 0, 0]);
+/// ```
+///
+/// For more information, see
+/// [Capacity and Reallocation](#capacity-and-reallocation).
+///
+/// Use a `Vec<T>` as an efficient stack:
+///
+/// ```
+/// let mut stack = Vec::new();
+///
+/// stack.push(1);
+/// stack.push(2);
+/// stack.push(3);
+///
+/// while let Some(top) = stack.pop() {
+/// // Prints 3, 2, 1
+/// println!("{}", top);
+/// }
+/// ```
+///
+/// # Indexing
+///
+/// The `Vec` type allows to access values by index, because it implements the
+/// [`Index`] trait. An example will be more explicit:
+///
+/// ```
+/// let v = vec![0, 2, 4, 6];
+/// println!("{}", v[1]); // it will display '2'
+/// ```
+///
+/// However be careful: if you try to access an index which isn't in the `Vec`,
+/// your software will panic! You cannot do this:
+///
+/// ```should_panic
+/// let v = vec![0, 2, 4, 6];
+/// println!("{}", v[6]); // it will panic!
+/// ```
+///
+/// Use [`get`] and [`get_mut`] if you want to check whether the index is in
+/// the `Vec`.
+///
+/// # Slicing
+///
+/// A `Vec` can be mutable. On the other hand, slices are read-only objects.
+/// To get a [slice][prim@slice], use [`&`]. Example:
+///
+/// ```
+/// fn read_slice(slice: &[usize]) {
+/// // ...
+/// }
+///
+/// let v = vec![0, 1];
+/// read_slice(&v);
+///
+/// // ... and that's all!
+/// // you can also do it like this:
+/// let u: &[usize] = &v;
+/// // or like this:
+/// let u: &[_] = &v;
+/// ```
+///
+/// In Rust, it's more common to pass slices as arguments rather than vectors
+/// when you just want to provide read access. The same goes for [`String`] and
+/// [`&str`].
+///
+/// # Capacity and reallocation
+///
+/// The capacity of a vector is the amount of space allocated for any future
+/// elements that will be added onto the vector. This is not to be confused with
+/// the *length* of a vector, which specifies the number of actual elements
+/// within the vector. If a vector's length exceeds its capacity, its capacity
+/// will automatically be increased, but its elements will have to be
+/// reallocated.
+///
+/// For example, a vector with capacity 10 and length 0 would be an empty vector
+/// with space for 10 more elements. Pushing 10 or fewer elements onto the
+/// vector will not change its capacity or cause reallocation to occur. However,
+/// if the vector's length is increased to 11, it will have to reallocate, which
+/// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
+/// whenever possible to specify how big the vector is expected to get.
+///
+/// # Guarantees
+///
+/// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
+/// about its design. This ensures that it's as low-overhead as possible in
+/// the general case, and can be correctly manipulated in primitive ways
+/// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
+/// If additional type parameters are added (e.g., to support custom allocators),
+/// overriding their defaults may change the behavior.
+///
+/// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
+/// triplet. No more, no less. The order of these fields is completely
+/// unspecified, and you should use the appropriate methods to modify these.
+/// The pointer will never be null, so this type is null-pointer-optimized.
+///
+/// However, the pointer might not actually point to allocated memory. In particular,
+/// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`],
+/// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`]
+/// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
+/// types inside a `Vec`, it will not allocate space for them. *Note that in this case
+/// the `Vec` might not report a [`capacity`] of 0*. `Vec` will allocate if and only
+/// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation
+/// details are very subtle &mdash; if you intend to allocate memory using a `Vec`
+/// and use it for something else (either to pass to unsafe code, or to build your
+/// own memory-backed collection), be sure to deallocate this memory by using
+/// `from_raw_parts` to recover the `Vec` and then dropping it.
+///
+/// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
+/// (as defined by the allocator Rust is configured to use by default), and its
+/// pointer points to [`len`] initialized, contiguous elements in order (what
+/// you would see if you coerced it to a slice), followed by [`capacity`]` -
+/// `[`len`] logically uninitialized, contiguous elements.
+///
+/// A vector containing the elements `'a'` and `'b'` with capacity 4 can be
+/// visualized as below. The top part is the `Vec` struct, it contains a
+/// pointer to the head of the allocation in the heap, length and capacity.
+/// The bottom part is the allocation on the heap, a contiguous memory block.
+///
+/// ```text
+/// ptr len capacity
+/// +--------+--------+--------+
+/// | 0x0123 | 2 | 4 |
+/// +--------+--------+--------+
+/// |
+/// v
+/// Heap +--------+--------+--------+--------+
+/// | 'a' | 'b' | uninit | uninit |
+/// +--------+--------+--------+--------+
+/// ```
+///
+/// - **uninit** represents memory that is not initialized, see [`MaybeUninit`].
+/// - Note: the ABI is not stable and `Vec` makes no guarantees about its memory
+/// layout (including the order of fields).
+///
+/// `Vec` will never perform a "small optimization" where elements are actually
+/// stored on the stack for two reasons:
+///
+/// * It would make it more difficult for unsafe code to correctly manipulate
+/// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
+/// only moved, and it would be more difficult to determine if a `Vec` had
+/// actually allocated memory.
+///
+/// * It would penalize the general case, incurring an additional branch
+/// on every access.
+///
+/// `Vec` will never automatically shrink itself, even if completely empty. This
+/// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
+/// and then filling it back up to the same [`len`] should incur no calls to
+/// the allocator. If you wish to free up unused memory, use
+/// [`shrink_to_fit`] or [`shrink_to`].
+///
+/// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
+/// sufficient. [`push`] and [`insert`] *will* (re)allocate if
+/// [`len`]` == `[`capacity`]. That is, the reported capacity is completely
+/// accurate, and can be relied on. It can even be used to manually free the memory
+/// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
+/// when not necessary.
+///
+/// `Vec` does not guarantee any particular growth strategy when reallocating
+/// when full, nor when [`reserve`] is called. The current strategy is basic
+/// and it may prove desirable to use a non-constant growth factor. Whatever
+/// strategy is used will of course guarantee *O*(1) amortized [`push`].
+///
+/// `vec![x; n]`, `vec![a, b, c, d]`, and
+/// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
+/// with exactly the requested capacity. If [`len`]` == `[`capacity`],
+/// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
+/// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
+///
+/// `Vec` will not specifically overwrite any data that is removed from it,
+/// but also won't specifically preserve it. Its uninitialized memory is
+/// scratch space that it may use however it wants. It will generally just do
+/// whatever is most efficient or otherwise easy to implement. Do not rely on
+/// removed data to be erased for security purposes. Even if you drop a `Vec`, its
+/// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory
+/// first, that might not actually happen because the optimizer does not consider
+/// this a side-effect that must be preserved. There is one case which we will
+/// not break, however: using `unsafe` code to write to the excess capacity,
+/// and then increasing the length to match, is always valid.
+///
+/// Currently, `Vec` does not guarantee the order in which elements are dropped.
+/// The order has changed in the past and may change again.
+///
+/// [`get`]: ../../std/vec/struct.Vec.html#method.get
+/// [`get_mut`]: ../../std/vec/struct.Vec.html#method.get_mut
+/// [`String`]: crate::string::String
+/// [`&str`]: type@str
+/// [`shrink_to_fit`]: Vec::shrink_to_fit
+/// [`shrink_to`]: Vec::shrink_to
+/// [`capacity`]: Vec::capacity
+/// [`mem::size_of::<T>`]: core::mem::size_of
+/// [`len`]: Vec::len
+/// [`push`]: Vec::push
+/// [`insert`]: Vec::insert
+/// [`reserve`]: Vec::reserve
+/// [`MaybeUninit`]: core::mem::MaybeUninit
+/// [owned slice]: Box
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "vec_type")]
+pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
+ buf: RawVec<T, A>,
+ len: usize,
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Inherent methods
+////////////////////////////////////////////////////////////////////////////////
+
+impl<T> Vec<T> {
+ /// Constructs a new, empty `Vec<T>`.
+ ///
+ /// The vector will not allocate until elements are pushed onto it.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![allow(unused_mut)]
+ /// let mut vec: Vec<i32> = Vec::new();
+ /// ```
+ #[inline]
+ #[rustc_const_stable(feature = "const_vec_new", since = "1.39.0")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub const fn new() -> Self {
+ Vec { buf: RawVec::NEW, len: 0 }
+ }
+
+ /// Constructs a new, empty `Vec<T>` with the specified capacity.
+ ///
+ /// The vector will be able to hold exactly `capacity` elements without
+ /// reallocating. If `capacity` is 0, the vector will not allocate.
+ ///
+ /// It is important to note that although the returned vector has the
+ /// *capacity* specified, the vector will have a zero *length*. For an
+ /// explanation of the difference between length and capacity, see
+ /// *[Capacity and reallocation]*.
+ ///
+ /// [Capacity and reallocation]: #capacity-and-reallocation
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ ///
+ /// // The vector contains no items, even though it has capacity for more
+ /// assert_eq!(vec.len(), 0);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // These are all done without reallocating...
+ /// for i in 0..10 {
+ /// vec.push(i);
+ /// }
+ /// assert_eq!(vec.len(), 10);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // ...but this may make the vector reallocate
+ /// vec.push(11);
+ /// assert_eq!(vec.len(), 11);
+ /// assert!(vec.capacity() >= 11);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[doc(alias = "malloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn with_capacity(capacity: usize) -> Self {
+ Self::with_capacity_in(capacity, Global)
+ }
+
+ /// Tries to construct a new, empty `Vec<T>` with the specified capacity.
+ ///
+ /// The vector will be able to hold exactly `capacity` elements without
+ /// reallocating. If `capacity` is 0, the vector will not allocate.
+ ///
+ /// It is important to note that although the returned vector has the
+ /// *capacity* specified, the vector will have a zero *length*. For an
+ /// explanation of the difference between length and capacity, see
+ /// *[Capacity and reallocation]*.
+ ///
+ /// [Capacity and reallocation]: #capacity-and-reallocation
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = Vec::try_with_capacity(10).unwrap();
+ ///
+ /// // The vector contains no items, even though it has capacity for more
+ /// assert_eq!(vec.len(), 0);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // These are all done without reallocating...
+ /// for i in 0..10 {
+ /// vec.push(i);
+ /// }
+ /// assert_eq!(vec.len(), 10);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // ...but this may make the vector reallocate
+ /// vec.push(11);
+ /// assert_eq!(vec.len(), 11);
+ /// assert!(vec.capacity() >= 11);
+ ///
+ /// let mut result = Vec::try_with_capacity(usize::MAX);
+ /// assert!(result.is_err());
+ /// ```
+ #[inline]
+ #[doc(alias = "malloc")]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
+ Self::try_with_capacity_in(capacity, Global)
+ }
+
+ /// Creates a `Vec<T>` directly from the raw components of another vector.
+ ///
+ /// # Safety
+ ///
+ /// This is highly unsafe, due to the number of invariants that aren't
+ /// checked:
+ ///
+ /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
+ /// (at least, it's highly likely to be incorrect if it wasn't).
+ /// * `T` needs to have the same size and alignment as what `ptr` was allocated with.
+ /// (`T` having a less strict alignment is not sufficient, the alignment really
+ /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
+ /// allocated and deallocated with the same layout.)
+ /// * `length` needs to be less than or equal to `capacity`.
+ /// * `capacity` needs to be the capacity that the pointer was allocated with.
+ ///
+ /// Violating these may cause problems like corrupting the allocator's
+ /// internal data structures. For example it is **not** safe
+ /// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`.
+ /// It's also not safe to build one from a `Vec<u16>` and its length, because
+ /// the allocator cares about the alignment, and these two types have different
+ /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after
+ /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1.
+ ///
+ /// The ownership of `ptr` is effectively transferred to the
+ /// `Vec<T>` which may then deallocate, reallocate or change the
+ /// contents of memory pointed to by the pointer at will. Ensure
+ /// that nothing else uses the pointer after calling this
+ /// function.
+ ///
+ /// [`String`]: crate::string::String
+ /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::ptr;
+ /// use std::mem;
+ ///
+ /// let v = vec![1, 2, 3];
+ ///
+ // FIXME Update this when vec_into_raw_parts is stabilized
+ /// // Prevent running `v`'s destructor so we are in complete control
+ /// // of the allocation.
