Trait tokio::io::AsyncRead

pub trait AsyncRead {
    // Required method
    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 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.

Implementations on Foreign Types

impl AsyncRead for &[u8]

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

impl<P> AsyncRead for Pin<P>

where P: DerefMut + Unpin, P::Target: AsyncRead,

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

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

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

impl<T: ?Sized + AsyncRead + Unpin> AsyncRead for &mut T

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

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

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

Implementors

impl AsyncRead for File

Available on crate feature fs only.

impl AsyncRead for TcpStream

Available on crate feature net only.

impl AsyncRead for UnixStream

Available on Unix and crate feature net only.

impl AsyncRead for tokio::net::tcp::OwnedReadHalf

Available on crate feature net only.

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

Available on crate feature net only.

impl AsyncRead for Receiver

Available on Unix and crate feature net only.

impl AsyncRead for tokio::net::unix::OwnedReadHalf

Available on Unix and crate feature net only.

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

Available on Unix and crate feature net only.

impl AsyncRead for NamedPipeClient

Available on Windows and crate feature net only.

impl AsyncRead for NamedPipeServer

Available on Windows and crate feature net only.

impl AsyncRead for ChildStderr

Available on crate feature process only.

impl AsyncRead for ChildStdout

Available on crate feature process only.

impl AsyncRead for DuplexStream

Available on crate feature io-util only.

impl AsyncRead for Empty

Available on crate feature io-util only.

impl AsyncRead for Repeat

Available on crate feature io-util only.

impl AsyncRead for Stdin

Available on crate feature io-std only.

impl<R, W> AsyncRead for Join<R, W>

where R: AsyncRead,

Available on crate feature io-util only.

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

Available on crate feature io-util only.

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

Available on crate feature io-util only.

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

Available on crate feature io-util only.

impl<T: AsyncRead> AsyncRead for tokio::io::ReadHalf<T>

Available on crate feature io-util only.

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

Available on crate feature io-util only.

impl AsyncRead for Mock

impl<L, R> AsyncRead for Either<L, R>

where L: AsyncRead, R: AsyncRead,

impl<R: AsyncRead, F: FnMut(&[u8])> AsyncRead for InspectReader<R, F>

impl<S, B, E> AsyncRead for StreamReader<S, B>

where S: Stream<Item = Result<B, E>>, B: Buf, E: Into<Error>,

impl<S: AsyncRead> AsyncRead for SinkWriter<S>

impl<T> AsyncRead for Compat<T>

where T: AsyncRead,

impl<W: AsyncRead, F> AsyncRead for InspectWriter<W, F>