surv/riscv64-kernel
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add more from the std

Browse Source
This commit is contained in:
Julien THILLARD
2026-03-17 23:40:39 +01:00
parent 10be5b301c
commit fd0770f813
15 changed files with 4526 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
crates/std/src/io.rs
View File

@@ -1,15 +1,22 @@
#[cfg(test)]
mod tests;
pub mod error;
pub use self::buffered::{BufReader, BufWriter, IntoInnerError, LineWriter};
pub use self::error::{Error, ErrorKind, Result, SimpleMessage, const_error};
pub mod buffered;
pub mod copy;
pub mod cursor;
pub mod prelude;
pub mod impls;
pub mod prelude;
pub mod util;
use crate::mem::{MaybeUninit, take};
use crate::ops::{Deref, DerefMut};
use crate::{cmp, fmt, slice, str, sys};
#[unstable(feature = "read_buf", issue = "78485")]
pub use core::io::{BorrowedBuf, BorrowedCursor};
use core::slice::memchr;
use crate::ops::{Deref, DerefMut};
use crate::fs::File;
use io::IoBase;
@@ -36,7 +43,6 @@ pub fn stdin() -> Stdin {
// Part took from the real std
const DEFAULT_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
struct Guard<'a> {
@@ -56,7 +62,10 @@ pub(crate) unsafe fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize
where
F: FnOnce(&mut Vec<u8>) -> Result<usize>,
{
let mut g = Guard { len: buf.len(), buf: unsafe { buf.as_mut_vec() } };
let mut g = Guard {
len: buf.len(),
buf: unsafe { buf.as_mut_vec() },
};
let ret = f(g.buf);
// SAFETY: the caller promises to only append data to `buf`
@@ -88,7 +97,10 @@ pub(crate) fn default_read_to_end<R: Read + ?Sized>(
// Optionally limit the maximum bytes read on each iteration.
// This adds an arbitrary fiddle factor to allow for more data than we expect.
let mut max_read_size = size_hint
.and_then(|s| s.checked_add(1024)?.checked_next_multiple_of(DEFAULT_BUF_SIZE))
.and_then(|s| {
s.checked_add(1024)?
.checked_next_multiple_of(DEFAULT_BUF_SIZE)
})
.unwrap_or(DEFAULT_BUF_SIZE);
let mut initialized = 0; // Extra initialized bytes from previous loop iteration
@@ -229,7 +241,10 @@ pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) ->
where
F: FnOnce(&mut [u8]) -> Result<usize>,
{
let buf = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b| &mut **b);
let buf = bufs
.iter_mut()
.find(|b| !b.is_empty())
.map_or(&mut [][..], |b| &mut **b);
read(buf)
}
@@ -237,7 +252,10 @@ pub(crate) fn default_write_vectored<F>(write: F, bufs: &[IoSlice<'_>]) -> Resul
where
F: FnOnce(&[u8]) -> Result<usize>,
{
let buf = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b| &**b);
let buf = bufs
.iter()
.find(|b| !b.is_empty())
.map_or(&[][..], |b| &**b);
write(buf)
}
@@ -252,7 +270,11 @@ pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [
Err(e) => return Err(e),
}
}
if !buf.is_empty() { Err(Error::READ_EXACT_EOF) } else { Ok(()) }
if !buf.is_empty() {
Err(Error::READ_EXACT_EOF)
} else {
Ok(())
}
}
pub(crate) fn default_read_buf<F>(read: F, mut cursor: BorrowedCursor<'_>) -> Result<()>
@@ -307,7 +329,10 @@ pub(crate) fn default_write_fmt<W: Write + ?Sized>(
}
}
let mut output = Adapter { inner: this, error: Ok(()) };
let mut output = Adapter {
inner: this,
error: Ok(()),
};
match fmt::write(&mut output, args) {
Ok(()) => Ok(()),
Err(..) => {
@@ -2230,7 +2255,10 @@ pub trait BufRead: Read {
where
Self: Sized,
{
Split { buf: self, delim: byte }
Split {
buf: self,
delim: byte,
}
}
/// Returns an iterator over the lines of this reader.
@@ -2435,7 +2463,11 @@ impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
}
fn consume(&mut self, amt: usize) {
if !self.done_first { self.first.consume(amt) } else { self.second.consume(amt) }
if !self.done_first {
self.first.consume(amt)
} else {
self.second.consume(amt)
}
}
fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> {
@@ -2465,7 +2497,10 @@ impl<T, U> SizeHint for Chain<T, U> {
#[inline]
fn upper_bound(&self) -> Option<usize> {
match (SizeHint::upper_bound(&self.first), SizeHint::upper_bound(&self.second)) {
match (
SizeHint::upper_bound(&self.first),
SizeHint::upper_bound(&self.second),
) {
(Some(first), Some(second)) => first.checked_add(second),
_ => None,
}

592
crates/std/src/io/buffered/bufreader.rs Normal file
View File

@@ -0,0 +1,592 @@
mod buffer;
use buffer::Buffer;
use crate::fmt;
use crate::io::{
self, BorrowedCursor, BufRead, DEFAULT_BUF_SIZE, IoSliceMut, Read, Seek, SeekFrom, SizeHint,
SpecReadByte, uninlined_slow_read_byte,
};
/// The `BufReader<R>` struct adds buffering to any reader.
///
/// It can be excessively inefficient to work directly with a [`Read`] instance.
/// For example, every call to [`read`][`TcpStream::read`] on [`TcpStream`]
/// results in a system call. A `BufReader<R>` performs large, infrequent reads on
/// the underlying [`Read`] and maintains an in-memory buffer of the results.
///
/// `BufReader<R>` can improve the speed of programs that make *small* and
/// *repeated* read calls to the same file or network socket. It does not
/// help when reading very large amounts at once, or reading just one or a few
/// times. It also provides no advantage when reading from a source that is
/// already in memory, like a <code>[Vec]\<u8></code>.
///
/// When the `BufReader<R>` is dropped, the contents of its buffer will be
/// discarded. Creating multiple instances of a `BufReader<R>` on the same
/// stream can cause data loss. Reading from the underlying reader after
/// unwrapping the `BufReader<R>` with [`BufReader::into_inner`] can also cause
/// data loss.
///
/// [`TcpStream::read`]: crate::net::TcpStream::read
/// [`TcpStream`]: crate::net::TcpStream
///
/// # Examples
///
/// ```no_run
/// use std::io::prelude::*;
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f = File::open("log.txt")?;
/// let mut reader = BufReader::new(f);
///
/// let mut line = String::new();
/// let len = reader.read_line(&mut line)?;
/// println!("First line is {len} bytes long");
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct BufReader<R: ?Sized> {
buf: Buffer,
inner: R,
}
impl<R: Read> BufReader<R> {
/// Creates a new `BufReader<R>` with a default buffer capacity. The default is currently 8 KiB,
/// but may change in the future.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f = File::open("log.txt")?;
/// let reader = BufReader::new(f);
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(inner: R) -> BufReader<R> {
BufReader::with_capacity(DEFAULT_BUF_SIZE, inner)
}
pub(crate) fn try_new_buffer() -> io::Result<Buffer> {
Buffer::try_with_capacity(DEFAULT_BUF_SIZE)
}
pub(crate) fn with_buffer(inner: R, buf: Buffer) -> Self {
Self { inner, buf }
}
/// Creates a new `BufReader<R>` with the specified buffer capacity.
///
/// # Examples
///
/// Creating a buffer with ten bytes of capacity:
///
/// ```no_run
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f = File::open("log.txt")?;
/// let reader = BufReader::with_capacity(10, f);
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn with_capacity(capacity: usize, inner: R) -> BufReader<R> {
BufReader { inner, buf: Buffer::with_capacity(capacity) }
}
}
impl<R: Read + ?Sized> BufReader<R> {
/// Attempt to look ahead `n` bytes.
///
/// `n` must be less than or equal to `capacity`.
///
/// The returned slice may be less than `n` bytes long if
/// end of file is reached.
///
/// After calling this method, you may call [`consume`](BufRead::consume)
/// with a value less than or equal to `n` to advance over some or all of
/// the returned bytes.
///
/// ## Examples
///
/// ```rust
/// #![feature(bufreader_peek)]
/// use std::io::{Read, BufReader};
///
/// 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(5).unwrap(), b"hello");
/// let mut s = String::new();
/// rdr.read_to_string(&mut s).unwrap();
/// assert_eq!(&s, "hello there");
/// assert_eq!(rdr.peek(1).unwrap().len(), 0);
/// ```
#[unstable(feature = "bufreader_peek", issue = "128405")]
pub fn peek(&mut self, n: usize) -> io::Result<&[u8]> {
assert!(n <= self.capacity());
while n > self.buf.buffer().len() {
if self.buf.pos() > 0 {
self.buf.backshift();
}
let new = self.buf.read_more(&mut self.inner)?;
if new == 0 {
// end of file, no more bytes to read
return Ok(&self.buf.buffer()[..]);
}
debug_assert_eq!(self.buf.pos(), 0);
}
Ok(&self.buf.buffer()[..n])
}
}
impl<R: ?Sized> BufReader<R> {
/// Gets a reference to the underlying reader.
///
/// It is inadvisable to directly read from the underlying reader.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f1 = File::open("log.txt")?;
/// let reader = BufReader::new(f1);
///
/// let f2 = reader.get_ref();
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &R {
&self.inner
}
/// Gets a mutable reference to the underlying reader.
///
/// It is inadvisable to directly read from the underlying reader.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f1 = File::open("log.txt")?;
/// let mut reader = BufReader::new(f1);
///
/// let f2 = reader.get_mut();
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_mut(&mut self) -> &mut R {
&mut self.inner
}
/// Returns a reference to the internally buffered data.
///
/// Unlike [`fill_buf`], this will not attempt to fill the buffer if it is empty.
///
/// [`fill_buf`]: BufRead::fill_buf
///
/// # Examples
///
/// ```no_run
/// use std::io::{BufReader, BufRead};
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f = File::open("log.txt")?;
/// let mut reader = BufReader::new(f);
/// assert!(reader.buffer().is_empty());
///
/// if reader.fill_buf()?.len() > 0 {
/// assert!(!reader.buffer().is_empty());
/// }
/// Ok(())
/// }
/// ```
#[stable(feature = "bufreader_buffer", since = "1.37.0")]
pub fn buffer(&self) -> &[u8] {
self.buf.buffer()
}
/// Returns the number of bytes the internal buffer can hold at once.
///
/// # Examples
///
/// ```no_run
/// use std::io::{BufReader, BufRead};
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f = File::open("log.txt")?;
/// let mut reader = BufReader::new(f);
///
/// let capacity = reader.capacity();
/// let buffer = reader.fill_buf()?;
/// assert!(buffer.len() <= capacity);
/// Ok(())
/// }
/// ```
#[stable(feature = "buffered_io_capacity", since = "1.46.0")]
pub fn capacity(&self) -> usize {
self.buf.capacity()
}
/// Unwraps this `BufReader<R>`, returning the underlying reader.
///
/// Note that any leftover data in the internal buffer is lost. Therefore,
/// a following read from the underlying reader may lead to data loss.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufReader;
/// use std::fs::File;
///
/// fn main() -> std::io::Result<()> {
/// let f1 = File::open("log.txt")?;
/// let reader = BufReader::new(f1);
///
/// let f2 = reader.into_inner();
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(self) -> R
where
R: Sized,
{
self.inner
}
/// Invalidates all data in the internal buffer.
#[inline]
pub(in crate::io) fn discard_buffer(&mut self) {
self.buf.discard_buffer()
}
}
// This is only used by a test which asserts that the initialization-tracking is correct.
#[cfg(test)]
impl<R: ?Sized> BufReader<R> {
#[allow(missing_docs)]
pub fn initialized(&self) -> usize {
self.buf.initialized()
}
}
impl<R: ?Sized + 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.
/// This method does not return the location of the underlying reader, so the caller
/// must track this information themselves if it is required.
#[stable(feature = "bufreader_seek_relative", since = "1.53.0")]
pub fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
let pos = self.buf.pos() as u64;
if offset < 0 {
if let Some(_) = pos.checked_sub((-offset) as u64) {
self.buf.unconsume((-offset) as usize);
return Ok(());
}
} else if let Some(new_pos) = pos.checked_add(offset as u64) {
if new_pos <= self.buf.filled() as u64 {
self.buf.consume(offset as usize);
return Ok(());
}
}
self.seek(SeekFrom::Current(offset)).map(drop)
}
}
impl<R> SpecReadByte for BufReader<R>
where
Self: Read,
{
#[inline]
fn spec_read_byte(&mut self) -> Option<io::Result<u8>> {
let mut byte = 0;
if self.buf.consume_with(1, |claimed| byte = claimed[0]) {
return Some(Ok(byte));
}
// Fallback case, only reached once per buffer refill.
uninlined_slow_read_byte(self)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<R: ?Sized + Read> Read for BufReader<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
// 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.len() >= self.capacity() {
self.discard_buffer();
return self.inner.read(buf);
}
let mut rem = self.fill_buf()?;
let nread = rem.read(buf)?;
self.consume(nread);
Ok(nread)
}
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() && cursor.capacity() >= self.capacity() {
self.discard_buffer();
return self.inner.read_buf(cursor);
}
let prev = cursor.written();
let mut rem = self.fill_buf()?;
rem.read_buf(cursor.reborrow())?; // actually never fails
self.consume(cursor.written() - prev); //slice impl of read_buf known to never unfill buf
Ok(())
}
// Small read_exacts from a BufReader are extremely common when used with a deserializer.
// The default implementation calls read in a loop, which results in surprisingly poor code
// generation for the common path where the buffer has enough bytes to fill the passed-in
// buffer.
fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
if self.buf.consume_with(buf.len(), |claimed| buf.copy_from_slice(claimed)) {
return Ok(());
}
crate::io::default_read_exact(self, buf)
}
fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
if self.buf.consume_with(cursor.capacity(), |claimed| cursor.append(claimed)) {
return Ok(());
}
crate::io::default_read_buf_exact(self, cursor)
}
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
let total_len = bufs.iter().map(|b| b.len()).sum::<usize>();
if self.buf.pos() == self.buf.filled() && total_len >= self.capacity() {
self.discard_buffer();
return self.inner.read_vectored(bufs);
}
let mut rem = self.fill_buf()?;
let nread = rem.read_vectored(bufs)?;
self.consume(nread);
Ok(nread)
}
fn is_read_vectored(&self) -> bool {
self.inner.is_read_vectored()
}
// The inner reader might have an optimized `read_to_end`. Drain our buffer and then
// delegate to the inner implementation.
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
let inner_buf = self.buffer();
buf.try_reserve(inner_buf.len())?;
buf.extend_from_slice(inner_buf);
let nread = inner_buf.len();
self.discard_buffer();
Ok(nread + self.inner.read_to_end(buf)?)
}
// The inner reader might have an optimized `read_to_end`. Drain our buffer and then
// delegate to the inner implementation.
fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
// In the general `else` case below we must read bytes into a side buffer, check
// that they are valid UTF-8, and then append them to `buf`. This requires a
// potentially large memcpy.
//
// If `buf` is empty--the most common case--we can leverage `append_to_string`
// to read directly into `buf`'s internal byte buffer, saving an allocation and
// a memcpy.
if buf.is_empty() {
// `append_to_string`'s safety relies on the buffer only being appended to since
// it only checks the UTF-8 validity of new data. If there were existing content in
// `buf` then an untrustworthy reader (i.e. `self.inner`) could not only append
// bytes but also modify existing bytes and render them invalid. On the other hand,
// if `buf` is empty then by definition any writes must be appends and
// `append_to_string` will validate all of the new bytes.
unsafe { crate::io::append_to_string(buf, |b| self.read_to_end(b)) }
} else {
// We cannot append our byte buffer directly onto the `buf` String as there could
// be an incomplete UTF-8 sequence that has only been partially read. We must read
// everything into a side buffer first and then call `from_utf8` on the complete
// buffer.
let mut bytes = Vec::new();
self.read_to_end(&mut bytes)?;
let string = crate::str::from_utf8(&bytes).map_err(|_| io::Error::INVALID_UTF8)?;
*buf += string;
Ok(string.len())
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<R: ?Sized + Read> BufRead for BufReader<R> {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
self.buf.fill_buf(&mut self.inner)
}
fn consume(&mut self, amt: usize) {
self.buf.consume(amt)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<R> fmt::Debug for BufReader<R>
where
R: ?Sized + fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("BufReader")
.field("reader", &&self.inner)
.field(
"buffer",
&format_args!("{}/{}", self.buf.filled() - self.buf.pos(), self.capacity()),
)
.finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<R: ?Sized + Seek> Seek for BufReader<R> {
/// Seek to an offset, in bytes, in the underlying reader.
///
/// The position used for seeking with <code>[SeekFrom::Current]\(_)</code> is the
/// position the underlying reader would be at if the `BufReader<R>` had no
/// internal buffer.
///
/// Seeking always discards the internal buffer, even if the seek position
/// would otherwise fall within it. This guarantees that calling
/// [`BufReader::into_inner()`] immediately after a seek yields the underlying reader
/// at the same position.
///
/// To seek without discarding the internal buffer, use [`BufReader::seek_relative`].
///
/// See [`std::io::Seek`] for more details.
///
/// Note: In the edge case where you're seeking with <code>[SeekFrom::Current]\(n)</code>
/// where `n` minus the internal buffer length overflows an `i64`, two
/// seeks will be performed instead of one. If the second seek returns
/// [`Err`], the underlying reader will be left at the same position it would
/// have if you called `seek` with <code>[SeekFrom::Current]\(0)</code>.
///
/// [`std::io::Seek`]: Seek
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
let result: u64;
if let SeekFrom::Current(n) = pos {
let remainder = (self.buf.filled() - self.buf.pos()) as i64;
// it should be safe to assume that remainder fits within an i64 as the alternative
// means we managed to allocate 8 exbibytes and that's absurd.
// But it's not out of the realm of possibility for some weird underlying reader to
// support seeking by i64::MIN so we need to handle underflow when subtracting
// remainder.
if let Some(offset) = n.checked_sub(remainder) {
result = self.inner.seek(SeekFrom::Current(offset))?;
} else {
// seek backwards by our remainder, and then by the offset
self.inner.seek(SeekFrom::Current(-remainder))?;
self.discard_buffer();
result = self.inner.seek(SeekFrom::Current(n))?;
}
} else {
// Seeking with Start/End doesn't care about our buffer length.
result = self.inner.seek(pos)?;
}
self.discard_buffer();
Ok(result)
}
/// Returns the current seek position from the start of the stream.
///
/// The value returned is equivalent to `self.seek(SeekFrom::Current(0))`
/// but does not flush the internal buffer. Due to this optimization the
/// function does not guarantee that calling `.into_inner()` immediately
/// afterwards will yield the underlying reader at the same position. Use
/// [`BufReader::seek`] instead if you require that guarantee.
///
/// # Panics
///
/// This function will panic if the position of the inner reader is smaller
/// than the amount of buffered data. That can happen if the inner reader
/// has an incorrect implementation of [`Seek::stream_position`], or if the
/// position has gone out of sync due to calling [`Seek::seek`] directly on
/// the underlying reader.
///
/// # Example
///
/// ```no_run
/// use std::{
/// io::{self, BufRead, BufReader, Seek},
/// fs::File,
/// };
///
/// fn main() -> io::Result<()> {
/// let mut f = BufReader::new(File::open("foo.txt")?);
///
/// let before = f.stream_position()?;
/// f.read_line(&mut String::new())?;
/// let after = f.stream_position()?;
///
/// println!("The first line was {} bytes long", after - before);
/// Ok(())
/// }
/// ```
fn stream_position(&mut self) -> io::Result<u64> {
let remainder = (self.buf.filled() - self.buf.pos()) as u64;
self.inner.stream_position().map(|pos| {
pos.checked_sub(remainder).expect(
"overflow when subtracting remaining buffer size from inner stream position",
)
})
}
/// 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. This method does not return
/// the location of the underlying reader, so the caller must track this
/// information themselves if it is required.
fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
self.seek_relative(offset)
}
}
impl<T: ?Sized> SizeHint for BufReader<T> {
#[inline]
fn lower_bound(&self) -> usize {
SizeHint::lower_bound(self.get_ref()) + self.buffer().len()
}
#[inline]
fn upper_bound(&self) -> Option<usize> {
SizeHint::upper_bound(self.get_ref()).and_then(|up| self.buffer().len().checked_add(up))
}
}

