ecbb896b9e
This is an API that allows types to indicate that they can be passed buffers of uninitialized memory which can improve performance.
1240 lines
39 KiB
Rust
1240 lines
39 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Buffering wrappers for I/O traits
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use io::prelude::*;
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use cmp;
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use error;
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use fmt;
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use io::{self, Initializer, DEFAULT_BUF_SIZE, Error, ErrorKind, SeekFrom};
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use memchr;
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/// The `BufReader` struct adds buffering to any reader.
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///
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/// It can be excessively inefficient to work directly with a [`Read`] instance.
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/// For example, every call to [`read`][`TcpStream::read`] on [`TcpStream`]
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/// results in a system call. A `BufReader` performs large, infrequent reads on
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/// the underlying [`Read`] and maintains an in-memory buffer of the results.
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///
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/// [`Read`]: ../../std/io/trait.Read.html
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/// [`TcpStream::read`]: ../../std/net/struct.TcpStream.html#method.read
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/// [`TcpStream`]: ../../std/net/struct.TcpStream.html
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///
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/// # Examples
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///
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/// ```
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/// use std::io::prelude::*;
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f = File::open("log.txt")?;
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/// let mut reader = BufReader::new(f);
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///
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/// let mut line = String::new();
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/// let len = reader.read_line(&mut line)?;
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/// println!("First line is {} bytes long", len);
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct BufReader<R> {
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inner: R,
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buf: Box<[u8]>,
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pos: usize,
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cap: usize,
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}
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impl<R: Read> BufReader<R> {
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/// Creates a new `BufReader` with a default buffer capacity.
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///
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/// # Examples
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///
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/// ```
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f = File::open("log.txt")?;
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/// let mut reader = BufReader::new(f);
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn new(inner: R) -> BufReader<R> {
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BufReader::with_capacity(DEFAULT_BUF_SIZE, inner)
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}
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/// Creates a new `BufReader` with the specified buffer capacity.
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///
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/// # Examples
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///
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/// Creating a buffer with ten bytes of capacity:
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///
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/// ```
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f = File::open("log.txt")?;
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/// let mut reader = BufReader::with_capacity(10, f);
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn with_capacity(cap: usize, inner: R) -> BufReader<R> {
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unsafe {
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let mut buffer = Vec::with_capacity(cap);
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buffer.set_len(cap);
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inner.initializer().initialize(&mut buffer);
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BufReader {
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inner: inner,
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buf: buffer.into_boxed_slice(),
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pos: 0,
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cap: 0,
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}
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}
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}
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/// Gets a reference to the underlying reader.
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///
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/// It is inadvisable to directly read from the underlying reader.
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///
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/// # Examples
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///
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/// ```
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f1 = File::open("log.txt")?;
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/// let mut reader = BufReader::new(f1);
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///
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/// let f2 = reader.get_ref();
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn get_ref(&self) -> &R { &self.inner }
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/// Gets a mutable reference to the underlying reader.
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///
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/// It is inadvisable to directly read from the underlying reader.
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///
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/// # Examples
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///
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/// ```
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f1 = File::open("log.txt")?;
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/// let mut reader = BufReader::new(f1);
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///
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/// let f2 = reader.get_mut();
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
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/// Unwraps this `BufReader`, returning the underlying reader.
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///
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/// Note that any leftover data in the internal buffer is lost.
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///
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/// # Examples
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///
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/// ```
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/// use std::io::BufReader;
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/// use std::fs::File;
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///
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/// # fn foo() -> std::io::Result<()> {
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/// let mut f1 = File::open("log.txt")?;
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/// let mut reader = BufReader::new(f1);
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///
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/// let f2 = reader.into_inner();
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/// # Ok(())
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/// # }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn into_inner(self) -> R { self.inner }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<R: Read> Read for BufReader<R> {
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fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
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// If we don't have any buffered data and we're doing a massive read
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// (larger than our internal buffer), bypass our internal buffer
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// entirely.