+ /// let mut v = mem::ManuallyDrop::new(v);
+ ///
+ /// // Pull out the various important pieces of information about `v`
+ /// let p = v.as_mut_ptr();
+ /// let len = v.len();
+ /// let cap = v.capacity();
+ ///
+ /// unsafe {
+ /// // Overwrite memory with 4, 5, 6
+ /// for i in 0..len as isize {
+ /// ptr::write(p.offset(i), 4 + i);
+ /// }
+ ///
+ /// // Put everything back together into a Vec
+ /// let rebuilt = Vec::from_raw_parts(p, len, cap);
+ /// assert_eq!(rebuilt, [4, 5, 6]);
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self {
+ unsafe { Self::from_raw_parts_in(ptr, length, capacity, Global) }
+ }
+}
+
+impl<T, A: Allocator> Vec<T, A> {
+ /// Constructs a new, empty `Vec<T, A>`.
+ ///
+ /// The vector will not allocate until elements are pushed onto it.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// # #[allow(unused_mut)]
+ /// let mut vec: Vec<i32, _> = Vec::new_in(System);
+ /// ```
+ #[inline]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ pub const fn new_in(alloc: A) -> Self {
+ Vec { buf: RawVec::new_in(alloc), len: 0 }
+ }
+
+ /// Constructs a new, empty `Vec<T, A>` with the specified capacity with the provided
+ /// allocator.
+ ///
+ /// The vector will be able to hold exactly `capacity` elements without
+ /// reallocating. If `capacity` is 0, the vector will not allocate.
+ ///
+ /// It is important to note that although the returned vector has the
+ /// *capacity* specified, the vector will have a zero *length*. For an
+ /// explanation of the difference between length and capacity, see
+ /// *[Capacity and reallocation]*.
+ ///
+ /// [Capacity and reallocation]: #capacity-and-reallocation
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut vec = Vec::with_capacity_in(10, System);
+ ///
+ /// // The vector contains no items, even though it has capacity for more
+ /// assert_eq!(vec.len(), 0);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // These are all done without reallocating...
+ /// for i in 0..10 {
+ /// vec.push(i);
+ /// }
+ /// assert_eq!(vec.len(), 10);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // ...but this may make the vector reallocate
+ /// vec.push(11);
+ /// assert_eq!(vec.len(), 11);
+ /// assert!(vec.capacity() >= 11);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
+ Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
+ }
+
+ /// Tries to construct a new, empty `Vec<T, A>` with the specified capacity
+ /// with the provided allocator.
+ ///
+ /// The vector will be able to hold exactly `capacity` elements without
+ /// reallocating. If `capacity` is 0, the vector will not allocate.
+ ///
+ /// It is important to note that although the returned vector has the
+ /// *capacity* specified, the vector will have a zero *length*. For an
+ /// explanation of the difference between length and capacity, see
+ /// *[Capacity and reallocation]*.
+ ///
+ /// [Capacity and reallocation]: #capacity-and-reallocation
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut vec = Vec::try_with_capacity_in(10, System).unwrap();
+ ///
+ /// // The vector contains no items, even though it has capacity for more
+ /// assert_eq!(vec.len(), 0);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // These are all done without reallocating...
+ /// for i in 0..10 {
+ /// vec.push(i);
+ /// }
+ /// assert_eq!(vec.len(), 10);
+ /// assert_eq!(vec.capacity(), 10);
+ ///
+ /// // ...but this may make the vector reallocate
+ /// vec.push(11);
+ /// assert_eq!(vec.len(), 11);
+ /// assert!(vec.capacity() >= 11);
+ ///
+ /// let mut result = Vec::try_with_capacity_in(usize::MAX, System);
+ /// assert!(result.is_err());
+ /// ```
+ #[inline]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
+ Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 })
+ }
+
+ /// Creates a `Vec<T, A>` directly from the raw components of another vector.
+ ///
+ /// # Safety
+ ///
+ /// This is highly unsafe, due to the number of invariants that aren't
+ /// checked:
+ ///
+ /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
+ /// (at least, it's highly likely to be incorrect if it wasn't).
+ /// * `T` needs to have the same size and alignment as what `ptr` was allocated with.
+ /// (`T` having a less strict alignment is not sufficient, the alignment really
+ /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
+ /// allocated and deallocated with the same layout.)
+ /// * `length` needs to be less than or equal to `capacity`.
+ /// * `capacity` needs to be the capacity that the pointer was allocated with.
+ ///
+ /// Violating these may cause problems like corrupting the allocator's
+ /// internal data structures. For example it is **not** safe
+ /// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`.
+ /// It's also not safe to build one from a `Vec<u16>` and its length, because
+ /// the allocator cares about the alignment, and these two types have different
+ /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after
+ /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1.
+ ///
+ /// The ownership of `ptr` is effectively transferred to the
+ /// `Vec<T>` which may then deallocate, reallocate or change the
+ /// contents of memory pointed to by the pointer at will. Ensure
+ /// that nothing else uses the pointer after calling this
+ /// function.
+ ///
+ /// [`String`]: crate::string::String
+ /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// use std::ptr;
+ /// use std::mem;
+ ///
+ /// let mut v = Vec::with_capacity_in(3, System);
+ /// v.push(1);
+ /// v.push(2);
+ /// v.push(3);
+ ///
+ // FIXME Update this when vec_into_raw_parts is stabilized
+ /// // Prevent running `v`'s destructor so we are in complete control
+ /// // of the allocation.
+ /// let mut v = mem::ManuallyDrop::new(v);
+ ///
+ /// // Pull out the various important pieces of information about `v`
+ /// let p = v.as_mut_ptr();
+ /// let len = v.len();
+ /// let cap = v.capacity();
+ /// let alloc = v.allocator();
+ ///
+ /// unsafe {
+ /// // Overwrite memory with 4, 5, 6
+ /// for i in 0..len as isize {
+ /// ptr::write(p.offset(i), 4 + i);
+ /// }
+ ///
+ /// // Put everything back together into a Vec
+ /// let rebuilt = Vec::from_raw_parts_in(p, len, cap, alloc.clone());
+ /// assert_eq!(rebuilt, [4, 5, 6]);
+ /// }
+ /// ```
+ #[inline]
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self {
+ unsafe { Vec { buf: RawVec::from_raw_parts_in(ptr, capacity, alloc), len: length } }
+ }
+
+ /// Decomposes a `Vec<T>` into its raw components.
+ ///
+ /// Returns the raw pointer to the underlying data, the length of
+ /// the vector (in elements), and the allocated capacity of the
+ /// data (in elements). These are the same arguments in the same
+ /// order as the arguments to [`from_raw_parts`].
+ ///
+ /// After calling this function, the caller is responsible for the
+ /// memory previously managed by the `Vec`. The only way to do
+ /// this is to convert the raw pointer, length, and capacity back
+ /// into a `Vec` with the [`from_raw_parts`] function, allowing
+ /// the destructor to perform the cleanup.
+ ///
+ /// [`from_raw_parts`]: Vec::from_raw_parts
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(vec_into_raw_parts)]
+ /// let v: Vec<i32> = vec![-1, 0, 1];
+ ///
+ /// let (ptr, len, cap) = v.into_raw_parts();
+ ///
+ /// let rebuilt = unsafe {
+ /// // We can now make changes to the components, such as
+ /// // transmuting the raw pointer to a compatible type.
+ /// let ptr = ptr as *mut u32;
+ ///
+ /// Vec::from_raw_parts(ptr, len, cap)
+ /// };
+ /// assert_eq!(rebuilt, [4294967295, 0, 1]);
+ /// ```
+ #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
+ pub fn into_raw_parts(self) -> (*mut T, usize, usize) {
+ let mut me = ManuallyDrop::new(self);
+ (me.as_mut_ptr(), me.len(), me.capacity())
+ }
+
+ /// Decomposes a `Vec<T>` into its raw components.
+ ///
+ /// Returns the raw pointer to the underlying data, the length of the vector (in elements),
+ /// the allocated capacity of the data (in elements), and the allocator. These are the same
+ /// arguments in the same order as the arguments to [`from_raw_parts_in`].
+ ///
+ /// After calling this function, the caller is responsible for the
+ /// memory previously managed by the `Vec`. The only way to do
+ /// this is to convert the raw pointer, length, and capacity back
+ /// into a `Vec` with the [`from_raw_parts_in`] function, allowing
+ /// the destructor to perform the cleanup.
+ ///
+ /// [`from_raw_parts_in`]: Vec::from_raw_parts_in
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(allocator_api, vec_into_raw_parts)]
+ ///
+ /// use std::alloc::System;
+ ///
+ /// let mut v: Vec<i32, System> = Vec::new_in(System);
+ /// v.push(-1);
+ /// v.push(0);
+ /// v.push(1);
+ ///
+ /// let (ptr, len, cap, alloc) = v.into_raw_parts_with_alloc();
+ ///
+ /// let rebuilt = unsafe {
+ /// // We can now make changes to the components, such as
+ /// // transmuting the raw pointer to a compatible type.
+ /// let ptr = ptr as *mut u32;
+ ///
+ /// Vec::from_raw_parts_in(ptr, len, cap, alloc)
+ /// };
+ /// assert_eq!(rebuilt, [4294967295, 0, 1]);
+ /// ```
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ // #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
+ pub fn into_raw_parts_with_alloc(self) -> (*mut T, usize, usize, A) {
+ let mut me = ManuallyDrop::new(self);
+ let len = me.len();
+ let capacity = me.capacity();
+ let ptr = me.as_mut_ptr();
+ let alloc = unsafe { ptr::read(me.allocator()) };
+ (ptr, len, capacity, alloc)
+ }
+
+ /// Returns the number of elements the vector can hold without
+ /// reallocating.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let vec: Vec<i32> = Vec::with_capacity(10);
+ /// assert_eq!(vec.capacity(), 10);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn capacity(&self) -> usize {
+ self.buf.capacity()
+ }
+
+ /// Reserves capacity for at least `additional` more elements to be inserted
+ /// in the given `Vec<T>`. The collection may reserve more space to avoid
+ /// frequent reallocations. After calling `reserve`, capacity will be
+ /// greater than or equal to `self.len() + additional`. Does nothing if
+ /// capacity is already sufficient.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1];
+ /// vec.reserve(10);
+ /// assert!(vec.capacity() >= 11);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[doc(alias = "realloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn reserve(&mut self, additional: usize) {
+ self.buf.reserve(self.len, additional);
+ }
+
+ /// Reserves the minimum capacity for exactly `additional` more elements to
+ /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
+ /// capacity will be greater than or equal to `self.len() + additional`.
+ /// Does nothing if the capacity is already sufficient.
+ ///
+ /// Note that the allocator may give the collection more space than it
+ /// requests. Therefore, capacity can not be relied upon to be precisely
+ /// minimal. Prefer `reserve` if future insertions are expected.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity overflows `usize`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1];
+ /// vec.reserve_exact(10);
+ /// assert!(vec.capacity() >= 11);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[doc(alias = "realloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn reserve_exact(&mut self, additional: usize) {
+ self.buf.reserve_exact(self.len, additional);
+ }
+
+ /// Tries to reserve capacity for at least `additional` more elements to be inserted
+ /// in the given `Vec<T>`. The collection may reserve more space to avoid
+ /// frequent reallocations. After calling `try_reserve`, capacity will be
+ /// greater than or equal to `self.len() + additional`. Does nothing if
+ /// capacity is already sufficient.
+ ///
+ /// # Errors
+ ///
+ /// If the capacity overflows, or the allocator reports a failure, then an error
+ /// is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(try_reserve)]
+ /// use std::collections::TryReserveError;
+ ///
+ /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> {
+ /// let mut output = Vec::new();
+ ///
+ /// // Pre-reserve the memory, exiting if we can't
+ /// output.try_reserve(data.len())?;
+ ///
+ /// // Now we know this can't OOM in the middle of our complex work
+ /// output.extend(data.iter().map(|&val| {
+ /// val * 2 + 5 // very complicated
+ /// }));
+ ///
+ /// Ok(output)
+ /// }
+ /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
+ /// ```
+ #[doc(alias = "realloc")]
+ #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+ pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
+ self.buf.try_reserve(self.len, additional)
+ }
+
+ /// Tries to reserve the minimum capacity for exactly `additional`
+ /// elements to be inserted in the given `Vec<T>`. After calling
+ /// `try_reserve_exact`, capacity will be greater than or equal to
+ /// `self.len() + additional` if it returns `Ok(())`.