155
crates/std/src/io/buffered/bufreader/buffer.rs Normal file
View File

@@ -0,0 +1,155 @@
//! An encapsulation of `BufReader`'s buffer management logic.
//!
//! This module factors out the basic functionality of `BufReader` in order to protect two core
//! invariants:
//! * `filled` bytes of `buf` are always initialized
//! * `pos` is always <= `filled`
//! Since this module encapsulates the buffer management logic, we can ensure that the range
//! `pos..filled` is always a valid index into the initialized region of the buffer. This means
//! 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, BorrowedBuf, ErrorKind, Read};
use crate::mem::MaybeUninit;
pub struct Buffer {
// The buffer.
buf: Box<[MaybeUninit<u8>]>,
// The current seek offset into `buf`, must always be <= `filled`.
pos: usize,
// 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, initialized: 0 }
}
#[inline]
pub fn try_with_capacity(capacity: usize) -> io::Result<Self> {
match Box::try_new_uninit_slice(capacity) {
Ok(buf) => Ok(Self { buf, pos: 0, filled: 0, initialized: 0 }),
Err(_) => {
Err(io::const_error!(ErrorKind::OutOfMemory, "failed to allocate read buffer"))
}
}
}
#[inline]
pub fn buffer(&self) -> &[u8] {
// SAFETY: self.pos and self.filled are valid, and self.filled >= self.pos, and
// that region is initialized because those are all invariants of this type.
unsafe { self.buf.get_unchecked(self.pos..self.filled).assume_init_ref() }
}
#[inline]
pub fn capacity(&self) -> usize {
self.buf.len()
}
#[inline]
pub fn filled(&self) -> usize {
self.filled
}
#[inline]
pub fn pos(&self) -> usize {
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;
self.filled = 0;
}
#[inline]
pub fn consume(&mut self, amt: usize) {
self.pos = cmp::min(self.pos + amt, self.filled);
}
/// If there are `amt` bytes available in the buffer, pass a slice containing those bytes to
/// `visitor` and return true. If there are not enough bytes available, return false.
#[inline]
pub fn consume_with<V>(&mut self, amt: usize, mut visitor: V) -> bool
where
V: FnMut(&[u8]),
{
if let Some(claimed) = self.buffer().get(..amt) {
visitor(claimed);
// If the indexing into self.buffer() succeeds, amt must be a valid increment.
self.pos += amt;
true
} else {
false
}
}
#[inline]
pub fn unconsume(&mut self, amt: usize) {
self.pos = self.pos.saturating_sub(amt);
}
/// 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.filled..]);
let old_init = self.initialized - self.filled;
unsafe {
buf.set_init(old_init);
}
reader.read_buf(buf.unfilled())?;
self.filled += buf.len();
self.initialized += buf.init_len() - old_init;
Ok(buf.len())
}
/// Remove bytes that have already been read from the buffer.
pub fn backshift(&mut self) {
self.buf.copy_within(self.pos..self.filled, 0);
self.filled -= self.pos;
self.pos = 0;
}
#[inline]
pub fn fill_buf(&mut self, mut reader: impl Read) -> io::Result<&[u8]> {
// If we've reached the end of our internal buffer then we need to fetch
// some more data from the reader.
// Branch using `>=` instead of the more correct `==`
// to tell the compiler that the pos..cap slice is always valid.
if self.pos >= self.filled {
debug_assert!(self.pos == self.filled);
let mut buf = BorrowedBuf::from(&mut *self.buf);
// SAFETY: `self.filled` bytes will always have been initialized.
unsafe {
buf.set_init(self.initialized);
}
let result = reader.read_buf(buf.unfilled());
self.pos = 0;
self.filled = buf.len();
self.initialized = buf.init_len();
result?;
}
Ok(self.buffer())
}
}

