diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs index d6561ebb489d7..780b4f86c0e82 100644 --- a/src/libstd/io/buffered.rs +++ b/src/libstd/io/buffered.rs @@ -252,14 +252,49 @@ impl Seek for BufReader { } } -/// Wraps a Writer and buffers output to it. +/// Wraps a writer and buffers its output. /// -/// It can be excessively inefficient to work directly with a `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 the -/// underlying `Write` in large, infrequent batches. +/// 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`: +/// +/// ```no_run +/// 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`: +/// +/// ```no_run +/// 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. #[stable(feature = "rust1", since = "1.0.0")] pub struct BufWriter { inner: Option, @@ -275,12 +310,33 @@ pub struct IntoInnerError(W, Error); impl BufWriter { /// Creates a new `BufWriter` with a default buffer capacity. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::BufWriter; + /// use std::net::TcpStream; + /// + /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn new(inner: W) -> BufWriter { BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner) } /// Creates a new `BufWriter` with the specified buffer capacity. + /// + /// # Examples + /// + /// Creating a buffer with a buffer of a hundred bytes. + /// + /// ```no_run + /// 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); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn with_capacity(cap: usize, inner: W) -> BufWriter { BufWriter { @@ -313,6 +369,18 @@ impl BufWriter { } /// Gets a reference to the underlying writer. + /// + /// # Examples + /// + /// ```no_run + /// 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(); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() } @@ -321,12 +389,36 @@ impl BufWriter { /// # Warning /// /// It is inadvisable to directly write to the underlying writer. + /// + /// # Examples + /// + /// ```no_run + /// 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(); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() } /// Unwraps this `BufWriter`, returning the underlying writer. /// /// The buffer is written out before returning the writer. + /// + /// # Examples + /// + /// ```no_run + /// 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(); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn into_inner(mut self) -> Result>> { match self.flush_buf() {