Struct async_buf::buf_reader::BufReader

pub struct BufReader<R> { /* private fields */ }

The BufReader<R> struct adds buffering to any reader.

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

BufReader<R> can improve the speed of programs that make small and repeated read calls to the same file or network socket. It does not help when reading very large amounts at once, or reading just one or a few times. It also provides no advantage when reading from a source that is already in memory, like a Vec<u8>.

When the BufReader<R> is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader<R> on the same stream can cause data loss. Reading from the underlying reader after unwrapping the BufReader<R> with BufReader::into_inner can also cause data loss.

Examples

Implementations

impl<R: AsyncRead> BufReader<R>

pub fn new(inner: R) -> BufReader<R>

Creates a new BufReader<R> with a default buffer capacity. The default is currently 8 KB, but may change in the future.

Examples

pub fn with_capacity(capacity: usize, inner: R) -> BufReader<R>

Creates a new BufReader<R> with the specified buffer capacity.

Examples

Creating a buffer with ten bytes of capacity:

impl<R> BufReader<R>

pub fn get_ref(&self) -> &R

Gets a reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

Examples

pub 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.

pub fn buffer(&self) -> &[u8]

Returns a reference to the internally buffered data.

Unlike fill_buf, this will not attempt to fill the buffer if it is empty.

Examples

pub fn capacity(&self) -> usize

Returns the number of bytes the internal buffer can hold at once.

Examples

pub fn into_inner(self) -> R

Unwraps this BufReader<R>, returning the underlying reader.

Note that any leftover data in the internal buffer is lost. Therefore, a following read from the underlying reader may lead to data loss.

Examples

Trait Implementations

impl<R: AsyncRead> AsyncBufRead for BufReader<R>

fn poll_fill_buf(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>
) -> Poll<Result<&[u8]>>

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&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 poll_read.

impl<R: AsyncRead> AsyncRead for BufReader<R>

fn poll_read(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>,
    buf: &mut [u8]
) -> Poll<Result<usize>>

Attempt to read from the AsyncRead into buf.

fn poll_read_vectored(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>,
    bufs: &mut [IoSliceMut<'_>]
) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into bufs using vectored IO operations.

impl<R> Debug for BufReader<R> where
    R: Debug, 

fn fmt(&self, fmt: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'__pin, R> Unpin for BufReader<R> where
    __Origin<'__pin, R>: Unpin,