Struct std::io::BufReader
pub struct BufReader<'a> { // some fields omitted }
Reads from a fixed-size byte slice
Example
use std::io::BufReader; let mut buf = [0, 1, 2, 3]; let mut r = BufReader::new(buf); assert_eq!(r.read_to_end().unwrap(), ~[0, 1, 2, 3]);
Methods
impl<'a> BufReader<'a>
fn new<'a>(buf: &'a [u8]) -> BufReader<'a>
Creates a new buffered reader which will read the specified buffer
fn eof(&self) -> bool
Tests whether this reader has read all bytes in its buffer.
If true
, then this will no longer return bytes from read
.
Trait Implementations
impl<'a> Reader for BufReader<'a>
fn read(&mut self, buf: &mut [u8]) -> IoResult<uint>
Read bytes, up to the length of buf
and place them in buf
.
Returns the number of bytes read. The number of bytes read my
be less than the number requested, even 0. Returns Err
on EOF.
Error
If an error occurs during this I/O operation, then it is returned as
Err(IoError)
. Note that end-of-file is considered an error, and can be
inspected for in the error's kind
field. Also note that reading 0
bytes is not considered an error in all circumstances
fn read_byte(&mut self) -> IoResult<u8>
Reads a single byte. Returns Err
on EOF.
fn fill(&mut self, buf: &mut [u8]) -> IoResult<()>
Fills the provided slice with bytes from this reader
This will continue to call read
until the slice has been completely
filled with bytes.
Error
If an error occurs at any point, that error is returned, and no further bytes are read.
fn push_exact(&mut self, buf: &mut ~[u8], len: uint) -> IoResult<()>
Reads exactly len
bytes and appends them to a vector.
May push fewer than the requested number of bytes on error
or EOF. If Ok(())
is returned, then all of the requested bytes were
pushed on to the vector, otherwise the amount len
bytes couldn't be
read (an error was encountered), and the error is returned.
fn read_exact(&mut self, len: uint) -> IoResult<~[u8]>
Reads exactly len
bytes and gives you back a new vector of length
len
Error
Fails with the same conditions as read
. Additionally returns error
on EOF. Note that if an error is returned, then some number of bytes may
have already been consumed from the underlying reader, and they are lost
(not returned as part of the error). If this is unacceptable, then it is
recommended to use the push_exact
or read
methods.
fn read_to_end(&mut self) -> IoResult<~[u8]>
Reads all remaining bytes from the stream.
Error
Returns any non-EOF error immediately. Previously read bytes are discarded when an error is returned.
When EOF is encountered, all bytes read up to that point are returned.
fn read_to_str(&mut self) -> IoResult<~str>
Reads all of the remaining bytes of this stream, interpreting them as a UTF-8 encoded stream. The corresponding string is returned.
Error
This function returns all of the same errors as read_to_end
with an
additional error if the reader's contents are not a valid sequence of
UTF-8 bytes.
fn bytes<'r>(&'r mut self) -> Bytes<'r, Self>
Create an iterator that reads a single byte on each iteration, until EOF.
Error
Any error other than EndOfFile
that is produced by the underlying Reader
is returned by the iterator and should be handled by the caller.
fn read_le_uint_n(&mut self, nbytes: uint) -> IoResult<u64>
Reads n
little-endian unsigned integer bytes.
n
must be between 1 and 8, inclusive.
fn read_le_int_n(&mut self, nbytes: uint) -> IoResult<i64>
Reads n
little-endian signed integer bytes.
n
must be between 1 and 8, inclusive.
fn read_be_uint_n(&mut self, nbytes: uint) -> IoResult<u64>
Reads n
big-endian unsigned integer bytes.
n
must be between 1 and 8, inclusive.
fn read_be_int_n(&mut self, nbytes: uint) -> IoResult<i64>
Reads n
big-endian signed integer bytes.
n
must be between 1 and 8, inclusive.
fn read_le_uint(&mut self) -> IoResult<uint>
Reads a little-endian unsigned integer.
The number of bytes returned is system-dependant.
fn read_le_int(&mut self) -> IoResult<int>
Reads a little-endian integer.
The number of bytes returned is system-dependant.
fn read_be_uint(&mut self) -> IoResult<uint>
Reads a big-endian unsigned integer.
The number of bytes returned is system-dependant.
fn read_be_int(&mut self) -> IoResult<int>
Reads a big-endian integer.
