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Message-ID: <6ba16a74-6fa4-4051-8cc6-f0e53a68d8b4@redhat.com>
Date: Mon, 4 Mar 2024 13:22:17 +0100
From: Danilo Krummrich <dakr@...hat.com>
To: ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com,
boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com,
benno.lossin@...ton.me, a.hindborg@...sung.com, aliceryhl@...gle.com
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] rust: str: add {make,to}_{upper,lower}case() to
CString
On 2/23/24 17:37, Danilo Krummrich wrote:
> Add functions to convert a CString to upper- / lowercase, either
> in-place or by creating a copy of the original CString.
>
> Naming followes the one from the Rust stdlib, where functions starting
> with 'to' create a copy and functions starting with 'make' perform an
> in-place conversion.
>
> This is required by the Nova project (GSP only Rust successor of
> Nouveau) to convert stringified enum values (representing different GPU
> chipsets) to strings in order to generate the corresponding firmware
> paths. See also [1].
Gentle ping.
>
> [1] https://rust-for-linux.zulipchat.com/#narrow/stream/288089-General/topic/String.20manipulation.20in.20kernel.20Rust
>
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Signed-off-by: Danilo Krummrich <dakr@...hat.com>
> ---
> Changes in V5:
> - remove unneeded return statements
> - use Vec::as_mut_slice() instead of a dereference
> Changes in V4:
> - move to_ascii_{lower,upper}case() to CStr
> - add a few comments suggested by Alice
> Changes in V3:
> - add an `impl DerefMut for CString`, such that these functions can be defined
> for `CStr` as `&mut self` and still be called on a `CString`
> Changes in V2:
> - expand commit message mentioning the use case
> - expand function doc comments to match the ones from Rust's stdlib
> - rename to_* to make_* and add the actual to_* implementations
> ---
> rust/kernel/str.rs | 87 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 86 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 7d848b83add4..c1c8ccc80c52 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -5,7 +5,7 @@
> use alloc::alloc::AllocError;
> use alloc::vec::Vec;
> use core::fmt::{self, Write};
> -use core::ops::{self, Deref, Index};
> +use core::ops::{self, Deref, DerefMut, Index};
>
> use crate::{
> bindings,
> @@ -143,6 +143,19 @@ pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError
> unsafe { core::mem::transmute(bytes) }
> }
>
> + /// Creates a mutable [`CStr`] from a `[u8]` without performing any
> + /// additional checks.
> + ///
> + /// # Safety
> + ///
> + /// `bytes` *must* end with a `NUL` byte, and should only have a single
> + /// `NUL` byte (or the string will be truncated).
> + #[inline]
> + pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
> + // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
> + unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
> + }
> +
> /// Returns a C pointer to the string.
> #[inline]
> pub const fn as_char_ptr(&self) -> *const core::ffi::c_char {
> @@ -206,6 +219,70 @@ pub unsafe fn as_str_unchecked(&self) -> &str {
> pub fn to_cstring(&self) -> Result<CString, AllocError> {
> CString::try_from(self)
> }
> +
> + /// Converts this [`CStr`] to its ASCII lower case equivalent in-place.
> + ///
> + /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
> + /// but non-ASCII letters are unchanged.
> + ///
> + /// To return a new lowercased value without modifying the existing one, use
> + /// [`to_ascii_lowercase()`].
> + ///
> + /// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
> + pub fn make_ascii_lowercase(&mut self) {
> + // INVARIANT: This doesn't introduce or remove NUL bytes in the C
> + // string.
> + self.0.make_ascii_lowercase();
> + }
> +
> + /// Converts this [`CStr`] to its ASCII upper case equivalent in-place.
> + ///
> + /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
> + /// but non-ASCII letters are unchanged.
> + ///
> + /// To return a new uppercased value without modifying the existing one, use
> + /// [`to_ascii_uppercase()`].
> + ///
> + /// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
> + pub fn make_ascii_uppercase(&mut self) {
> + // INVARIANT: This doesn't introduce or remove NUL bytes in the C
> + // string.
> + self.0.make_ascii_uppercase();
> + }
> +
> + /// Returns a copy of this [`CString`] 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`].
> + ///
> + /// [`make_ascii_lowercase`]: str::make_ascii_lowercase
> + pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
> + let mut s = self.to_cstring()?;
> +
> + s.make_ascii_lowercase();
> +
> + Ok(s)
> + }
> +
> + /// Returns a copy of this [`CString`] 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`].
> + ///
> + /// [`make_ascii_uppercase`]: str::make_ascii_uppercase
> + pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
> + let mut s = self.to_cstring()?;
> +
> + s.make_ascii_uppercase();
> +
> + Ok(s)
> + }
> }
>
> impl fmt::Display for CStr {
> @@ -593,6 +670,14 @@ fn deref(&self) -> &Self::Target {
> }
> }
>
> +impl DerefMut for CString {
> + fn deref_mut(&mut self) -> &mut Self::Target {
> + // SAFETY: A `CString` is always NUL-terminated and contains no other
> + // NUL bytes.
> + unsafe { CStr::from_bytes_with_nul_unchecked_mut(self.buf.as_mut_slice()) }
> + }
> +}
> +
> impl<'a> TryFrom<&'a CStr> for CString {
> type Error = AllocError;
>
>
> base-commit: 39133352cbed6626956d38ed72012f49b0421e7b
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