+ /// Does nothing if the capacity is already sufficient.
+ ///
+ /// Note that the allocator may give the collection more space than it
+ /// requests. Therefore, capacity can not be relied upon to be precisely
+ /// minimal. Prefer `reserve` if future insertions are expected.
+ ///
+ /// # Errors
+ ///
+ /// If the capacity overflows, or the allocator reports a failure, then an error
+ /// is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(try_reserve)]
+ /// use std::collections::TryReserveError;
+ ///
+ /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> {
+ /// let mut output = Vec::new();
+ ///
+ /// // Pre-reserve the memory, exiting if we can't
+ /// output.try_reserve_exact(data.len())?;
+ ///
+ /// // Now we know this can't OOM in the middle of our complex work
+ /// output.extend(data.iter().map(|&val| {
+ /// val * 2 + 5 // very complicated
+ /// }));
+ ///
+ /// Ok(output)
+ /// }
+ /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
+ /// ```
+ #[doc(alias = "realloc")]
+ #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
+ pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
+ self.buf.try_reserve_exact(self.len, additional)
+ }
+
+ /// Shrinks the capacity of the vector as much as possible.
+ ///
+ /// It will drop down as close as possible to the length but the allocator
+ /// may still inform the vector that there is space for a few more elements.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ /// assert_eq!(vec.capacity(), 10);
+ /// vec.shrink_to_fit();
+ /// assert!(vec.capacity() >= 3);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[doc(alias = "realloc")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn shrink_to_fit(&mut self) {
+ // The capacity is never less than the length, and there's nothing to do when
+ // they are equal, so we can avoid the panic case in `RawVec::shrink_to_fit`
+ // by only calling it with a greater capacity.
+ if self.capacity() > self.len {
+ self.buf.shrink_to_fit(self.len);
+ }
+ }
+
+ /// Tries to shrink the capacity of the vector as much as possible.
+ ///
+ /// It will drop down as close as possible to the length but the allocator
+ /// may still inform the vector that there is space for a few more elements.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ /// assert_eq!(vec.capacity(), 10);
+ /// vec.try_shrink_to_fit().unwrap();
+ /// assert!(vec.capacity() >= 3);
+ /// ```
+ #[doc(alias = "realloc")]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_shrink_to_fit(&mut self) -> Result<(), TryReserveError> {
+ // The capacity is never less than the length, and there's nothing to do when
+ // they are equal, so we can avoid the panic case in `RawVec::try_shrink_to_fit`
+ // by only calling it with a greater capacity.
+ if self.capacity() <= self.len {
+ return Ok(());
+ }
+
+ self.buf.try_shrink_to_fit(self.len)
+ }
+
+ /// Shrinks the capacity of the vector with a lower bound.
+ ///
+ /// The capacity will remain at least as large as both the length
+ /// and the supplied value.
+ ///
+ /// If the current capacity is less than the lower limit, this is a no-op.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(shrink_to)]
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ /// assert_eq!(vec.capacity(), 10);
+ /// vec.shrink_to(4);
+ /// assert!(vec.capacity() >= 4);
+ /// vec.shrink_to(0);
+ /// assert!(vec.capacity() >= 3);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[doc(alias = "realloc")]
+ #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")]
+ pub fn shrink_to(&mut self, min_capacity: usize) {
+ if self.capacity() > min_capacity {
+ self.buf.shrink_to_fit(cmp::max(self.len, min_capacity));
+ }
+ }
+
+ /// Converts the vector into [`Box<[T]>`][owned slice].
+ ///
+ /// Note that this will drop any excess capacity.
+ ///
+ /// [owned slice]: Box
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let v = vec![1, 2, 3];
+ ///
+ /// let slice = v.into_boxed_slice();
+ /// ```
+ ///
+ /// Any excess capacity is removed:
+ ///
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ ///
+ /// assert_eq!(vec.capacity(), 10);
+ /// let slice = vec.into_boxed_slice();
+ /// assert_eq!(slice.into_vec().capacity(), 3);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn into_boxed_slice(mut self) -> Box<[T], A> {
+ unsafe {
+ self.shrink_to_fit();
+ let me = ManuallyDrop::new(self);
+ let buf = ptr::read(&me.buf);
+ let len = me.len();
+ buf.into_box(len).assume_init()
+ }
+ }
+
+ /// Tries to convert the vector into [`Box<[T]>`][owned slice].
+ ///
+ /// Note that this will drop any excess capacity.
+ ///
+ /// [owned slice]: Box
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let v = vec![1, 2, 3];
+ ///
+ /// let slice = v.try_into_boxed_slice().unwrap();
+ /// ```
+ ///
+ /// Any excess capacity is removed:
+ ///
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ ///
+ /// assert_eq!(vec.capacity(), 10);
+ /// let slice = vec.try_into_boxed_slice().unwrap();
+ /// assert_eq!(slice.into_vec().capacity(), 3);
+ /// ```
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_into_boxed_slice(mut self) -> Result<Box<[T], A>, TryReserveError> {
+ unsafe {
+ self.try_shrink_to_fit()?;
+ let me = ManuallyDrop::new(self);
+ let buf = ptr::read(&me.buf);
+ let len = me.len();
+ Ok(buf.into_box(len).assume_init())
+ }
+ }
+
+ /// Shortens the vector, keeping the first `len` elements and dropping
+ /// the rest.
+ ///
+ /// If `len` is greater than the vector's current length, this has no
+ /// effect.
+ ///
+ /// The [`drain`] method can emulate `truncate`, but causes the excess
+ /// elements to be returned instead of dropped.
+ ///
+ /// Note that this method has no effect on the allocated capacity
+ /// of the vector.
+ ///
+ /// # Examples
+ ///
+ /// Truncating a five element vector to two elements:
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3, 4, 5];
+ /// vec.truncate(2);
+ /// assert_eq!(vec, [1, 2]);
+ /// ```
+ ///
+ /// No truncation occurs when `len` is greater than the vector's current
+ /// length:
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// vec.truncate(8);
+ /// assert_eq!(vec, [1, 2, 3]);
+ /// ```
+ ///
+ /// Truncating when `len == 0` is equivalent to calling the [`clear`]
+ /// method.
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// vec.truncate(0);
+ /// assert_eq!(vec, []);
+ /// ```
+ ///
+ /// [`clear`]: Vec::clear
+ /// [`drain`]: Vec::drain
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn truncate(&mut self, len: usize) {
+ // This is safe because:
+ //
+ // * the slice passed to `drop_in_place` is valid; the `len > self.len`
+ // case avoids creating an invalid slice, and
+ // * the `len` of the vector is shrunk before calling `drop_in_place`,
+ // such that no value will be dropped twice in case `drop_in_place`
+ // were to panic once (if it panics twice, the program aborts).
+ unsafe {
+ // Note: It's intentional that this is `>` and not `>=`.
+ // Changing it to `>=` has negative performance
+ // implications in some cases. See #78884 for more.
+ if len > self.len {
+ return;
+ }
+ let remaining_len = self.len - len;
+ let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len);
+ self.len = len;
+ ptr::drop_in_place(s);
+ }
+ }
+
+ /// Extracts a slice containing the entire vector.
+ ///
+ /// Equivalent to `&s[..]`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::io::{self, Write};
+ /// let buffer = vec![1, 2, 3, 5, 8];
+ /// io::sink().write(buffer.as_slice()).unwrap();
+ /// ```
+ #[inline]
+ #[stable(feature = "vec_as_slice", since = "1.7.0")]
+ pub fn as_slice(&self) -> &[T] {
+ self
+ }
+
+ /// Extracts a mutable slice of the entire vector.
+ ///
+ /// Equivalent to `&mut s[..]`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::io::{self, Read};
+ /// let mut buffer = vec![0; 3];
+ /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
+ /// ```
+ #[inline]
+ #[stable(feature = "vec_as_slice", since = "1.7.0")]
+ pub fn as_mut_slice(&mut self) -> &mut [T] {
+ self
+ }
+
+ /// Returns a raw pointer to the vector's buffer.
+ ///
+ /// The caller must ensure that the vector outlives the pointer this
+ /// function returns, or else it will end up pointing to garbage.
+ /// Modifying the vector may cause its buffer to be reallocated,
+ /// which would also make any pointers to it invalid.
+ ///
+ /// The caller must also ensure that the memory the pointer (non-transitively) points to
+ /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer
+ /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let x = vec![1, 2, 4];
+ /// let x_ptr = x.as_ptr();
+ ///
+ /// unsafe {
+ /// for i in 0..x.len() {
+ /// assert_eq!(*x_ptr.add(i), 1 << i);
+ /// }
+ /// }
+ /// ```
+ ///
+ /// [`as_mut_ptr`]: Vec::as_mut_ptr
+ #[stable(feature = "vec_as_ptr", since = "1.37.0")]
+ #[inline]
+ pub fn as_ptr(&self) -> *const T {
+ // We shadow the slice method of the same name to avoid going through
+ // `deref`, which creates an intermediate reference.
+ let ptr = self.buf.ptr();
+ unsafe {
+ assume(!ptr.is_null());
+ }
+ ptr
+ }
+
+ /// Returns an unsafe mutable pointer to the vector's buffer.
+ ///
+ /// The caller must ensure that the vector outlives the pointer this
+ /// function returns, or else it will end up pointing to garbage.
+ /// Modifying the vector may cause its buffer to be reallocated,
+ /// which would also make any pointers to it invalid.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// // Allocate vector big enough for 4 elements.
+ /// let size = 4;
+ /// let mut x: Vec<i32> = Vec::with_capacity(size);
+ /// let x_ptr = x.as_mut_ptr();
+ ///
+ /// // Initialize elements via raw pointer writes, then set length.
+ /// unsafe {
+ /// for i in 0..size {
+ /// *x_ptr.add(i) = i as i32;
+ /// }
+ /// x.set_len(size);
+ /// }
+ /// assert_eq!(&*x, &[0, 1, 2, 3]);
+ /// ```
+ #[stable(feature = "vec_as_ptr", since = "1.37.0")]
+ #[inline]
+ pub fn as_mut_ptr(&mut self) -> *mut T {
+ // We shadow the slice method of the same name to avoid going through
+ // `deref_mut`, which creates an intermediate reference.
+ let ptr = self.buf.ptr();
+ unsafe {
+ assume(!ptr.is_null());
+ }
+ ptr
+ }
+
+ /// Returns a reference to the underlying allocator.
+ #[unstable(feature = "allocator_api", issue = "32838")]
+ #[inline]
+ pub fn allocator(&self) -> &A {
+ self.buf.allocator()
+ }
+
+ /// Forces the length of the vector to `new_len`.
+ ///
+ /// This is a low-level operation that maintains none of the normal
+ /// invariants of the type. Normally changing the length of a vector
+ /// is done using one of the safe operations instead, such as
+ /// [`truncate`], [`resize`], [`extend`], or [`clear`].
+ ///
+ /// [`truncate`]: Vec::truncate
+ /// [`resize`]: Vec::resize
+ /// [`extend`]: Extend::extend
+ /// [`clear`]: Vec::clear
+ ///
+ /// # Safety
+ ///
+ /// - `new_len` must be less than or equal to [`capacity()`].
+ /// - The elements at `old_len..new_len` must be initialized.
+ ///
+ /// [`capacity()`]: Vec::capacity
+ ///
+ /// # Examples
+ ///
+ /// This method can be useful for situations in which the vector
+ /// is serving as a buffer for other code, particularly over FFI:
+ ///
+ /// ```no_run
+ /// # #![allow(dead_code)]
+ /// # // This is just a minimal skeleton for the doc example;
+ /// # // don't use this as a starting point for a real library.
+ /// # pub struct StreamWrapper { strm: *mut std::ffi::c_void }
+ /// # const Z_OK: i32 = 0;
+ /// # extern "C" {
+ /// # fn deflateGetDictionary(
+ /// # strm: *mut std::ffi::c_void,
+ /// # dictionary: *mut u8,
+ /// # dictLength: *mut usize,
+ /// # ) -> i32;
+ /// # }
+ /// # impl StreamWrapper {
+ /// pub fn get_dictionary(&self) -> Option<Vec<u8>> {
+ /// // Per the FFI method's docs, "32768 bytes is always enough".
+ /// let mut dict = Vec::with_capacity(32_768);
+ /// let mut dict_length = 0;
+ /// // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that:
+ /// // 1. `dict_length` elements were initialized.