The number of bytes returned is system-dependant.
fn read_be_u64(&mut self) -> IoResult<u64>
Reads a big-endian u64
.
u64
s are 8 bytes long.
fn read_be_u32(&mut self) -> IoResult<u32>
Reads a big-endian u32
.
u32
s are 4 bytes long.
fn read_be_u16(&mut self) -> IoResult<u16>
Reads a big-endian u16
.
u16
s are 2 bytes long.
fn read_be_i64(&mut self) -> IoResult<i64>
Reads a big-endian i64
.
i64
s are 8 bytes long.
fn read_be_i32(&mut self) -> IoResult<i32>
Reads a big-endian i32
.
i32
s are 4 bytes long.
fn read_be_i16(&mut self) -> IoResult<i16>
Reads a big-endian i16
.
i16
s are 2 bytes long.
fn read_be_f64(&mut self) -> IoResult<f64>
Reads a big-endian f64
.
f64
s are 8 byte, IEEE754 double-precision floating point numbers.
fn read_be_f32(&mut self) -> IoResult<f32>
Reads a big-endian f32
.
f32
s are 4 byte, IEEE754 single-precision floating point numbers.
fn read_le_u64(&mut self) -> IoResult<u64>
Reads a little-endian u64
.
u64
s are 8 bytes long.
fn read_le_u32(&mut self) -> IoResult<u32>
Reads a little-endian u32
.
u32
s are 4 bytes long.
fn read_le_u16(&mut self) -> IoResult<u16>
Reads a little-endian u16
.
u16
s are 2 bytes long.
fn read_le_i64(&mut self) -> IoResult<i64>
Reads a little-endian i64
.
i64
s are 8 bytes long.
fn read_le_i32(&mut self) -> IoResult<i32>
Reads a little-endian i32
.
i32
s are 4 bytes long.
fn read_le_i16(&mut self) -> IoResult<i16>
Reads a little-endian i16
.
i16
s are 2 bytes long.
fn read_le_f64(&mut self) -> IoResult<f64>
Reads a little-endian f64
.
f64
s are 8 byte, IEEE754 double-precision floating point numbers.
fn read_le_f32(&mut self) -> IoResult<f32>
Reads a little-endian f32
.
f32
s are 4 byte, IEEE754 single-precision floating point numbers.
fn read_u8(&mut self) -> IoResult<u8>
Read a u8.
u8
s are 1 byte.
fn read_i8(&mut self) -> IoResult<i8>
Read an i8.
i8
s are 1 byte.
fn by_ref<'a>(&'a mut self) -> RefReader<'a, Self>
Creates a wrapper around a mutable reference to the reader.
This is useful to allow applying adaptors while still retaining ownership of the original value.
impl<'a> Seek for BufReader<'a>
fn tell(&self) -> IoResult<u64>
Return position of file cursor in the stream
fn seek(&mut self, pos: i64, style: SeekStyle) -> IoResult<()>
Seek to an offset in a stream
A successful seek clears the EOF indicator. Seeking beyond EOF is allowed, but seeking before position 0 is not allowed.
Errors
- Seeking to a negative offset is considered an error
- Seeking past the end of the stream does not modify the underlying stream, but the next write may cause the previous data to be filled in with a bit pattern.
impl<'a> Buffer for BufReader<'a>
fn fill_buf<'a>(&'a mut self) -> IoResult<&'a [u8]>
Fills the internal buffer of this object, returning the buffer contents.
Note that 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.
Error
This function will return an I/O error if the underlying reader was read, but returned an error. Note that it is not an error to return a 0-length buffer.
fn consume(&mut self, amt: uint)
Tells this buffer that amt
bytes have been consumed from the buffer,
so they should no longer be returned in calls to fill
or read
.
fn read_line(&mut self) -> IoResult<~str>
Reads the next line of input, interpreted as a sequence of UTF-8 encoded unicode codepoints. If a newline is encountered, then the newline is contained in the returned string.
Example
use std::io; let mut reader = io::stdin(); let input = reader.read_line().ok().unwrap_or(~"nothing");
Error
This function has the same error semantics as read_until
:
- All non-EOF errors will be returned immediately
- If an error is returned previously consumed bytes are lost
- EOF is only returned if no bytes have been read
- Reach EOF may mean that the delimiter is not present in the return value
Additionally, this function can fail if the line of input read is not a valid UTF-8 sequence of bytes.
fn lines<'r>(&'r mut self) -> Lines<'r, Self>
Create an iterator that reads a line on each iteration until EOF.
Error
Any error other than EndOfFile
that is produced by the underlying Reader
is returned by the iterator and should be handled by the caller.
fn read_until(&mut self, byte: u8) -> IoResult<~[u8]>
Reads a sequence of bytes leading up to a specified delimiter. Once the specified byte is encountered, reading ceases and the bytes up to and including the delimiter are returned.
Error
If any I/O error is encountered other than EOF, the error is immediately returned. Note that this may discard bytes which have already been read, and those bytes will not be returned. It is recommended to use other methods if this case is worrying.
If EOF is encountered, then this function will return EOF if 0 bytes have been read, otherwise the pending byte buffer is returned. This is the reason that the byte buffer returned may not always contain the delimiter.
fn read_char(&mut self) -> IoResult<char>
Reads the next utf8-encoded character from the underlying stream.
Error
If an I/O error occurs, or EOF, then this function will return Err
.
This function will also return error if the stream does not contain a
valid utf-8 encoded codepoint as the next few bytes in the stream.
fn chars<'r>(&'r mut self) -> Chars<'r, Self>
Create an iterator that reads a utf8-encoded character on each iteration until EOF.
Error
Any error other than EndOfFile
that is produced by the underlying Reader
is returned by the iterator and should be handled by the caller.