Commit 87482d6d authored by Andreas Hindborg's avatar Andreas Hindborg Committed by Jens Axboe
Browse files

rust: str: allow `str::Formatter` to format into `&mut [u8]`. 



Improve `Formatter` so that it can write to an array or slice buffer.

Reviewed-by: default avatarDaniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250902-rnull-up-v6-16-v7-2-b5212cc89b98@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d5d060d6

rust/kernel/str.rs

+17 −6
Original line number Diff line number Diff line
@@ -7,7 +7,10 @@ 
    fmt::{self, Write},

    prelude::*,

};

use core::ops::{self, Deref, DerefMut, Index};

use core::{

    marker::PhantomData,

    ops::{self, Deref, DerefMut, Index},

};



/// Byte string without UTF-8 validity guarantee.

#[repr(transparent)]
@@ -825,9 +828,9 @@ fn write_str(&mut self, s: &str) -> fmt::Result { 
/// Allows formatting of [`fmt::Arguments`] into a raw buffer.

///

/// Fails if callers attempt to write more than will fit in the buffer.

pub(crate) struct Formatter(RawFormatter);

pub(crate) struct Formatter<'a>(RawFormatter, PhantomData<&'a mut ()>);



impl Formatter {

impl Formatter<'_> {

    /// Creates a new instance of [`Formatter`] with the given buffer.

    ///

    /// # Safety
@@ -836,11 +839,19 @@ impl Formatter { 
    /// for the lifetime of the returned [`Formatter`].

    pub(crate) unsafe fn from_buffer(buf: *mut u8, len: usize) -> Self {

        // SAFETY: The safety requirements of this function satisfy those of the callee.

        Self(unsafe { RawFormatter::from_buffer(buf, len) })

        Self(unsafe { RawFormatter::from_buffer(buf, len) }, PhantomData)

    }



    /// Create a new [`Self`] instance.

    #[expect(dead_code)]

    pub(crate) fn new(buffer: &mut [u8]) -> Self {

        // SAFETY: `buffer` is valid for writes for the entire length for

        // the lifetime of `Self`.

        unsafe { Formatter::from_buffer(buffer.as_mut_ptr(), buffer.len()) }

    }

}



impl Deref for Formatter {

impl Deref for Formatter<'_> {

    type Target = RawFormatter;



    fn deref(&self) -> &Self::Target {
@@ -848,7 +859,7 @@ fn deref(&self) -> &Self::Target { 
    }

}



impl fmt::Write for Formatter {

impl fmt::Write for Formatter<'_> {

    fn write_str(&mut self, s: &str) -> fmt::Result {

        self.0.write_str(s)?;