680
crates/std/src/io/buffered/bufwriter.rs Normal file
View File

@@ -0,0 +1,680 @@
use crate::io::{
self, DEFAULT_BUF_SIZE, ErrorKind, IntoInnerError, IoSlice, Seek, SeekFrom, Write,
};
use crate::mem::{self, ManuallyDrop};
use crate::{error, fmt, ptr};
/// Wraps a writer and buffers its output.
///
/// It can be excessively inefficient to work directly with something that
/// implements [`Write`]. For example, every call to
/// [`write`][`TcpStream::write`] on [`TcpStream`] results in a system call. A
/// `BufWriter<W>` keeps an in-memory buffer of data and writes it to an underlying
/// writer in large, infrequent batches.
///
/// `BufWriter<W>` can improve the speed of programs that make *small* and
/// *repeated* write calls to the same file or network socket. It does not
/// help when writing very large amounts at once, or writing just one or a few
/// times. It also provides no advantage when writing to a destination that is
/// in memory, like a <code>[Vec]\<u8></code>.
///
/// It is critical to call [`flush`] before `BufWriter<W>` is dropped. Though
/// dropping will attempt to flush the contents of the buffer, any errors
/// that happen in the process of dropping will be ignored. Calling [`flush`]
/// ensures that the buffer is empty and thus dropping will not even attempt
/// file operations.
///
/// # Examples
///
/// Let's write the numbers one through ten to a [`TcpStream`]:
///
/// ```no_run
/// use std::io::prelude::*;
/// use std::net::TcpStream;
///
/// let mut stream = TcpStream::connect("127.0.0.1:34254").unwrap();
///
/// for i in 0..10 {
/// stream.write(&[i+1]).unwrap();
/// }
/// ```
///
/// Because we're not buffering, we write each one in turn, incurring the
/// overhead of a system call per byte written. We can fix this with a
/// `BufWriter<W>`:
///
/// ```no_run
/// use std::io::prelude::*;
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// for i in 0..10 {
/// stream.write(&[i+1]).unwrap();
/// }
/// stream.flush().unwrap();
/// ```
///
/// By wrapping the stream with a `BufWriter<W>`, these ten writes are all grouped
/// together by the buffer and will all be written out in one system call when
/// the `stream` is flushed.
///
/// [`TcpStream::write`]: crate::net::TcpStream::write
/// [`TcpStream`]: crate::net::TcpStream
/// [`flush`]: BufWriter::flush
#[stable(feature = "rust1", since = "1.0.0")]
pub struct BufWriter<W: ?Sized + Write> {
// The buffer. Avoid using this like a normal `Vec` in common code paths.
// That is, don't use `buf.push`, `buf.extend_from_slice`, or any other
// methods that require bounds checking or the like. This makes an enormous
// difference to performance (we may want to stop using a `Vec` entirely).
buf: Vec<u8>,
// #30888: If the inner writer panics in a call to write, we don't want to
// write the buffered data a second time in BufWriter's destructor. This
// flag tells the Drop impl if it should skip the flush.
panicked: bool,
inner: W,
}
impl<W: Write> BufWriter<W> {
/// Creates a new `BufWriter<W>` with a default buffer capacity. The default is currently 8 KiB,
/// but may change in the future.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(inner: W) -> BufWriter<W> {
BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
}
pub(crate) fn try_new_buffer() -> io::Result<Vec<u8>> {
Vec::try_with_capacity(DEFAULT_BUF_SIZE).map_err(|_| {
io::const_error!(ErrorKind::OutOfMemory, "failed to allocate write buffer")
})
}
pub(crate) fn with_buffer(inner: W, buf: Vec<u8>) -> Self {
Self { inner, buf, panicked: false }
}
/// Creates a new `BufWriter<W>` with at least the specified buffer capacity.
///
/// # Examples
///
/// Creating a buffer with a buffer of at least a hundred bytes.
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let stream = TcpStream::connect("127.0.0.1:34254").unwrap();
/// let mut buffer = BufWriter::with_capacity(100, stream);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W> {
BufWriter { inner, buf: Vec::with_capacity(capacity), panicked: false }
}
/// Unwraps this `BufWriter<W>`, returning the underlying writer.
///
/// The buffer is written out before returning the writer.
///
/// # Errors
///
/// An [`Err`] will be returned if an error occurs while flushing the buffer.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // unwrap the TcpStream and flush the buffer
/// let stream = buffer.into_inner().unwrap();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
match self.flush_buf() {
Err(e) => Err(IntoInnerError::new(self, e)),
Ok(()) => Ok(self.into_parts().0),
}
}
/// Disassembles this `BufWriter<W>`, returning the underlying writer, and any buffered but
/// unwritten data.
///
/// If the underlying writer panicked, it is not known what portion of the data was written.
/// In this case, we return `WriterPanicked` for the buffered data (from which the buffer
/// contents can still be recovered).
///
/// `into_parts` makes no attempt to flush data and cannot fail.
///
/// # Examples
///
/// ```
/// use std::io::{BufWriter, Write};
///
/// let mut buffer = [0u8; 10];
/// let mut stream = BufWriter::new(buffer.as_mut());
/// write!(stream, "too much data").unwrap();
/// stream.flush().expect_err("it doesn't fit");
/// let (recovered_writer, buffered_data) = stream.into_parts();
/// assert_eq!(recovered_writer.len(), 0);
/// assert_eq!(&buffered_data.unwrap(), b"ata");
/// ```
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
pub fn into_parts(self) -> (W, Result<Vec<u8>, WriterPanicked>) {
let mut this = ManuallyDrop::new(self);
let buf = mem::take(&mut this.buf);
let buf = if !this.panicked { Ok(buf) } else { Err(WriterPanicked { buf }) };
// SAFETY: double-drops are prevented by putting `this` in a ManuallyDrop that is never dropped
let inner = unsafe { ptr::read(&this.inner) };
(inner, buf)
}
}
impl<W: ?Sized + Write> BufWriter<W> {
/// Send data in our local buffer into the inner writer, looping as
/// necessary until either it's all been sent or an error occurs.
///
/// Because all the data in the buffer has been reported to our owner as
/// "successfully written" (by returning nonzero success values from
/// `write`), any 0-length writes from `inner` must be reported as i/o
/// errors from this method.
pub(in crate::io) fn flush_buf(&mut self) -> io::Result<()> {
/// Helper struct to ensure the buffer is updated after all the writes
/// are complete. It tracks the number of written bytes and drains them
/// all from the front of the buffer when dropped.
struct BufGuard<'a> {
buffer: &'a mut Vec<u8>,
written: usize,
}
impl<'a> BufGuard<'a> {
fn new(buffer: &'a mut Vec<u8>) -> Self {
Self { buffer, written: 0 }
}
/// The unwritten part of the buffer
fn remaining(&self) -> &[u8] {
&self.buffer[self.written..]
}
/// Flag some bytes as removed from the front of the buffer
fn consume(&mut self, amt: usize) {
self.written += amt;
}
/// true if all of the bytes have been written
fn done(&self) -> bool {
self.written >= self.buffer.len()
}
}
impl Drop for BufGuard<'_> {
fn drop(&mut self) {
if self.written > 0 {
self.buffer.drain(..self.written);
}
}
}
let mut guard = BufGuard::new(&mut self.buf);
while !guard.done() {
self.panicked = true;
let r = self.inner.write(guard.remaining());
self.panicked = false;
match r {
Ok(0) => {
return Err(io::const_error!(
ErrorKind::WriteZero,
"failed to write the buffered data",
));
}
Ok(n) => guard.consume(n),
Err(ref e) if e.is_interrupted() => {}
Err(e) => return Err(e),
}
}
Ok(())
}
/// Buffer some data without flushing it, regardless of the size of the
/// data. Writes as much as possible without exceeding capacity. Returns
/// the number of bytes written.
pub(super) fn write_to_buf(&mut self, buf: &[u8]) -> usize {
let available = self.spare_capacity();
let amt_to_buffer = available.min(buf.len());
// SAFETY: `amt_to_buffer` is <= buffer's spare capacity by construction.
unsafe {
self.write_to_buffer_unchecked(&buf[..amt_to_buffer]);
}
amt_to_buffer
}
/// Gets a reference to the underlying writer.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // we can use reference just like buffer
/// let reference = buffer.get_ref();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &W {
&self.inner
}
/// Gets a mutable reference to the underlying writer.
///
/// It is inadvisable to directly write to the underlying writer.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // we can use reference just like buffer
/// let reference = buffer.get_mut();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_mut(&mut self) -> &mut W {
&mut self.inner
}
/// Returns a reference to the internally buffered data.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // See how many bytes are currently buffered
/// let bytes_buffered = buf_writer.buffer().len();
/// ```
#[stable(feature = "bufreader_buffer", since = "1.37.0")]
pub fn buffer(&self) -> &[u8] {
&self.buf
}
/// Returns a mutable reference to the internal buffer.
///
/// This can be used to write data directly into the buffer without triggering writers
/// to the underlying writer.
///
/// That the buffer is a `Vec` is an implementation detail.
/// Callers should not modify the capacity as there currently is no public API to do so
/// and thus any capacity changes would be unexpected by the user.
pub(in crate::io) fn buffer_mut(&mut self) -> &mut Vec<u8> {
&mut self.buf
}
/// Returns the number of bytes the internal buffer can hold without flushing.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // Check the capacity of the inner buffer
/// let capacity = buf_writer.capacity();
/// // Calculate how many bytes can be written without flushing
/// let without_flush = capacity - buf_writer.buffer().len();
/// ```
#[stable(feature = "buffered_io_capacity", since = "1.46.0")]
pub fn capacity(&self) -> usize {
self.buf.capacity()
}
// Ensure this function does not get inlined into `write`, so that it
// remains inlineable and its common path remains as short as possible.
// If this function ends up being called frequently relative to `write`,
// it's likely a sign that the client is using an improperly sized buffer
// or their write patterns are somewhat pathological.
#[cold]
#[inline(never)]
fn write_cold(&mut self, buf: &[u8]) -> io::Result<usize> {
if buf.len() > self.spare_capacity() {
self.flush_buf()?;
}
// Why not len > capacity? To avoid a needless trip through the buffer when the input
// exactly fills it. We'd just need to flush it to the underlying writer anyway.
if buf.len() >= self.buf.capacity() {
self.panicked = true;
let r = self.get_mut().write(buf);
self.panicked = false;
r
} else {
// Write to the buffer. In this case, we write to the buffer even if it fills it
// exactly. Doing otherwise would mean flushing the buffer, then writing this
// input to the inner writer, which in many cases would be a worse strategy.
// SAFETY: There was either enough spare capacity already, or there wasn't and we
// flushed the buffer to ensure that there is. In the latter case, we know that there
// is because flushing ensured that our entire buffer is spare capacity, and we entered
// this block because the input buffer length is less than that capacity. In either
// case, it's safe to write the input buffer to our buffer.
unsafe {
self.write_to_buffer_unchecked(buf);
}
Ok(buf.len())
}
}
// Ensure this function does not get inlined into `write_all`, so that it
// remains inlineable and its common path remains as short as possible.
// If this function ends up being called frequently relative to `write_all`,
// it's likely a sign that the client is using an improperly sized buffer
// or their write patterns are somewhat pathological.
#[cold]
#[inline(never)]
fn write_all_cold(&mut self, buf: &[u8]) -> io::Result<()> {
// Normally, `write_all` just calls `write` in a loop. We can do better
// by calling `self.get_mut().write_all()` directly, which avoids
// round trips through the buffer in the event of a series of partial
// writes in some circumstances.
if buf.len() > self.spare_capacity() {
self.flush_buf()?;
}
// Why not len > capacity? To avoid a needless trip through the buffer when the input
// exactly fills it. We'd just need to flush it to the underlying writer anyway.
if buf.len() >= self.buf.capacity() {
self.panicked = true;
let r = self.get_mut().write_all(buf);
self.panicked = false;
r
} else {
// Write to the buffer. In this case, we write to the buffer even if it fills it
// exactly. Doing otherwise would mean flushing the buffer, then writing this
// input to the inner writer, which in many cases would be a worse strategy.
// SAFETY: There was either enough spare capacity already, or there wasn't and we
// flushed the buffer to ensure that there is. In the latter case, we know that there
// is because flushing ensured that our entire buffer is spare capacity, and we entered
// this block because the input buffer length is less than that capacity. In either
// case, it's safe to write the input buffer to our buffer.
unsafe {
self.write_to_buffer_unchecked(buf);
}
Ok(())
}
}
// SAFETY: Requires `buf.len() <= self.buf.capacity() - self.buf.len()`,
// i.e., that input buffer length is less than or equal to spare capacity.
#[inline]
unsafe fn write_to_buffer_unchecked(&mut self, buf: &[u8]) {
debug_assert!(buf.len() <= self.spare_capacity());
let old_len = self.buf.len();
let buf_len = buf.len();
let src = buf.as_ptr();
unsafe {
let dst = self.buf.as_mut_ptr().add(old_len);
ptr::copy_nonoverlapping(src, dst, buf_len);
self.buf.set_len(old_len + buf_len);
}
}
#[inline]
fn spare_capacity(&self) -> usize {
self.buf.capacity() - self.buf.len()
}
}
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
/// Error returned for the buffered data from `BufWriter::into_parts`, when the underlying
/// writer has previously panicked. Contains the (possibly partly written) buffered data.
///
/// # Example
///
/// ```
/// use std::io::{self, BufWriter, Write};
/// use std::panic::{catch_unwind, AssertUnwindSafe};
///
/// struct PanickingWriter;
/// impl Write for PanickingWriter {
/// fn write(&mut self, buf: &[u8]) -> io::Result<usize> { panic!() }
/// fn flush(&mut self) -> io::Result<()> { panic!() }
/// }
///
/// let mut stream = BufWriter::new(PanickingWriter);
/// write!(stream, "some data").unwrap();
/// let result = catch_unwind(AssertUnwindSafe(|| {
/// stream.flush().unwrap()
/// }));
/// assert!(result.is_err());
/// let (recovered_writer, buffered_data) = stream.into_parts();
/// assert!(matches!(recovered_writer, PanickingWriter));
/// assert_eq!(buffered_data.unwrap_err().into_inner(), b"some data");
/// ```
pub struct WriterPanicked {
buf: Vec<u8>,
}
impl WriterPanicked {
/// Returns the perhaps-unwritten data. Some of this data may have been written by the
/// panicking call(s) to the underlying writer, so simply writing it again is not a good idea.
#[must_use = "`self` will be dropped if the result is not used"]
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
pub fn into_inner(self) -> Vec<u8> {
self.buf
}
}
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
impl error::Error for WriterPanicked {}
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
impl fmt::Display for WriterPanicked {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
"BufWriter inner writer panicked, what data remains unwritten is not known".fmt(f)
}
}
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
impl fmt::Debug for WriterPanicked {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("WriterPanicked")
.field("buffer", &format_args!("{}/{}", self.buf.len(), self.buf.capacity()))
.finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write> Write for BufWriter<W> {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
// Use < instead of <= to avoid a needless trip through the buffer in some cases.
// See `write_cold` for details.
if buf.len() < self.spare_capacity() {
// SAFETY: safe by above conditional.
unsafe {
self.write_to_buffer_unchecked(buf);
}
Ok(buf.len())
} else {
self.write_cold(buf)
}
}
#[inline]
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
// Use < instead of <= to avoid a needless trip through the buffer in some cases.
// See `write_all_cold` for details.
if buf.len() < self.spare_capacity() {
// SAFETY: safe by above conditional.
unsafe {
self.write_to_buffer_unchecked(buf);
}
Ok(())
} else {
self.write_all_cold(buf)
}
}
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
// FIXME: Consider applying `#[inline]` / `#[inline(never)]` optimizations already applied
// to `write` and `write_all`. The performance benefits can be significant. See #79930.
if self.get_ref().is_write_vectored() {
// We have to handle the possibility that the total length of the buffers overflows
// `usize` (even though this can only happen if multiple `IoSlice`s reference the
// same underlying buffer, as otherwise the buffers wouldn't fit in memory). If the
// computation overflows, then surely the input cannot fit in our buffer, so we forward
// to the inner writer's `write_vectored` method to let it handle it appropriately.
let mut saturated_total_len: usize = 0;
for buf in bufs {
saturated_total_len = saturated_total_len.saturating_add(buf.len());
if saturated_total_len > self.spare_capacity() && !self.buf.is_empty() {
// Flush if the total length of the input exceeds our buffer's spare capacity.
// If we would have overflowed, this condition also holds, and we need to flush.
self.flush_buf()?;
}
if saturated_total_len >= self.buf.capacity() {
// Forward to our inner writer if the total length of the input is greater than or
// equal to our buffer capacity. If we would have overflowed, this condition also
// holds, and we punt to the inner writer.
self.panicked = true;
let r = self.get_mut().write_vectored(bufs);
self.panicked = false;
return r;
}
}
// `saturated_total_len < self.buf.capacity()` implies that we did not saturate.
// SAFETY: We checked whether or not the spare capacity was large enough above. If
// it was, then we're safe already. If it wasn't, we flushed, making sufficient
// room for any input <= the buffer size, which includes this input.
unsafe {
bufs.iter().for_each(|b| self.write_to_buffer_unchecked(b));
};
Ok(saturated_total_len)
} else {
let mut iter = bufs.iter();
let mut total_written = if let Some(buf) = iter.by_ref().find(|&buf| !buf.is_empty()) {
// This is the first non-empty slice to write, so if it does
// not fit in the buffer, we still get to flush and proceed.
if buf.len() > self.spare_capacity() {
self.flush_buf()?;
}
if buf.len() >= self.buf.capacity() {
// The slice is at least as large as the buffering capacity,
// so it's better to write it directly, bypassing the buffer.
self.panicked = true;
let r = self.get_mut().write(buf);
self.panicked = false;
return r;
} else {
// SAFETY: We checked whether or not the spare capacity was large enough above.
// If it was, then we're safe already. If it wasn't, we flushed, making
// sufficient room for any input <= the buffer size, which includes this input.
unsafe {
self.write_to_buffer_unchecked(buf);
}
buf.len()
}
} else {
return Ok(0);
};
debug_assert!(total_written != 0);
for buf in iter {
if buf.len() <= self.spare_capacity() {
// SAFETY: safe by above conditional.
unsafe {
self.write_to_buffer_unchecked(buf);
}
// This cannot overflow `usize`. If we are here, we've written all of the bytes
// so far to our buffer, and we've ensured that we never exceed the buffer's
// capacity. Therefore, `total_written` <= `self.buf.capacity()` <= `usize::MAX`.
total_written += buf.len();
} else {
break;
}
}
Ok(total_written)
}
}
fn is_write_vectored(&self) -> bool {
true
}
fn flush(&mut self) -> io::Result<()> {
self.flush_buf().and_then(|()| self.get_mut().flush())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write> fmt::Debug for BufWriter<W>
where
W: fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("BufWriter")
.field("writer", &&self.inner)
.field("buffer", &format_args!("{}/{}", self.buf.len(), self.buf.capacity()))
.finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write + Seek> Seek for BufWriter<W> {
/// Seek to the offset, in bytes, in the underlying writer.
///
/// Seeking always writes out the internal buffer before seeking.
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
self.flush_buf()?;
self.get_mut().seek(pos)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write> Drop for BufWriter<W> {
fn drop(&mut self) {
if !self.panicked {
// dtors should not panic, so we ignore a failed flush
let _r = self.flush_buf();
}
}
}

235
crates/std/src/io/buffered/linewriter.rs Normal file
View File

@@ -0,0 +1,235 @@
use crate::fmt;
use crate::io::buffered::LineWriterShim;
use crate::io::{self, BufWriter, IntoInnerError, IoSlice, Write};
/// Wraps a writer and buffers output to it, flushing whenever a newline
/// (`0x0a`, `'\n'`) is detected.
///
/// The [`BufWriter`] struct wraps a writer and buffers its output.
/// But it only does this batched write when it goes out of scope, or when the
/// internal buffer is full. Sometimes, you'd prefer to write each line as it's
/// completed, rather than the entire buffer at once. Enter `LineWriter`. It
/// does exactly that.
///
/// Like [`BufWriter`], a `LineWriter`’s buffer will also be flushed when the
/// `LineWriter` goes out of scope or when its internal buffer is full.
///
/// If there's still a partial line in the buffer when the `LineWriter` is
/// dropped, it will flush those contents.
///
/// # Examples
///
/// We can use `LineWriter` to write one line at a time, significantly
/// reducing the number of actual writes to the file.
///
/// ```no_run
/// use std::fs::{self, File};
/// use std::io::prelude::*;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let road_not_taken = b"I shall be telling this with a sigh
/// Somewhere ages and ages hence:
/// Two roads diverged in a wood, and I -
/// I took the one less traveled by,
/// And that has made all the difference.";
///
/// let file = File::create("poem.txt")?;
/// let mut file = LineWriter::new(file);
///
/// file.write_all(b"I shall be telling this with a sigh")?;
///
/// // No bytes are written until a newline is encountered (or
/// // the internal buffer is filled).
/// assert_eq!(fs::read_to_string("poem.txt")?, "");
/// file.write_all(b"\n")?;
/// assert_eq!(
/// fs::read_to_string("poem.txt")?,
/// "I shall be telling this with a sigh\n",
/// );
///
/// // Write the rest of the poem.
/// file.write_all(b"Somewhere ages and ages hence:
/// Two roads diverged in a wood, and I -
/// I took the one less traveled by,
/// And that has made all the difference.")?;
///
/// // The last line of the poem doesn't end in a newline, so
/// // we have to flush or drop the `LineWriter` to finish
/// // writing.
/// file.flush()?;
///
/// // Confirm the whole poem was written.
/// assert_eq!(fs::read("poem.txt")?, &road_not_taken[..]);
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct LineWriter<W: ?Sized + Write> {
inner: BufWriter<W>,
}
impl<W: Write> LineWriter<W> {
/// Creates a new `LineWriter`.
///
/// # Examples
///
/// ```no_run
/// use std::fs::File;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let file = File::create("poem.txt")?;
/// let file = LineWriter::new(file);
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(inner: W) -> LineWriter<W> {
// Lines typically aren't that long, don't use a giant buffer
LineWriter::with_capacity(1024, inner)
}
/// Creates a new `LineWriter` with at least the specified capacity for the
/// internal buffer.
///
/// # Examples
///
/// ```no_run
/// use std::fs::File;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let file = File::create("poem.txt")?;
/// let file = LineWriter::with_capacity(100, file);
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W> {
LineWriter { inner: BufWriter::with_capacity(capacity, inner) }
}
/// Gets a mutable reference to the underlying writer.
///
/// Caution must be taken when calling methods on the mutable reference
/// returned as extra writes could corrupt the output stream.
///
/// # Examples
///
/// ```no_run
/// use std::fs::File;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let file = File::create("poem.txt")?;
/// let mut file = LineWriter::new(file);
///
/// // we can use reference just like file
/// let reference = file.get_mut();
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_mut(&mut self) -> &mut W {
self.inner.get_mut()
}
/// Unwraps this `LineWriter`, returning the underlying writer.
///
/// The internal buffer is written out before returning the writer.
///
/// # Errors
///
/// An [`Err`] will be returned if an error occurs while flushing the buffer.
///
/// # Examples
///
/// ```no_run
/// use std::fs::File;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let file = File::create("poem.txt")?;
///
/// let writer: LineWriter<File> = LineWriter::new(file);
///
/// let file: File = writer.into_inner()?;
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>> {
self.inner.into_inner().map_err(|err| err.new_wrapped(|inner| LineWriter { inner }))
}
}
impl<W: ?Sized + Write> LineWriter<W> {
/// Gets a reference to the underlying writer.
///
/// # Examples
///
/// ```no_run
/// use std::fs::File;
/// use std::io::LineWriter;
///
/// fn main() -> std::io::Result<()> {
/// let file = File::create("poem.txt")?;
/// let file = LineWriter::new(file);
///
/// let reference = file.get_ref();
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &W {
self.inner.get_ref()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write> Write for LineWriter<W> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
LineWriterShim::new(&mut self.inner).write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.inner.flush()
}
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
LineWriterShim::new(&mut self.inner).write_vectored(bufs)
}
fn is_write_vectored(&self) -> bool {
self.inner.is_write_vectored()
}
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
LineWriterShim::new(&mut self.inner).write_all(buf)
}
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
LineWriterShim::new(&mut self.inner).write_all_vectored(bufs)
}
fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> io::Result<()> {
LineWriterShim::new(&mut self.inner).write_fmt(fmt)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: ?Sized + Write> fmt::Debug for LineWriter<W>
where
W: fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("LineWriter")
.field("writer", &self.get_ref())
.field(
"buffer",
&format_args!("{}/{}", self.inner.buffer().len(), self.inner.capacity()),
)
.finish_non_exhaustive()
}
}

