diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs index 50c44299dc7..60ac89790aa 100644 --- a/src/libstd/io/mod.rs +++ b/src/libstd/io/mod.rs @@ -505,24 +505,69 @@ fn read_until(r: &mut R, delim: u8, buf: &mut Vec) } } -/// A `BufRead` is a type of reader which has some form of internal buffering to -/// allow certain kinds of reading operations to be more optimized than others. +/// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it +/// to perform extra ways of reading. /// -/// This type extends the `Read` trait with a few methods that are not -/// possible to reasonably implement with purely a read interface. +/// For example, reading line-by-line requires using a buffer, so if you want +/// to read by line, you'll need `BufRead`, which includes a +/// [`read_line()`][readline] method as well as a [`lines()`][lines] iterator. +/// +/// [readline]: #method.read_line +/// [lines]: #method.lines +/// +/// # Examples +/// +/// A locked standard input implements `BufRead`: +/// +/// ``` +/// use std::io; +/// use std::io::BufRead; +/// +/// let stdin = io::stdin(); +/// for line in stdin.lock().lines() { +/// println!("{}", line.unwrap()); +/// } +/// ``` +/// +/// If you have something that implements `Read`, you can use the [`BufReader` +/// type][bufreader] to turn it into a `BufRead`. +/// +/// For example, [`File`][file] implements `Read`, but not `BufRead`. +/// `BufReader` to the rescue! +/// +/// [bufreader]: struct.BufReader.html +/// [file]: ../fs/struct.File.html +/// +/// ``` +/// use std::io; +/// use std::fs::File; +/// use std::io::BufRead; +/// use std::io::BufReader; +/// +/// # fn foo() -> io::Result<()> { +/// let f = try!(File::open("foo.txt")); +/// let f = BufReader::new(f); +/// +/// for line in f.lines() { +/// println!("{}", line.unwrap()); +/// } +/// +/// # Ok(()) +/// # } +/// ``` /// -/// You can use the [`BufReader` wrapper type](struct.BufReader.html) to turn any -/// reader into a buffered reader. #[stable(feature = "rust1", since = "1.0.0")] pub trait BufRead: Read { /// Fills the internal buffer of this object, returning the buffer contents. /// - /// None of the contents will be "read" in the sense that later calling - /// `read` may return the same contents. + /// This function is a lower-level call. It needs to be paired with the + /// [`consume`][consume] method to function properly. When calling this + /// method, none of the contents will be "read" in the sense that later + /// calling `read` may return the same contents. As such, `consume` must be + /// called with the number of bytes that are consumed from this buffer to + /// ensure that the bytes are never returned twice. /// - /// The `consume` function must be called with the number of bytes that are - /// consumed from this buffer returned to ensure that the bytes are never - /// returned twice. + /// [consume]: #tymethod.consume /// /// An empty buffer returned indicates that the stream has reached EOF. /// @@ -530,34 +575,66 @@ pub trait BufRead: Read { /// /// This function will return an I/O error if the underlying reader was /// read, but returned an error. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`: + /// + /// ``` + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// let mut stdin = stdin.lock(); + /// + /// // we can't have two `&mut` references to `stdin`, so use a block + /// // to end the borrow early. + /// let length = { + /// let buffer = stdin.fill_buf().unwrap(); + /// + /// // work with buffer + /// println!("{:?}", buffer); + /// + /// buffer.len() + /// }; + /// + /// // ensure the bytes we worked with aren't returned again later + /// stdin.consume(length); + /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn fill_buf(&mut self) -> Result<&[u8]>; /// Tells this buffer that `amt` bytes have been consumed from the buffer, /// so they should no longer be returned in calls to `read`. /// - /// This function does not perform any I/O, it simply informs this object - /// that some amount of its buffer, returned from `fill_buf`, has been - /// consumed and should no longer be returned. + /// This function is a lower-level call. It needs to be paired with the + /// [`fill_buf`][fillbuf] method to function properly. This function does + /// not perform any I/O, it simply informs this object that some amount of + /// its buffer, returned from `fill_buf`, has been consumed and should no + /// longer be returned. As such, this function may do odd things if + /// `fill_buf` isn't called before calling it. /// - /// This function is used to tell the buffer how many bytes you've consumed - /// from the return value of `fill_buf`, and so may do odd things if - /// `fill_buf` isn't called before calling this. + /// [fillbuf]: #tymethod.fill_buff /// - /// The `amt` must be `<=` the number of bytes in the buffer returned by `fill_buf`. + /// The `amt` must be `<=` the number of bytes in the buffer returned by + /// `fill_buf`. + /// + /// # Examples + /// + /// Since `consume()` is