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

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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: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice 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: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Tamir Duberstein
2025-07-04 16:14:56 -04:00
committed by Miguel Ojeda
parent 0f6d225671
commit 10a7108d4b
1 changed files with 34 additions and 3 deletions
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37
rust/kernel/str.rs
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@@ -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 @@ impl 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