Struct bitflags::__core::io::BufWriter

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

[−] Expand description

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.

The buffer will be written out when 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.