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if self.pos == self.cap && buf.len() >= self.buf.len() {
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return self.inner.read(buf);
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}
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let nread = {
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let mut rem = self.fill_buf()?;
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rem.read(buf)?
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};
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self.consume(nread);
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Ok(nread)
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}
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// we can't skip unconditionally because of the large buffer case in read.
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unsafe fn initializer(&self) -> Initializer {
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self.inner.initializer()
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<R: Read> BufRead for BufReader<R> {
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fn fill_buf(&mut self) -> io::Result<&[u8]> {
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// If we've reached the end of our internal buffer then we need to fetch
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// some more data from the underlying reader.
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// Branch using `>=` instead of the more correct `==`
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// to tell the compiler that the pos..cap slice is always valid.
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if self.pos >= self.cap {
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debug_assert!(self.pos == self.cap);
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self.cap = self.inner.read(&mut self.buf)?;
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self.pos = 0;
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}
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Ok(&self.buf[self.pos..self.cap])
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}
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fn consume(&mut self, amt: usize) {
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self.pos = cmp::min(self.pos + amt, self.cap);
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<R> fmt::Debug for BufReader<R> where R: fmt::Debug {
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fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
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fmt.debug_struct("BufReader")
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.field("reader", &self.inner)
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.field("buffer", &format_args!("{}/{}", self.cap - self.pos, self.buf.len()))
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.finish()
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<R: Seek> Seek for BufReader<R> {
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/// Seek to an offset, in bytes, in the underlying reader.
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///
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/// The position used for seeking with `SeekFrom::Current(_)` is the
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/// position the underlying reader would be at if the `BufReader` had no
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/// internal buffer.
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///
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/// Seeking always discards the internal buffer, even if the seek position
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/// would otherwise fall within it. This guarantees that calling
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/// `.into_inner()` immediately after a seek yields the underlying reader
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/// at the same position.
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///
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/// See `std::io::Seek` for more details.
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///
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/// Note: In the edge case where you're seeking with `SeekFrom::Current(n)`
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/// where `n` minus the internal buffer length underflows an `i64`, two
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/// seeks will be performed instead of one. If the second seek returns
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/// `Err`, the underlying reader will be left at the same position it would
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/// have if you seeked to `SeekFrom::Current(0)`.
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fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
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let result: u64;
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if let SeekFrom::Current(n) = pos {
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let remainder = (self.cap - self.pos) as i64;
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// it should be safe to assume that remainder fits within an i64 as the alternative
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// means we managed to allocate 8 exbibytes and that's absurd.
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// But it's not out of the realm of possibility for some weird underlying reader to
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// support seeking by i64::min_value() so we need to handle underflow when subtracting
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// remainder.
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if let Some(offset) = n.checked_sub(remainder) {
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result = self.inner.seek(SeekFrom::Current(offset))?;
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} else {
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// seek backwards by our remainder, and then by the offset
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self.inner.seek(SeekFrom::Current(-remainder))?;
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self.pos = self.cap; // empty the buffer
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result = self.inner.seek(SeekFrom::Current(n))?;
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}
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} else {
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// Seeking with Start/End doesn't care about our buffer length.
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result = self.inner.seek(pos)?;
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}
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self.pos = self.cap; // empty the buffer
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Ok(result)
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}
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}
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/// Wraps a writer and buffers its output.
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///
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/// It can be excessively inefficient to work directly with something that
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/// implements [`Write`]. For example, every call to
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/// [`write`][`Tcpstream::write`] on [`TcpStream`] results in a system call. A
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/// `BufWriter` keeps an in-memory buffer of data and writes it to an underlying
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/// writer in large, infrequent batches.
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///
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/// The buffer will be written out when the writer is dropped.
