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Rollup merge of #136967 - DaniPopes:io-repeat-fill, r=joboet

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Use `slice::fill` in `io::Repeat` implementation

Use the existing `fill` methods on slices instead of manually writing the fill loop.
This commit is contained in:
Matthias Krüger 2025-02-14 16:23:32 +01:00 committed by GitHub
commit b5fce2ab8e
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2 changed files with 11 additions and 18 deletions
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28
library/std/src/io/util.rs
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@ -7,6 +7,7 @@ use crate::fmt;
use crate::io::{ use crate::io::{
self, BorrowedCursor, BufRead, IoSlice, IoSliceMut, Read, Seek, SeekFrom, SizeHint, Write, self, BorrowedCursor, BufRead, IoSlice, IoSliceMut, Read, Seek, SeekFrom, SizeHint, Write,
}; };
use crate::mem::MaybeUninit;
/// `Empty` ignores any data written via [`Write`], and will always be empty /// `Empty` ignores any data written via [`Write`], and will always be empty
/// (returning zero bytes) when read via [`Read`]. /// (returning zero bytes) when read via [`Read`].
@ -182,35 +183,26 @@ pub const fn repeat(byte: u8) -> Repeat {
impl Read for Repeat { impl Read for Repeat {
#[inline] #[inline]
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
for slot in &mut *buf { buf.fill(self.byte);
*slot = self.byte;
}
Ok(buf.len()) Ok(buf.len())
} }
#[inline]
fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> { fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
for slot in &mut *buf { buf.fill(self.byte);
*slot = self.byte;
}
Ok(()) Ok(())
} }
#[inline]
fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> io::Result<()> { fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> io::Result<()> {
// SAFETY: No uninit bytes are being written // SAFETY: No uninit bytes are being written.
for slot in unsafe { buf.as_mut() } { MaybeUninit::fill(unsafe { buf.as_mut() }, self.byte);
slot.write(self.byte); // SAFETY: the entire unfilled portion of buf has been initialized.
} unsafe { buf.advance_unchecked(buf.capacity()) };
let remaining = buf.capacity();
// SAFETY: the entire unfilled portion of buf has been initialized
unsafe {
buf.advance_unchecked(remaining);
}
Ok(()) Ok(())
} }
#[inline]
fn read_buf_exact(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> { fn read_buf_exact(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
self.read_buf(buf) self.read_buf(buf)
} }

1
library/std/src/lib.rs
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@ -302,6 +302,7 @@
#![feature(link_cfg)] #![feature(link_cfg)]
#![feature(linkage)] #![feature(linkage)]
#![feature(macro_metavar_expr_concat)] #![feature(macro_metavar_expr_concat)]
#![feature(maybe_uninit_fill)]
#![feature(min_specialization)] #![feature(min_specialization)]
#![feature(must_not_suspend)] #![feature(must_not_suspend)]
#![feature(needs_panic_runtime)] #![feature(needs_panic_runtime)]