[−][src]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>>;

    unsafe default fn initializer(&self) -> Initializer { ... }

    default fn poll_vectored_read(
        self: Pin<&mut Self>, 
        cx: &mut Context, 
        vec: &mut [&mut IoVec]
    ) -> 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 Ok(Poll::Ready(num_bytes_read)).

If no data is available for reading, the method returns Ok(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

unsafe default fn initializer(&self) -> Initializer

Determines if this AsyncReader can work with buffers of uninitialized memory.

The default implementation returns an initializer which will zero buffers.

Safety

This method is unsafe because and AsyncReader could otherwise return a non-zeroing Initializer from another AsyncRead type without an unsafe block.

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into vec 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 Ok(Poll::Ready(num_bytes_read)).

If no data is available for reading, the method returns Ok(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 buffer in vec. 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 Repeat[src]

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

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

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

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

impl<'a, T> AsyncRead for &'a mut T where
    T: AsyncRead + Unpin + ?Sized, [src]

impl<'a> AsyncRead for &'a [u8][src]

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

impl<'a, T> AsyncRead for Pin<&'a mut T> where
    T: AsyncRead + ?Sized, [src]

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Implementors

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

unsafe default fn initializer(&self) -> Initializer[src]

impl<R: AsyncRead01> AsyncRead for Compat01As03<R>[src]

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

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

unsafe default fn initializer(&self) -> Initializer[src]

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

impl<T> AsyncRead for AllowStdIo<T> where
    T: Read, [src]

unsafe default fn initializer(&self) -> Initializer[src]

default fn poll_vectored_read(
    self: Pin<&mut Self>,
    cx: &mut Context,
    vec: &mut [&mut IoVec]
) -> Poll<Result<usize, Error>>[src]

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