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///
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/// # Examples
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///
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/// Let's write the numbers one through ten to a [`TcpStream`]:
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///
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/// ```no_run
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/// use std::io::prelude::*;
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/// use std::net::TcpStream;
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///
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/// let mut stream = TcpStream::connect("127.0.0.1:34254").unwrap();
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///
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/// for i in 1..10 {
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/// stream.write(&[i]).unwrap();
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/// }
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/// ```
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///
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/// Because we're not buffering, we write each one in turn, incurring the
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/// overhead of a system call per byte written. We can fix this with a
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/// `BufWriter`:
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///
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/// ```no_run
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/// use std::io::prelude::*;
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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///
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/// for i in 1..10 {
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/// stream.write(&[i]).unwrap();
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/// }
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/// ```
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///
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/// By wrapping the stream with a `BufWriter`, these ten writes are all grouped
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/// together by the buffer, and will all be written out in one system call when
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/// the `stream` is dropped.
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///
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/// [`Write`]: ../../std/io/trait.Write.html
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/// [`Tcpstream::write`]: ../../std/net/struct.TcpStream.html#method.write
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/// [`TcpStream`]: ../../std/net/struct.TcpStream.html
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct BufWriter<W: Write> {
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inner: Option<W>,
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buf: Vec<u8>,
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// #30888: If the inner writer panics in a call to write, we don't want to
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// write the buffered data a second time in BufWriter's destructor. This
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// flag tells the Drop impl if it should skip the flush.
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panicked: bool,
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}
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/// An error returned by `into_inner` which combines an error that
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/// happened while writing out the buffer, and the buffered writer object
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/// which may be used to recover from the condition.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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///
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/// // do stuff with the stream
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///
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/// // we want to get our `TcpStream` back, so let's try:
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///
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/// let stream = match stream.into_inner() {
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/// Ok(s) => s,
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/// Err(e) => {
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/// // Here, e is an IntoInnerError
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/// panic!("An error occurred");
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/// }
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/// };
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/// ```
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#[derive(Debug)]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct IntoInnerError<W>(W, Error);
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impl<W: Write> BufWriter<W> {
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/// Creates a new `BufWriter` with a default buffer capacity.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn new(inner: W) -> BufWriter<W> {
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BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
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}
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/// Creates a new `BufWriter` with the specified buffer capacity.
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///
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/// # Examples
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///
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/// Creating a buffer with a buffer of a hundred bytes.
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let stream = TcpStream::connect("127.0.0.1:34254").unwrap();
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/// let mut buffer = BufWriter::with_capacity(100, stream);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn with_capacity(cap: usize, inner: W) -> BufWriter<W> {
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BufWriter {
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inner: Some(inner),
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buf: Vec::with_capacity(cap),
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panicked: false,
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}
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}
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fn flush_buf(&mut self) -> io::Result<()> {
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let mut written = 0;
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let len = self.buf.len();
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let mut ret = Ok(());
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while written < len {
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self.panicked = true;
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let r = self.inner.as_mut().unwrap().write(&self.buf[written..]);
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self.panicked = false;
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match r {
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Ok(0) => {
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ret = Err(Error::new(ErrorKind::WriteZero,
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"failed to write the buffered data"));
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break;
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}
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Ok(n) => written += n,
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Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {}
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Err(e) => { ret = Err(e); break }
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}
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}
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if written > 0 {
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self.buf.drain(..written);
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}
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ret
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}
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/// Gets a reference to the underlying writer.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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///
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/// // we can use reference just like buffer
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/// let reference = buffer.get_ref();
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() }
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/// Gets a mutable reference to the underlying writer.
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///
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/// It is inadvisable to directly write to the underlying writer.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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///
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/// // we can use reference just like buffer
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/// let reference = buffer.get_mut();
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
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/// Unwraps this `BufWriter`, returning the underlying writer.
