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Fix crash in BufReader::peek() #137832

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Merged
merged 2 commits into from
Mar 7, 2025
Merged

Fix crash in BufReader::peek() #137832

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b119671
Tweak BufReader::peek() doctest to expose bug in Buffer::read_more()
wgwoods Mar 1, 2025
6d07144
Fix logic error in Buffer::read_more()
wgwoods Mar 1, 2025
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6 changes: 3 additions & 3 deletions library/std/src/io/buffered/bufreader.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -118,16 +118,16 @@ impl<R: Read + ?Sized> BufReader<R> {
/// #![feature(bufreader_peek)]
/// use std::io::{Read, BufReader};
///
/// let mut bytes = &b"oh, hello"[..];
/// let mut bytes = &b"oh, hello there"[..];
/// let mut rdr = BufReader::with_capacity(6, &mut bytes);
/// assert_eq!(rdr.peek(2).unwrap(), b"oh");
/// let mut buf = [0; 4];
/// rdr.read(&mut buf[..]).unwrap();
/// assert_eq!(&buf, b"oh, ");
/// assert_eq!(rdr.peek(2).unwrap(), b"he");
/// assert_eq!(rdr.peek(5).unwrap(), b"hello");
/// let mut s = String::new();
/// rdr.read_to_string(&mut s).unwrap();
/// assert_eq!(&s, "hello");
/// assert_eq!(&s, "hello there");
/// assert_eq!(rdr.peek(1).unwrap().len(), 0);
/// ```
#[unstable(feature = "bufreader_peek", issue = "128405")]
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4 changes: 2 additions & 2 deletions library/std/src/io/buffered/bufreader/buffer.rs
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Expand Up @@ -109,8 +109,8 @@ impl Buffer {

/// Read more bytes into the buffer without discarding any of its contents
pub fn read_more(&mut self, mut reader: impl Read) -> io::Result<usize> {
let mut buf = BorrowedBuf::from(&mut self.buf[self.pos..]);
let old_init = self.initialized - self.pos;
let mut buf = BorrowedBuf::from(&mut self.buf[self.filled..]);
let old_init = self.initialized - self.filled;
unsafe {
buf.set_init(old_init);
}
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