+ /// // 2. `dict_length` <= the capacity (32_768)
+ /// // which makes `set_len` safe to call.
+ /// unsafe {
+ /// // Make the FFI call...
+ /// let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length);
+ /// if r == Z_OK {
+ /// // ...and update the length to what was initialized.
+ /// dict.set_len(dict_length);
+ /// Some(dict)
+ /// } else {
+ /// None
+ /// }
+ /// }
+ /// }
+ /// # }
+ /// ```
+ ///
+ /// While the following example is sound, there is a memory leak since
+ /// the inner vectors were not freed prior to the `set_len` call:
+ ///
+ /// ```
+ /// let mut vec = vec![vec![1, 0, 0],
+ /// vec![0, 1, 0],
+ /// vec![0, 0, 1]];
+ /// // SAFETY:
+ /// // 1. `old_len..0` is empty so no elements need to be initialized.
+ /// // 2. `0 <= capacity` always holds whatever `capacity` is.
+ /// unsafe {
+ /// vec.set_len(0);
+ /// }
+ /// ```
+ ///
+ /// Normally, here, one would use [`clear`] instead to correctly drop
+ /// the contents and thus not leak memory.
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub unsafe fn set_len(&mut self, new_len: usize) {
+ debug_assert!(new_len <= self.capacity());
+
+ self.len = new_len;
+ }
+
+ /// Removes an element from the vector and returns it.
+ ///
+ /// The removed element is replaced by the last element of the vector.
+ ///
+ /// This does not preserve ordering, but is O(1).
+ ///
+ /// # Panics
+ ///
+ /// Panics if `index` is out of bounds.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = vec!["foo", "bar", "baz", "qux"];
+ ///
+ /// assert_eq!(v.swap_remove(1), "bar");
+ /// assert_eq!(v, ["foo", "qux", "baz"]);
+ ///
+ /// assert_eq!(v.swap_remove(0), "foo");
+ /// assert_eq!(v, ["baz", "qux"]);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn swap_remove(&mut self, index: usize) -> T {
+ #[cold]
+ #[inline(never)]
+ fn assert_failed(index: usize, len: usize) -> ! {
+ panic!("swap_remove index (is {}) should be < len (is {})", index, len);
+ }
+
+ let len = self.len();
+ if index >= len {
+ assert_failed(index, len);
+ }
+ unsafe {
+ // We replace self[index] with the last element. Note that if the
+ // bounds check above succeeds there must be a last element (which
+ // can be self[index] itself).
+ let last = ptr::read(self.as_ptr().add(len - 1));
+ let hole = self.as_mut_ptr().add(index);
+ self.set_len(len - 1);
+ ptr::replace(hole, last)
+ }
+ }
+
+ /// Inserts an element at position `index` within the vector, shifting all
+ /// elements after it to the right.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `index > len`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// vec.insert(1, 4);
+ /// assert_eq!(vec, [1, 4, 2, 3]);
+ /// vec.insert(4, 5);
+ /// assert_eq!(vec, [1, 4, 2, 3, 5]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn insert(&mut self, index: usize, element: T) {
+ #[cold]
+ #[inline(never)]
+ fn assert_failed(index: usize, len: usize) -> ! {
+ panic!("insertion index (is {}) should be <= len (is {})", index, len);
+ }
+
+ let len = self.len();
+ if index > len {
+ assert_failed(index, len);
+ }
+
+ // space for the new element
+ if len == self.buf.capacity() {
+ self.reserve(1);
+ }
+
+ unsafe {
+ // infallible
+ // The spot to put the new value
+ {
+ let p = self.as_mut_ptr().add(index);
+ // Shift everything over to make space. (Duplicating the
+ // `index`th element into two consecutive places.)
+ ptr::copy(p, p.offset(1), len - index);
+ // Write it in, overwriting the first copy of the `index`th
+ // element.
+ ptr::write(p, element);
+ }
+ self.set_len(len + 1);
+ }
+ }
+
+ /// Removes and returns the element at position `index` within the vector,
+ /// shifting all elements after it to the left.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `index` is out of bounds.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = vec![1, 2, 3];
+ /// assert_eq!(v.remove(1), 2);
+ /// assert_eq!(v, [1, 3]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn remove(&mut self, index: usize) -> T {
+ #[cold]
+ #[inline(never)]
+ fn assert_failed(index: usize, len: usize) -> ! {
+ panic!("removal index (is {}) should be < len (is {})", index, len);
+ }
+
+ let len = self.len();
+ if index >= len {
+ assert_failed(index, len);
+ }
+ unsafe {
+ // infallible
+ let ret;
+ {
+ // the place we are taking from.
+ let ptr = self.as_mut_ptr().add(index);
+ // copy it out, unsafely having a copy of the value on
+ // the stack and in the vector at the same time.
+ ret = ptr::read(ptr);
+
+ // Shift everything down to fill in that spot.
+ ptr::copy(ptr.offset(1), ptr, len - index - 1);
+ }
+ self.set_len(len - 1);
+ ret
+ }
+ }
+
+ /// Retains only the elements specified by the predicate.
+ ///
+ /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
+ /// This method operates in place, visiting each element exactly once in the
+ /// original order, and preserves the order of the retained elements.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3, 4];
+ /// vec.retain(|&x| x % 2 == 0);
+ /// assert_eq!(vec, [2, 4]);
+ /// ```
+ ///
+ /// Because the elements are visited exactly once in the original order,
+ /// external state may be used to decide which elements to keep.
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3, 4, 5];
+ /// let keep = [false, true, true, false, true];
+ /// let mut iter = keep.iter();
+ /// vec.retain(|_| *iter.next().unwrap());
+ /// assert_eq!(vec, [2, 3, 5]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn retain<F>(&mut self, mut f: F)
+ where
+ F: FnMut(&T) -> bool,
+ {
+ let original_len = self.len();
+ // Avoid double drop if the drop guard is not executed,
+ // since we may make some holes during the process.
+ unsafe { self.set_len(0) };
+
+ // Vec: [Kept, Kept, Hole, Hole, Hole, Hole, Unchecked, Unchecked]
+ // |<- processed len ->| ^- next to check
+ // |<- deleted cnt ->|
+ // |<- original_len ->|
+ // Kept: Elements which predicate returns true on.
+ // Hole: Moved or dropped element slot.
+ // Unchecked: Unchecked valid elements.
+ //
+ // This drop guard will be invoked when predicate or `drop` of element panicked.
+ // It shifts unchecked elements to cover holes and `set_len` to the correct length.
+ // In cases when predicate and `drop` never panick, it will be optimized out.
+ struct BackshiftOnDrop<'a, T, A: Allocator> {
+ v: &'a mut Vec<T, A>,
+ processed_len: usize,
+ deleted_cnt: usize,
+ original_len: usize,
+ }
+
+ impl<T, A: Allocator> Drop for BackshiftOnDrop<'_, T, A> {
+ fn drop(&mut self) {
+ if self.deleted_cnt > 0 {
+ // SAFETY: Trailing unchecked items must be valid since we never touch them.
+ unsafe {
+ ptr::copy(
+ self.v.as_ptr().add(self.processed_len),
+ self.v.as_mut_ptr().add(self.processed_len - self.deleted_cnt),
+ self.original_len - self.processed_len,
+ );
+ }
+ }
+ // SAFETY: After filling holes, all items are in contiguous memory.
+ unsafe {
+ self.v.set_len(self.original_len - self.deleted_cnt);
+ }
+ }
+ }
+
+ let mut g = BackshiftOnDrop { v: self, processed_len: 0, deleted_cnt: 0, original_len };
+
+ while g.processed_len < original_len {
+ // SAFETY: Unchecked element must be valid.
+ let cur = unsafe { &mut *g.v.as_mut_ptr().add(g.processed_len) };
+ if !f(cur) {
+ // Advance early to avoid double drop if `drop_in_place` panicked.
+ g.processed_len += 1;
+ g.deleted_cnt += 1;
+ // SAFETY: We never touch this element again after dropped.
+ unsafe { ptr::drop_in_place(cur) };
+ // We already advanced the counter.
+ continue;
+ }
+ if g.deleted_cnt > 0 {
+ // SAFETY: `deleted_cnt` > 0, so the hole slot must not overlap with current element.
+ // We use copy for move, and never touch this element again.
+ unsafe {
+ let hole_slot = g.v.as_mut_ptr().add(g.processed_len - g.deleted_cnt);
+ ptr::copy_nonoverlapping(cur, hole_slot, 1);
+ }
+ }
+ g.processed_len += 1;
+ }
+
+ // All item are processed. This can be optimized to `set_len` by LLVM.
+ drop(g);
+ }
+
+ /// Removes all but the first of consecutive elements in the vector that resolve to the same
+ /// key.
+ ///
+ /// If the vector is sorted, this removes all duplicates.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![10, 20, 21, 30, 20];
+ ///
+ /// vec.dedup_by_key(|i| *i / 10);
+ ///
+ /// assert_eq!(vec, [10, 20, 30, 20]);
+ /// ```
+ #[stable(feature = "dedup_by", since = "1.16.0")]
+ #[inline]
+ pub fn dedup_by_key<F, K>(&mut self, mut key: F)
+ where
+ F: FnMut(&mut T) -> K,
+ K: PartialEq,
+ {
+ self.dedup_by(|a, b| key(a) == key(b))
+ }
+
+ /// Removes all but the first of consecutive elements in the vector satisfying a given equality
+ /// relation.
+ ///
+ /// The `same_bucket` function is passed references to two elements from the vector and
+ /// must determine if the elements compare equal. The elements are passed in opposite order
+ /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is removed.
+ ///
+ /// If the vector is sorted, this removes all duplicates.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
+ ///
+ /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
+ ///
+ /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]);
+ /// ```
+ #[stable(feature = "dedup_by", since = "1.16.0")]
+ pub fn dedup_by<F>(&mut self, mut same_bucket: F)
+ where
+ F: FnMut(&mut T, &mut T) -> bool,
+ {
+ let len = self.len();
+ if len <= 1 {
+ return;
+ }
+
+ /* INVARIANT: vec.len() > read >= write > write-1 >= 0 */
+ struct FillGapOnDrop<'a, T, A: core::alloc::Allocator> {
+ /* Offset of the element we want to check if it is duplicate */
+ read: usize,
+
+ /* Offset of the place where we want to place the non-duplicate
+ * when we find it. */
+ write: usize,
+
+ /* The Vec that would need correction if `same_bucket` panicked */
+ vec: &'a mut Vec<T, A>,
+ }
+
+ impl<'a, T, A: core::alloc::Allocator> Drop for FillGapOnDrop<'a, T, A> {
+ fn drop(&mut self) {
+ /* This code gets executed when `same_bucket` panics */
+
+ /* SAFETY: invariant guarantees that `read - write`
+ * and `len - read` never overflow and that the copy is always
+ * in-bounds. */
+ unsafe {
+ let ptr = self.vec.as_mut_ptr();
+ let len = self.vec.len();
+
+ /* How many items were left when `same_bucket` paniced.
+ * Basically vec[read..].len() */
+ let items_left = len.wrapping_sub(self.read);
+
+ /* Pointer to first item in vec[write..write+items_left] slice */
+ let dropped_ptr = ptr.add(self.write);
+ /* Pointer to first item in vec[read..] slice */
+ let valid_ptr = ptr.add(self.read);
+
+ /* Copy `vec[read..]` to `vec[write..write+items_left]`.
+ * The slices can overlap, so `copy_nonoverlapping` cannot be used */
+ ptr::copy(valid_ptr, dropped_ptr, items_left);
+
+ /* How many items have been already dropped
+ * Basically vec[read..write].len() */
+ let dropped = self.read.wrapping_sub(self.write);
+
+ self.vec.set_len(len - dropped);
+ }
+ }
+ }
+
+ let mut gap = FillGapOnDrop { read: 1, write: 1, vec: self };
+ let ptr = gap.vec.as_mut_ptr();
+
+ /* Drop items while going through Vec, it should be more efficient than
+ * doing slice partition_dedup + truncate */
+
+ /* SAFETY: Because of the invariant, read_ptr, prev_ptr and write_ptr
+ * are always in-bounds and read_ptr never aliases prev_ptr */
+ unsafe {
+ while gap.read < len {
+ let read_ptr = ptr.add(gap.read);
+ let prev_ptr = ptr.add(gap.write.wrapping_sub(1));
+
+ if same_bucket(&mut *read_ptr, &mut *prev_ptr) {
+ // Increase `gap.read` now since the drop may panic.
