diff options
Diffstat (limited to 'library/std/src/io/buffered')
| -rw-r--r-- | library/std/src/io/buffered/bufreader.rs | 22 | ||||
| -rw-r--r-- | library/std/src/io/buffered/bufreader/buffer.rs | 27 | ||||
| -rw-r--r-- | library/std/src/io/buffered/tests.rs | 58 |
3 files changed, 79 insertions, 28 deletions
diff --git a/library/std/src/io/buffered/bufreader.rs b/library/std/src/io/buffered/bufreader.rs index f7fbaa9c2..4f339a18a 100644 --- a/library/std/src/io/buffered/bufreader.rs +++ b/library/std/src/io/buffered/bufreader.rs @@ -2,7 +2,7 @@ mod buffer; use crate::fmt; use crate::io::{ - self, BufRead, IoSliceMut, Read, ReadBuf, Seek, SeekFrom, SizeHint, DEFAULT_BUF_SIZE, + self, BorrowedCursor, BufRead, IoSliceMut, Read, Seek, SeekFrom, SizeHint, DEFAULT_BUF_SIZE, }; use buffer::Buffer; @@ -224,6 +224,14 @@ impl<R> BufReader<R> { } } +// This is only used by a test which asserts that the initialization-tracking is correct. +#[cfg(test)] +impl<R> BufReader<R> { + pub fn initialized(&self) -> usize { + self.buf.initialized() + } +} + impl<R: Seek> BufReader<R> { /// Seeks relative to the current position. If the new position lies within the buffer, /// the buffer will not be flushed, allowing for more efficient seeks. @@ -266,21 +274,21 @@ impl<R: Read> Read for BufReader<R> { Ok(nread) } - fn read_buf(&mut self, buf: &mut ReadBuf<'_>) -> io::Result<()> { + fn read_buf(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> { // If we don't have any buffered data and we're doing a massive read // (larger than our internal buffer), bypass our internal buffer // entirely. - if self.buf.pos() == self.buf.filled() && buf.remaining() >= self.capacity() { + if self.buf.pos() == self.buf.filled() && cursor.capacity() >= self.capacity() { self.discard_buffer(); - return self.inner.read_buf(buf); + return self.inner.read_buf(cursor); } - let prev = buf.filled_len(); + let prev = cursor.written(); let mut rem = self.fill_buf()?; - rem.read_buf(buf)?; + rem.read_buf(cursor.reborrow())?; - self.consume(buf.filled_len() - prev); //slice impl of read_buf known to never unfill buf + self.consume(cursor.written() - prev); //slice impl of read_buf known to never unfill buf Ok(()) } diff --git a/library/std/src/io/buffered/bufreader/buffer.rs b/library/std/src/io/buffered/bufreader/buffer.rs index 8ae01f3b0..e9e29d60c 100644 --- a/library/std/src/io/buffered/bufreader/buffer.rs +++ b/library/std/src/io/buffered/bufreader/buffer.rs @@ -9,7 +9,7 @@ /// that user code which wants to do reads from a `BufReader` via `buffer` + `consume` can do so /// without encountering any runtime bounds checks. use crate::cmp; -use crate::io::{self, Read, ReadBuf}; +use crate::io::{self, BorrowedBuf, Read}; use crate::mem::MaybeUninit; pub struct Buffer { @@ -20,13 +20,19 @@ pub struct Buffer { // Each call to `fill_buf` sets `filled` to indicate how many bytes at the start of `buf` are // initialized with bytes from a read. filled: usize, + // This is the max number of bytes returned across all `fill_buf` calls. We track this so that we + // can accurately tell `read_buf` how many bytes of buf are initialized, to bypass as much of its + // defensive initialization as possible. Note that while this often the same as `filled`, it + // doesn't need to be. Calls to `fill_buf` are not required to actually fill the buffer, and + // omitting this is a huge perf regression for `Read` impls that do not. + initialized: usize, } impl Buffer { #[inline] pub fn with_capacity(capacity: usize) -> Self { let buf = Box::new_uninit_slice(capacity); - Self { buf, pos: 0, filled: 0 } + Self { buf, pos: 0, filled: 0, initialized: 0 } } #[inline] @@ -51,6 +57,12 @@ impl Buffer { self.pos } + // This is only used by a test which asserts that the initialization-tracking is correct. + #[cfg(test)] + pub fn initialized(&self) -> usize { + self.initialized + } + #[inline] pub fn discard_buffer(&mut self) { self.pos = 0; @@ -93,12 +105,17 @@ impl Buffer { if self.pos >= self.filled { debug_assert!