297
crates/std/src/io/buffered/linewritershim.rs Normal file
View File

@@ -0,0 +1,297 @@
use core::slice::memchr;
use crate::io::{self, BufWriter, IoSlice, Write};
/// Private helper struct for implementing the line-buffered writing logic.
///
/// This shim temporarily wraps a BufWriter, and uses its internals to
/// implement a line-buffered writer (specifically by using the internal
/// methods like write_to_buf and flush_buf). In this way, a more
/// efficient abstraction can be created than one that only had access to
/// `write` and `flush`, without needlessly duplicating a lot of the
/// implementation details of BufWriter. This also allows existing
/// `BufWriters` to be temporarily given line-buffering logic; this is what
/// enables Stdout to be alternately in line-buffered or block-buffered mode.
#[derive(Debug)]
pub struct LineWriterShim<'a, W: ?Sized + Write> {
buffer: &'a mut BufWriter<W>,
}
impl<'a, W: ?Sized + Write> LineWriterShim<'a, W> {
pub fn new(buffer: &'a mut BufWriter<W>) -> Self {
Self { buffer }
}
/// Gets a reference to the inner writer (that is, the writer
/// wrapped by the BufWriter).
fn inner(&self) -> &W {
self.buffer.get_ref()
}
/// Gets a mutable reference to the inner writer (that is, the writer
/// wrapped by the BufWriter). Be careful with this writer, as writes to
/// it will bypass the buffer.
fn inner_mut(&mut self) -> &mut W {
self.buffer.get_mut()
}
/// Gets the content currently buffered in self.buffer
fn buffered(&self) -> &[u8] {
self.buffer.buffer()
}
/// Flushes the buffer iff the last byte is a newline (indicating that an
/// earlier write only succeeded partially, and we want to retry flushing
/// the buffered line before continuing with a subsequent write).
fn flush_if_completed_line(&mut self) -> io::Result<()> {
match self.buffered().last().copied() {
Some(b'\n') => self.buffer.flush_buf(),
_ => Ok(()),
}
}
}
impl<'a, W: ?Sized + Write> Write for LineWriterShim<'a, W> {
/// Writes some data into this BufWriter with line buffering.
///
/// This means that, if any newlines are present in the data, the data up to
/// the last newline is sent directly to the underlying writer, and data
/// after it is buffered. Returns the number of bytes written.
///
/// This function operates on a "best effort basis"; in keeping with the
/// convention of `Write::write`, it makes at most one attempt to write
/// new data to the underlying writer. If that write only reports a partial
/// success, the remaining data will be buffered.
///
/// Because this function attempts to send completed lines to the underlying
/// writer, it will also flush the existing buffer if it ends with a
/// newline, even if the incoming data does not contain any newlines.
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let newline_idx = match memchr::memrchr(b'\n', buf) {
// If there are no new newlines (that is, if this write is less than
// one line), just do a regular buffered write (which may flush if
// we exceed the inner buffer's size)
None => {
self.flush_if_completed_line()?;
return self.buffer.write(buf);
}
// Otherwise, arrange for the lines to be written directly to the
// inner writer.
Some(newline_idx) => newline_idx + 1,
};
// Flush existing content to prepare for our write. We have to do this
// before attempting to write `buf` in order to maintain consistency;
// if we add `buf` to the buffer then try to flush it all at once,
// we're obligated to return Ok(), which would mean suppressing any
// errors that occur during flush.
self.buffer.flush_buf()?;
// This is what we're going to try to write directly to the inner
// writer. The rest will be buffered, if nothing goes wrong.
let lines = &buf[..newline_idx];
// Write `lines` directly to the inner writer. In keeping with the
// `write` convention, make at most one attempt to add new (unbuffered)
// data. Because this write doesn't touch the BufWriter state directly,
// and the buffer is known to be empty, we don't need to worry about
// self.buffer.panicked here.
let flushed = self.inner_mut().write(lines)?;
// If buffer returns Ok(0), propagate that to the caller without
// doing additional buffering; otherwise we're just guaranteeing
// an "ErrorKind::WriteZero" later.
if flushed == 0 {
return Ok(0);
}
// Now that the write has succeeded, buffer the rest (or as much of
// the rest as possible). If there were any unwritten newlines, we
// only buffer out to the last unwritten newline that fits in the
// buffer; this helps prevent flushing partial lines on subsequent
// calls to LineWriterShim::write.
// Handle the cases in order of most-common to least-common, under
// the presumption that most writes succeed in totality, and that most
// writes are smaller than the buffer.
// - Is this a partial line (ie, no newlines left in the unwritten tail)
// - If not, does the data out to the last unwritten newline fit in
// the buffer?
// - If not, scan for the last newline that *does* fit in the buffer
let tail = if flushed >= newline_idx {
let tail = &buf[flushed..];
// Avoid unnecessary short writes by not splitting the remaining
// bytes if they're larger than the buffer.
// They can be written in full by the next call to write.
if tail.len() >= self.buffer.capacity() {
return Ok(flushed);
}
tail
} else if newline_idx - flushed <= self.buffer.capacity() {
&buf[flushed..newline_idx]
} else {
let scan_area = &buf[flushed..];
let scan_area = &scan_area[..self.buffer.capacity()];
match memchr::memrchr(b'\n', scan_area) {
Some(newline_idx) => &scan_area[..newline_idx + 1],
None => scan_area,
}
};
let buffered = self.buffer.write_to_buf(tail);
Ok(flushed + buffered)
}
fn flush(&mut self) -> io::Result<()> {
self.buffer.flush()
}
/// Writes some vectored data into this BufWriter with line buffering.
///
/// This means that, if any newlines are present in the data, the data up to
/// and including the buffer containing the last newline is sent directly to
/// the inner writer, and the data after it is buffered. Returns the number
/// of bytes written.
///
/// This function operates on a "best effort basis"; in keeping with the
/// convention of `Write::write`, it makes at most one attempt to write
/// new data to the underlying writer.
///
/// Because this function attempts to send completed lines to the underlying
/// writer, it will also flush the existing buffer if it contains any
/// newlines.
///
/// Because sorting through an array of `IoSlice` can be a bit convoluted,
/// This method differs from write in the following ways:
///
/// - It attempts to write the full content of all the buffers up to and
/// including the one containing the last newline. This means that it
/// may attempt to write a partial line, that buffer has data past the
/// newline.
/// - If the write only reports partial success, it does not attempt to
/// find the precise location of the written bytes and buffer the rest.
///
/// If the underlying vector doesn't support vectored writing, we instead
/// simply write the first non-empty buffer with `write`. This way, we
/// get the benefits of more granular partial-line handling without losing
/// anything in efficiency
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
// If there's no specialized behavior for write_vectored, just use
// write. This has the benefit of more granular partial-line handling.
if !self.is_write_vectored() {
return match bufs.iter().find(|buf| !buf.is_empty()) {
Some(buf) => self.write(buf),
None => Ok(0),
};
}
// Find the buffer containing the last newline
// FIXME: This is overly slow if there are very many bufs and none contain
// newlines. e.g. writev() on Linux only writes up to 1024 slices, so
// scanning the rest is wasted effort. This makes write_all_vectored()
// quadratic.
let last_newline_buf_idx = bufs
.iter()
.enumerate()
.rev()
.find_map(|(i, buf)| memchr::memchr(b'\n', buf).map(|_| i));
// If there are no new newlines (that is, if this write is less than
// one line), just do a regular buffered write
let last_newline_buf_idx = match last_newline_buf_idx {
// No newlines; just do a normal buffered write
None => {
self.flush_if_completed_line()?;
return self.buffer.write_vectored(bufs);
}
Some(i) => i,
};
// Flush existing content to prepare for our write
self.buffer.flush_buf()?;
// This is what we're going to try to write directly to the inner
// writer. The rest will be buffered, if nothing goes wrong.
let (lines, tail) = bufs.split_at(last_newline_buf_idx + 1);
// Write `lines` directly to the inner writer. In keeping with the
// `write` convention, make at most one attempt to add new (unbuffered)
// data. Because this write doesn't touch the BufWriter state directly,
// and the buffer is known to be empty, we don't need to worry about
// self.panicked here.
let flushed = self.inner_mut().write_vectored(lines)?;
// If inner returns Ok(0), propagate that to the caller without
// doing additional buffering; otherwise we're just guaranteeing
// an "ErrorKind::WriteZero" later.
if flushed == 0 {
return Ok(0);
}
// Don't try to reconstruct the exact amount written; just bail
// in the event of a partial write
let mut lines_len: usize = 0;
for buf in lines {
// With overlapping/duplicate slices the total length may in theory
// exceed usize::MAX
lines_len = lines_len.saturating_add(buf.len());
if flushed < lines_len {
return Ok(flushed);
}
}
// Now that the write has succeeded, buffer the rest (or as much of the
// rest as possible)
let buffered: usize = tail
.iter()
.filter(|buf| !buf.is_empty())
.map(|buf| self.buffer.write_to_buf(buf))
.take_while(|&n| n > 0)
.sum();
Ok(flushed + buffered)
}
fn is_write_vectored(&self) -> bool {
self.inner().is_write_vectored()
}
/// Writes some data into this BufWriter with line buffering.
///
/// This means that, if any newlines are present in the data, the data up to
/// the last newline is sent directly to the underlying writer, and data
/// after it is buffered.
///
/// Because this function attempts to send completed lines to the underlying
/// writer, it will also flush the existing buffer if it contains any
/// newlines, even if the incoming data does not contain any newlines.
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
match memchr::memrchr(b'\n', buf) {
// If there are no new newlines (that is, if this write is less than
// one line), just do a regular buffered write (which may flush if
// we exceed the inner buffer's size)
None => {
self.flush_if_completed_line()?;
self.buffer.write_all(buf)
}
Some(newline_idx) => {
let (lines, tail) = buf.split_at(newline_idx + 1);
if self.buffered().is_empty() {
self.inner_mut().write_all(lines)?;
} else {
// If there is any buffered data, we add the incoming lines
// to that buffer before flushing, which saves us at least
// one write call. We can't really do this with `write`,
// since we can't do this *and* not suppress errors *and*
// report a consistent state to the caller in a return
// value, but here in write_all it's fine.
self.buffer.write_all(lines)?;
self.buffer.flush_buf()?;
}
self.buffer.write_all(tail)
}
}
}
}

189
crates/std/src/io/buffered/mod.rs Normal file
View File

@@ -0,0 +1,189 @@
//! Buffering wrappers for I/O traits
mod bufreader;
mod bufwriter;
mod linewriter;
mod linewritershim;
#[cfg(test)]
mod tests;
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
pub use bufwriter::WriterPanicked;
use linewritershim::LineWriterShim;
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::{bufreader::BufReader, bufwriter::BufWriter, linewriter::LineWriter};
use crate::io::Error;
use crate::{error, fmt};
/// An error returned by [`BufWriter::into_inner`] which combines an error that
/// happened while writing out the buffer, and the buffered writer object
/// which may be used to recover from the condition.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // do stuff with the stream
///
/// // we want to get our `TcpStream` back, so let's try:
///
/// let stream = match stream.into_inner() {
/// Ok(s) => s,
/// Err(e) => {
/// // Here, e is an IntoInnerError
/// panic!("An error occurred");
/// }
/// };
/// ```
#[derive(Debug)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IntoInnerError<W>(W, Error);
impl<W> IntoInnerError<W> {
/// Constructs a new IntoInnerError
fn new(writer: W, error: Error) -> Self {
Self(writer, error)
}
/// Helper to construct a new IntoInnerError; intended to help with
/// adapters that wrap other adapters
fn new_wrapped<W2>(self, f: impl FnOnce(W) -> W2) -> IntoInnerError<W2> {
let Self(writer, error) = self;
IntoInnerError::new(f(writer), error)
}
/// Returns the error which caused the call to [`BufWriter::into_inner()`]
/// to fail.
///
/// This error was returned when attempting to write the internal buffer.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // do stuff with the stream
///
/// // we want to get our `TcpStream` back, so let's try:
///
/// let stream = match stream.into_inner() {
/// Ok(s) => s,
/// Err(e) => {
/// // Here, e is an IntoInnerError, let's log the inner error.
/// //
/// // We'll just 'log' to stdout for this example.
/// println!("{}", e.error());
///
/// panic!("An unexpected error occurred.");
/// }
/// };
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn error(&self) -> &Error {
&self.1
}
/// Returns the buffered writer instance which generated the error.
///
/// The returned object can be used for error recovery, such as
/// re-inspecting the buffer.
///
/// # Examples
///
/// ```no_run
/// use std::io::BufWriter;
/// use std::net::TcpStream;
///
/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
///
/// // do stuff with the stream
///
/// // we want to get our `TcpStream` back, so let's try:
///
/// let stream = match stream.into_inner() {
/// Ok(s) => s,
/// Err(e) => {
/// // Here, e is an IntoInnerError, let's re-examine the buffer:
/// let buffer = e.into_inner();
///
/// // do stuff to try to recover
///
/// // afterwards, let's just return the stream
/// buffer.into_inner().unwrap()
/// }
/// };
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(self) -> W {
self.0
}
/// Consumes the [`IntoInnerError`] and returns the error which caused the call to
/// [`BufWriter::into_inner()`] to fail. Unlike `error`, this can be used to
/// obtain ownership of the underlying error.
///
/// # Example
/// ```
/// use std::io::{BufWriter, ErrorKind, Write};
///
/// let mut not_enough_space = [0u8; 10];
/// let mut stream = BufWriter::new(not_enough_space.as_mut());
/// write!(stream, "this cannot be actually written").unwrap();
/// let into_inner_err = stream.into_inner().expect_err("now we discover it's too small");
/// let err = into_inner_err.into_error();
/// assert_eq!(err.kind(), ErrorKind::WriteZero);
/// ```
#[stable(feature = "io_into_inner_error_parts", since = "1.55.0")]
pub fn into_error(self) -> Error {
self.1
}
/// Consumes the [`IntoInnerError`] and returns the error which caused the call to
/// [`BufWriter::into_inner()`] to fail, and the underlying writer.
///
/// This can be used to simply obtain ownership of the underlying error; it can also be used for
/// advanced error recovery.
///
/// # Example
/// ```
/// use std::io::{BufWriter, ErrorKind, Write};
///
/// let mut not_enough_space = [0u8; 10];
/// let mut stream = BufWriter::new(not_enough_space.as_mut());
/// write!(stream, "this cannot be actually written").unwrap();
/// let into_inner_err = stream.into_inner().expect_err("now we discover it's too small");
/// let (err, recovered_writer) = into_inner_err.into_parts();
/// assert_eq!(err.kind(), ErrorKind::WriteZero);
/// assert_eq!(recovered_writer.buffer(), b"t be actually written");
/// ```
#[stable(feature = "io_into_inner_error_parts", since = "1.55.0")]
pub fn into_parts(self) -> (Error, W) {
(self.1, self.0)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W> From<IntoInnerError<W>> for Error {
fn from(iie: IntoInnerError<W>) -> Error {
iie.1
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W> fmt::Display for IntoInnerError<W> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.error().fmt(f)
}
}