+ gap.read += 1;
+ /* We have found duplicate, drop it in-place */
+ ptr::drop_in_place(read_ptr);
+ } else {
+ let write_ptr = ptr.add(gap.write);
+
+ /* Because `read_ptr` can be equal to `write_ptr`, we either
+ * have to use `copy` or conditional `copy_nonoverlapping`.
+ * Looks like the first option is faster. */
+ ptr::copy(read_ptr, write_ptr, 1);
+
+ /* We have filled that place, so go further */
+ gap.write += 1;
+ gap.read += 1;
+ }
+ }
+
+ /* Technically we could let `gap` clean up with its Drop, but
+ * when `same_bucket` is guaranteed to not panic, this bloats a little
+ * the codegen, so we just do it manually */
+ gap.vec.set_len(gap.write);
+ mem::forget(gap);
+ }
+ }
+
+ /// Appends an element to the back of a collection.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2];
+ /// vec.push(3);
+ /// assert_eq!(vec, [1, 2, 3]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn push(&mut self, value: T) {
+ // This will panic or abort if we would allocate > isize::MAX bytes
+ // or if the length increment would overflow for zero-sized types.
+ if self.len == self.buf.capacity() {
+ self.reserve(1);
+ }
+ unsafe {
+ let end = self.as_mut_ptr().add(self.len);
+ ptr::write(end, value);
+ self.len += 1;
+ }
+ }
+
+ /// Tries to append an element to the back of a collection.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2];
+ /// vec.try_push(3).unwrap();
+ /// assert_eq!(vec, [1, 2, 3]);
+ /// ```
+ #[inline]
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_push(&mut self, value: T) -> Result<(), TryReserveError> {
+ if self.len == self.buf.capacity() {
+ self.try_reserve(1)?;
+ }
+ unsafe {
+ let end = self.as_mut_ptr().add(self.len);
+ ptr::write(end, value);
+ self.len += 1;
+ }
+ Ok(())
+ }
+
+ /// Removes the last element from a vector and returns it, or [`None`] if it
+ /// is empty.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// assert_eq!(vec.pop(), Some(3));
+ /// assert_eq!(vec, [1, 2]);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn pop(&mut self) -> Option<T> {
+ if self.len == 0 {
+ None
+ } else {
+ unsafe {
+ self.len -= 1;
+ Some(ptr::read(self.as_ptr().add(self.len())))
+ }
+ }
+ }
+
+ /// Moves all the elements of `other` into `Self`, leaving `other` empty.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the number of elements in the vector overflows a `usize`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// let mut vec2 = vec![4, 5, 6];
+ /// vec.append(&mut vec2);
+ /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
+ /// assert_eq!(vec2, []);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "append", since = "1.4.0")]
+ pub fn append(&mut self, other: &mut Self) {
+ unsafe {
+ self.append_elements(other.as_slice() as _);
+ other.set_len(0);
+ }
+ }
+
+ /// Appends elements to `Self` from other buffer.
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ unsafe fn append_elements(&mut self, other: *const [T]) {
+ let count = unsafe { (*other).len() };
+ self.reserve(count);
+ let len = self.len();
+ unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) };
+ self.len += count;
+ }
+
+ /// Tries to append elements to `Self` from other buffer.
+ #[inline]
+ unsafe fn try_append_elements(&mut self, other: *const [T]) -> Result<(), TryReserveError> {
+ let count = unsafe { (*other).len() };
+ self.try_reserve(count)?;
+ let len = self.len();
+ unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) };
+ self.len += count;
+ Ok(())
+ }
+
+ /// Creates a draining iterator that removes the specified range in the vector
+ /// and yields the removed items.
+ ///
+ /// When the iterator **is** dropped, all elements in the range are removed
+ /// from the vector, even if the iterator was not fully consumed. If the
+ /// iterator **is not** dropped (with [`mem::forget`] for example), it is
+ /// unspecified how many elements are removed.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the starting point is greater than the end point or if
+ /// the end point is greater than the length of the vector.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = vec![1, 2, 3];
+ /// let u: Vec<_> = v.drain(1..).collect();
+ /// assert_eq!(v, &[1]);
+ /// assert_eq!(u, &[2, 3]);
+ ///
+ /// // A full range clears the vector
+ /// v.drain(..);
+ /// assert_eq!(v, &[]);
+ /// ```
+ #[stable(feature = "drain", since = "1.6.0")]
+ pub fn drain<R>(&mut self, range: R) -> Drain<'_, T, A>
+ where
+ R: RangeBounds<usize>,
+ {
+ // Memory safety
+ //
+ // When the Drain is first created, it shortens the length of
+ // the source vector to make sure no uninitialized or moved-from elements
+ // are accessible at all if the Drain's destructor never gets to run.
+ //
+ // Drain will ptr::read out the values to remove.
+ // When finished, remaining tail of the vec is copied back to cover
+ // the hole, and the vector length is restored to the new length.
+ //
+ let len = self.len();
+ let Range { start, end } = slice::range(range, ..len);
+
+ unsafe {
+ // set self.vec length's to start, to be safe in case Drain is leaked
+ self.set_len(start);
+ // Use the borrow in the IterMut to indicate borrowing behavior of the
+ // whole Drain iterator (like &mut T).
+ let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start);
+ Drain {
+ tail_start: end,
+ tail_len: len - end,
+ iter: range_slice.iter(),
+ vec: NonNull::from(self),
+ }
+ }
+ }
+
+ /// Clears the vector, removing all values.
+ ///
+ /// Note that this method has no effect on the allocated capacity
+ /// of the vector.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = vec![1, 2, 3];
+ ///
+ /// v.clear();
+ ///
+ /// assert!(v.is_empty());
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn clear(&mut self) {
+ self.truncate(0)
+ }
+
+ /// Returns the number of elements in the vector, also referred to
+ /// as its 'length'.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let a = vec![1, 2, 3];
+ /// assert_eq!(a.len(), 3);
+ /// ```
+ #[doc(alias = "length")]
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn len(&self) -> usize {
+ self.len
+ }
+
+ /// Returns `true` if the vector contains no elements.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = Vec::new();
+ /// assert!(v.is_empty());
+ ///
+ /// v.push(1);
+ /// assert!(!v.is_empty());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn is_empty(&self) -> bool {
+ self.len() == 0
+ }
+
+ /// Splits the collection into two at the given index.
+ ///
+ /// Returns a newly allocated vector containing the elements in the range
+ /// `[at, len)`. After the call, the original vector will be left containing
+ /// the elements `[0, at)` with its previous capacity unchanged.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `at > len`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// let vec2 = vec.split_off(1);
+ /// assert_eq!(vec, [1]);
+ /// assert_eq!(vec2, [2, 3]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[must_use = "use `.truncate()` if you don't need the other half"]
+ #[stable(feature = "split_off", since = "1.4.0")]
+ pub fn split_off(&mut self, at: usize) -> Self
+ where
+ A: Clone,
+ {
+ #[cold]
+ #[inline(never)]
+ fn assert_failed(at: usize, len: usize) -> ! {
+ panic!("`at` split index (is {}) should be <= len (is {})", at, len);
+ }
+
+ if at > self.len() {
+ assert_failed(at, self.len());
+ }
+
+ if at == 0 {
+ // the new vector can take over the original buffer and avoid the copy
+ return mem::replace(
+ self,
+ Vec::with_capacity_in(self.capacity(), self.allocator().clone()),
+ );
+ }
+
+ let other_len = self.len - at;
+ let mut other = Vec::with_capacity_in(other_len, self.allocator().clone());
+
+ // Unsafely `set_len` and copy items to `other`.
+ unsafe {
+ self.set_len(at);
+ other.set_len(other_len);
+
+ ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len());
+ }
+ other
+ }
+
+ /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
+ ///
+ /// If `new_len` is greater than `len`, the `Vec` is extended by the
+ /// difference, with each additional slot filled with the result of
+ /// calling the closure `f`. The return values from `f` will end up
+ /// in the `Vec` in the order they have been generated.
+ ///
+ /// If `new_len` is less than `len`, the `Vec` is simply truncated.
+ ///
+ /// This method uses a closure to create new values on every push. If
+ /// you'd rather [`Clone`] a given value, use [`Vec::resize`]. If you
+ /// want to use the [`Default`] trait to generate values, you can
+ /// pass [`Default::default`] as the second argument.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 3];
+ /// vec.resize_with(5, Default::default);
+ /// assert_eq!(vec, [1, 2, 3, 0, 0]);
+ ///
+ /// let mut vec = vec![];
+ /// let mut p = 1;
+ /// vec.resize_with(4, || { p *= 2; p });
+ /// assert_eq!(vec, [2, 4, 8, 16]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "vec_resize_with", since = "1.33.0")]
+ pub fn resize_with<F>(&mut self, new_len: usize, f: F)
+ where
+ F: FnMut() -> T,
+ {
+ let len = self.len();
+ if new_len > len {
+ self.extend_with(new_len - len, ExtendFunc(f));
+ } else {
+ self.truncate(new_len);
+ }
+ }
+
+ /// Consumes and leaks the `Vec`, returning a mutable reference to the contents,
+ /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime
+ /// `'a`. If the type has only static references, or none at all, then this
+ /// may be chosen to be `'static`.
+ ///
+ /// This function is similar to the [`leak`][Box::leak] function on [`Box`]
+ /// except that there is no way to recover the leaked memory.
+ ///
+ /// This function is mainly useful for data that lives for the remainder of
+ /// the program's life. Dropping the returned reference will cause a memory
+ /// leak.
+ ///
+ /// # Examples
+ ///
+ /// Simple usage:
+ ///
+ /// ```
+ /// let x = vec![1, 2, 3];
+ /// let static_ref: &'static mut [usize] = x.leak();
+ /// static_ref[0] += 1;
+ /// assert_eq!(static_ref, &[2, 2, 3]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "vec_leak", since = "1.47.0")]
+ #[inline]
+ pub fn leak<'a>(self) -> &'a mut [T]
+ where
+ A: 'a,
+ {
+ Box::leak(self.into_boxed_slice())
+ }
+
+ /// Returns the remaining spare capacity of the vector as a slice of
+ /// `MaybeUninit<T>`.
+ ///
+ /// The returned slice can be used to fill the vector with data (e.g. by
+ /// reading from a file) before marking the data as initialized using the
+ /// [`set_len`] method.
+ ///
+ /// [`set_len`]: Vec::set_len
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(vec_spare_capacity, maybe_uninit_extra)]
+ ///
+ /// // Allocate vector big enough for 10 elements.
+ /// let mut v = Vec::with_capacity(10);
+ ///
+ /// // Fill in the first 3 elements.
+ /// let uninit = v.spare_capacity_mut();
+ /// uninit[0].write(0);
+ /// uninit[1].write(1);
+ /// uninit[2].write(2);
+ ///
+ /// // Mark the first 3 elements of the vector as being initialized.
+ /// unsafe {
+ /// v.set_len(3);
+ /// }
+ ///
+ /// assert_eq!(&v, &[0, 1, 2]);
+ /// ```
+ #[unstable(feature = "vec_spare_capacity", issue = "75017")]
+ #[inline]
+ pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<T>] {
+ // Note:
+ // This method is not implemented in terms of `split_at_spare_mut`,
+ // to prevent invalidation of pointers to the buffer.
+ unsafe {
+ slice::from_raw_parts_mut(
+ self.as_mut_ptr().add(self.len) as *mut MaybeUninit<T>,
+ self.buf.capacity() - self.len,
+ )
+ }
+ }
+
+ /// Returns vector content as a slice of `T`, along with the remaining spare
+ /// capacity of the vector as a slice of `MaybeUninit<T>`.
+ ///
+ /// The returned spare capacity slice can be used to fill the vector with data
+ /// (e.g. by reading from a file) before marking the data as initialized using
+ /// the [`set_len`] method.
+ ///
+ /// [`set_len`]: Vec::set_len
+ ///
+ /// Note that this is a low-level API, which should be used with care for
+ /// optimization purposes. If you need to append data to a `Vec`
+ /// you can use [`push`], [`extend`], [`extend_from_slice`],
+ /// [`extend_from_within`], [`insert`], [`append`], [`resize`] or
+ /// [`resize_with`], depending on your exact needs.