meant to be used with [`fill_buf()`][fillbuf], + /// that method's example includes an example of `consume()`. #[stable(feature = "rust1", since = "1.0.0")] fn consume(&mut self, amt: usize); - /// Read all bytes until the delimiter `byte` is reached. + /// Read all bytes into `buf` until the delimiter `byte` is reached. /// - /// This function will continue to read (and buffer) bytes from the - /// underlying stream until the delimiter or EOF is found. Once found, all - /// bytes up to, and including, the delimiter (if found) will be appended to - /// `buf`. + /// This function will read bytes from the underlying stream until the + /// delimiter or EOF is found. Once found, all bytes up to, and including, + /// the delimiter (if found) will be appended to `buf`. /// - /// If this buffered reader is currently at EOF, then this function will not - /// place any more bytes into `buf` and will return `Ok(n)` where `n` is the - /// number of bytes which were read. + /// If this reader is currently at EOF then this function will not modify + /// `buf` and will return `Ok(n)` where `n` is the number of bytes which + /// were read. /// /// # Errors /// @@ -566,18 +643,39 @@ pub trait BufRead: Read { /// /// If an I/O error is encountered then all bytes read so far will be /// present in `buf` and its length will have been adjusted appropriately. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`. In this example, we'll + /// read from standard input until we see an `a` byte. + /// + /// ``` + /// use std::io; + /// use std::io::prelude::*; + /// + /// fn foo() -> io::Result<()> { + /// let stdin = io::stdin(); + /// let mut stdin = stdin.lock(); + /// let mut buffer = Vec::new(); + /// + /// try!(stdin.read_until(b'a', &mut buffer)); + /// + /// println!("{:?}", buffer); + /// # Ok(()) + /// # } + /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn read_until(&mut self, byte: u8, buf: &mut Vec) -> Result { read_until(self, byte, buf) } - /// Read all bytes until a newline (the 0xA byte) is reached, and - /// append them to the provided buffer. + /// Read all bytes until a newline (the 0xA byte) is reached, and append + /// them to the provided buffer. /// - /// This function will continue to read (and buffer) bytes from the - /// underlying stream until the newline delimiter (the 0xA byte) or EOF is - /// found. Once found, all bytes up to, and including, the delimiter (if - /// found) will be appended to `buf`. + /// This function will read bytes from the underlying stream until the + /// newline delimiter (the 0xA byte) or EOF is found. Once found, all bytes + /// up to, and including, the delimiter (if found) will be appended to + /// `buf`. /// /// If this reader is currently at EOF then this function will not modify /// `buf` and will return `Ok(n)` where `n` is the number of bytes which @@ -589,6 +687,31 @@ pub trait BufRead: Read { /// return an error if the read bytes are not valid UTF-8. If an I/O error /// is encountered then `buf` may contain some bytes already read in the /// event that all data read so far was valid UTF-8. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`. In this example, we'll + /// read all of the lines from standard input. If we were to do this in + /// an actual project, the [`lines()`][lines] method would be easier, of + /// course. + /// + /// [lines]: #method.lines + /// + /// ``` + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// let mut stdin = stdin.lock(); + /// let mut buffer = String::new(); + /// + /// while stdin.read_line(&mut buffer).unwrap() > 0 { + /// // work with buffer + /// println!("{:?}", buffer); + /// + /// buffer.clear(); + /// } + /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn read_line(&mut self, buf: &mut String) -> Result { // Note that we are not calling the `.read_until` method here, but @@ -606,6 +729,22 @@ pub trait BufRead: Read { /// /// This function will yield errors whenever `read_until` would have also /// yielded an error. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`. In this example, we'll + /// read some input from standard input, splitting on commas. + /// + /// ``` + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// + /// for content in stdin.lock().split(b',') { + /// println!("{:?}", content.unwrap()); + /// } + /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn split(self, byte: u8) -> Split where Self: Sized { Split { buf: self, delim: byte } @@ -616,6 +755,21 @@ pub trait BufRead: Read { /// The iterator returned from this function will yield instances of /// `io::Result`. Each string returned will *not* have a newline /// byte (the 0xA byte) at the end. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`: + /// + /// ``` + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// + /// for line in stdin.lock().lines() { + /// println!("{}", line.unwrap()); + /// } + /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn lines(self) -> Lines where Self: Sized { Lines { buf: self }