Trait rd_interface::AsyncRead

pub trait AsyncRead {
    fn poll_read(
        self: Pin<&mut Self>, 
        cx: &mut Context<'_>, 
        buf: &mut ReadBuf<'_>
    ) -> Poll<Result<(), Error>>;
}

Reads bytes from a source.

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.

Specifically, this means that the poll_read function will return one of the following:

• Poll::Ready(Ok(())) means that data was immediately read and placed into the output buffer. The amount of data read can be determined by the increase in the length of the slice returned by ReadBuf::filled. If the difference is 0, EOF has been reached.

• Poll::Pending means that no data was read into the buffer provided. The I/O object is not currently readable but may become readable in the future. Most importantly, the current future’s task is scheduled to get unparked when the object is readable. This means that like Future::poll you’ll receive a notification when the I/O object is readable again.

• Poll::Ready(Err(e)) for other errors are standard I/O errors coming from the underlying object.

This trait importantly means that the read method only works in the context of a future’s task. The object may panic if used outside of a task.

Utilities for working with AsyncRead values are provided by AsyncReadExt.

Required methods

fn poll_read(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

Attempts to read from the AsyncRead into buf.

On success, returns Poll::Ready(Ok(())) and places data in the unfilled portion of buf. If no data was read (buf.filled().len() is unchanged), it implies that EOF has been reached.

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

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Implementations on Foreign Types

impl AsyncRead for Empty

pub fn poll_read(
    self: Pin<&mut Empty>,
    &mut Context<'_>,
    &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

pub fn poll_read(
    self: Pin<&mut Cursor<T>>,
    _cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

pub fn poll_read(
    self: Pin<&mut Pin<P>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

impl<T> AsyncRead for ReadHalf<T> where
    T: AsyncRead, 

pub fn poll_read(
    self: Pin<&mut ReadHalf<T>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

impl<W> AsyncRead for BufWriter<W> where
    W: AsyncWrite + AsyncRead, 

pub fn poll_read(
    self: Pin<&mut BufWriter<W>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

pub fn poll_read(
    self: Pin<&mut &'_ mut T>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

impl<RW> AsyncRead for BufStream<RW> where
    RW: AsyncRead + AsyncWrite, 

pub fn poll_read(
    self: Pin<&mut BufStream<RW>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

impl AsyncRead for Repeat

pub fn poll_read(
    self: Pin<&mut Repeat>,
    &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

impl AsyncRead for DuplexStream

pub fn poll_read(
    self: Pin<&mut DuplexStream>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

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

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

pub fn poll_read(
    self: Pin<&mut BufReader<R>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

pub fn poll_read(
    self: Pin<&mut Take<R>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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

pub fn poll_read(
    self: Pin<&mut Box<T, Global>>,
    cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

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Implementors

impl AsyncRead for PeekableTcpStream

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

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