+ ///
+ /// [`push`]: Vec::push
+ /// [`extend`]: Vec::extend
+ /// [`extend_from_slice`]: Vec::extend_from_slice
+ /// [`extend_from_within`]: Vec::extend_from_within
+ /// [`insert`]: Vec::insert
+ /// [`append`]: Vec::append
+ /// [`resize`]: Vec::resize
+ /// [`resize_with`]: Vec::resize_with
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(vec_split_at_spare, maybe_uninit_extra)]
+ ///
+ /// let mut v = vec![1, 1, 2];
+ ///
+ /// // Reserve additional space big enough for 10 elements.
+ /// v.reserve(10);
+ ///
+ /// let (init, uninit) = v.split_at_spare_mut();
+ /// let sum = init.iter().copied().sum::<u32>();
+ ///
+ /// // Fill in the next 4 elements.
+ /// uninit[0].write(sum);
+ /// uninit[1].write(sum * 2);
+ /// uninit[2].write(sum * 3);
+ /// uninit[3].write(sum * 4);
+ ///
+ /// // Mark the 4 elements of the vector as being initialized.
+ /// unsafe {
+ /// let len = v.len();
+ /// v.set_len(len + 4);
+ /// }
+ ///
+ /// assert_eq!(&v, &[1, 1, 2, 4, 8, 12, 16]);
+ /// ```
+ #[unstable(feature = "vec_split_at_spare", issue = "81944")]
+ #[inline]
+ pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]) {
+ // SAFETY:
+ // - len is ignored and so never changed
+ let (init, spare, _) = unsafe { self.split_at_spare_mut_with_len() };
+ (init, spare)
+ }
+
+ /// Safety: changing returned .2 (&mut usize) is considered the same as calling `.set_len(_)`.
+ ///
+ /// This method provides unique access to all vec parts at once in `extend_from_within`.
+ unsafe fn split_at_spare_mut_with_len(
+ &mut self,
+ ) -> (&mut [T], &mut [MaybeUninit<T>], &mut usize) {
+ let Range { start: ptr, end: spare_ptr } = self.as_mut_ptr_range();
+ let spare_ptr = spare_ptr.cast::<MaybeUninit<T>>();
+ let spare_len = self.buf.capacity() - self.len;
+
+ // SAFETY:
+ // - `ptr` is guaranteed to be valid for `len` elements
+ // - `spare_ptr` is pointing one element past the buffer, so it doesn't overlap with `initialized`
+ unsafe {
+ let initialized = slice::from_raw_parts_mut(ptr, self.len);
+ let spare = slice::from_raw_parts_mut(spare_ptr, spare_len);
+
+ (initialized, spare, &mut self.len)
+ }
+ }
+}
+
+impl<T: Clone, A: Allocator> Vec<T, A> {
+ /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
+ ///
+ /// If `new_len` is greater than `len`, the `Vec` is extended by the
+ /// difference, with each additional slot filled with `value`.
+ /// If `new_len` is less than `len`, the `Vec` is simply truncated.
+ ///
+ /// This method requires `T` to implement [`Clone`],
+ /// in order to be able to clone the passed value.
+ /// If you need more flexibility (or want to rely on [`Default`] instead of
+ /// [`Clone`]), use [`Vec::resize_with`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec!["hello"];
+ /// vec.resize(3, "world");
+ /// assert_eq!(vec, ["hello", "world", "world"]);
+ ///
+ /// let mut vec = vec![1, 2, 3, 4];
+ /// vec.resize(2, 0);
+ /// assert_eq!(vec, [1, 2]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "vec_resize", since = "1.5.0")]
+ pub fn resize(&mut self, new_len: usize, value: T) {
+ let len = self.len();
+
+ if new_len > len {
+ self.extend_with(new_len - len, ExtendElement(value))
+ } else {
+ self.truncate(new_len);
+ }
+ }
+
+ /// Tries to resize the `Vec` in-place so that `len` is equal to `new_len`.
+ ///
+ /// If `new_len` is greater than `len`, the `Vec` is extended by the
+ /// difference, with each additional slot filled with `value`.
+ /// If `new_len` is less than `len`, the `Vec` is simply truncated.
+ ///
+ /// This method requires `T` to implement [`Clone`],
+ /// in order to be able to clone the passed value.
+ /// If you need more flexibility (or want to rely on [`Default`] instead of
+ /// [`Clone`]), use [`Vec::resize_with`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec!["hello"];
+ /// vec.try_resize(3, "world").unwrap();
+ /// assert_eq!(vec, ["hello", "world", "world"]);
+ ///
+ /// let mut vec = vec![1, 2, 3, 4];
+ /// vec.try_resize(2, 0).unwrap();
+ /// assert_eq!(vec, [1, 2]);
+ ///
+ /// let mut vec = vec![42];
+ /// let result = vec.try_resize(usize::MAX, 0);
+ /// assert!(result.is_err());
+ /// ```
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_resize(&mut self, new_len: usize, value: T) -> Result<(), TryReserveError> {
+ let len = self.len();
+
+ if new_len > len {
+ self.try_extend_with(new_len - len, ExtendElement(value))
+ } else {
+ self.truncate(new_len);
+ Ok(())
+ }
+ }
+
+ /// Clones and appends all elements in a slice to the `Vec`.
+ ///
+ /// Iterates over the slice `other`, clones each element, and then appends
+ /// it to this `Vec`. The `other` vector is traversed in-order.
+ ///
+ /// Note that this function is same as [`extend`] except that it is
+ /// specialized to work with slices instead. If and when Rust gets
+ /// specialization this function will likely be deprecated (but still
+ /// available).
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1];
+ /// vec.extend_from_slice(&[2, 3, 4]);
+ /// assert_eq!(vec, [1, 2, 3, 4]);
+ /// ```
+ ///
+ /// [`extend`]: Vec::extend
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
+ pub fn extend_from_slice(&mut self, other: &[T]) {
+ self.spec_extend(other.iter())
+ }
+
+ /// Tries to clone and append all elements in a slice to the `Vec`.
+ ///
+ /// Iterates over the slice `other`, clones each element, and then appends
+ /// it to this `Vec`. The `other` vector is traversed in-order.
+ ///
+ /// Note that this function is same as [`extend`] except that it is
+ /// specialized to work with slices instead. If and when Rust gets
+ /// specialization this function will likely be deprecated (but still
+ /// available).
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1];
+ /// vec.try_extend_from_slice(&[2, 3, 4]).unwrap();
+ /// assert_eq!(vec, [1, 2, 3, 4]);
+ /// ```
+ ///
+ /// [`extend`]: Vec::extend
+ #[stable(feature = "kernel", since = "1.0.0")]
+ pub fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), TryReserveError> {
+ self.try_spec_extend(other.iter())
+ }
+
+ /// Copies elements from `src` range to the end of the vector.
+ ///
+ /// ## Examples
+ ///
+ /// ```
+ /// let mut vec = vec![0, 1, 2, 3, 4];
+ ///
+ /// vec.extend_from_within(2..);
+ /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4]);
+ ///
+ /// vec.extend_from_within(..2);
+ /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1]);
+ ///
+ /// vec.extend_from_within(4..8);
+ /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[stable(feature = "vec_extend_from_within", since = "1.53.0")]
+ pub fn extend_from_within<R>(&mut self, src: R)
+ where
+ R: RangeBounds<usize>,
+ {
+ let range = slice::range(src, ..self.len());
+ self.reserve(range.len());
+
+ // SAFETY:
+ // - `slice::range` guarantees that the given range is valid for indexing self
+ unsafe {
+ self.spec_extend_from_within(range);
+ }
+ }
+}
+
+// This code generalizes `extend_with_{element,default}`.
+trait ExtendWith<T> {
+ fn next(&mut self) -> T;
+ fn last(self) -> T;
+}
+
+struct ExtendElement<T>(T);
+impl<T: Clone> ExtendWith<T> for ExtendElement<T> {
+ fn next(&mut self) -> T {
+ self.0.clone()
+ }
+ fn last(self) -> T {
+ self.0
+ }
+}
+
+struct ExtendDefault;
+impl<T: Default> ExtendWith<T> for ExtendDefault {
+ fn next(&mut self) -> T {
+ Default::default()
+ }
+ fn last(self) -> T {
+ Default::default()
+ }
+}
+
+struct ExtendFunc<F>(F);
+impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> {
+ fn next(&mut self) -> T {
+ (self.0)()
+ }
+ fn last(mut self) -> T {
+ (self.0)()
+ }
+}
+
+impl<T, A: Allocator> Vec<T, A> {
+ #[cfg(not(no_global_oom_handling))]
+ /// Extend the vector by `n` values, using the given generator.
+ fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) {
+ self.reserve(n);
+
+ unsafe {
+ let mut ptr = self.as_mut_ptr().add(self.len());
+ // Use SetLenOnDrop to work around bug where compiler
+ // may not realize the store through `ptr` through self.set_len()
+ // don't alias.
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+
+ // Write all elements except the last one
+ for _ in 1..n {
+ ptr::write(ptr, value.next());
+ ptr = ptr.offset(1);
+ // Increment the length in every step in case next() panics
+ local_len.increment_len(1);
+ }
+
+ if n > 0 {
+ // We can write the last element directly without cloning needlessly
+ ptr::write(ptr, value.last());
+ local_len.increment_len(1);
+ }
+
+ // len set by scope guard
+ }
+ }
+
+ /// Try to extend the vector by `n` values, using the given generator.
+ fn try_extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) -> Result<(), TryReserveError> {
+ self.try_reserve(n)?;
+
+ unsafe {
+ let mut ptr = self.as_mut_ptr().add(self.len());
+ // Use SetLenOnDrop to work around bug where compiler
+ // may not realize the store through `ptr` through self.set_len()
+ // don't alias.
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+
+ // Write all elements except the last one
+ for _ in 1..n {
+ ptr::write(ptr, value.next());
+ ptr = ptr.offset(1);
+ // Increment the length in every step in case next() panics
+ local_len.increment_len(1);
+ }
+
+ if n > 0 {
+ // We can write the last element directly without cloning needlessly
+ ptr::write(ptr, value.last());
+ local_len.increment_len(1);
+ }
+
+ // len set by scope guard
+ Ok(())
+ }
+ }
+}
+
+impl<T: PartialEq, A: Allocator> Vec<T, A> {
+ /// Removes consecutive repeated elements in the vector according to the
+ /// [`PartialEq`] trait implementation.
+ ///
+ /// If the vector is sorted, this removes all duplicates.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut vec = vec![1, 2, 2, 3, 2];
+ ///
+ /// vec.dedup();
+ ///
+ /// assert_eq!(vec, [1, 2, 3, 2]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn dedup(&mut self) {
+ self.dedup_by(|a, b| a == b)
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Internal methods and functions
+////////////////////////////////////////////////////////////////////////////////
+
+#[doc(hidden)]
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
+ <T as SpecFromElem>::from_elem(elem, n, Global)
+}
+
+#[doc(hidden)]
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "allocator_api", issue = "32838")]
+pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> {
+ <T as SpecFromElem>::from_elem(elem, n, alloc)
+}
+
+trait ExtendFromWithinSpec {
+ /// # Safety
+ ///
+ /// - `src` needs to be valid index
+ /// - `self.capacity() - self.len()` must be `>= src.len()`
+ unsafe fn spec_extend_from_within(&mut self, src: Range<usize>);
+}
+
+impl<T: Clone, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
+ default unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) {
+ // SAFETY:
+ // - len is increased only after initializing elements
+ let (this, spare, len) = unsafe { self.split_at_spare_mut_with_len() };
+
+ // SAFETY:
+ // - caller guaratees that src is a valid index
+ let to_clone = unsafe { this.get_unchecked(src) };
+
+ iter::zip(to_clone, spare)
+ .map(|(src, dst)| dst.write(src.clone()))
+ // Note:
+ // - Element was just initialized with `MaybeUninit::write`, so it's ok to increase len
+ // - len is increased after each element to prevent leaks (see issue #82533)
+ .for_each(|_| *len += 1);
+ }
+}
+
+impl<T: Copy, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
+ unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) {
+ let count = src.len();
+ {
+ let (init, spare) = self.split_at_spare_mut();
+
+ // SAFETY:
+ // - caller guaratees that `src` is a valid index
+ let source = unsafe { init.get_unchecked(src) };
+
+ // SAFETY:
+ // - Both pointers are created from unique slice references (`&mut [_]`)
+ // so they are valid and do not overlap.
