# Struct bitflags::__core::io::BufReader [−] [src]

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

1.0.0

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

    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> BufReader<R> where R: Read`

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

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

# Examples

    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:

    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

    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

    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

    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 for BufReader<R> where R: Read`

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

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

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

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>`1.6.0

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

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

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

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

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

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

#### `fn fill_buf(&mut self) -> Result<&[u8], Error>`

#### `fn consume(&mut self, amt: usize)`

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

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

#### `fn split(self, byte: u8) -> Split<Self>`

#### `fn lines(self) -> Lines<Self>`

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

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

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

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

Seek to an offset, in bytes, in the underlying reader.

The position used for seeking with `SeekFrom::Current(_)` is the position the underlying reader would be at if the `BufReader` had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling `.unwrap()` immediately after a seek yields the underlying reader at the same position.

See `std::io::Seek` for more details.

Note: In the edge case where you're seeking with `SeekFrom::Current(n)` where `n` minus the internal buffer length underflows an `i64`, two seeks will be performed instead of one. If the second seek returns `Err`, the underlying reader will be left at the same position it would have if you seeked to `SeekFrom::Current(0)`.

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)