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Struct std::io::BufWriter

pub struct BufWriter<W: Write> { /* fields omitted */ }

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 on TcpStream results in a system call. A BufWriter keeps an in-memory buffer of data and writes it to an underlying writer in large, infrequent batches.

When the BufWriter is dropped, the contents of its buffer will be written out. However, any errors that happen in the process of flushing the buffer when the writer is dropped will be ignored. Code that wishes to handle such errors must manually call flush before the writer is dropped.

Examples

Let's write the numbers one through ten to a TcpStream:

use std::io::prelude::*;
use std::net::TcpStream;

let mut stream = TcpStream::connect("127.0.0.1:34254").unwrap();

for i in 1..10 {
    stream.write(&[i]).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:

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 1..10 {
    stream.write(&[i]).unwrap();
}

By wrapping the stream with a BufWriter, these ten writes are all grouped together by the buffer, and will all be written out in one system call when the stream is dropped.

Methods

impl<W: Write> BufWriter<W> [src]

[src]

Creates a new BufWriter with a default buffer capacity.

Examples

use std::io::BufWriter;
use std::net::TcpStream;

let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());

[src]

Creates a new BufWriter with the specified buffer capacity.

Examples

Creating a buffer with a buffer of a hundred bytes.

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);

[src]

Gets a reference to the underlying writer.

Examples

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();

[src]

Gets a mutable reference to the underlying writer.

It is inadvisable to directly write to the underlying writer.

Examples

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();

[src]

Unwraps this BufWriter, returning the underlying writer.

The buffer is written out before returning the writer.

Examples

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();

Trait Implementations

impl<W: Write> Write for BufWriter<W> [src]

[src]

Write a buffer into this object, returning how many bytes were written. Read more

[src]

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

[src]

Attempts to write an entire buffer into this write. Read more

[src]

Writes a formatted string into this writer, returning any error encountered. Read more

[src]

Creates a "by reference" adaptor for this instance of Write. Read more

impl<W: Write> Debug for BufWriter<W> where
    W: Debug,  [src]

[src]

Formats the value using the given formatter. Read more

impl<W: Write + Seek> Seek for BufWriter<W> [src]

[src]

Seek to the offset, in bytes, in the underlying writer.

Seeking always writes out the internal buffer before seeking.

impl<W: Write> Drop for BufWriter<W> [src]

[src]

Executes the destructor for this type. Read more

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/io/struct.BufWriter.html