297
crates/std/src/io/copy.rs Normal file
View File

@@ -0,0 +1,297 @@
use super::{BorrowedBuf, BufReader, BufWriter, DEFAULT_BUF_SIZE, Read, Result, Write};
use crate::alloc::Allocator;
use crate::cmp;
use alloc_crate::collections::VecDeque;
use crate::io::IoSlice;
use crate::mem::MaybeUninit;
use crate::sys::io::{CopyState, kernel_copy};
#[cfg(test)]
mod tests;
/// Copies the entire contents of a reader into a writer.
///
/// This function will continuously read data from `reader` and then
/// write it into `writer` in a streaming fashion until `reader`
/// returns EOF.
///
/// On success, the total number of bytes that were copied from
/// `reader` to `writer` is returned.
///
/// If you want to copy the contents of one file to another and you’re
/// working with filesystem paths, see the [`fs::copy`] function.
///
/// [`fs::copy`]: crate::fs::copy
///
/// # Errors
///
/// This function will return an error immediately if any call to [`read`] or
/// [`write`] returns an error. All instances of [`ErrorKind::Interrupted`] are
/// handled by this function and the underlying operation is retried.
///
/// [`read`]: Read::read
/// [`write`]: Write::write
/// [`ErrorKind::Interrupted`]: crate::io::ErrorKind::Interrupted
///
/// # Examples
///
/// ```
/// use std::io;
///
/// fn main() -> io::Result<()> {
/// let mut reader: &[u8] = b"hello";
/// let mut writer: Vec<u8> = vec![];
///
/// io::copy(&mut reader, &mut writer)?;
///
/// assert_eq!(&b"hello"[..], &writer[..]);
/// Ok(())
/// }
/// ```
///
/// # Platform-specific behavior
///
/// On Linux (including Android), this function uses `copy_file_range(2)`,
/// `sendfile(2)` or `splice(2)` syscalls to move data directly between file
/// descriptors if possible.
///
/// Note that platform-specific behavior [may change in the future][changes].
///
/// [changes]: crate::io#platform-specific-behavior
#[stable(feature = "rust1", since = "1.0.0")]
pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
where
R: Read,
W: Write,
{
match kernel_copy(reader, writer)? {
CopyState::Ended(copied) => Ok(copied),
CopyState::Fallback(copied) => {
generic_copy(reader, writer).map(|additional| copied + additional)
}
}
}
/// The userspace read-write-loop implementation of `io::copy` that is used when
/// OS-specific specializations for copy offloading are not available or not applicable.
fn generic_copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
where
R: Read,
W: Write,
{
let read_buf = BufferedReaderSpec::buffer_size(reader);
let write_buf = BufferedWriterSpec::buffer_size(writer);
if read_buf >= DEFAULT_BUF_SIZE && read_buf >= write_buf {
return BufferedReaderSpec::copy_to(reader, writer);
}
BufferedWriterSpec::copy_from(writer, reader)
}
/// Specialization of the read-write loop that reuses the internal
/// buffer of a BufReader. If there's no buffer then the writer side
/// should be used instead.
trait BufferedReaderSpec {
fn buffer_size(&self) -> usize;
fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64>;
}
impl<T> BufferedReaderSpec for T
where
Self: Read,
T: ?Sized,
{
#[inline]
default fn buffer_size(&self) -> usize {
0
}
default fn copy_to(&mut self, _to: &mut (impl Write + ?Sized)) -> Result<u64> {
unreachable!("only called from specializations")
}
}
impl BufferedReaderSpec for &[u8] {
fn buffer_size(&self) -> usize {
// prefer this specialization since the source "buffer" is all we'll ever need,
// even if it's small
usize::MAX
}
fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
let len = self.len();
to.write_all(self)?;
*self = &self[len..];
Ok(len as u64)
}
}
impl<A: Allocator> BufferedReaderSpec for VecDeque<u8, A> {
fn buffer_size(&self) -> usize {
// prefer this specialization since the source "buffer" is all we'll ever need,
// even if it's small
usize::MAX
}
fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
let len = self.len();
let (front, back) = self.as_slices();
let bufs = &mut [IoSlice::new(front), IoSlice::new(back)];
to.write_all_vectored(bufs)?;
self.clear();
Ok(len as u64)
}
}
impl<I> BufferedReaderSpec for BufReader<I>
where
Self: Read,
I: ?Sized,
{
fn buffer_size(&self) -> usize {
self.capacity()
}
fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
let mut len = 0;
loop {
// Hack: this relies on `impl Read for BufReader` always calling fill_buf
// if the buffer is empty, even for empty slices.
// It can't be called directly here since specialization prevents us
// from adding I: Read
match self.read(&mut []) {
Ok(_) => {}
Err(e) if e.is_interrupted() => continue,
Err(e) => return Err(e),
}
let buf = self.buffer();
if self.buffer().len() == 0 {
return Ok(len);
}
// In case the writer side is a BufWriter then its write_all
// implements an optimization that passes through large
// buffers to the underlying writer. That code path is #[cold]
// but we're still avoiding redundant memcopies when doing
// a copy between buffered inputs and outputs.
to.write_all(buf)?;
len += buf.len() as u64;
self.discard_buffer();
}
}
}
/// Specialization of the read-write loop that either uses a stack buffer
/// or reuses the internal buffer of a BufWriter
trait BufferedWriterSpec: Write {
fn buffer_size(&self) -> usize;
fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64>;
}
impl<W: Write + ?Sized> BufferedWriterSpec for W {
#[inline]
default fn buffer_size(&self) -> usize {
0
}
default fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
stack_buffer_copy(reader, self)
}
}
impl<I: Write + ?Sized> BufferedWriterSpec for BufWriter<I> {
fn buffer_size(&self) -> usize {
self.capacity()
}
fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
if self.capacity() < DEFAULT_BUF_SIZE {
return stack_buffer_copy(reader, self);
}
let mut len = 0;
let mut init = 0;
loop {
let buf = self.buffer_mut();
let mut read_buf: BorrowedBuf<'_> = buf.spare_capacity_mut().into();
unsafe {
// SAFETY: init is either 0 or the init_len from the previous iteration.
read_buf.set_init(init);
}
if read_buf.capacity() >= DEFAULT_BUF_SIZE {
let mut cursor = read_buf.unfilled();
match reader.read_buf(cursor.reborrow()) {
Ok(()) => {
let bytes_read = cursor.written();
if bytes_read == 0 {
return Ok(len);
}
init = read_buf.init_len() - bytes_read;
len += bytes_read as u64;
// SAFETY: BorrowedBuf guarantees all of its filled bytes are init
unsafe { buf.set_len(buf.len() + bytes_read) };
// Read again if the buffer still has enough capacity, as BufWriter itself would do
// This will occur if the reader returns short reads
}
Err(ref e) if e.is_interrupted() => {}
Err(e) => return Err(e),
}
} else {
// All the bytes that were already in the buffer are initialized,
// treat them as such when the buffer is flushed.
init += buf.len();
self.flush_buf()?;
}
}
}
}
impl BufferedWriterSpec for Vec<u8> {
fn buffer_size(&self) -> usize {
cmp::max(DEFAULT_BUF_SIZE, self.capacity() - self.len())
}
fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
reader.read_to_end(self).map(|bytes| u64::try_from(bytes).expect("usize overflowed u64"))
}
}
fn stack_buffer_copy<R: Read + ?Sized, W: Write + ?Sized>(
reader: &mut R,
writer: &mut W,
) -> Result<u64> {
let buf: &mut [_] = &mut [MaybeUninit::uninit(); DEFAULT_BUF_SIZE];
let mut buf: BorrowedBuf<'_> = buf.into();
let mut len = 0;
loop {
match reader.read_buf(buf.unfilled()) {
Ok(()) => {}
Err(e) if e.is_interrupted() => continue,
Err(e) => return Err(e),
};
if buf.filled().is_empty() {
break;
}
len += buf.filled().len() as u64;
writer.write_all(buf.filled())?;
buf.clear();
}
Ok(len)
}

4
crates/std/src/io/cursor.rs
View File

@@ -1,5 +1,5 @@
// #[cfg(test)]
// mod tests;
#[cfg(test)]
mod tests;
use crate::alloc::Allocator;
use crate::cmp;

567
crates/std/src/io/cursor/tests.rs Normal file
View File

@@ -0,0 +1,567 @@
use crate::io::prelude::*;
use crate::io::{Cursor, IoSlice, IoSliceMut, SeekFrom};
#[test]
fn test_vec_writer() {
let mut writer = Vec::new();
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(
writer
.write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
.unwrap(),
3
);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(writer, b);
}
#[test]
fn test_mem_writer() {
let mut writer = Cursor::new(Vec::new());
writer.set_position(10);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(
writer
.write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
.unwrap(),
3
);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(&writer.get_ref()[..10], &[0; 10]);
assert_eq!(&writer.get_ref()[10..], b);
}
#[test]
fn test_mem_writer_preallocated() {
let mut writer = Cursor::new(vec![0, 0, 0, 0, 0, 0, 0, 0, 8, 9, 10]);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(&writer.get_ref()[..], b);
}
#[test]
fn test_mem_mut_writer() {
let mut vec = Vec::new();
let mut writer = Cursor::new(&mut vec);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(
writer
.write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
.unwrap(),
3
);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(&writer.get_ref()[..], b);
}
fn test_slice_writer<T>(writer: &mut Cursor<T>)
where
T: AsRef<[u8]>,
Cursor<T>: Write,
{
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[]).unwrap(), 0);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
assert_eq!(writer.write(&[10]).unwrap(), 0);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
assert_eq!(writer.get_ref().as_ref(), b);
}
fn test_slice_writer_vectored<T>(writer: &mut Cursor<T>)
where
T: AsRef<[u8]>,
Cursor<T>: Write,
{
assert_eq!(writer.position(), 0);
assert_eq!(writer.write_vectored(&[IoSlice::new(&[0])]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(
writer.write_vectored(&[IoSlice::new(&[1, 2, 3]), IoSlice::new(&[4, 5, 6, 7]),]).unwrap(),
7,
);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write_vectored(&[IoSlice::new(&[8, 9])]).unwrap(), 1);
assert_eq!(writer.write_vectored(&[IoSlice::new(&[10])]).unwrap(), 0);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
assert_eq!(writer.get_ref().as_ref(), b);
}
#[test]
fn test_box_slice_writer() {
let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
test_slice_writer(&mut writer);
}
#[test]
fn test_box_slice_writer_vectored() {
let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
test_slice_writer_vectored(&mut writer);
}
#[test]
fn test_array_writer() {
let mut writer = Cursor::new([0u8; 9]);
test_slice_writer(&mut writer);
}
#[test]
fn test_array_writer_vectored() {
let mut writer = Cursor::new([0u8; 9]);
test_slice_writer_vectored(&mut writer);
}
#[test]
fn test_buf_writer() {
let mut buf = [0 as u8; 9];
let mut writer = Cursor::new(&mut buf[..]);
test_slice_writer(&mut writer);
}
#[test]
fn test_buf_writer_vectored() {
let mut buf = [0 as u8; 9];
let mut writer = Cursor::new(&mut buf[..]);
test_slice_writer_vectored(&mut writer);
}
#[test]
fn test_buf_writer_seek() {
let mut buf = [0 as u8; 8];
{
let mut writer = Cursor::new(&mut buf[..]);
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[1]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.seek(SeekFrom::Start(2)).unwrap(), 2);
assert_eq!(writer.position(), 2);
assert_eq!(writer.write(&[2]).unwrap(), 1);
assert_eq!(writer.position(), 3);
assert_eq!(writer.seek(SeekFrom::Current(-2)).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[3]).unwrap(), 1);
assert_eq!(writer.position(), 2);
assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
assert_eq!(writer.position(), 7);
assert_eq!(writer.write(&[4]).unwrap(), 1);
assert_eq!(writer.position(), 8);
}
let b: &[_] = &[1, 3, 2, 0, 0, 0, 0, 4];
assert_eq!(buf, b);
}
#[test]
fn test_buf_writer_error() {
let mut buf = [0 as u8; 2];
let mut writer = Cursor::new(&mut buf[..]);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[0, 0]).unwrap(), 1);
assert_eq!(writer.write(&[0, 0]).unwrap(), 0);
}
#[test]
fn test_mem_reader() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_mem_reader_vectored() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
let mut buf = [];
assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(
reader.read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),]).unwrap(),
1,
);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf1 = [0; 4];
let mut buf2 = [0; 4];
assert_eq!(
reader
.read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2),])
.unwrap(),
7,
);
let b1: &[_] = &[1, 2, 3, 4];
let b2: &[_] = &[5, 6, 7];
assert_eq!(buf1, b1);
assert_eq!(&buf2[..3], b2);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_boxed_slice_reader() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_boxed_slice_reader_vectored() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
let mut buf = [];
assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(
reader.read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),]).unwrap(),
1,
);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf1 = [0; 4];
let mut buf2 = [0; 4];
assert_eq!(
reader
.read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
.unwrap(),
7,
);
let b1: &[_] = &[1, 2, 3, 4];
let b2: &[_] = &[5, 6, 7];
assert_eq!(buf1, b1);
assert_eq!(&buf2[..3], b2);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn read_to_end() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
let mut v = Vec::new();
reader.read_to_end(&mut v).unwrap();
assert_eq!(v, [0, 1, 2, 3, 4, 5, 6, 7]);
}
#[test]
fn test_slice_reader() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let reader = &mut &in_buf[..];
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.len(), 7);
let b: &[_] = &[0];
assert_eq!(&buf[..], b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.len(), 3);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(&buf[..], b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_slice_reader_vectored() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let reader = &mut &in_buf[..];
let mut buf = [];
assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
let mut buf = [0];
assert_eq!(
reader.read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),]).unwrap(),
1,
);
assert_eq!(reader.len(), 7);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf1 = [0; 4];
let mut buf2 = [0; 4];
assert_eq!(
reader
.read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
.unwrap(),
7,
);
let b1: &[_] = &[1, 2, 3, 4];
let b2: &[_] = &[5, 6, 7];
assert_eq!(buf1, b1);
assert_eq!(&buf2[..3], b2);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_read_exact() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let reader = &mut &in_buf[..];
let mut buf = [];
assert!(reader.read_exact(&mut buf).is_ok());
let mut buf = [8];
assert!(reader.read_exact(&mut buf).is_ok());
assert_eq!(buf[0], 0);
assert_eq!(reader.len(), 7);
let mut buf = [0, 0, 0, 0, 0, 0, 0];
assert!(reader.read_exact(&mut buf).is_ok());
assert_eq!(buf, [1, 2, 3, 4, 5, 6, 7]);
assert_eq!(reader.len(), 0);
let mut buf = [0];
assert!(reader.read_exact(&mut buf).is_err());
}
#[test]
fn test_buf_reader() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let mut reader = Cursor::new(&in_buf[..]);
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn seek_past_end() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.read(&mut [0]).unwrap(), 0);
let mut r = Cursor::new(vec![10]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.read(&mut [0]).unwrap(), 0);
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 0);
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 0);
}
#[test]
fn seek_past_i64() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut r = Cursor::new(vec![10]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
}
#[test]
fn seek_before_0() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut r = Cursor::new(vec![10]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert!(r.seek(SeekFrom::End(-2)).is_err());
}
#[test]
fn test_seekable_mem_writer() {
let mut writer = Cursor::new(Vec::<u8>::new());
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(writer.position(), 8);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::Start(0)).unwrap(), 0);
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[3, 4]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::Current(1)).unwrap(), 3);
assert_eq!(writer.write(&[0, 1]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
assert_eq!(writer.write(&[1, 2]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::End(1)).unwrap(), 10);
assert_eq!(writer.write(&[1]).unwrap(), 1);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
assert_eq!(&writer.get_ref()[..], b);
}
#[test]
fn vec_seek_past_end() {
let mut r = Cursor::new(Vec::new());
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 1);
}
#[test]
fn vec_seek_before_0() {
let mut r = Cursor::new(Vec::new());
assert!(r.seek(SeekFrom::End(-2)).is_err());
}
#[test]
#[cfg(target_pointer_width = "32")]
fn vec_seek_and_write_past_usize_max() {
let mut c = Cursor::new(Vec::new());
c.set_position(usize::MAX as u64 + 1);
assert!(c.write_all(&[1, 2, 3]).is_err());
}
#[test]
fn test_partial_eq() {
assert_eq!(Cursor::new(Vec::<u8>::new()), Cursor::new(Vec::<u8>::new()));
}
#[test]
fn test_eq() {
struct AssertEq<T: Eq>(pub T);
let _: AssertEq<Cursor<Vec<u8>>> = AssertEq(Cursor::new(Vec::new()));
}
#[allow(dead_code)]
fn const_cursor() {
const CURSOR: Cursor<&[u8]> = Cursor::new(&[0]);
const _: &&[u8] = CURSOR.get_ref();
const _: u64 = CURSOR.position();
}
#[bench]
fn bench_write_vec(b: &mut test::Bencher) {
let slice = &[1; 128];
b.iter(|| {
let mut buf = b"some random data to overwrite".to_vec();
let mut cursor = Cursor::new(&mut buf);
let _ = cursor.write_all(slice);
test::black_box(&cursor);
})
}
#[bench]
fn bench_write_vec_vectored(b: &mut test::Bencher) {
let slices = [
IoSlice::new(&[1; 128]),
IoSlice::new(&[2; 256]),
IoSlice::new(&[3; 512]),
IoSlice::new(&[4; 1024]),
IoSlice::new(&[5; 2048]),
IoSlice::new(&[6; 4096]),
IoSlice::new(&[7; 8192]),
IoSlice::new(&[8; 8192 * 2]),
];
b.iter(|| {
let mut buf = b"some random data to overwrite".to_vec();
let mut cursor = Cursor::new(&mut buf);
let mut slices = slices;
let _ = cursor.write_all_vectored(&mut slices);
test::black_box(&cursor);
})
}

