[][src]Trait tokio::io::AsyncRead

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

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<()>>

Attempts to read from the AsyncRead into buf.

On success, returns Poll::Ready(Ok(())) and fills buf with data read. If no data was read (buf.filled().is_empty()) 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.

Loading content...

Implementations on Foreign Types

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

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

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

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

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

Loading content...


impl AsyncRead for File[src]

impl AsyncRead for DuplexStream[src]

impl AsyncRead for Empty[src]

impl AsyncRead for Repeat[src]

impl AsyncRead for Stdin[src]

impl AsyncRead for TcpStream[src]

impl AsyncRead for UnixStream[src]

impl AsyncRead for tokio::net::tcp::OwnedReadHalf[src]

impl AsyncRead for tokio::net::unix::OwnedReadHalf[src]

impl AsyncRead for ChildStderr[src]

impl AsyncRead for ChildStdout[src]

impl<'_> AsyncRead for tokio::net::tcp::ReadHalf<'_>[src]

impl<'_> AsyncRead for tokio::net::unix::ReadHalf<'_>[src]

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

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

impl<RW: AsyncRead + AsyncWrite> AsyncRead for BufStream<RW>[src]

impl<T: AsyncRead> AsyncRead for tokio::io::ReadHalf<T>[src]

impl<W: AsyncWrite + AsyncRead> AsyncRead for BufWriter<W>[src]

Loading content...