Trait futures_util::io::AsyncRead

pub trait AsyncRead {
    fn poll_read(
        self: Pin<&mut Self>, 
        cx: &mut Context, 
        buf: &mut [u8]
    ) -> Poll<Result<usize, Error>>;

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

Read bytes asynchronously.

This trait is analogous to the std::io::Read trait, but integrates with the asynchronous task system. In particular, the poll_read method, unlike Read::read, will automatically queue the current task for wakeup and return if data is not yet available, rather than blocking the calling thread.

Required methods

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

Attempt to read from the AsyncRead into buf.

On success, returns Poll::Ready(Ok(num_bytes_read)).

If no data is available for reading, the method returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object becomes readable or is closed.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

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Provided methods

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.

This method is similar to poll_read, but allows data to be read into multiple buffers using a single operation.

On success, returns Poll::Ready(Ok(num_bytes_read)).

If no data is available for reading, the method returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object becomes readable or is closed. By default, this method delegates to using poll_read on the first nonempty buffer in bufs, or an empty one if none exists. Objects which support vectored IO should override this method.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

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Implementations on Foreign Types

impl<'_> AsyncRead for &'_ [u8]

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

fn poll_read_vectored(
    self: Pin<&mut &'_ [u8]>,
    &mut Context,
    bufs: &mut [IoSliceMut]
) -> Poll<Result<usize, Error>>

impl<'_, T> AsyncRead for &'_ mut T where
    T: AsyncRead + Unpin + ?Sized, 

fn poll_read(
    self: Pin<&mut &'_ mut T>,
    cx: &mut Context,
    buf: &mut [u8]
) -> Poll<Result<usize, Error>>

fn poll_read_vectored(
    self: Pin<&mut &'_ mut T>,
    cx: &mut Context,
    bufs: &mut [IoSliceMut]
) -> Poll<Result<usize, Error>>

impl<P> AsyncRead for Pin<P> where
    P: DerefMut + Unpin,
    <P as Deref>::Target: AsyncRead, 

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

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

impl<T> AsyncRead for Box<T> where
    T: AsyncRead + Unpin + ?Sized, 

fn poll_read(
    self: Pin<&mut Box<T>>,
    cx: &mut Context,
    buf: &mut [u8]
) -> Poll<Result<usize, Error>>

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

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Implementors

impl AsyncRead for Empty

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

impl AsyncRead for Repeat

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

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

impl<A, B> AsyncRead for Either<A, B> where
    A: AsyncRead,
    B: AsyncRead, 

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

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

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

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

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

impl<R: AsyncRead> AsyncRead for ReadHalf<R>

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

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

impl<R: AsyncRead> AsyncRead for Take<R>

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

impl<St> AsyncRead for IntoAsyncRead<St> where
    St: TryStream<Error = Error> + Unpin,
    St::Ok: AsRef<[u8]>, 

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

impl<T> AsyncRead for AllowStdIo<T> where
    T: Read, 

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

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

impl<T, U> AsyncRead for Chain<T, U> where
    T: AsyncRead,
    U: AsyncRead, 

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

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

impl<T: AsRef<[u8]> + Unpin> AsyncRead for Cursor<T>

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

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

impl<W: AsyncRead> AsyncRead for BufWriter<W>

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

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

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