4
crates/std/src/io/impls.rs
View File

@@ -1,5 +1,5 @@
// #[cfg(test)]
// mod tests;
#[cfg(test)]
mod tests;
use crate::alloc::Allocator;
use alloc_crate::collections::VecDeque;

57
crates/std/src/io/impls/tests.rs Normal file
View File

@@ -0,0 +1,57 @@
use crate::io::prelude::*;
#[bench]
fn bench_read_slice(b: &mut test::Bencher) {
let buf = [5; 1024];
let mut dst = [0; 128];
b.iter(|| {
let mut rd = &buf[..];
for _ in 0..8 {
let _ = rd.read(&mut dst);
test::black_box(&dst);
}
})
}
#[bench]
fn bench_write_slice(b: &mut test::Bencher) {
let mut buf = [0; 1024];
let src = [5; 128];
b.iter(|| {
let mut wr = &mut buf[..];
for _ in 0..8 {
let _ = wr.write_all(&src);
test::black_box(&wr);
}
})
}
#[bench]
fn bench_read_vec(b: &mut test::Bencher) {
let buf = vec![5; 1024];
let mut dst = [0; 128];
b.iter(|| {
let mut rd = &buf[..];
for _ in 0..8 {
let _ = rd.read(&mut dst);
test::black_box(&dst);
}
})
}
#[bench]
fn bench_write_vec(b: &mut test::Bencher) {
let mut buf = Vec::with_capacity(1024);
let src = [5; 128];
b.iter(|| {
let mut wr = &mut buf[..];
for _ in 0..8 {
let _ = wr.write_all(&src);
test::black_box(&wr);
}
})
}

