Add two functions `pin_init_array_from_fn` and `init_array_from_fn` that
take a function that generates initializers for `T` from usize, the added
functions then return an initializer for `[T; N]` where every element is
initialized by an element returned from the generator function.
Suggested-by: Asahi Lina <[email protected]>
Reviewed-by: Björn Roy Baron <[email protected]>
Signed-off-by: Benno Lossin <[email protected]>
---
v1 -> v2:
* fix warnings and errors in doctests
* replace dropping loop with `drop_in_place` and `slice_from_raw_parts_mut`
inside of `{pin_}init_array_from_fn` functions
rust/kernel/init.rs | 86 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 86 insertions(+)
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 460f808ebf84..fa1ebdbf5f4b 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -875,6 +875,92 @@ pub fn uninit<T, E>() -> impl Init<MaybeUninit<T>, E> {
unsafe { init_from_closure(|_| Ok(())) }
}
+/// Initializes an array by initializing each element via the provided initializer.
+///
+/// # Examples
+///
+/// ```rust
+/// use kernel::{error::Error, init::init_array_from_fn};
+/// let array: Box<[usize; 1_000_000_000]>= Box::init::<Error>(init_array_from_fn(|i| i)).unwrap();
+/// pr_info!("{array:?}");
+/// ```
+pub fn init_array_from_fn<I, const N: usize, T, E>(
+ mut make_init: impl FnMut(usize) -> I,
+) -> impl Init<[T; N], E>
+where
+ I: Init<T, E>,
+{
+ let init = move |slot: *mut [T; N]| {
+ let slot = slot.cast::<T>();
+ for i in 0..N {
+ let init = make_init(i);
+ // SAFETY: since 0 <= `i` < N, it is still in bounds of `[T; N]`.
+ let ptr = unsafe { slot.add(i) };
+ // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
+ // requirements.
+ match unsafe { init.__init(ptr) } {
+ Ok(()) => {}
+ Err(e) => {
+ // We now free every element that has been initialized before:
+ // SAFETY: The loop initialized exactly the values from 0..i and since we
+ // return `Err` below, the caller will consider the memory at `slot` as
+ // uninitialized.
+ unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
+ return Err(e);
+ }
+ }
+ }
+ Ok(())
+ };
+ // SAFETY: The initializer above initializes every element of the array. On failure it drops
+ // any initialized elements and returns `Err`.
+ unsafe { init_from_closure(init) }
+}
+
+/// Initializes an array by initializing each element via the provided initializer.
+///
+/// # Examples
+///
+/// ```rust
+/// use kernel::{sync::{Arc, Mutex}, init::pin_init_array_from_fn, new_mutex};
+/// let array: Arc<[Mutex<usize>; 1_000_000_000]>=
+/// Arc::pin_init(pin_init_array_from_fn(|i| new_mutex!(i))).unwrap();
+/// pr_info!("{}", array.len());
+/// ```
+pub fn pin_init_array_from_fn<I, const N: usize, T, E>(
+ mut make_init: impl FnMut(usize) -> I,
+) -> impl PinInit<[T; N], E>
+where
+ I: PinInit<T, E>,
+{
+ let init = move |slot: *mut [T; N]| {
+ let slot = slot.cast::<T>();
+ for i in 0..N {
+ let init = make_init(i);
+ // SAFETY: since 0 <= `i` < N, it is still in bounds of `[T; N]`.
+ let ptr = unsafe { slot.add(i) };
+ // SAFETY: The pointer is derived from `slot` and thus satisfies the `__pinned_init`
+ // requirements.
+ match unsafe { init.__pinned_init(ptr) } {
+ Ok(()) => {}
+ Err(e) => {
+ // We now have to free every element that has been initialized before, since we
+ // have to abide by the drop guarantee.
+ // SAFETY: The loop initialized exactly the values from 0..i and since we
+ // return `Err` below, the caller will consider the memory at `slot` as
+ // uninitialized.
+ unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
+ return Err(e);
+ }
+ }
+ }
+ Ok(())
+ };
+ // SAFETY: The initializer above initializes every element of the array. On failure it drops
+ // any initialized elements and returns `Err`.
+ unsafe { pin_init_from_closure(init) }
+}
+
// SAFETY: Every type can be initialized by-value.
unsafe impl<T, E> Init<T, E> for T {
unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
--
2.41.0
> Add two functions `pin_init_array_from_fn` and `init_array_from_fn` that
> take a function that generates initializers for `T` from usize, the added
> functions then return an initializer for `[T; N]` where every element is
> initialized by an element returned from the generator function.
>
> Suggested-by: Asahi Lina <[email protected]>
> Reviewed-by: Björn Roy Baron <[email protected]>
> Signed-off-by: Benno Lossin <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
On 7/19/23 11:20, Benno Lossin wrote:
> Add two functions `pin_init_array_from_fn` and `init_array_from_fn` that
> take a function that generates initializers for `T` from usize, the added
> functions then return an initializer for `[T; N]` where every element is
> initialized by an element returned from the generator function.
>
> Suggested-by: Asahi Lina <[email protected]>
> Reviewed-by: Björn Roy Baron <[email protected]>
> Signed-off-by: Benno Lossin <[email protected]>
> ---
> [...]
> +/// Initializes an array by initializing each element via the provided initializer.
> +///
> +/// # Examples
> +///
> +/// ```rust
> +/// use kernel::{error::Error, init::init_array_from_fn};
> +/// let array: Box<[usize; 1_000_000_000]>= Box::init::<Error>(init_array_from_fn(|i| i)).unwrap();
> +/// pr_info!("{array:?}");
> +/// ```
Rather than debug printing the array I'd suggest to assert the struct
size or its elements instead.
> [...]
> +
> +/// Initializes an array by initializing each element via the provided initializer.
> +///
> +/// # Examples
> +///
> +/// ```rust
> +/// use kernel::{sync::{Arc, Mutex}, init::pin_init_array_from_fn, new_mutex};
> +/// let array: Arc<[Mutex<usize>; 1_000_000_000]>=
> +/// Arc::pin_init(pin_init_array_from_fn(|i| new_mutex!(i))).unwrap();
> +/// pr_info!("{}", array.len());
> +/// ```
> [...]
Same as above.