Struct BufReader

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

Available on crate feature io-util only.

The BufReader struct adds buffering to any reader.

It can be excessively inefficient to work directly with a AsyncRead instance. A BufReader performs large, infrequent reads on the underlying AsyncRead and maintains an in-memory buffer of the results.

BufReader 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 is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader on the same stream can cause data loss.

Implementations

impl<R: AsyncRead> BufReader<R>

pub fn new(inner: R) -> Self

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

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

Creates a new BufReader with the specified buffer capacity.

pub fn get_ref(&self) -> &R

Gets a reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

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 get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut R>

Gets a pinned mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

pub fn into_inner(self) -> R

Consumes this BufWriter, returning the underlying reader.

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

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.

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.

unsafe fn prepare_uninitialized_buffer( &self, buf: &mut [MaybeUninit<u8>], ) -> bool

Prepares an uninitialized buffer to be safe to pass to read. Returns true if the supplied buffer was zeroed out.

fn poll_read_buf<B: BufMut>( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut B, ) -> Poll<Result<usize>>

where Self: Sized,

Pull some bytes from this source into the specified BufMut, returning how many bytes were read.

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

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

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempt to flush the object, ensuring that any buffered data reach their destination.

fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

fn poll_write_buf<B: Buf>( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut B, ) -> Poll<Result<usize, Error>>

where Self: Sized,

Write a Buf into this value, returning how many bytes were written.

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

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

Formats the value using the given formatter.

impl<RW> From<BufReader<BufWriter<RW>>> for BufStream<RW>

fn from(b: BufReader<BufWriter<RW>>) -> Self

Converts to this type from the input type.

impl<'__pin, R> Unpin for BufReader<R>

where __Origin<'__pin, R>: Unpin,