947
crates/std/src/io/tests.rs Normal file
View File

@@ -0,0 +1,947 @@
use super::{BorrowedBuf, Cursor, SeekFrom, repeat};
use crate::cmp::{self, min};
use crate::io::{
self, BufRead, BufReader, DEFAULT_BUF_SIZE, IoSlice, IoSliceMut, Read, Seek, Write,
};
use crate::mem::MaybeUninit;
use crate::ops::Deref;
#[test]
fn read_until() {
let mut buf = Cursor::new(&b"12"[..]);
let mut v = Vec::new();
assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 2);
assert_eq!(v, b"12");
let mut buf = Cursor::new(&b"1233"[..]);
let mut v = Vec::new();
assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 3);
assert_eq!(v, b"123");
v.truncate(0);
assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 1);
assert_eq!(v, b"3");
v.truncate(0);
assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 0);
assert_eq!(v, []);
}
#[test]
fn skip_until() {
let bytes: &[u8] = b"read\0ignore\0read\0ignore\0read\0ignore\0";
let mut reader = BufReader::new(bytes);
// read from the bytes, alternating between
// consuming `read\0`s and skipping `ignore\0`s
loop {
// consume `read\0`
let mut out = Vec::new();
let read = reader.read_until(0, &mut out).unwrap();
if read == 0 {
// eof
break;
} else {
assert_eq!(out, b"read\0");
assert_eq!(read, b"read\0".len());
}
// skip past `ignore\0`
let skipped = reader.skip_until(0).unwrap();
assert_eq!(skipped, b"ignore\0".len());
}
// ensure we are at the end of the byte slice and that we can skip no further
// also ensure skip_until matches the behavior of read_until at EOF
let skipped = reader.skip_until(0).unwrap();
assert_eq!(skipped, 0);
}
#[test]
fn split() {
let buf = Cursor::new(&b"12"[..]);
let mut s = buf.split(b'3');
assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']);
assert!(s.next().is_none());
let buf = Cursor::new(&b"1233"[..]);
let mut s = buf.split(b'3');
assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']);
assert_eq!(s.next().unwrap().unwrap(), vec![]);
assert!(s.next().is_none());
}
#[test]
fn read_line() {
let mut buf = Cursor::new(&b"12"[..]);
let mut v = String::new();
assert_eq!(buf.read_line(&mut v).unwrap(), 2);
assert_eq!(v, "12");
let mut buf = Cursor::new(&b"12\n\n"[..]);
let mut v = String::new();
assert_eq!(buf.read_line(&mut v).unwrap(), 3);
assert_eq!(v, "12\n");
v.truncate(0);
assert_eq!(buf.read_line(&mut v).unwrap(), 1);
assert_eq!(v, "\n");
v.truncate(0);
assert_eq!(buf.read_line(&mut v).unwrap(), 0);
assert_eq!(v, "");
}
#[test]
fn lines() {
let buf = Cursor::new(&b"12\r"[..]);
let mut s = buf.lines();
assert_eq!(s.next().unwrap().unwrap(), "12\r".to_string());
assert!(s.next().is_none());
let buf = Cursor::new(&b"12\r\n\n"[..]);
let mut s = buf.lines();
assert_eq!(s.next().unwrap().unwrap(), "12".to_string());
assert_eq!(s.next().unwrap().unwrap(), "".to_string());
assert!(s.next().is_none());
}
#[test]
fn buf_read_has_data_left() {
let mut buf = Cursor::new(&b"abcd"[..]);
assert!(buf.has_data_left().unwrap());
buf.read_exact(&mut [0; 2]).unwrap();
assert!(buf.has_data_left().unwrap());
buf.read_exact(&mut [0; 2]).unwrap();
assert!(!buf.has_data_left().unwrap());
}
#[test]
fn read_to_end() {
let mut c = Cursor::new(&b""[..]);
let mut v = Vec::new();
assert_eq!(c.read_to_end(&mut v).unwrap(), 0);
assert_eq!(v, []);
let mut c = Cursor::new(&b"1"[..]);
let mut v = Vec::new();
assert_eq!(c.read_to_end(&mut v).unwrap(), 1);
assert_eq!(v, b"1");
let cap = if cfg!(miri) { 1024 } else { 1024 * 1024 };
let data = (0..cap).map(|i| (i / 3) as u8).collect::<Vec<_>>();
let mut v = Vec::new();
let (a, b) = data.split_at(data.len() / 2);
assert_eq!(Cursor::new(a).read_to_end(&mut v).unwrap(), a.len());
assert_eq!(Cursor::new(b).read_to_end(&mut v).unwrap(), b.len());
assert_eq!(v, data);
}
#[test]
fn read_to_string() {
let mut c = Cursor::new(&b""[..]);
let mut v = String::new();
assert_eq!(c.read_to_string(&mut v).unwrap(), 0);
assert_eq!(v, "");
let mut c = Cursor::new(&b"1"[..]);
let mut v = String::new();
assert_eq!(c.read_to_string(&mut v).unwrap(), 1);
assert_eq!(v, "1");
let mut c = Cursor::new(&b"\xff"[..]);
let mut v = String::new();
assert!(c.read_to_string(&mut v).is_err());
}
#[test]
fn read_exact() {
let mut buf = [0; 4];
let mut c = Cursor::new(&b""[..]);
assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
let mut c = Cursor::new(&b"123"[..]).chain(Cursor::new(&b"456789"[..]));
c.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"1234");
c.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"5678");
assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
}
#[test]
fn read_exact_slice() {
let mut buf = [0; 4];
let mut c = &b""[..];
assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
let mut c = &b"123"[..];
assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
// make sure the optimized (early returning) method is being used
assert_eq!(&buf, &[0; 4]);
let mut c = &b"1234"[..];
c.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"1234");
let mut c = &b"56789"[..];
c.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"5678");
assert_eq!(c, b"9");
}
#[test]
fn read_buf_exact() {
let buf: &mut [_] = &mut [0; 4];
let mut buf: BorrowedBuf<'_> = buf.into();
let mut c = Cursor::new(&b""[..]);
assert_eq!(c.read_buf_exact(buf.unfilled()).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
let mut c = Cursor::new(&b"123456789"[..]);
c.read_buf_exact(buf.unfilled()).unwrap();
assert_eq!(buf.filled(), b"1234");
buf.clear();
c.read_buf_exact(buf.unfilled()).unwrap();
assert_eq!(buf.filled(), b"5678");
buf.clear();
assert_eq!(c.read_buf_exact(buf.unfilled()).unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
}
#[test]
#[should_panic]
fn borrowed_cursor_advance_overflow() {
let mut buf = [0; 512];
let mut buf = BorrowedBuf::from(&mut buf[..]);
buf.unfilled().advance(1);
buf.unfilled().advance(usize::MAX);
}
#[test]
fn take_eof() {
struct R;
impl Read for R {
fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
Err(io::const_error!(io::ErrorKind::Other, ""))
}
}
impl BufRead for R {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
Err(io::const_error!(io::ErrorKind::Other, ""))
}
fn consume(&mut self, _amt: usize) {}
}
let mut buf = [0; 1];
assert_eq!(0, R.take(0).read(&mut buf).unwrap());
assert_eq!(b"", R.take(0).fill_buf().unwrap());
}
fn cmp_bufread<Br1: BufRead, Br2: BufRead>(mut br1: Br1, mut br2: Br2, exp: &[u8]) {
let mut cat = Vec::new();
loop {
let consume = {
let buf1 = br1.fill_buf().unwrap();
let buf2 = br2.fill_buf().unwrap();
let minlen = if buf1.len() < buf2.len() { buf1.len() } else { buf2.len() };
assert_eq!(buf1[..minlen], buf2[..minlen]);
cat.extend_from_slice(&buf1[..minlen]);
minlen
};
if consume == 0 {
break;
}
br1.consume(consume);
br2.consume(consume);
}
assert_eq!(br1.fill_buf().unwrap().len(), 0);
assert_eq!(br2.fill_buf().unwrap().len(), 0);
assert_eq!(&cat[..], &exp[..])
}
#[test]
fn chain_bufread() {
let testdata = b"ABCDEFGHIJKL";
let chain1 =
(&testdata[..3]).chain(&testdata[3..6]).chain(&testdata[6..9]).chain(&testdata[9..]);
let chain2 = (&testdata[..4]).chain(&testdata[4..8]).chain(&testdata[8..]);
cmp_bufread(chain1, chain2, &testdata[..]);
}
#[test]
fn chain_splitted_char() {
let chain = b"\xc3".chain(b"\xa9".as_slice());
assert_eq!(crate::io::read_to_string(chain).unwrap(), "é");
let mut chain = b"\xc3".chain(b"\xa9\n".as_slice());
let mut buf = String::new();
assert_eq!(chain.read_line(&mut buf).unwrap(), 3);
assert_eq!(buf, "é\n");
}
#[test]
fn bufreader_size_hint() {
let testdata = b"ABCDEFGHIJKL";
let mut buf_reader = BufReader::new(&testdata[..]);
assert_eq!(buf_reader.buffer().len(), 0);
let buffer_length = testdata.len();
buf_reader.fill_buf().unwrap();
// Check that size hint matches buffer contents
let mut buffered_bytes = buf_reader.bytes();
let (lower_bound, _upper_bound) = buffered_bytes.size_hint();
assert_eq!(lower_bound, buffer_length);
// Check that size hint matches buffer contents after advancing
buffered_bytes.next().unwrap().unwrap();
let (lower_bound, _upper_bound) = buffered_bytes.size_hint();
assert_eq!(lower_bound, buffer_length - 1);
}
#[test]
fn empty_size_hint() {
let size_hint = io::empty().bytes().size_hint();
assert_eq!(size_hint, (0, Some(0)));
}
#[test]
fn slice_size_hint() {
let size_hint = (&[1, 2, 3]).bytes().size_hint();
assert_eq!(size_hint, (3, Some(3)));
}
#[test]
fn take_size_hint() {
let size_hint = (&[1, 2, 3]).take(2).bytes().size_hint();
assert_eq!(size_hint, (2, Some(2)));
let size_hint = (&[1, 2, 3]).take(4).bytes().size_hint();
assert_eq!(size_hint, (3, Some(3)));
let size_hint = io::repeat(0).take(3).bytes().size_hint();
assert_eq!(size_hint, (3, Some(3)));
}
#[test]
fn chain_empty_size_hint() {
let chain = io::empty().chain(io::empty());
let size_hint = chain.bytes().size_hint();
assert_eq!(size_hint, (0, Some(0)));
}
#[test]
fn chain_size_hint() {
let testdata = b"ABCDEFGHIJKL";
let mut buf_reader_1 = BufReader::new(&testdata[..6]);
let mut buf_reader_2 = BufReader::new(&testdata[6..]);
buf_reader_1.fill_buf().unwrap();
buf_reader_2.fill_buf().unwrap();
let chain = buf_reader_1.chain(buf_reader_2);
let size_hint = chain.bytes().size_hint();
assert_eq!(size_hint, (testdata.len(), Some(testdata.len())));
}
#[test]
fn chain_zero_length_read_is_not_eof() {
let a = b"A";
let b = b"B";
let mut s = String::new();
let mut chain = (&a[..]).chain(&b[..]);
chain.read(&mut []).unwrap();
chain.read_to_string(&mut s).unwrap();
assert_eq!("AB", s);
}
#[bench]
#[cfg_attr(miri, ignore)] // Miri isn't fast...
fn bench_read_to_end(b: &mut test::Bencher) {
b.iter(|| {
let mut lr = repeat(1).take(10000000);
let mut vec = Vec::with_capacity(1024);
super::default_read_to_end(&mut lr, &mut vec, None)
});
}
#[test]
fn seek_len() -> io::Result<()> {
let mut c = Cursor::new(vec![0; 15]);
assert_eq!(c.stream_len()?, 15);
c.seek(SeekFrom::End(0))?;
let old_pos = c.stream_position()?;
assert_eq!(c.stream_len()?, 15);
assert_eq!(c.stream_position()?, old_pos);
c.seek(SeekFrom::Start(7))?;
c.seek(SeekFrom::Current(2))?;
let old_pos = c.stream_position()?;
assert_eq!(c.stream_len()?, 15);
assert_eq!(c.stream_position()?, old_pos);
Ok(())
}
#[test]
fn seek_position() -> io::Result<()> {
// All `asserts` are duplicated here to make sure the method does not
// change anything about the seek state.
let mut c = Cursor::new(vec![0; 15]);
assert_eq!(c.stream_position()?, 0);
assert_eq!(c.stream_position()?, 0);
c.seek(SeekFrom::End(0))?;
assert_eq!(c.stream_position()?, 15);
assert_eq!(c.stream_position()?, 15);
c.seek(SeekFrom::Start(7))?;
c.seek(SeekFrom::Current(2))?;
assert_eq!(c.stream_position()?, 9);
assert_eq!(c.stream_position()?, 9);
c.seek(SeekFrom::End(-3))?;
c.seek(SeekFrom::Current(1))?;
c.seek(SeekFrom::Current(-5))?;
assert_eq!(c.stream_position()?, 8);
assert_eq!(c.stream_position()?, 8);
c.rewind()?;
assert_eq!(c.stream_position()?, 0);
assert_eq!(c.stream_position()?, 0);
Ok(())
}
#[test]
fn take_seek() -> io::Result<()> {
let mut buf = Cursor::new(b"0123456789");
buf.set_position(2);
let mut take = buf.by_ref().take(4);
let mut buf1 = [0u8; 1];
let mut buf2 = [0u8; 2];
assert_eq!(take.position(), 0);
assert_eq!(take.seek(SeekFrom::Start(0))?, 0);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'2', b'3']);
assert_eq!(take.seek(SeekFrom::Start(1))?, 1);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'3', b'4']);
assert_eq!(take.seek(SeekFrom::Start(2))?, 2);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'4', b'5']);
assert_eq!(take.seek(SeekFrom::Start(3))?, 3);
take.read_exact(&mut buf1)?;
assert_eq!(buf1, [b'5']);
assert_eq!(take.seek(SeekFrom::Start(4))?, 4);
assert_eq!(take.read(&mut buf1)?, 0);
assert_eq!(take.seek(SeekFrom::End(0))?, 4);
assert_eq!(take.seek(SeekFrom::End(-1))?, 3);
take.read_exact(&mut buf1)?;
assert_eq!(buf1, [b'5']);
assert_eq!(take.seek(SeekFrom::End(-2))?, 2);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'4', b'5']);
assert_eq!(take.seek(SeekFrom::End(-3))?, 1);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'3', b'4']);
assert_eq!(take.seek(SeekFrom::End(-4))?, 0);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'2', b'3']);
assert_eq!(take.seek(SeekFrom::Current(0))?, 2);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'4', b'5']);
assert_eq!(take.seek(SeekFrom::Current(-3))?, 1);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'3', b'4']);
assert_eq!(take.seek(SeekFrom::Current(-1))?, 2);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'4', b'5']);
assert_eq!(take.seek(SeekFrom::Current(-4))?, 0);
take.read_exact(&mut buf2)?;
assert_eq!(buf2, [b'2', b'3']);
assert_eq!(take.seek(SeekFrom::Current(2))?, 4);
assert_eq!(take.read(&mut buf1)?, 0);
Ok(())
}
#[test]
fn take_seek_error() {
let buf = Cursor::new(b"0123456789");
let mut take = buf.take(2);
assert!(take.seek(SeekFrom::Start(3)).is_err());
assert!(take.seek(SeekFrom::End(1)).is_err());
assert!(take.seek(SeekFrom::End(-3)).is_err());
assert!(take.seek(SeekFrom::Current(-1)).is_err());
assert!(take.seek(SeekFrom::Current(3)).is_err());
}
struct ExampleHugeRangeOfZeroes {
position: u64,
}
impl Read for ExampleHugeRangeOfZeroes {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let max = buf.len().min(usize::MAX);
for i in 0..max {
if self.position == u64::MAX {
return Ok(i);
}
self.position += 1;
buf[i] = 0;
}
Ok(max)
}
}
impl Seek for ExampleHugeRangeOfZeroes {
fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
match pos {
io::SeekFrom::Start(i) => self.position = i,
io::SeekFrom::End(i) if i >= 0 => self.position = u64::MAX,
io::SeekFrom::End(i) => self.position = self.position - i.unsigned_abs(),
io::SeekFrom::Current(i) => {
self.position = if i >= 0 {
self.position.saturating_add(i.unsigned_abs())
} else {
self.position.saturating_sub(i.unsigned_abs())
};
}
}
Ok(self.position)
}
}
#[test]
fn take_seek_big_offsets() -> io::Result<()> {
let inner = ExampleHugeRangeOfZeroes { position: 1 };
let mut take = inner.take(u64::MAX - 2);
assert_eq!(take.seek(io::SeekFrom::Start(u64::MAX - 2))?, u64::MAX - 2);
assert_eq!(take.inner.position, u64::MAX - 1);
assert_eq!(take.seek(io::SeekFrom::Start(0))?, 0);
assert_eq!(take.inner.position, 1);
assert_eq!(take.seek(io::SeekFrom::End(-1))?, u64::MAX - 3);
assert_eq!(take.inner.position, u64::MAX - 2);
Ok(())
}
// A simple example reader which uses the default implementation of
// read_to_end.
struct ExampleSliceReader<'a> {
slice: &'a [u8],
}
impl<'a> Read for ExampleSliceReader<'a> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let len = cmp::min(self.slice.len(), buf.len());
buf[..len].copy_from_slice(&self.slice[..len]);
self.slice = &self.slice[len..];
Ok(len)
}
}
#[test]
fn test_read_to_end_capacity() -> io::Result<()> {
let input = &b"foo"[..];
// read_to_end() takes care not to over-allocate when a buffer is the
// exact size needed.
let mut vec1 = Vec::with_capacity(input.len());
ExampleSliceReader { slice: input }.read_to_end(&mut vec1)?;
assert_eq!(vec1.len(), input.len());
assert_eq!(vec1.capacity(), input.len(), "did not allocate more");
Ok(())
}
#[test]
fn io_slice_mut_advance_slices() {
let mut buf1 = [1; 8];
let mut buf2 = [2; 16];
let mut buf3 = [3; 8];
let mut bufs = &mut [
IoSliceMut::new(&mut buf1),
IoSliceMut::new(&mut buf2),
IoSliceMut::new(&mut buf3),
][..];
// Only in a single buffer..
IoSliceMut::advance_slices(&mut bufs, 1);
assert_eq!(bufs[0].deref(), [1; 7].as_ref());
assert_eq!(bufs[1].deref(), [2; 16].as_ref());
assert_eq!(bufs[2].deref(), [3; 8].as_ref());
// Removing a buffer, leaving others as is.
IoSliceMut::advance_slices(&mut bufs, 7);
assert_eq!(bufs[0].deref(), [2; 16].as_ref());
assert_eq!(bufs[1].deref(), [3; 8].as_ref());
// Removing a buffer and removing from the next buffer.
IoSliceMut::advance_slices(&mut bufs, 18);
assert_eq!(bufs[0].deref(), [3; 6].as_ref());
}
#[test]
#[should_panic]
fn io_slice_mut_advance_slices_empty_slice() {
let mut empty_bufs = &mut [][..];
IoSliceMut::advance_slices(&mut empty_bufs, 1);
}
#[test]
#[should_panic]
fn io_slice_mut_advance_slices_beyond_total_length() {
let mut buf1 = [1; 8];
let mut bufs = &mut [IoSliceMut::new(&mut buf1)][..];
IoSliceMut::advance_slices(&mut bufs, 9);
assert!(bufs.is_empty());
}
#[test]
fn io_slice_advance_slices() {
let buf1 = [1; 8];
let buf2 = [2; 16];
let buf3 = [3; 8];
let mut bufs = &mut [IoSlice::new(&buf1), IoSlice::new(&buf2), IoSlice::new(&buf3)][..];
// Only in a single buffer..
IoSlice::advance_slices(&mut bufs, 1);
assert_eq!(bufs[0].deref(), [1; 7].as_ref());
assert_eq!(bufs[1].deref(), [2; 16].as_ref());
assert_eq!(bufs[2].deref(), [3; 8].as_ref());
// Removing a buffer, leaving others as is.
IoSlice::advance_slices(&mut bufs, 7);
assert_eq!(bufs[0].deref(), [2; 16].as_ref());
assert_eq!(bufs[1].deref(), [3; 8].as_ref());
// Removing a buffer and removing from the next buffer.
IoSlice::advance_slices(&mut bufs, 18);
assert_eq!(bufs[0].deref(), [3; 6].as_ref());
}
#[test]
#[should_panic]
fn io_slice_advance_slices_empty_slice() {
let mut empty_bufs = &mut [][..];
IoSlice::advance_slices(&mut empty_bufs, 1);
}
#[test]
#[should_panic]
fn io_slice_advance_slices_beyond_total_length() {
let buf1 = [1; 8];
let mut bufs = &mut [IoSlice::new(&buf1)][..];
IoSlice::advance_slices(&mut bufs, 9);
assert!(bufs.is_empty());
}
#[test]
fn io_slice_as_slice() {
let buf = [1; 8];
let slice = IoSlice::new(&buf).as_slice();
assert_eq!(slice, buf);
}
#[test]
fn io_slice_into_slice() {
let mut buf = [1; 8];
let slice = IoSliceMut::new(&mut buf).into_slice();
assert_eq!(slice, [1; 8]);
}
/// Creates a new writer that reads from at most `n_bufs` and reads
/// `per_call` bytes (in total) per call to write.
fn test_writer(n_bufs: usize, per_call: usize) -> TestWriter {
TestWriter { n_bufs, per_call, written: Vec::new() }
}
struct TestWriter {
n_bufs: usize,
per_call: usize,
written: Vec<u8>,
}
impl Write for TestWriter {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.write_vectored(&[IoSlice::new(buf)])
}
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
let mut left = self.per_call;
let mut written = 0;
for buf in bufs.iter().take(self.n_bufs) {
let n = min(left, buf.len());
self.written.extend_from_slice(&buf[0..n]);
left -= n;
written += n;
}
Ok(written)
}
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
#[test]
fn test_writer_read_from_one_buf() {
let mut writer = test_writer(1, 2);
assert_eq!(writer.write(&[]).unwrap(), 0);
assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
// Read at most 2 bytes.
assert_eq!(writer.write(&[1, 1, 1]).unwrap(), 2);
let bufs = &[IoSlice::new(&[2, 2, 2])];
assert_eq!(writer.write_vectored(bufs).unwrap(), 2);
// Only read from first buf.
let bufs = &[IoSlice::new(&[3]), IoSlice::new(&[4, 4])];
assert_eq!(writer.write_vectored(bufs).unwrap(), 1);
assert_eq!(writer.written, &[1, 1, 2, 2, 3]);
}
#[test]
fn test_writer_read_from_multiple_bufs() {
let mut writer = test_writer(3, 3);
// Read at most 3 bytes from two buffers.
let bufs = &[IoSlice::new(&[1]), IoSlice::new(&[2, 2, 2])];
assert_eq!(writer.write_vectored(bufs).unwrap(), 3);
// Read at most 3 bytes from three buffers.
let bufs = &[IoSlice::new(&[3]), IoSlice::new(&[4]), IoSlice::new(&[5, 5])];
assert_eq!(writer.write_vectored(bufs).unwrap(), 3);
assert_eq!(writer.written, &[1, 2, 2, 3, 4, 5]);
}
#[test]
fn test_write_all_vectored() {
#[rustfmt::skip] // Becomes unreadable otherwise.
let tests: Vec<(_, &'static [u8])> = vec![
(vec![], &[]),
(vec![IoSlice::new(&[]), IoSlice::new(&[])], &[]),
(vec![IoSlice::new(&[1])], &[1]),
(vec![IoSlice::new(&[1, 2])], &[1, 2]),
(vec![IoSlice::new(&[1, 2, 3])], &[1, 2, 3]),
(vec![IoSlice::new(&[1, 2, 3, 4])], &[1, 2, 3, 4]),
(vec![IoSlice::new(&[1, 2, 3, 4, 5])], &[1, 2, 3, 4, 5]),
(vec![IoSlice::new(&[1]), IoSlice::new(&[2])], &[1, 2]),
(vec![IoSlice::new(&[1]), IoSlice::new(&[2, 2])], &[1, 2, 2]),
(vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2])], &[1, 1, 2, 2]),
(vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 2, 2, 2]),
(vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 2, 2, 2]),
(vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 1, 2, 2, 2]),
(vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2, 2])], &[1, 1, 1, 2, 2, 2, 2]),
(vec![IoSlice::new(&[1, 1, 1, 1]), IoSlice::new(&[2, 2, 2, 2])], &[1, 1, 1, 1, 2, 2, 2, 2]),
(vec![IoSlice::new(&[1]), IoSlice::new(&[2]), IoSlice::new(&[3])], &[1, 2, 3]),
(vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2]), IoSlice::new(&[3, 3])], &[1, 1, 2, 2, 3, 3]),
(vec![IoSlice::new(&[1]), IoSlice::new(&[2, 2]), IoSlice::new(&[3, 3, 3])], &[1, 2, 2, 3, 3, 3]),
(vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2]), IoSlice::new(&[3, 3, 3])], &[1, 1, 1, 2, 2, 2, 3, 3, 3]),
];
let writer_configs = &[(1, 1), (1, 2), (1, 3), (2, 2), (2, 3), (3, 3)];
for (n_bufs, per_call) in writer_configs.iter().copied() {
for (mut input, wanted) in tests.clone().into_iter() {
let mut writer = test_writer(n_bufs, per_call);
assert!(writer.write_all_vectored(&mut *input).is_ok());
assert_eq!(&*writer.written, &*wanted);
}
}
}
// Issue 94981
#[test]
#[should_panic = "number of read bytes exceeds limit"]
fn test_take_wrong_length() {
struct LieAboutSize(bool);
impl Read for LieAboutSize {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
// Lie about the read size at first time of read.
if core::mem::take(&mut self.0) { Ok(buf.len() + 1) } else { Ok(buf.len()) }
}
}
let mut buffer = vec![0; 4];
let mut reader = LieAboutSize(true).take(4);
// Primed the `Limit` by lying about the read size.
let _ = reader.read(&mut buffer[..]);
}
#[test]
fn slice_read_exact_eof() {
let slice = &b"123456"[..];
let mut r = slice;
assert!(r.read_exact(&mut [0; 10]).is_err());
assert!(r.is_empty());
let mut r = slice;
let buf = &mut [0; 10];
let mut buf = BorrowedBuf::from(buf.as_mut_slice());
assert!(r.read_buf_exact(buf.unfilled()).is_err());
assert!(r.is_empty());
assert_eq!(buf.filled(), b"123456");
}
#[test]
fn cursor_read_exact_eof() {
let slice = Cursor::new(b"123456");
let mut r = slice.clone();
assert!(r.read_exact(&mut [0; 10]).is_err());
assert!(Cursor::split(&r).1.is_empty());
let mut r = slice;
let buf = &mut [0; 10];
let mut buf = BorrowedBuf::from(buf.as_mut_slice());
assert!(r.read_buf_exact(buf.unfilled()).is_err());
assert!(Cursor::split(&r).1.is_empty());
assert_eq!(buf.filled(), b"123456");
}
#[bench]
fn bench_take_read(b: &mut test::Bencher) {
b.iter(|| {
let mut buf = [0; 64];
[255; 128].take(64).read(&mut buf).unwrap();
});
}
#[bench]
fn bench_take_read_buf(b: &mut test::Bencher) {
b.iter(|| {
let buf: &mut [_] = &mut [MaybeUninit::uninit(); 64];
let mut buf: BorrowedBuf<'_> = buf.into();
[255; 128].take(64).read_buf(buf.unfilled()).unwrap();
});
}
// Issue #120603
#[test]
#[should_panic]
fn read_buf_broken_read() {
struct MalformedRead;
impl Read for MalformedRead {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
// broken length calculation
Ok(buf.len() + 1)
}
}
let _ = BufReader::new(MalformedRead).fill_buf();
}
#[test]
fn read_buf_full_read() {
struct FullRead;
impl Read for FullRead {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
Ok(buf.len())
}
}
assert_eq!(BufReader::new(FullRead).fill_buf().unwrap().len(), DEFAULT_BUF_SIZE);
}
struct DataAndErrorReader(&'static [u8]);
impl Read for DataAndErrorReader {
fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
panic!("We want tests to use `read_buf`")
}
fn read_buf(&mut self, buf: io::BorrowedCursor<'_>) -> io::Result<()> {
self.0.read_buf(buf).unwrap();
Err(io::Error::other("error"))
}
}
#[test]
fn read_buf_data_and_error_take() {
let mut buf = [0; 64];
let mut buf = io::BorrowedBuf::from(buf.as_mut_slice());
let mut r = DataAndErrorReader(&[4, 5, 6]).take(1);
assert!(r.read_buf(buf.unfilled()).is_err());
assert_eq!(buf.filled(), &[4]);
assert!(r.read_buf(buf.unfilled()).is_ok());
assert_eq!(buf.filled(), &[4]);
assert_eq!(r.get_ref().0, &[5, 6]);
}
#[test]
fn read_buf_data_and_error_buf() {
let mut r = BufReader::new(DataAndErrorReader(&[4, 5, 6]));
assert!(r.fill_buf().is_err());
assert_eq!(r.fill_buf().unwrap(), &[4, 5, 6]);
}
#[test]
fn read_buf_data_and_error_read_to_end() {
let mut r = DataAndErrorReader(&[4, 5, 6]);
let mut v = Vec::with_capacity(200);
assert!(r.read_to_end(&mut v).is_err());
assert_eq!(v, &[4, 5, 6]);
}
#[test]
fn read_to_end_error() {
struct ErrorReader;
impl Read for ErrorReader {
fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
Err(io::Error::other("error"))
}
}
let mut r = [4, 5, 6].chain(ErrorReader);
let mut v = Vec::with_capacity(200);
assert!(r.read_to_end(&mut v).is_err());
assert_eq!(v, &[4, 5, 6]);
}
#[test]
fn try_oom_error() {
use alloc::alloc::Layout;
use alloc::collections::{TryReserveError, TryReserveErrorKind};
// We simulate a `Vec::try_reserve` error rather than attempting a huge size for real. This way
// we're not subject to the whims of optimization that might skip the actual allocation, and it
// also works for 32-bit targets and miri that might not OOM at all.
let layout = Layout::new::<u8>();
let kind = TryReserveErrorKind::AllocError { layout, non_exhaustive: () };
let reserve_err = TryReserveError::from(kind);
let io_err = io::Error::from(reserve_err);
assert_eq!(io::ErrorKind::OutOfMemory, io_err.kind());
}