+ // - Elements are :Copy so it's OK to to copy them, without doing
+ // anything with the original values
+ // - `count` is equal to the len of `source`, so source is valid for
+ // `count` reads
+ // - `.reserve(count)` guarantees that `spare.len() >= count` so spare
+ // is valid for `count` writes
+ unsafe { ptr::copy_nonoverlapping(source.as_ptr(), spare.as_mut_ptr() as _, count) };
+ }
+
+ // SAFETY:
+ // - The elements were just initialized by `copy_nonoverlapping`
+ self.len += count;
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Common trait implementations for Vec
+////////////////////////////////////////////////////////////////////////////////
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> ops::Deref for Vec<T, A> {
+ type Target = [T];
+
+ fn deref(&self) -> &[T] {
+ unsafe { slice::from_raw_parts(self.as_ptr(), self.len) }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
+ fn deref_mut(&mut self) -> &mut [T] {
+ unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
+ #[cfg(not(test))]
+ fn clone(&self) -> Self {
+ let alloc = self.allocator().clone();
+ <[T]>::to_vec_in(&**self, alloc)
+ }
+
+ // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
+ // required for this method definition, is not available. Instead use the
+ // `slice::to_vec` function which is only available with cfg(test)
+ // NB see the slice::hack module in slice.rs for more information
+ #[cfg(test)]
+ fn clone(&self) -> Self {
+ let alloc = self.allocator().clone();
+ crate::slice::to_vec(&**self, alloc)
+ }
+
+ fn clone_from(&mut self, other: &Self) {
+ // drop anything that will not be overwritten
+ self.truncate(other.len());
+
+ // self.len <= other.len due to the truncate above, so the
+ // slices here are always in-bounds.
+ let (init, tail) = other.split_at(self.len());
+
+ // reuse the contained values' allocations/resources.
+ self.clone_from_slice(init);
+ self.extend_from_slice(tail);
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Hash, A: Allocator> Hash for Vec<T, A> {
+ #[inline]
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ Hash::hash(&**self, state)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented(
+ message = "vector indices are of type `usize` or ranges of `usize`",
+ label = "vector indices are of type `usize` or ranges of `usize`"
+)]
+impl<T, I: SliceIndex<[T]>, A: Allocator> Index<I> for Vec<T, A> {
+ type Output = I::Output;
+
+ #[inline]
+ fn index(&self, index: I) -> &Self::Output {
+ Index::index(&**self, index)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented(
+ message = "vector indices are of type `usize` or ranges of `usize`",
+ label = "vector indices are of type `usize` or ranges of `usize`"
+)]
+impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> {
+ #[inline]
+ fn index_mut(&mut self, index: I) -> &mut Self::Output {
+ IndexMut::index_mut(&mut **self, index)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> FromIterator<T> for Vec<T> {
+ #[inline]
+ fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
+ <Self as SpecFromIter<T, I::IntoIter>>::from_iter(iter.into_iter())
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> IntoIterator for Vec<T, A> {
+ type Item = T;
+ type IntoIter = IntoIter<T, A>;
+
+ /// Creates a consuming iterator, that is, one that moves each value out of
+ /// the vector (from start to end). The vector cannot be used after calling
+ /// this.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let v = vec!["a".to_string(), "b".to_string()];
+ /// for s in v.into_iter() {
+ /// // s has type String, not &String
+ /// println!("{}", s);
+ /// }
+ /// ```
+ #[inline]
+ fn into_iter(self) -> IntoIter<T, A> {
+ unsafe {
+ let mut me = ManuallyDrop::new(self);
+ let alloc = ptr::read(me.allocator());
+ let begin = me.as_mut_ptr();
+ let end = if mem::size_of::<T>() == 0 {
+ arith_offset(begin as *const i8, me.len() as isize) as *const T
+ } else {
+ begin.add(me.len()) as *const T
+ };
+ let cap = me.buf.capacity();
+ IntoIter {
+ buf: NonNull::new_unchecked(begin),
+ phantom: PhantomData,
+ cap,
+ alloc,
+ ptr: begin,
+ end,
+ }
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T, A: Allocator> IntoIterator for &'a Vec<T, A> {
+ type Item = &'a T;
+ type IntoIter = slice::Iter<'a, T>;
+
+ fn into_iter(self) -> slice::Iter<'a, T> {
+ self.iter()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> {
+ type Item = &'a mut T;
+ type IntoIter = slice::IterMut<'a, T>;
+
+ fn into_iter(self) -> slice::IterMut<'a, T> {
+ self.iter_mut()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> Extend<T> for Vec<T, A> {
+ #[inline]
+ fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
+ <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter())
+ }
+
+ #[inline]
+ fn extend_one(&mut self, item: T) {
+ self.push(item);
+ }
+
+ #[inline]
+ fn extend_reserve(&mut self, additional: usize) {
+ self.reserve(additional);
+ }
+}
+
+impl<T, A: Allocator> Vec<T, A> {
+ // leaf method to which various SpecFrom/SpecExtend implementations delegate when
+ // they have no further optimizations to apply
+ #[cfg(not(no_global_oom_handling))]
+ fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
+ // This is the case for a general iterator.
+ //
+ // This function should be the moral equivalent of:
+ //
+ // for item in iterator {
+ // self.push(item);
+ // }
+ while let Some(element) = iterator.next() {
+ let len = self.len();
+ if len == self.capacity() {
+ let (lower, _) = iterator.size_hint();
+ self.reserve(lower.saturating_add(1));
+ }
+ unsafe {
+ ptr::write(self.as_mut_ptr().add(len), element);
+ // NB can't overflow since we would have had to alloc the address space
+ self.set_len(len + 1);
+ }
+ }
+ }
+
+ // leaf method to which various SpecFrom/SpecExtend implementations delegate when
+ // they have no further optimizations to apply
+ fn try_extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) -> Result<(), TryReserveError> {
+ // This is the case for a general iterator.
+ //
+ // This function should be the moral equivalent of:
+ //
+ // for item in iterator {
+ // self.push(item);
+ // }
+ while let Some(element) = iterator.next() {
+ let len = self.len();
+ if len == self.capacity() {
+ let (lower, _) = iterator.size_hint();
+ self.try_reserve(lower.saturating_add(1))?;
+ }
+ unsafe {
+ ptr::write(self.as_mut_ptr().add(len), element);
+ // NB can't overflow since we would have had to alloc the address space
+ self.set_len(len + 1);
+ }
+ }
+
+ Ok(())
+ }
+
+ /// Creates a splicing iterator that replaces the specified range in the vector
+ /// with the given `replace_with` iterator and yields the removed items.
+ /// `replace_with` does not need to be the same length as `range`.
+ ///
+ /// `range` is removed even if the iterator is not consumed until the end.
+ ///
+ /// It is unspecified how many elements are removed from the vector
+ /// if the `Splice` value is leaked.
+ ///
+ /// The input iterator `replace_with` is only consumed when the `Splice` value is dropped.
+ ///
+ /// This is optimal if:
+ ///
+ /// * The tail (elements in the vector after `range`) is empty,
+ /// * or `replace_with` yields fewer or equal elements than `range`’s length
+ /// * or the lower bound of its `size_hint()` is exact.
+ ///
+ /// Otherwise, a temporary vector is allocated and the tail is moved twice.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the starting point is greater than the end point or if
+ /// the end point is greater than the length of the vector.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut v = vec![1, 2, 3];
+ /// let new = [7, 8];
+ /// let u: Vec<_> = v.splice(..2, new).collect();
+ /// assert_eq!(v, &[7, 8, 3]);
+ /// assert_eq!(u, &[1, 2]);
+ /// ```
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ #[stable(feature = "vec_splice", since = "1.21.0")]
+ pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, A>
+ where
+ R: RangeBounds<usize>,
+ I: IntoIterator<Item = T>,
+ {
+ Splice { drain: self.drain(range), replace_with: replace_with.into_iter() }
+ }
+
+ /// Creates an iterator which uses a closure to determine if an element should be removed.
+ ///
+ /// If the closure returns true, then the element is removed and yielded.
+ /// If the closure returns false, the element will remain in the vector and will not be yielded
+ /// by the iterator.
+ ///
+ /// Using this method is equivalent to the following code:
+ ///
+ /// ```
+ /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 };
+ /// # let mut vec = vec![1, 2, 3, 4, 5, 6];
+ /// let mut i = 0;
+ /// while i < vec.len() {
+ /// if some_predicate(&mut vec[i]) {
+ /// let val = vec.remove(i);
+ /// // your code here
+ /// } else {
+ /// i += 1;
+ /// }
+ /// }
+ ///
+ /// # assert_eq!(vec, vec![1, 4, 5]);
+ /// ```
+ ///
+ /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
+ /// because it can backshift the elements of the array in bulk.
+ ///
+ /// Note that `drain_filter` also lets you mutate every element in the filter closure,
+ /// regardless of whether you choose to keep or remove it.
+ ///
+ /// # Examples
+ ///
+ /// Splitting an array into evens and odds, reusing the original allocation:
+ ///
+ /// ```
+ /// #![feature(drain_filter)]
+ /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
+ ///
+ /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ /// let odds = numbers;
+ ///
+ /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
+ /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
+ /// ```
+ #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+ pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A>
+ where
+ F: FnMut(&mut T) -> bool,
+ {
+ let old_len = self.len();
+
+ // Guard against us getting leaked (leak amplification)
+ unsafe {
+ self.set_len(0);
+ }
+
+ DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false }
+ }
+}
+
+/// Extend implementation that copies elements out of references before pushing them onto the Vec.
+///
+/// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to
+/// append the entire slice at once.
+///
+/// [`copy_from_slice`]: slice::copy_from_slice
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "extend_ref", since = "1.2.0")]
+impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> {
+ fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
+ self.spec_extend(iter.into_iter())
+ }
+
+ #[inline]
+ fn extend_one(&mut self, &item: &'a T) {
+ self.push(item);
+ }
+
+ #[inline]
+ fn extend_reserve(&mut self, additional: usize) {
+ self.reserve(additional);
+ }
+}
+
+/// Implements comparison of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> {
+ #[inline]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ PartialOrd::partial_cmp(&**self, &**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Eq, A: Allocator> Eq for Vec<T, A> {}
+
+/// Implements ordering of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Ord, A: Allocator> Ord for Vec<T, A> {
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ Ord::cmp(&**self, &**other)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> {
+ fn drop(&mut self) {
+ unsafe {
+ // use drop for [T]
+ // use a raw slice to refer to the elements of the vector as weakest necessary type;
+ // could avoid questions of validity in certain cases
+ ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.as_mut_ptr(), self.len))
+ }
+ // RawVec handles deallocation
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Default for Vec<T> {
+ /// Creates an empty `Vec<T>`.
+ fn default() -> Vec<T> {
+ Vec::new()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Vec<T, A> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> AsRef<Vec<T, A>> for Vec<T, A> {
+ fn as_ref(&self) -> &Vec<T, A> {
+ self
+ }
+}
+
+#[stable(feature = "vec_as_mut", since = "1.5.0")]
+impl<T, A: Allocator> AsMut<Vec<T, A>> for Vec<T, A> {
+ fn as_mut(&mut self) -> &mut Vec<T, A> {
+ self
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> AsRef<[T]> for Vec<T, A> {
+ fn as_ref(&self) -> &[T] {
+ self
+ }
+}
+
+#[stable(feature = "vec_as_mut", since = "1.5.0")]
+impl<T, A: Allocator> AsMut<[T]> for Vec<T, A> {
+ fn as_mut(&mut self) -> &mut [T] {
+ self
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone> From<&[T]> for Vec<T> {
+ /// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]);
+ /// ```
+ #[cfg(not(test))]
+ fn from(s: &[T]) -> Vec<T> {
+ s.to_vec()
+ }
+ #[cfg(test)]
+ fn from(s: &[T]) -> Vec<T> {
+ crate::slice::to_vec(s, Global)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "vec_from_mut", since = "1.19.0")]
+impl<T: Clone> From<&mut [T]> for Vec<T> {
+ /// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]);
+ /// ```
+ #[cfg(not(test))]
+ fn from(s: &mut [T]) -> Vec<T> {
+ s.to_vec()
+ }
+ #[cfg(test)]
+ fn from(s: &mut [T]) -> Vec<T> {
+ crate::slice::to_vec(s, Global)
+ }
+}
+
+#[stable(feature = "vec_from_array", since = "1.44.0")]
+impl<T, const N: usize> From<[T; N]> for Vec<T> {
+ #[cfg(not(test))]
+ fn from(s: [T; N]) -> Vec<T> {
+ <[T]>::into_vec(box s)
+ }
+ /// Allocate a `Vec<T>` and move `s`'s items into it.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]);
+ /// ```
+ #[cfg(test)]
+ fn from(s: [T; N]) -> Vec<T> {
+ crate::slice::into_vec(box s)
+ }
+}
+
+#[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
+impl<'a, T> From<Cow<'a, [T]>> for Vec<T>
+where
+ [T]: ToOwned<Owned = Vec<T>>,
+{
+ /// Convert a clone-on-write slice into a vector.
