std::io

Trait std::io::BufRead [−] [src]

pub trait BufRead: Read {
    fn fill_buf(&mut self) -> Result<&[u8]>;
    fn consume(&mut self, amt: usize);

    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> { ... }
    fn read_line(&mut self, buf: &mut String) -> Result<usize> { ... }
    fn split(self, byte: u8) -> Split<Self> where Self: Sized { ... }
    fn lines(self) -> Lines<Self> where Self: Sized { ... }
}

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.

This type extends the Read trait with a few methods that are not possible to reasonably implement with purely a read interface.

You can use the BufReader wrapper type to turn any reader into a buffered reader.

Required Methods

fn fill_buf(&mut self) -> Result<&[u8]>

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.

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.

An empty buffer returned indicates that the stream has reached EOF.

Errors

This function will return an I/O error if the underlying reader was read, but returned an error.

fn consume(&mut self, amt: usize)

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 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.

The amt must be <= the number of bytes in the buffer returned by fill_buf.

Provided Methods

fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes 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.

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.

Errors

This function will ignore all instances of ErrorKind::Interrupted and will otherwise return any errors returned by fill_buf.

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.

fn read_line(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until a newline byte (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.

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

This function has the same error semantics as read_until and will also 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.

fn split(self, byte: u8) -> Split<Self> where Self: Sized

Returns an iterator over the contents of this reader split on the byte byte.

The iterator returned from this function will return instances of io::Result<Vec<u8>>. Each vector returned will not have the delimiter byte at the end.

This function will yield errors whenever read_until would have also yielded an error.

fn lines(self) -> Lines<Self> where Self: Sized

Returns an iterator over the lines of this reader.

The iterator returned from this function will yield instances of io::Result<String>. Each string returned will not have a newline byte (the 0xA byte) at the end.

Implementors