448
crates/std/src/io/util.rs Normal file
View File

@@ -0,0 +1,448 @@
#![allow(missing_copy_implementations)]
#[cfg(test)]
mod tests;
use crate::fmt;
use crate::io::{
self, BorrowedCursor, BufRead, IoSlice, IoSliceMut, Read, Seek, SeekFrom, SizeHint, Write,
};
/// `Empty` ignores any data written via [`Write`], and will always be empty
/// (returning zero bytes) when read via [`Read`].
///
/// This struct is generally created by calling [`empty()`]. Please
/// see the documentation of [`empty()`] for more details.
#[stable(feature = "rust1", since = "1.0.0")]
#[non_exhaustive]
#[derive(Copy, Clone, Debug, Default)]
pub struct Empty;
/// Creates a value that is always at EOF for reads, and ignores all data written.
///
/// All calls to [`write`] on the returned instance will return [`Ok(buf.len())`]
/// and the contents of the buffer will not be inspected.
///
/// All calls to [`read`] from the returned reader will return [`Ok(0)`].
///
/// [`Ok(buf.len())`]: Ok
/// [`Ok(0)`]: Ok
///
/// [`write`]: Write::write
/// [`read`]: Read::read
///
/// # Examples
///
/// ```rust
/// use std::io::{self, Write};
///
/// let buffer = vec![1, 2, 3, 5, 8];
/// let num_bytes = io::empty().write(&buffer).unwrap();
/// assert_eq!(num_bytes, 5);
/// ```
///
///
/// ```rust
/// use std::io::{self, Read};
///
/// let mut buffer = String::new();
/// io::empty().read_to_string(&mut buffer).unwrap();
/// assert!(buffer.is_empty());
/// ```
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_io_structs", since = "1.79.0")]
pub const fn empty() -> Empty {
Empty
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Read for Empty {
#[inline]
fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
Ok(0)
}
#[inline]
fn read_buf(&mut self, _cursor: BorrowedCursor<'_>) -> io::Result<()> {
Ok(())
}
#[inline]
fn read_vectored(&mut self, _bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
Ok(0)
}
#[inline]
fn is_read_vectored(&self) -> bool {
// Do not force `Chain<Empty, T>` or `Chain<T, Empty>` to use vectored
// reads, unless the other reader is vectored.
false
}
#[inline]
fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
if !buf.is_empty() { Err(io::Error::READ_EXACT_EOF) } else { Ok(()) }
}
#[inline]
fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
if cursor.capacity() != 0 { Err(io::Error::READ_EXACT_EOF) } else { Ok(()) }
}
#[inline]
fn read_to_end(&mut self, _buf: &mut Vec<u8>) -> io::Result<usize> {
Ok(0)
}
#[inline]
fn read_to_string(&mut self, _buf: &mut String) -> io::Result<usize> {
Ok(0)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl BufRead for Empty {
#[inline]
fn fill_buf(&mut self) -> io::Result<&[u8]> {
Ok(&[])
}
#[inline]
fn consume(&mut self, _n: usize) {}
#[inline]
fn has_data_left(&mut self) -> io::Result<bool> {
Ok(false)
}
#[inline]
fn read_until(&mut self, _byte: u8, _buf: &mut Vec<u8>) -> io::Result<usize> {
Ok(0)
}
#[inline]
fn skip_until(&mut self, _byte: u8) -> io::Result<usize> {
Ok(0)
}
#[inline]
fn read_line(&mut self, _buf: &mut String) -> io::Result<usize> {
Ok(0)
}
}
#[stable(feature = "empty_seek", since = "1.51.0")]
impl Seek for Empty {
#[inline]
fn seek(&mut self, _pos: SeekFrom) -> io::Result<u64> {
Ok(0)
}
#[inline]
fn stream_len(&mut self) -> io::Result<u64> {
Ok(0)
}
#[inline]
fn stream_position(&mut self) -> io::Result<u64> {
Ok(0)
}
}
impl SizeHint for Empty {
#[inline]
fn upper_bound(&self) -> Option<usize> {
Some(0)
}
}
#[stable(feature = "empty_write", since = "1.73.0")]
impl Write for Empty {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Ok(buf.len())
}
#[inline]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
let total_len = bufs.iter().map(|b| b.len()).sum();
Ok(total_len)
}
#[inline]
fn is_write_vectored(&self) -> bool {
true
}
#[inline]
fn write_all(&mut self, _buf: &[u8]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_all_vectored(&mut self, _bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> io::Result<()> {
Ok(())
}
#[inline]
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
#[stable(feature = "empty_write", since = "1.73.0")]
impl Write for &Empty {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Ok(buf.len())
}
#[inline]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
let total_len = bufs.iter().map(|b| b.len()).sum();
Ok(total_len)
}
#[inline]
fn is_write_vectored(&self) -> bool {
true
}
#[inline]
fn write_all(&mut self, _buf: &[u8]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_all_vectored(&mut self, _bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> io::Result<()> {
Ok(())
}
#[inline]
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
/// A reader which yields one byte over and over and over and over and over and...
///
/// This struct is generally created by calling [`repeat()`]. Please
/// see the documentation of [`repeat()`] for more details.
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Repeat {
byte: u8,
}
/// Creates an instance of a reader that infinitely repeats one byte.
///
/// All reads from this reader will succeed by filling the specified buffer with
/// the given byte.
///
/// # Examples
///
/// ```
/// use std::io::{self, Read};
///
/// let mut buffer = [0; 3];
/// io::repeat(0b101).read_exact(&mut buffer).unwrap();
/// assert_eq!(buffer, [0b101, 0b101, 0b101]);
/// ```
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_io_structs", since = "1.79.0")]
pub const fn repeat(byte: u8) -> Repeat {
Repeat { byte }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Read for Repeat {
#[inline]
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
buf.fill(self.byte);
Ok(buf.len())
}
#[inline]
fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
buf.fill(self.byte);
Ok(())
}
#[inline]
fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> io::Result<()> {
// SAFETY: No uninit bytes are being written.
unsafe { buf.as_mut() }.write_filled(self.byte);
// SAFETY: the entire unfilled portion of buf has been initialized.
unsafe { buf.advance_unchecked(buf.capacity()) };
Ok(())
}
#[inline]
fn read_buf_exact(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
self.read_buf(buf)
}
/// This function is not supported by `io::Repeat`, because there's no end of its data
fn read_to_end(&mut self, _: &mut Vec<u8>) -> io::Result<usize> {
Err(io::Error::from(io::ErrorKind::OutOfMemory))
}
/// This function is not supported by `io::Repeat`, because there's no end of its data
fn read_to_string(&mut self, _: &mut String) -> io::Result<usize> {
Err(io::Error::from(io::ErrorKind::OutOfMemory))
}
#[inline]
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
let mut nwritten = 0;
for buf in bufs {
nwritten += self.read(buf)?;
}
Ok(nwritten)
}
#[inline]
fn is_read_vectored(&self) -> bool {
true
}
}
impl SizeHint for Repeat {
#[inline]
fn lower_bound(&self) -> usize {
usize::MAX
}
#[inline]
fn upper_bound(&self) -> Option<usize> {
None
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Repeat {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Repeat").finish_non_exhaustive()
}
}
/// A writer which will move data into the void.
///
/// This struct is generally created by calling [`sink()`]. Please
/// see the documentation of [`sink()`] for more details.
#[stable(feature = "rust1", since = "1.0.0")]
#[non_exhaustive]
#[derive(Copy, Clone, Debug, Default)]
pub struct Sink;
/// Creates an instance of a writer which will successfully consume all data.
///
/// All calls to [`write`] on the returned instance will return [`Ok(buf.len())`]
/// and the contents of the buffer will not be inspected.
///
/// [`write`]: Write::write
/// [`Ok(buf.len())`]: Ok
///
/// # Examples
///
/// ```rust
/// use std::io::{self, Write};
///
/// let buffer = vec![1, 2, 3, 5, 8];
/// let num_bytes = io::sink().write(&buffer).unwrap();
/// assert_eq!(num_bytes, 5);
/// ```
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_io_structs", since = "1.79.0")]
pub const fn sink() -> Sink {
Sink
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Write for Sink {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Ok(buf.len())
}
#[inline]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
let total_len = bufs.iter().map(|b| b.len()).sum();
Ok(total_len)
}
#[inline]
fn is_write_vectored(&self) -> bool {
true
}
#[inline]
fn write_all(&mut self, _buf: &[u8]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_all_vectored(&mut self, _bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> io::Result<()> {
Ok(())
}
#[inline]
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
#[stable(feature = "write_mt", since = "1.48.0")]
impl Write for &Sink {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Ok(buf.len())
}
#[inline]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
let total_len = bufs.iter().map(|b| b.len()).sum();
Ok(total_len)
}
#[inline]
fn is_write_vectored(&self) -> bool {
true
}
#[inline]
fn write_all(&mut self, _buf: &[u8]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_all_vectored(&mut self, _bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
Ok(())
}
#[inline]
fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> io::Result<()> {
Ok(())
}
#[inline]
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}

11
justfile
View File

@@ -31,8 +31,19 @@ update_std:
@just cp_std "io/error.rs"
@just cp_std "io/error/repr_bitpacked.rs"
@just cp_std "io/cursor.rs"
@just cp_std "io/cursor/tests.rs"
@just cp_std "io/prelude.rs"
@just cp_std "io/impls.rs"
@just cp_std "io/impls/tests.rs"
@just cp_std "io/tests.rs"
@just cp_std "io/util.rs"
@just cp_std "io/copy.rs"
@just cp_std "io/buffered/mod.rs"
@just cp_std "io/buffered/bufreader.rs"
@just cp_std "io/buffered/bufreader/buffer.rs"
@just cp_std "io/buffered/bufwriter.rs"
@just cp_std "io/buffered/linewriter.rs"
@just cp_std "io/buffered/linewritershim.rs"
@just cp_std "hash/mod.rs"
@just cp_std "hash/random.rs"
@just cp_std "num/mod.rs"