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///
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/// The buffer is written out before returning the writer.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::io::BufWriter;
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/// use std::net::TcpStream;
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///
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/// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
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///
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/// // unwrap the TcpStream and flush the buffer
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/// let stream = buffer.into_inner().unwrap();
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
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match self.flush_buf() {
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Err(e) => Err(IntoInnerError(self, e)),
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Ok(()) => Ok(self.inner.take().unwrap())
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<W: Write> Write for BufWriter<W> {
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fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
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if self.buf.len() + buf.len() > self.buf.capacity() {
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self.flush_buf()?;
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}
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if buf.len() >= self.buf.capacity() {
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self.panicked = true;
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let r = self.inner.as_mut().unwrap().write(buf);
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self.panicked = false;
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r
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} else {
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Write::write(&mut self.buf, buf)
|
|
}
|
|
}
|
|
fn flush(&mut self) -> io::Result<()> {
|
|
self.flush_buf().and_then(|()| self.get_mut().flush())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<W: 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.as_ref().unwrap())
|
|
.field("buffer", &format_args!("{}/{}", self.buf.len(), self.buf.capacity()))
|
|
.finish()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<W: 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().and_then(|_| self.get_mut().seek(pos))
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<W: Write> Drop for BufWriter<W> {
|
|
fn drop(&mut self) {
|
|
if self.inner.is_some() && !self.panicked {
|
|
// dtors should not panic, so we ignore a failed flush
|
|
let _r = self.flush_buf();
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<W> IntoInnerError<W> {
|
|
/// Returns the error which caused the call to `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 }
|
|
}
|
|
|
|
#[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> {
|
|
fn description(&self) -> &str {
|
|
error::Error::description(self.error())
|
|
}
|
|
}
|
|
|
|
#[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)
|
|
}
|
|
}
|
|
|
|
/// Wraps a writer and buffers output to it, flushing whenever a newline
|
|
/// (`0x0a`, `'\n'`) is detected.
|
|
///
|
|
/// The [`BufWriter`][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.
|
|
///
|
|
/// [bufwriter]: struct.BufWriter.html
|
|
///
|
|
/// 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.
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::prelude::*;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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);
|
|
///
|
|
/// for &byte in road_not_taken.iter() {
|
|
/// file.write(&[byte]).unwrap();
|
|
/// }
|
|
///
|
|
/// // let's check we did the right thing.
|
|
/// let mut file = File::open("poem.txt")?;
|
|
/// let mut contents = String::new();
|
|
///
|
|
/// file.read_to_string(&mut contents)?;
|
|
///
|
|
/// assert_eq!(contents.as_bytes(), &road_not_taken[..]);
|
|
/// # Ok(())
|
|
/// # }
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub struct LineWriter<W: Write> {
|
|
inner: BufWriter<W>,
|
|
need_flush: bool,
|
|
}
|
|
|
|
impl<W: Write> LineWriter<W> {
|
|
/// Creates a new `LineWriter`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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 a specified capacity for the internal
|
|
/// buffer.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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(cap: usize, inner: W) -> LineWriter<W> {
|
|
LineWriter {
|
|
inner: BufWriter::with_capacity(cap, inner),
|
|
need_flush: false,
|
|
}
|
|
}
|
|
|
|
/// Gets a reference to the underlying writer.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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() }
|
|
|
|
/// 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
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::fs::File;
|
|
/// use std::io::LineWriter;
|
|
///
|
|
/// # fn foo() -> 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(|IntoInnerError(buf, e)| {
|
|
IntoInnerError(LineWriter {
|
|
inner: buf,
|
|
need_flush: false,
|
|
}, e)
|
|
})
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<W: Write> Write for LineWriter<W> {
|
|
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
|
|
if self.need_flush {
|
|
self.flush()?;
|
|
}
|
|
|
|
// Find the last newline character in the buffer provided. If found then
|
|
// we're going to write all the data up to that point and then flush,
|
|
// otherewise we just write the whole block to the underlying writer.
|
|
let i = match memchr::memrchr(b'\n', buf) {
|
|
Some(i) => i,
|
|
None => return self.inner.write(buf),
|
|
};
|
|
|
|
|
|
// Ok, we're going to write a partial amount of the data given first
|
|
// followed by flushing the newline. After we've successfully written
|
|
// some data then we *must* report that we wrote that data, so future
|
|
// errors are ignored. We set our internal `need_flush` flag, though, in
|
|
// case flushing fails and we need to try it first next time.
