# Struct std::io::BufReader [−] [src]

    pub struct BufReader<R> {
        // some fields omitted
    }

The `BufReader` struct adds buffering to any reader.

It can be excessively inefficient to work directly with a `Read` instance. For example, every call to `read` on `TcpStream` results in a system call. A `BufReader` performs large, infrequent reads on the underlying `Read` and maintains an in-memory buffer of the results.

# Examples

fn main() { use std::io::prelude::*; use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::open("log.txt")); let mut reader = BufReader::new(f); let mut line = String::new(); let len = try!(reader.read_line(&mut line)); println!("First line is {} bytes long", len); Ok(()) } }

    use std::io::prelude::*;
    use std::io::BufReader;
    use std::fs::File;

    let mut f = try!(File::open("log.txt"));
    let mut reader = BufReader::new(f);

    let mut line = String::new();
    let len = try!(reader.read_line(&mut line));
    println!("First line is {} bytes long", len);

## Methods

### `impl<R: Read> BufReader<R>`

#### `fn new(inner: R) -> BufReader<R>`

Creates a new `BufReader` with a default buffer capacity.

# Examples

fn main() { use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::open("log.txt")); let mut reader = BufReader::new(f); Ok(()) } }

    use std::io::BufReader;
    use std::fs::File;

    let mut f = try!(File::open("log.txt"));
    let mut reader = BufReader::new(f);

#### `fn with_capacity(cap: usize, inner: R) -> BufReader<R>`

Creates a new `BufReader` with the specified buffer capacity.

# Examples

Creating a buffer with ten bytes of capacity:

fn main() { use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::open("log.txt")); let mut reader = BufReader::with_capacity(10, f); Ok(()) } }

    use std::io::BufReader;
    use std::fs::File;

    let mut f = try!(File::open("log.txt"));
    let mut reader = BufReader::with_capacity(10, f);

#### `fn get_ref(&self) -> &R`

Gets a reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

# Examples

fn main() { use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f1 = try!(File::open("log.txt")); let mut reader = BufReader::new(f1); let f2 = reader.get_ref(); Ok(()) } }

    use std::io::BufReader;
    use std::fs::File;

    let mut f1 = try!(File::open("log.txt"));
    let mut reader = BufReader::new(f1);

    let f2 = reader.get_ref();

#### `fn get_mut(&mut self) -> &mut R`

Gets a mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

# Examples

fn main() { use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f1 = try!(File::open("log.txt")); let mut reader = BufReader::new(f1); let f2 = reader.get_mut(); Ok(()) } }

    use std::io::BufReader;
    use std::fs::File;

    let mut f1 = try!(File::open("log.txt"));
    let mut reader = BufReader::new(f1);

    let f2 = reader.get_mut();

#### `fn into_inner(self) -> R`

Unwraps this `BufReader`, returning the underlying reader.

Note that any leftover data in the internal buffer is lost.

# Examples

fn main() { use std::io::BufReader; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f1 = try!(File::open("log.txt")); let mut reader = BufReader::new(f1); let f2 = reader.into_inner(); Ok(()) } }

    use std::io::BufReader;
    use std::fs::File;

    let mut f1 = try!(File::open("log.txt"));
    let mut reader = BufReader::new(f1);

    let f2 = reader.into_inner();

## Trait Implementations

### `impl<R: Read> Read for BufReader<R>`

#### `fn read(&mut self, buf: &mut [u8]) -> Result<usize>`

#### `fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>`

#### `fn read_to_string(&mut self, buf: &mut String) -> Result<usize>`

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn bytes(self) -> Bytes<Self> where Self: Sized`

#### `fn chars(self) -> Chars<Self> where Self: Sized`

#### `fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized`

#### `fn take(self, limit: u64) -> Take<Self> where Self: Sized`

#### `fn tee<W: Write>(self, out: W) -> Tee<Self, W> where Self: Sized`

### `impl<R: Read> BufRead for BufReader<R>`

#### `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`

### `impl<R> Debug for BufReader<R> where R: Debug`

#### `fn fmt(&self, fmt: &mut Formatter) -> Result`

### `impl<R: Seek> Seek for BufReader<R>`

#### `fn seek(&mut self, pos: SeekFrom) -> Result<u64>`

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