(self.pos == self.filled); - let mut readbuf = ReadBuf::uninit(&mut self.buf); + let mut buf = BorrowedBuf::from(&mut *self.buf); + // SAFETY: `self.filled` bytes will always have been initialized. + unsafe { + buf.set_init(self.initialized); + } - reader.read_buf(&mut readbuf)?; + reader.read_buf(buf.unfilled())?; - self.filled = readbuf.filled_len(); self.pos = 0; + self.filled = buf.len(); + self.initialized = buf.init_len(); } Ok(self.buffer()) } diff --git a/library/std/src/io/buffered/tests.rs b/library/std/src/io/buffered/tests.rs index fe45b1326..f4e688eb9 100644 --- a/library/std/src/io/buffered/tests.rs +++ b/library/std/src/io/buffered/tests.rs @@ -1,5 +1,7 @@ use crate::io::prelude::*; -use crate::io::{self, BufReader, BufWriter, ErrorKind, IoSlice, LineWriter, ReadBuf, SeekFrom}; +use crate::io::{ + self, BorrowedBuf, BufReader, BufWriter, ErrorKind, IoSlice, LineWriter, SeekFrom, +}; use crate::mem::MaybeUninit; use crate::panic; use crate::sync::atomic::{AtomicUsize, Ordering}; @@ -61,48 +63,48 @@ fn test_buffered_reader_read_buf() { let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4]; let mut reader = BufReader::with_capacity(2, inner); - let mut buf = [MaybeUninit::uninit(); 3]; - let mut buf = ReadBuf::uninit(&mut buf); + let buf: &mut [_] = &mut [MaybeUninit::uninit(); 3]; + let mut buf: BorrowedBuf<'_> = buf.into(); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); assert_eq!(buf.filled(), [5, 6, 7]); assert_eq!(reader.buffer(), []); - let mut buf = [MaybeUninit::uninit(); 2]; - let mut buf = ReadBuf::uninit(&mut buf); + let buf: &mut [_] = &mut [MaybeUninit::uninit(); 2]; + let mut buf: BorrowedBuf<'_> = buf.into(); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); assert_eq!(buf.filled(), [0, 1]); assert_eq!(reader.buffer(), []); - let mut buf = [MaybeUninit::uninit(); 1]; - let mut buf = ReadBuf::uninit(&mut buf); + let buf: &mut [_] = &mut [MaybeUninit::uninit(); 1]; + let mut buf: BorrowedBuf<'_> = buf.into(); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); assert_eq!(buf.filled(), [2]); assert_eq!(reader.buffer(), [3]); - let mut buf = [MaybeUninit::uninit(); 3]; - let mut buf = ReadBuf::uninit(&mut buf); + let buf: &mut [_] = &mut [MaybeUninit::uninit(); 3]; + let mut buf: BorrowedBuf<'_> = buf.into(); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); assert_eq!(buf.filled(), [3]); assert_eq!(reader.buffer(), []); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); assert_eq!(buf.filled(), [3, 4]); assert_eq!(reader.buffer(), []); buf.clear(); - reader.read_buf(&mut buf).unwrap(); + reader.read_buf(buf.unfilled()).unwrap(); - assert_eq!(buf.filled_len(), 0); + assert!(buf.filled().is_empty()); } #[test] @@ -1037,3 +1039,27 @@ fn single_formatted_write() { writeln!(&mut writer, "{}, {}!", "hello", "world").unwrap(); assert_eq!(writer.get_ref().events, [RecordedEvent::Write("hello, world!\n".to_string())]); } + +#[test] +fn bufreader_full_initialize() { + struct OneByteReader; + impl Read for OneByteReader { + fn read(&mut self, buf: &mut [u8]) -> crate::io::Result<usize> { + if buf.len() > 0 { + buf[0] = 0; + Ok(1) + } else { + Ok(0) + } + } + } + let mut reader = BufReader::new(OneByteReader); + // Nothing is initialized yet. + assert_eq!(reader.initialized(), 0); + + let buf = reader.fill_buf().unwrap(); + // We read one byte... + assert_eq!(buf.len(), 1); + // But we initialized the whole buffer! + assert_eq!(reader.initialized(), reader.capacity()); +} |