Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
References: <20230503141016.683634-1-aliceryhl@google.com>
User-agent: mu4e 1.10.3; emacs 28.2.50
From:   Andreas Hindborg <nmi@metaspace.dk>
To:     Alice Ryhl <aliceryhl@google.com>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Martin Rodriguez Reboredo <yakoyoku@gmail.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev, Andreas Hindborg <a.hindborg@samsung.com>
Subject: Re: [PATCH v2] rust: str: add conversion from `CStr` to `CString`
Date:   Mon, 15 May 2023 20:36:47 +0200
In-reply-to: <20230503141016.683634-1-aliceryhl@google.com>
Message-ID: <87bkilo2vu.fsf@metaspace.dk>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk


Alice Ryhl <aliceryhl@google.com> writes:

> These methods can be used to copy the data in a temporary c string into
> a separate allocation, so that it can be accessed later even if the
> original is deallocated.
>
> The API in this change mirrors the standard library API for the `&str`
> and `String` types. The `ToOwned` trait is not implemented because it
> assumes that allocations are infallible.
>
> Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---

Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>


>  rust/kernel/str.rs | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index b771310fa4a4..f3dc5b24ea55 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -2,6 +2,7 @@
>  
>  //! String representations.
>  
> +use alloc::alloc::AllocError;
>  use alloc::vec::Vec;
>  use core::fmt::{self, Write};
>  use core::ops::{self, Deref, Index};
> @@ -199,6 +200,12 @@ impl CStr {
>      pub unsafe fn as_str_unchecked(&self) -> &str {
>          unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
>      }
> +
> +    /// Convert this [`CStr`] into a [`CString`] by allocating memory and
> +    /// copying over the string data.
> +    pub fn to_cstring(&self) -> Result<CString, AllocError> {
> +        CString::try_from(self)
> +    }
>  }
>  
>  impl fmt::Display for CStr {
> @@ -584,6 +591,21 @@ impl Deref for CString {
>      }
>  }
>  
> +impl<'a> TryFrom<&'a CStr> for CString {
> +    type Error = AllocError;
> +
> +    fn try_from(cstr: &'a CStr) -> Result<CString, AllocError> {
> +        let mut buf = Vec::new();
> +
> +        buf.try_extend_from_slice(cstr.as_bytes_with_nul())
> +            .map_err(|_| AllocError)?;
> +
> +        // INVARIANT: The `CStr` and `CString` types have the same invariants for
> +        // the string data, and we copied it over without changes.
> +        Ok(CString { buf })
> +    }
> +}
> +
>  /// A convenience alias for [`core::format_args`].
>  #[macro_export]
>  macro_rules! fmt {
>
> base-commit: ea76e08f4d901a450619831a255e9e0a4c0ed162