[][src]Struct futures_util::io::BufReader

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

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.

Methods

impl<R: AsyncRead> BufReader<R>[src]

pub fn new(inner: R) -> Self[src]

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[src]

Creates a new BufReader with the specified buffer capacity.

pub fn get_ref(&self) -> &R[src]

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[src]

Gets a mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

pub fn get_pin_mut<'a>(self: Pin<&'a mut Self>) -> Pin<&'a mut R>[src]

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[src]

Consumes this BufWriter, returning the underlying reader.

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

Important traits for &'_ [u8]
pub fn buffer(&self) -> &[u8][src]

Returns a reference to the internally buffered data.

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

impl<R: AsyncRead + AsyncSeek> BufReader<R>[src]

pub fn poll_seek_relative(
    self: Pin<&mut Self>,
    cx: &mut Context,
    offset: i64
) -> Poll<Result<()>>
[src]

Seeks relative to the current position. If the new position lies within the buffer, the buffer will not be flushed, allowing for more efficient seeks. This method does not return the location of the underlying reader, so the caller must track this information themselves if it is required.

Trait Implementations

impl<R: AsyncRead + Debug> Debug for BufReader<R>[src]

impl<R: AsyncRead> AsyncRead for BufReader<R>[src]

impl<R: AsyncRead + AsyncSeek> AsyncSeek for BufReader<R>[src]

fn poll_seek(
    self: Pin<&mut Self>,
    cx: &mut Context,
    pos: SeekFrom
) -> Poll<Result<u64>>
[src]

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 .into_inner() immediately after a seek yields the underlying reader at the same position.

To seek without discarding the internal buffer, use BufReader::poll_seek_relative.

See AsyncSeek for more details.

Note: In the edge case where you're seeking with SeekFrom::Current(n) where n minus the internal buffer length overflows 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 called seek with SeekFrom::Current(0).

impl<R: AsyncRead> AsyncBufRead for BufReader<R>[src]

Auto Trait Implementations

impl<R> Send for BufReader<R> where
    R: Send

impl<R> Unpin for BufReader<R> where
    R: Unpin

impl<R> Sync for BufReader<R> where
    R: Sync

impl<R> UnwindSafe for BufReader<R> where
    R: UnwindSafe

impl<R> RefUnwindSafe for BufReader<R> where
    R: RefUnwindSafe

Blanket Implementations

impl<R> AsyncReadExt for R where
    R: AsyncRead + ?Sized
[src]

Important traits for CopyInto<'_, R, W>
fn copy_into<W: ?Sized>(self, writer: &mut W) -> CopyInto<Self, W> where
    Self: Sized,
    W: AsyncWrite + Unpin
[src]

Creates a future which copies all the bytes from one object to another. Read more

Important traits for Read<'_, R>
fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self> where
    Self: Unpin
[src]

Tries to read some bytes directly into the given buf in asynchronous manner, returning a future type. Read more

Important traits for ReadVectored<'_, R>
fn read_vectored<'a>(
    &'a mut self,
    bufs: &'a mut [IoSliceMut<'a>]
) -> ReadVectored<'a, Self> where
    Self: Unpin
[src]

Creates a future which will read from the AsyncRead into bufs using vectored IO operations. Read more

Important traits for ReadExact<'_, R>
fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExact<'a, Self> where
    Self: Unpin
[src]

Creates a future which will read exactly enough bytes to fill buf, returning an error if end of file (EOF) is hit sooner. Read more

Important traits for ReadToEnd<'_, A>
fn read_to_end<'a>(&'a mut self, buf: &'a mut Vec<u8>) -> ReadToEnd<'a, Self> where
    Self: Unpin
[src]

Creates a future which will read all the bytes from this AsyncRead. Read more

fn split(self) -> (ReadHalf<Self>, WriteHalf<Self>) where
    Self: AsyncWrite + Sized
[src]

Helper method for splitting this read/write object into two halves. Read more

Important traits for Compat<R>
fn compat(self) -> Compat<Self> where
    Self: Sized + Unpin
[src]

Wraps an AsyncRead in a compatibility wrapper that allows it to be used as a futures 0.1 / tokio-io 0.1 AsyncRead. If the wrapped type implements AsyncWrite as well, the result will also implement the futures 0.1 / tokio 0.1 AsyncWrite trait. Read more

impl<S> AsyncSeekExt for S where
    S: AsyncSeek + ?Sized
[src]

Important traits for Seek<'_, S>
fn seek(&mut self, pos: SeekFrom) -> Seek<Self> where
    Self: Unpin
[src]

Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more

impl<R> AsyncBufReadExt for R where
    R: AsyncBufRead + ?Sized
[src]

Important traits for CopyBufInto<'_, R, W>
fn copy_buf_into<W: ?Sized>(self, writer: &mut W) -> CopyBufInto<Self, W> where
    Self: Sized,
    W: AsyncWrite + Unpin
[src]

Creates a future which copies all the bytes from one object to another. Read more

Important traits for ReadUntil<'_, R>
fn read_until<'a>(
    &'a mut self,
    byte: u8,
    buf: &'a mut Vec<u8>
) -> ReadUntil<'a, Self> where
    Self: Unpin
[src]

Creates a future which will read all the bytes associated with this I/O object into buf until the delimiter byte or EOF is reached. This method is the async equivalent to BufRead::read_until. Read more

Important traits for ReadLine<'_, R>
fn read_line<'a>(&'a mut self, buf: &'a mut String) -> ReadLine<'a, Self> where
    Self: Unpin
[src]

Creates a future which will read all the bytes associated with this I/O object into buf until a newline (the 0xA byte) or EOF is reached, This method is the async equivalent to BufRead::read_line. Read more

fn lines(self) -> Lines<Self> where
    Self: Sized
[src]

Returns a stream over the lines of this reader. This method is the async equivalent to BufRead::lines. Read more

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<V, T> VZip<V> for T where
    V: MultiLane<T>,