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Improve several Read implementations #122441

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May 4, 2024
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21 changes: 21 additions & 0 deletions library/std/src/io/cursor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -364,6 +364,27 @@ where
self.pos += n as u64;
Ok(())
}

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
let content = self.remaining_slice();
let len = content.len();
buf.try_reserve(len)?;
buf.extend_from_slice(content);
self.pos += len as u64;

Ok(len)
}

fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
let content =
crate::str::from_utf8(self.remaining_slice()).map_err(|_| io::Error::INVALID_UTF8)?;
let len = content.len();
buf.try_reserve(len)?;
buf.push_str(content);
self.pos += len as u64;

Ok(len)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
Expand Down
13 changes: 4 additions & 9 deletions library/std/src/io/impls.rs
Original file line number Diff line number Diff line change
Expand Up @@ -329,8 +329,9 @@ impl Read for &[u8] {
#[inline]
fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
let content = str::from_utf8(self).map_err(|_| io::Error::INVALID_UTF8)?;
buf.push_str(content);
let len = self.len();
buf.try_reserve(len)?;
buf.push_str(content);
*self = &self[len..];
Ok(len)
}
Expand Down Expand Up @@ -473,14 +474,8 @@ impl<A: Allocator> Read for VecDeque<u8, A> {

#[inline]
fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
// We have to use a single contiguous slice because the `VecDequeue` might be split in the
// middle of an UTF-8 character.
let len = self.len();
let content = self.make_contiguous();
let string = str::from_utf8(content).map_err(|_| io::Error::INVALID_UTF8)?;
buf.push_str(string);
self.clear();
Ok(len)
// SAFETY: We only append to the buffer
unsafe { io::append_to_string(buf, |buf| self.read_to_end(buf)) }
}
}

Expand Down
5 changes: 4 additions & 1 deletion library/std/src/io/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,10 @@ where
{
let mut g = Guard { len: buf.len(), buf: buf.as_mut_vec() };
let ret = f(g.buf);
if str::from_utf8(&g.buf[g.len..]).is_err() {

// SAFETY: the caller promises to only append data to `buf`
let appended = g.buf.get_unchecked(g.len..);
if str::from_utf8(appended).is_err() {
ret.and_then(|_| Err(Error::INVALID_UTF8))
} else {
g.len = g.buf.len();
Expand Down
4 changes: 4 additions & 0 deletions library/std/src/process.rs
Original file line number Diff line number Diff line change
Expand Up @@ -486,6 +486,10 @@ impl Read for ChildStderr {
fn is_read_vectored(&self) -> bool {
self.inner.is_read_vectored()
}

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
self.inner.read_to_end(buf)
}
}

impl AsInner<AnonPipe> for ChildStderr {
Expand Down
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