Struct std::io::BufWriter
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pub struct BufWriter<W: Write> {
// some 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.
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.
Methods
impl<W: Write> BufWriter<W>
fn new(inner: W) -> BufWriter<W>
Creates a new BufWriter with a default buffer capacity.
Examples
fn main() { use std::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); }use std::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
fn with_capacity(cap: usize, inner: W) -> BufWriter<W>
Creates a new BufWriter with the specified buffer capacity.
Examples
Creating a buffer with a buffer of a hundred bytes.
fn main() { 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); }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);
fn get_ref(&self) -> &W
Gets a reference to the underlying writer.
Examples
fn main() { 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(); }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();
fn get_mut(&mut self) -> &mut W
Gets a mutable reference to the underlying writer.
It is inadvisable to directly write to the underlying writer.
Examples
fn main() { 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(); }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();
fn into_inner(self) -> Result<W, IntoInnerError<BufWriter<W>>>
Unwraps this BufWriter, returning the underlying writer.
The buffer is written out before returning the writer.
Examples
fn main() { 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(); }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();