|
|
let n = self.inner.write(&buf[..i + 1])?;
|
|
self.need_flush = true;
|
|
if self.flush().is_err() || n != i + 1 {
|
|
return Ok(n)
|
|
}
|
|
|
|
// At this point we successfully wrote `i + 1` bytes and flushed it out,
|
|
// meaning that the entire line is now flushed out on the screen. While
|
|
// we can attempt to finish writing the rest of the data provided.
|
|
// Remember though that we ignore errors here as we've successfully
|
|
// written data, so we need to report that.
|
|
match self.inner.write(&buf[i + 1..]) {
|
|
Ok(i) => Ok(n + i),
|
|
Err(_) => Ok(n),
|
|
}
|
|
}
|
|
|
|
fn flush(&mut self) -> io::Result<()> {
|
|
self.inner.flush()?;
|
|
self.need_flush = false;
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<W: 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.inner.inner)
|
|
.field("buffer",
|
|
&format_args!("{}/{}", self.inner.buf.len(), self.inner.buf.capacity()))
|
|
.finish()
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use io::prelude::*;
|
|
use io::{self, BufReader, BufWriter, LineWriter, SeekFrom};
|
|
use sync::atomic::{AtomicUsize, Ordering};
|
|
use thread;
|
|
use test;
|
|
|
|
/// A dummy reader intended at testing short-reads propagation.
|
|
pub struct ShortReader {
|
|
lengths: Vec<usize>,
|
|
}
|
|
|
|
impl Read for ShortReader {
|
|
fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
|
|
if self.lengths.is_empty() {
|
|
Ok(0)
|
|
} else {
|
|
Ok(self.lengths.remove(0))
|
|
}
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_reader() {
|
|
let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
|
|
let mut reader = BufReader::with_capacity(2, inner);
|
|
|
|
let mut buf = [0, 0, 0];
|
|
let nread = reader.read(&mut buf);
|
|
assert_eq!(nread.unwrap(), 3);
|
|
let b: &[_] = &[5, 6, 7];
|
|
assert_eq!(buf, b);
|
|
|
|
let mut buf = [0, 0];
|
|
let nread = reader.read(&mut buf);
|
|
assert_eq!(nread.unwrap(), 2);
|
|
let b: &[_] = &[0, 1];
|
|
assert_eq!(buf, b);
|
|
|
|
let mut buf = [0];
|
|
let nread = reader.read(&mut buf);
|
|
assert_eq!(nread.unwrap(), 1);
|
|
let b: &[_] = &[2];
|
|
assert_eq!(buf, b);
|
|
|
|
let mut buf = [0, 0, 0];
|
|
let nread = reader.read(&mut buf);
|
|
assert_eq!(nread.unwrap(), 1);
|
|
let b: &[_] = &[3, 0, 0];
|
|
assert_eq!(buf, b);
|
|
|
|
let nread = reader.read(&mut buf);
|
|
assert_eq!(nread.unwrap(), 1);
|
|
let b: &[_] = &[4, 0, 0];
|
|
assert_eq!(buf, b);
|
|
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_reader_seek() {
|
|
let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
|
|
let mut reader = BufReader::with_capacity(2, io::Cursor::new(inner));
|
|
|
|
assert_eq!(reader.seek(SeekFrom::Start(3)).ok(), Some(3));
|
|
assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
|
|
assert_eq!(reader.seek(SeekFrom::Current(0)).ok(), Some(3));
|
|
assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
|
|
assert_eq!(reader.seek(SeekFrom::Current(1)).ok(), Some(4));
|
|
assert_eq!(reader.fill_buf().ok(), Some(&[1, 2][..]));
|
|
reader.consume(1);
|
|
assert_eq!(reader.seek(SeekFrom::Current(-2)).ok(), Some(3));
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_reader_seek_underflow() {
|
|
// gimmick reader that yields its position modulo 256 for each byte
|
|
struct PositionReader {
|
|
pos: u64
|
|
}
|
|
impl Read for PositionReader {
|
|
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
|
|
let len = buf.len();
|
|
for x in buf {
|
|
*x = self.pos as u8;
|
|
self.pos = self.pos.wrapping_add(1);
|
|
}
|
|
Ok(len)
|
|
}
|
|
}
|
|
impl Seek for PositionReader {
|
|
