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Use libc::memchr instead of iter().rposition(), closes #30076 #30151

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Use libc::memchr instead of iter().rposition(), closes #30076 #30151

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25 changes: 17 additions & 8 deletions src/libstd/io/buffered.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -746,14 +746,23 @@ impl<W: Write> LineWriter<W> {
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> Write for LineWriter<W> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
match buf.iter().rposition(|b| *b == b'\n') {
Some(i) => {
let n = try!(self.inner.write(&buf[..i + 1]));
if n != i + 1 { return Ok(n) }
try!(self.inner.flush());
self.inner.write(&buf[i + 1..]).map(|i| n + i)
}
None => self.inner.write(buf),
use libc;

let p = unsafe {
libc::memchr(
buf.as_ptr() as *const libc::c_void,
b'\n' as libc::c_int,
buf.len() as libc::size_t)
};
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Best to have a safe wrapper function for memchr — and then the structure of fn write doesn't need to change at all either.


if p.is_null() {
self.inner.write(buf)
} else {
let i = p as usize - (buf.as_ptr() as usize);
let n = try!(self.inner.write(&buf[..i + 1]));
if n != i + 1 { return Ok(n) }
try!(self.inner.flush());
self.inner.write(&buf[i + 1..]).map(|i| n + i)
}
}

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