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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
commit | 94a0819fe3a0d679c3042a77bfe6a2afc505daea (patch) | |
tree | 2b827afe6a05f3538db3f7803a88c4587fe85648 /library/std/src/io/buffered/bufreader | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.tar.xz rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.zip |
Adding upstream version 1.66.0+dfsg1.upstream/1.66.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/std/src/io/buffered/bufreader')
-rw-r--r-- | library/std/src/io/buffered/bufreader/buffer.rs | 27 |
1 files changed, 22 insertions, 5 deletions
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()) } |