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
|
|
match pos {
|
|
SeekFrom::Start(n) => {
|
|
self.pos = n;
|
|
}
|
|
SeekFrom::Current(n) => {
|
|
self.pos = self.pos.wrapping_add(n as u64);
|
|
}
|
|
SeekFrom::End(n) => {
|
|
self.pos = u64::max_value().wrapping_add(n as u64);
|
|
}
|
|
}
|
|
Ok(self.pos)
|
|
}
|
|
}
|
|
|
|
let mut reader = BufReader::with_capacity(5, PositionReader { pos: 0 });
|
|
assert_eq!(reader.fill_buf().ok(), Some(&[0, 1, 2, 3, 4][..]));
|
|
assert_eq!(reader.seek(SeekFrom::End(-5)).ok(), Some(u64::max_value()-5));
|
|
assert_eq!(reader.fill_buf().ok().map(|s| s.len()), Some(5));
|
|
// the following seek will require two underlying seeks
|
|
let expected = 9223372036854775802;
|
|
assert_eq!(reader.seek(SeekFrom::Current(i64::min_value())).ok(), Some(expected));
|
|
assert_eq!(reader.fill_buf().ok().map(|s| s.len()), Some(5));
|
|
// seeking to 0 should empty the buffer.
|
|
assert_eq!(reader.seek(SeekFrom::Current(0)).ok(), Some(expected));
|
|
assert_eq!(reader.get_ref().pos, expected);
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_writer() {
|
|
let inner = Vec::new();
|
|
let mut writer = BufWriter::with_capacity(2, inner);
|
|
|
|
writer.write(&[0, 1]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1]);
|
|
|
|
writer.write(&[2]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1]);
|
|
|
|
writer.write(&[3]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1]);
|
|
|
|
writer.flush().unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
|
|
|
|
writer.write(&[4]).unwrap();
|
|
writer.write(&[5]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
|
|
|
|
writer.write(&[6]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5]);
|
|
|
|
writer.write(&[7, 8]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8]);
|
|
|
|
writer.write(&[9, 10, 11]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
|
|
|
|
writer.flush().unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_writer_inner_flushes() {
|
|
let mut w = BufWriter::with_capacity(3, Vec::new());
|
|
w.write(&[0, 1]).unwrap();
|
|
assert_eq!(*w.get_ref(), []);
|
|
let w = w.into_inner().unwrap();
|
|
assert_eq!(w, [0, 1]);
|
|
}
|
|
|
|
#[test]
|
|
fn test_buffered_writer_seek() {
|
|
let mut w = BufWriter::with_capacity(3, io::Cursor::new(Vec::new()));
|
|
w.write_all(&[0, 1, 2, 3, 4, 5]).unwrap();
|
|
w.write_all(&[6, 7]).unwrap();
|
|
assert_eq!(w.seek(SeekFrom::Current(0)).ok(), Some(8));
|
|
assert_eq!(&w.get_ref().get_ref()[..], &[0, 1, 2, 3, 4, 5, 6, 7][..]);
|
|
assert_eq!(w.seek(SeekFrom::Start(2)).ok(), Some(2));
|
|
w.write_all(&[8, 9]).unwrap();
|
|
assert_eq!(&w.into_inner().unwrap().into_inner()[..], &[0, 1, 8, 9, 4, 5, 6, 7]);
|
|
}
|
|
|
|
#[test]
|
|
fn test_read_until() {
|
|
let inner: &[u8] = &[0, 1, 2, 1, 0];
|
|
let mut reader = BufReader::with_capacity(2, inner);
|
|
let mut v = Vec::new();
|
|
reader.read_until(0, &mut v).unwrap();
|
|
assert_eq!(v, [0]);
|
|
v.truncate(0);
|
|
reader.read_until(2, &mut v).unwrap();
|
|
assert_eq!(v, [1, 2]);
|
|
v.truncate(0);
|
|
reader.read_until(1, &mut v).unwrap();
|
|
assert_eq!(v, [1]);
|
|
v.truncate(0);
|
|
reader.read_until(8, &mut v).unwrap();
|
|
assert_eq!(v, [0]);
|
|
v.truncate(0);
|
|
reader.read_until(9, &mut v).unwrap();
|
|
assert_eq!(v, []);
|
|
}
|
|
|
|
#[test]
|
|
fn test_line_buffer_fail_flush() {
|
|
// Issue #32085
|
|
struct FailFlushWriter<'a>(&'a mut Vec<u8>);
|
|
|
|
impl<'a> Write for FailFlushWriter<'a> {
|
|
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
|
|
self.0.extend_from_slice(buf);
|
|
Ok(buf.len())
