Struct docktape::io::BufWriter 1.0.0[−][src]
pub struct BufWriter<W> where
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.
BufWriter
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 Vec<u8>
.
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 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
:
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(); }
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> BufWriter<W> where
W: Write,
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impl<W> BufWriter<W> where
W: Write,
ⓘImportant traits for BufWriter<W>pub fn new(inner: W) -> BufWriter<W>
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pub fn new(inner: W) -> BufWriter<W>
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());
ⓘImportant traits for BufWriter<W>pub fn with_capacity(cap: usize, inner: W) -> BufWriter<W>
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pub 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.
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);
ⓘImportant traits for &'a mut Rpub fn get_ref(&self) -> &W
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pub fn get_ref(&self) -> &W
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();
ⓘImportant traits for &'a mut Rpub fn get_mut(&mut self) -> &mut W
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pub 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
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();
pub fn into_inner(self) -> Result<W, IntoInnerError<BufWriter<W>>>
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pub 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.
Errors
An Err
will be returned if an error occurs while flushing the buffer.
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> Debug for BufWriter<W> where
W: Write + Debug,
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impl<W> Debug for BufWriter<W> where
W: Write + Debug,
fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>
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fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl<W> Drop for BufWriter<W> where
W: Write,
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impl<W> Drop for BufWriter<W> where
W: Write,
impl<W> Seek for BufWriter<W> where
W: Write + Seek,
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impl<W> Seek for BufWriter<W> where
W: Write + Seek,
fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
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fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
Seek to the offset, in bytes, in the underlying writer.
Seeking always writes out the internal buffer before seeking.
impl<W> Write for BufWriter<W> where
W: Write,
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impl<W> Write for BufWriter<W> where
W: Write,
fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
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fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
Write a buffer into this object, returning how many bytes were written. Read more
fn flush(&mut self) -> Result<(), Error>
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fn flush(&mut self) -> Result<(), Error>
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
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fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
Attempts to write an entire buffer into this write. Read more
fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>
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fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>
Writes a formatted string into this writer, returning any error encountered. Read more
ⓘImportant traits for &'a mut Rfn by_ref(&mut self) -> &mut Self
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fn by_ref(&mut self) -> &mut Self
Creates a "by reference" adaptor for this instance of Write
. Read more
impl<T> AsyncWrite for BufWriter<T> where
T: AsyncWrite,
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impl<T> AsyncWrite for BufWriter<T> where
T: AsyncWrite,
fn shutdown(&mut self) -> Result<Async<()>, Error>
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fn shutdown(&mut self) -> Result<Async<()>, Error>
Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
fn poll_write(&mut self, buf: &[u8]) -> Result<Async<usize>, Error>
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fn poll_write(&mut self, buf: &[u8]) -> Result<Async<usize>, Error>
Attempt to write bytes from buf
into the object. Read more
fn poll_flush(&mut self) -> Result<Async<()>, Error>
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fn poll_flush(&mut self) -> Result<Async<()>, Error>
Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
fn write_buf<B>(&mut self, buf: &mut B) -> Result<Async<usize>, Error> where
B: Buf,
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fn write_buf<B>(&mut self, buf: &mut B) -> Result<Async<usize>, Error> where
B: Buf,
Write a Buf
into this value, returning how many bytes were written. Read more