Struct Channel 

pub struct Channel<S, R> { /* private fields */ }

A bounded, bi-directional channel for sending and receiving messages. Relies on Tokio’s mpsc channel.

Channel also implements the Stream and Sink traits for convenience.

Implementations

impl<S: Send + 'static, R> Channel<S, R>

pub async fn send(&mut self, msg: S) -> Result<(), PollSendError<S>>

Sends a value, waiting until there is capacity.

A successful send occurs when it is determined that the other end of the channel has not hung up already. An unsuccessful send would be one where the corresponding receiver has already been closed. Note that a return value of Err means that the data will never be received, but a return value of Ok does not mean that the data will be received. It is possible for the corresponding receiver to hang up immediately after this function returns Ok.

pub fn try_send(&mut self, msg: S) -> Result<(), TrySendError<S>>

Attempts to immediately send a message on this channel.

This method differs from send by returning immediately if the channel’s buffer is full or no receiver is waiting to acquire some data. Compared with send, this function has two failure cases instead of one (one for disconnection, one for a full buffer).

pub async fn recv(&mut self) -> Option<R>

Receives the next value for this channel.

This method returns None if the channel has been closed and there are no remaining messages in the channel’s buffer. This indicates that no further values can ever be received from this Receiver. The channel is closed when all senders have been dropped, or when close is called.

If there are no messages in the channel’s buffer, but the channel has not yet been closed, this method will sleep until a message is sent or the channel is closed. Note that if close is called, but there are still outstanding Permits from before it was closed, the channel is not considered closed by recv until the permits are released.

pub fn try_recv(&mut self) -> Result<R, TryRecvError>

Tries to receive the next value for this receiver.

This method returns the Empty error if the channel is currently empty, but there are still outstanding senders or permits.

This method returns the Disconnected error if the channel is currently empty, and there are no outstanding senders or permits.

Unlike the poll_recv method, this method will never return an Empty error spuriously.

pub fn poll_recv(&mut self, cx: &mut Context<'_>) -> Poll<Option<R>>

Polls to receive the next message on this channel.

This method returns:

• Poll::Pending if no messages are available but the channel is not closed, or if a spurious failure happens.
• Poll::Ready(Some(message)) if a message is available.
• Poll::Ready(None) if the channel has been closed and all messages sent before it was closed have been received.

When the method returns Poll::Pending, the Waker in the provided Context is scheduled to receive a wakeup when a message is sent on any receiver, or when the channel is closed. Note that on multiple calls to poll_recv, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup.

If this method returns Poll::Pending due to a spurious failure, then the Waker will be notified when the situation causing the spurious failure has been resolved. Note that receiving such a wakeup does not guarantee that the next call will succeed — it could fail with another spurious failure.

Trait Implementations

impl<S: Send + 'static, R> Sink<S> for Channel<S, R>

type Error = PollSendError<S>

The type of value produced by the sink when an error occurs.

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

Attempts to prepare the Sink to receive a value.

fn start_send(self: Pin<&mut Self>, item: S) -> Result<(), Self::Error>

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())).

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

Flush any remaining output from this sink.

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

Flush any remaining output and close this sink, if necessary.

impl<S, R> Stream for Channel<S, R>

type Item = R

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.