|
|
}
|
|
fn flush(&mut self) -> io::Result<()> {
|
|
Err(io::Error::new(io::ErrorKind::Other, "flush failed"))
|
|
}
|
|
}
|
|
|
|
let mut buf = Vec::new();
|
|
{
|
|
let mut writer = LineWriter::new(FailFlushWriter(&mut buf));
|
|
let to_write = b"abc\ndef";
|
|
if let Ok(written) = writer.write(to_write) {
|
|
assert!(written < to_write.len(), "didn't flush on new line");
|
|
// PASS
|
|
return;
|
|
}
|
|
}
|
|
assert!(buf.is_empty(), "write returned an error but wrote data");
|
|
}
|
|
|
|
#[test]
|
|
fn test_line_buffer() {
|
|
let mut writer = LineWriter::new(Vec::new());
|
|
writer.write(&[0]).unwrap();
|
|
assert_eq!(*writer.get_ref(), []);
|
|
writer.write(&[1]).unwrap();
|
|
assert_eq!(*writer.get_ref(), []);
|
|
writer.flush().unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1]);
|
|
writer.write(&[0, b'\n', 1, b'\n', 2]).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n']);
|
|
writer.flush().unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2]);
|
|
writer.write(&[3, b'\n']).unwrap();
|
|
assert_eq!(*writer.get_ref(), [0, 1, 0, b'\n', 1, b'\n', 2, 3, b'\n']);
|
|
}
|
|
|
|
#[test]
|
|
fn test_read_line() {
|
|
let in_buf: &[u8] = b"a\nb\nc";
|
|
let mut reader = BufReader::with_capacity(2, in_buf);
|
|
let mut s = String::new();
|
|
reader.read_line(&mut s).unwrap();
|
|
assert_eq!(s, "a\n");
|
|
s.truncate(0);
|
|
reader.read_line(&mut s).unwrap();
|
|
assert_eq!(s, "b\n");
|
|
s.truncate(0);
|
|
reader.read_line(&mut s).unwrap();
|
|
assert_eq!(s, "c");
|
|
s.truncate(0);
|
|
reader.read_line(&mut s).unwrap();
|
|
assert_eq!(s, "");
|
|
}
|
|
|
|
#[test]
|
|
fn test_lines() {
|
|
let in_buf: &[u8] = b"a\nb\nc";
|
|
let reader = BufReader::with_capacity(2, in_buf);
|
|
let mut it = reader.lines();
|
|
assert_eq!(it.next().unwrap().unwrap(), "a".to_string());
|
|
assert_eq!(it.next().unwrap().unwrap(), "b".to_string());
|
|
assert_eq!(it.next().unwrap().unwrap(), "c".to_string());
|
|
assert!(it.next().is_none());
|
|
}
|
|
|
|
#[test]
|
|
fn test_short_reads() {
|
|
let inner = ShortReader{lengths: vec![0, 1, 2, 0, 1, 0]};
|
|
let mut reader = BufReader::new(inner);
|
|
let mut buf = [0, 0];
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 0);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 1);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 2);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 0);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 1);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 0);
|
|
assert_eq!(reader.read(&mut buf).unwrap(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn read_char_buffered() {
|
|
let buf = [195, 159];
|
|
let reader = BufReader::with_capacity(1, &buf[..]);
|
|
assert_eq!(reader.chars().next().unwrap().unwrap(), 'ß');
|
|
}
|
|
|
|
#[test]
|
|
fn test_chars() {
|
|
let buf = [195, 159, b'a'];
|
|
let reader = BufReader::with_capacity(1, &buf[..]);
|
|
let mut it = reader.chars();
|
|
assert_eq!(it.next().unwrap().unwrap(), 'ß');
|
|
assert_eq!(it.next().unwrap().unwrap(), 'a');
|
|
assert!(it.next().is_none());
|
|
}
|
|
|
|
#[test]
|
|
#[should_panic]
|
|
fn dont_panic_in_drop_on_panicked_flush() {
|
|
struct FailFlushWriter;
|
|
|
|
impl Write for FailFlushWriter {
|
|
fn write(&mut self, buf: &[u8]) -> io::Result<usize> { Ok(buf.len()) }
|
|
fn flush(&mut self) -> io::Result<()> {
|
|
Err(io::Error::last_os_error())
|
|
}
|
|
}
|
|
|
|
let writer = FailFlushWriter;
|
|
let _writer = BufWriter::new(writer);
|
|
|
|
// If writer panics *again* due to the flush error then the process will
|
|
// abort.
