Commit 10a7108d authored by Tamir Duberstein's avatar Tamir Duberstein Committed by Miguel Ojeda
Browse files

rust: str: add `CStr` methods matching `core::ffi::CStr` 

Prepare for replacing `CStr` with `core::ffi::CStr` by soft-deprecating
methods which don't exist on `core::ffi::CStr`.

We could keep `as_bytes{,_with_nul}` through an extension trait but
seeing as we have to introduce `as_char_ptr_in_const_context` as a free
function, we may as well introduce `to_bytes{,_with_nul}` here to allow
downstream code to migrate in one cycle rather than two.

Link: https://github.com/Rust-for-Linux/linux/issues/1075


Signed-off-by: default avatarTamir Duberstein <tamird@gmail.com>
Reviewed-by: default avatarBenno Lossin <lossin@kernel.org>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250704-core-cstr-prepare-v1-5-a91524037783@gmail.com


[ Reworded title. - Miguel ]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 0f6d2256

rust/kernel/str.rs

+34 −3
Original line number Diff line number Diff line
@@ -175,6 +175,15 @@ macro_rules! b_str { 
    }};

}



/// Returns a C pointer to the string.

// It is a free function rather than a method on an extension trait because:

//

// - error[E0379]: functions in trait impls cannot be declared const

#[inline]

pub const fn as_char_ptr_in_const_context(c_str: &CStr) -> *const c_char {

    c_str.0.as_ptr()

}



/// Possible errors when using conversion functions in [`CStr`].

#[derive(Debug, Clone, Copy)]

pub enum CStrConvertError {
@@ -294,23 +303,45 @@ pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr { 
    }



    /// Returns a C pointer to the string.

    ///

    /// Using this function in a const context is deprecated in favor of

    /// [`as_char_ptr_in_const_context`] in preparation for replacing `CStr` with `core::ffi::CStr`

    /// which does not have this method.

    #[inline]

    pub const fn as_char_ptr(&self) -> *const c_char {

        self.0.as_ptr()

        as_char_ptr_in_const_context(self)

    }



    /// Convert the string to a byte slice without the trailing `NUL` byte.

    #[inline]

    pub fn as_bytes(&self) -> &[u8] {

    pub fn to_bytes(&self) -> &[u8] {

        &self.0[..self.len()]

    }



    /// Convert the string to a byte slice without the trailing `NUL` byte.

    ///

    /// This function is deprecated in favor of [`Self::to_bytes`] in preparation for replacing

    /// `CStr` with `core::ffi::CStr` which does not have this method.

    #[inline]

    pub fn as_bytes(&self) -> &[u8] {

        self.to_bytes()

    }



    /// Convert the string to a byte slice containing the trailing `NUL` byte.

    #[inline]

    pub const fn as_bytes_with_nul(&self) -> &[u8] {

    pub const fn to_bytes_with_nul(&self) -> &[u8] {

        &self.0

    }



    /// Convert the string to a byte slice containing the trailing `NUL` byte.

    ///

    /// This function is deprecated in favor of [`Self::to_bytes_with_nul`] in preparation for

    /// replacing `CStr` with `core::ffi::CStr` which does not have this method.

    #[inline]

    pub const fn as_bytes_with_nul(&self) -> &[u8] {

        self.to_bytes_with_nul()

    }



    /// Yields a [`&str`] slice if the [`CStr`] contains valid UTF-8.

    ///

    /// If the contents of the [`CStr`] are valid UTF-8 data, this