+ ///
+ /// If `s` already owns a `Vec<T>`, it will be returned directly.
+ /// If `s` is borrowing a slice, a new `Vec<T>` will be allocated and
+ /// filled by cloning `s`'s items into it.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # use std::borrow::Cow;
+ /// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
+ /// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
+ /// assert_eq!(Vec::from(o), Vec::from(b));
+ /// ```
+ fn from(s: Cow<'a, [T]>) -> Vec<T> {
+ s.into_owned()
+ }
+}
+
+// note: test pulls in libstd, which causes errors here
+#[cfg(not(test))]
+#[stable(feature = "vec_from_box", since = "1.18.0")]
+impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> {
+ /// Convert a boxed slice into a vector by transferring ownership of
+ /// the existing heap allocation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice();
+ /// assert_eq!(Vec::from(b), vec![1, 2, 3]);
+ /// ```
+ fn from(s: Box<[T], A>) -> Self {
+ s.into_vec()
+ }
+}
+
+// note: test pulls in libstd, which causes errors here
+#[cfg(not(no_global_oom_handling))]
+#[cfg(not(test))]
+#[stable(feature = "box_from_vec", since = "1.20.0")]
+impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
+ /// Convert a vector into a boxed slice.
+ ///
+ /// If `v` has excess capacity, its items will be moved into a
+ /// newly-allocated buffer with exactly the right capacity.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());
+ /// ```
+ fn from(v: Vec<T, A>) -> Self {
+ v.into_boxed_slice()
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl From<&str> for Vec<u8> {
+ /// Allocate a `Vec<u8>` and fill it with a UTF-8 string.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']);
+ /// ```
+ fn from(s: &str) -> Vec<u8> {
+ From::from(s.as_bytes())
+ }
+}
+
+#[stable(feature = "array_try_from_vec", since = "1.48.0")]
+impl<T, A: Allocator, const N: usize> TryFrom<Vec<T, A>> for [T; N] {
+ type Error = Vec<T, A>;
+
+ /// Gets the entire contents of the `Vec<T>` as an array,
+ /// if its size exactly matches that of the requested array.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::convert::TryInto;
+ /// assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3]));
+ /// assert_eq!(<Vec<i32>>::new().try_into(), Ok([]));
+ /// ```
+ ///
+ /// If the length doesn't match, the input comes back in `Err`:
+ /// ```
+ /// use std::convert::TryInto;
+ /// let r: Result<[i32; 4], _> = (0..10).collect::<Vec<_>>().try_into();
+ /// assert_eq!(r, Err(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));
+ /// ```
+ ///
+ /// If you're fine with just getting a prefix of the `Vec<T>`,
+ /// you can call [`.truncate(N)`](Vec::truncate) first.
+ /// ```
+ /// use std::convert::TryInto;
+ /// let mut v = String::from("hello world").into_bytes();
+ /// v.sort();
+ /// v.truncate(2);
+ /// let [a, b]: [_; 2] = v.try_into().unwrap();
+ /// assert_eq!(a, b' ');
+ /// assert_eq!(b, b'd');
+ /// ```
+ fn try_from(mut vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>> {
+ if vec.len() != N {
+ return Err(vec);
+ }
+
+ // SAFETY: `.set_len(0)` is always sound.
+ unsafe { vec.set_len(0) };
+
+ // SAFETY: A `Vec`'s pointer is always aligned properly, and
+ // the alignment the array needs is the same as the items.
+ // We checked earlier that we have sufficient items.
+ // The items will not double-drop as the `set_len`
+ // tells the `Vec` not to also drop them.
+ let array = unsafe { ptr::read(vec.as_ptr() as *const [T; N]) };
+ Ok(array)
+ }
+}
diff --git a/rust/alloc/vec/partial_eq.rs b/rust/alloc/vec/partial_eq.rs
new file mode 100644
index 00000000000..273e99bed48
--- /dev/null
+++ b/rust/alloc/vec/partial_eq.rs
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::Allocator;
+#[cfg(not(no_global_oom_handling))]
+use crate::borrow::Cow;
+
+use super::Vec;
+
+macro_rules! __impl_slice_eq1 {
+ ([$($vars:tt)*] $lhs:ty, $rhs:ty $(where $ty:ty: $bound:ident)?, #[$stability:meta]) => {
+ #[$stability]
+ impl<T, U, $($vars)*> PartialEq<$rhs> for $lhs
+ where
+ T: PartialEq<U>,
+ $($ty: $bound)?
+ {
+ #[inline]
+ fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] }
+ #[inline]
+ fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] }
+ }
+ }
+}
+
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, Vec<U, A>, #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &[U], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &mut [U], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] &[T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
+__impl_slice_eq1! { [A: Allocator] &mut [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, [U], #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")] }
+__impl_slice_eq1! { [A: Allocator] [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")] }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [A: Allocator] Cow<'_, [T]>, Vec<U, A> where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [] Cow<'_, [T]>, &[U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [] Cow<'_, [T]>, &mut [U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, [U; N], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, &[U; N], #[stable(feature = "rust1", since = "1.0.0")] }
+
+// NOTE: some less important impls are omitted to reduce code bloat
+// FIXME(Centril): Reconsider this?
+//__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], }
+//__impl_slice_eq1! { [const N: usize] [A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] &[A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] &mut [A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], }
diff --git a/rust/alloc/vec/set_len_on_drop.rs b/rust/alloc/vec/set_len_on_drop.rs
new file mode 100644
index 00000000000..448bf5076a0
--- /dev/null
+++ b/rust/alloc/vec/set_len_on_drop.rs
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
+//
+// The idea is: The length field in SetLenOnDrop is a local variable
+// that the optimizer will see does not alias with any stores through the Vec's data
+// pointer. This is a workaround for alias analysis issue #32155
+pub(super) struct SetLenOnDrop<'a> {
+ len: &'a mut usize,
+ local_len: usize,
+}
+
+impl<'a> SetLenOnDrop<'a> {
+ #[inline]
+ pub(super) fn new(len: &'a mut usize) -> Self {
+ SetLenOnDrop { local_len: *len, len }
+ }
+
+ #[inline]
+ pub(super) fn increment_len(&mut self, increment: usize) {
+ self.local_len += increment;
+ }
+}
+
+impl Drop for SetLenOnDrop<'_> {
+ #[inline]
+ fn drop(&mut self) {
+ *self.len = self.local_len;
+ }
+}
diff --git a/rust/alloc/vec/spec_extend.rs b/rust/alloc/vec/spec_extend.rs
new file mode 100644
index 00000000000..5a64c7ce239
--- /dev/null
+++ b/rust/alloc/vec/spec_extend.rs
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::Allocator;
+use crate::vec::TryReserveError;
+use core::iter::TrustedLen;
+use core::ptr::{self};
+use core::slice::{self};
+
+use super::{IntoIter, SetLenOnDrop, Vec};
+
+// Specialization trait used for Vec::extend
+#[cfg(not(no_global_oom_handling))]
+pub(super) trait SpecExtend<T, I> {
+ fn spec_extend(&mut self, iter: I);
+}
+
+// Specialization trait used for Vec::try_extend
+pub(super) trait TrySpecExtend<T, I> {
+ fn try_spec_extend(&mut self, iter: I) -> Result<(), TryReserveError>;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
+where
+ I: Iterator<Item = T>,
+{
+ default fn spec_extend(&mut self, iter: I) {
+ self.extend_desugared(iter)
+ }
+}
+
+impl<T, I, A: Allocator> TrySpecExtend<T, I> for Vec<T, A>
+where
+ I: Iterator<Item = T>,
+{
+ default fn try_spec_extend(&mut self, iter: I) -> Result<(), TryReserveError> {
+ self.try_extend_desugared(iter)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
+where
+ I: TrustedLen<Item = T>,
+{
+ default fn spec_extend(&mut self, iterator: I) {
+ // This is the case for a TrustedLen iterator.
+ let (low, high) = iterator.size_hint();
+ if let Some(additional) = high {
+ debug_assert_eq!(
+ low,
+ additional,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+ self.reserve(additional);
+ unsafe {
+ let mut ptr = self.as_mut_ptr().add(self.len());
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+ iterator.for_each(move |element| {
+ ptr::write(ptr, element);
+ ptr = ptr.offset(1);
+ // NB can't overflow since we would have had to alloc the address space
+ local_len.increment_len(1);
+ });
+ }
+ } else {
+ // Per TrustedLen contract a `None` upper bound means that the iterator length
+ // truly exceeds usize::MAX, which would eventually lead to a capacity overflow anyway.
+ // Since the other branch already panics eagerly (via `reserve()`) we do the same here.
+ // This avoids additional codegen for a fallback code path which would eventually
+ // panic anyway.
+ panic!("capacity overflow");
+ }
+ }
+}
+
+impl<T, I, A: Allocator> TrySpecExtend<T, I> for Vec<T, A>
+where
+ I: TrustedLen<Item = T>,
+{
+ default fn try_spec_extend(&mut self, iterator: I) -> Result<(), TryReserveError> {
+ // This is the case for a TrustedLen iterator.
+ let (low, high) = iterator.size_hint();
+ if let Some(additional) = high {
+ debug_assert_eq!(
+ low,
+ additional,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+ self.try_reserve(additional)?;
+ unsafe {
+ let mut ptr = self.as_mut_ptr().add(self.len());
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+ iterator.for_each(move |element| {
+ ptr::write(ptr, element);
+ ptr = ptr.offset(1);
+ // NB can't overflow since we would have had to alloc the address space
+ local_len.increment_len(1);
+ });
+ }
+ Ok(())
+ } else {
+ Err(TryReserveError::CapacityOverflow)
+ }
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T, A: Allocator> SpecExtend<T, IntoIter<T>> for Vec<T, A> {
+ fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
+ unsafe {
+ self.append_elements(iterator.as_slice() as _);
+ }
+ iterator.ptr = iterator.end;
+ }
+}
+
+impl<T, A: Allocator> TrySpecExtend<T, IntoIter<T>> for Vec<T, A> {
+ fn try_spec_extend(&mut self, mut iterator: IntoIter<T>) -> Result<(), TryReserveError> {
+ unsafe {
+ self.try_append_elements(iterator.as_slice() as _)?;
+ }
+ iterator.ptr = iterator.end;
+ Ok(())
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<'a, T: 'a, I, A: Allocator + 'a> SpecExtend<&'a T, I> for Vec<T, A>
+where
+ I: Iterator<Item = &'a T>,
+ T: Clone,
+{
+ default fn spec_extend(&mut self, iterator: I) {
+ self.spec_extend(iterator.cloned())
+ }
+}
+
+impl<'a, T: 'a, I, A: Allocator + 'a> TrySpecExtend<&'a T, I> for Vec<T, A>
+where
+ I: Iterator<Item = &'a T>,
+ T: Clone,
+{
+ default fn try_spec_extend(&mut self, iterator: I) -> Result<(), TryReserveError> {
+ self.try_spec_extend(iterator.cloned())
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<'a, T: 'a, A: Allocator + 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T, A>
+where
+ T: Copy,
+{
+ fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
+ let slice = iterator.as_slice();
+ unsafe { self.append_elements(slice) };
+ }
+}
+
+impl<'a, T: 'a, A: Allocator + 'a> TrySpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T, A>
+where
+ T: Copy,
+{
+ fn try_spec_extend(&mut self, iterator: slice::Iter<'a, T>) -> Result<(), TryReserveError> {
+ let slice = iterator.as_slice();
+ unsafe { self.try_append_elements(slice) }
+ }
+}
--
2.32.0