|
|
panic!();
|
|
}
|
|
|
|
#[test]
|
|
#[cfg_attr(target_os = "emscripten", ignore)]
|
|
fn panic_in_write_doesnt_flush_in_drop() {
|
|
static WRITES: AtomicUsize = AtomicUsize::new(0);
|
|
|
|
struct PanicWriter;
|
|
|
|
impl Write for PanicWriter {
|
|
fn write(&mut self, _: &[u8]) -> io::Result<usize> {
|
|
WRITES.fetch_add(1, Ordering::SeqCst);
|
|
panic!();
|
|
}
|
|
fn flush(&mut self) -> io::Result<()> { Ok(()) }
|
|
}
|
|
|
|
thread::spawn(|| {
|
|
let mut writer = BufWriter::new(PanicWriter);
|
|
let _ = writer.write(b"hello world");
|
|
let _ = writer.flush();
|
|
}).join().unwrap_err();
|
|
|
|
assert_eq!(WRITES.load(Ordering::SeqCst), 1);
|
|
}
|
|
|
|
#[bench]
|
|
fn bench_buffered_reader(b: &mut test::Bencher) {
|
|
b.iter(|| {
|
|
BufReader::new(io::empty())
|
|
});
|
|
}
|
|
|
|
#[bench]
|
|
fn bench_buffered_writer(b: &mut test::Bencher) {
|
|
b.iter(|| {
|
|
BufWriter::new(io::sink())
|
|
});
|
|
}
|
|
|
|
struct AcceptOneThenFail {
|
|
written: bool,
|
|
flushed: bool,
|
|
}
|
|
|
|
impl Write for AcceptOneThenFail {
|
|
fn write(&mut self, data: &[u8]) -> io::Result<usize> {
|
|
if !self.written {
|
|
assert_eq!(data, b"a\nb\n");
|
|
self.written = true;
|
|
Ok(data.len())
|
|
} else {
|
|
Err(io::Error::new(io::ErrorKind::NotFound, "test"))
|
|
}
|
|
}
|
|
|
|
fn flush(&mut self) -> io::Result<()> {
|
|
assert!(self.written);
|
|
assert!(!self.flushed);
|
|
self.flushed = true;
|
|
Err(io::Error::new(io::ErrorKind::Other, "test"))
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn erroneous_flush_retried() {
|
|
let a = AcceptOneThenFail {
|
|
written: false,
|
|
flushed: false,
|
|
};
|
|
|
|
let mut l = LineWriter::new(a);
|
|
assert_eq!(l.write(b"a\nb\na").unwrap(), 4);
|
|
assert!(l.get_ref().written);
|
|
assert!(l.get_ref().flushed);
|
|
l.get_mut().flushed = false;
|
|
|
|
assert_eq!(l.write(b"a").unwrap_err().kind(), io::ErrorKind::Other)
|
|
}
|
|
}
|