added Receiver::recv_owned
#83
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Added `Receiver::recv_owned` as well as supporting types `RecvOwned` and `RecvOwnedInner`.
| @@ -580,6 +580,19 @@ impl<T> Receiver<T> { | |||
| }) | |||
| } | |||
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| /// Receives a message from the channel. | |||
| /// | |||
| /// Like [`Receiver::recv`], but uses a cloned `Receiver`. | |||
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| /// Like [`Receiver::recv`], but uses a cloned `Receiver`. | |
| /// This function is similar to [`Receiver::recv`], but it uses a cloned `Receiver`. |
Avoid using sentence fragments in documentation.
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Yes, it could be useful for send.
I'll clean up my doc comments.
| pub fn recv_owned(&self) -> RecvOwned<T> { | ||
| RecvOwned::_new(RecvOwnedInner { | ||
| receiver: self.clone(), | ||
| listener: None, | ||
| _pin: PhantomPinned, | ||
| }) | ||
| } | ||
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Add an example for this function, preferably one that points out where it could be useful.
| easy_wrapper! { | ||
| /// A future returned by [`Receiver::recv_owned()`]. | ||
| #[derive(Debug)] | ||
| #[must_use = "futures do nothing unless you `.await` or poll them"] | ||
| pub struct RecvOwned<T>(RecvOwnedInner<T> => Result<T, RecvError>); | ||
| #[cfg(all(feature = "std", not(target_family = "wasm")))] | ||
| pub(crate) wait(); | ||
| } | ||
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| pin_project! { | ||
| #[derive(Debug)] | ||
| #[project(!Unpin)] | ||
| struct RecvOwnedInner<T> { | ||
| // Reference to the receiver. | ||
| receiver: Receiver<T>, | ||
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| // Listener waiting on the channel. | ||
| listener: Option<EventListener>, | ||
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| // Keeping this type `!Unpin` enables future optimizations. | ||
| #[pin] | ||
| _pin: PhantomPinned | ||
| } | ||
| } | ||
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| impl<T> EventListenerFuture for RecvOwnedInner<T> { | ||
| type Output = Result<T, RecvError>; | ||
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| /// Run this future with the given `Strategy`. | ||
| fn poll_with_strategy<'x, S: Strategy<'x>>( | ||
| self: Pin<&mut Self>, | ||
| strategy: &mut S, | ||
| cx: &mut S::Context, | ||
| ) -> Poll<Result<T, RecvError>> { | ||
| let this = self.project(); | ||
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| loop { | ||
| // Attempt to receive a message. | ||
| match this.receiver.try_recv() { | ||
| Ok(msg) => return Poll::Ready(Ok(msg)), | ||
| Err(TryRecvError::Closed) => return Poll::Ready(Err(RecvError)), | ||
| Err(TryRecvError::Empty) => {} | ||
| } | ||
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| // Receiving failed - now start listening for notifications or wait for one. | ||
| if this.listener.is_some() { | ||
| // Poll using the given strategy | ||
| ready!(S::poll(strategy, &mut *this.listener, cx)); | ||
| } else { | ||
| *this.listener = Some(this.receiver.channel.recv_ops.listen()); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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Rather than duplicating all of this code from Recv, why not extract it into a common type? For instance, you could do this:
struct RecvInner<T, Channel: Borrow<Receiver<T>> { ... }...then do this:
pub struct Recv<'a, T>(RecvInner<T, &'a Receiver<T>>);
pub struct RecvOwned<T>(RecvInner<T, Receiver<T>>);This would prevent duplicating around 250 lines of code.
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I'm playing around with this suggestion, but the compiler complains about T being unused.
I'll figure it out.
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Use PhantomData to ensure that T is captured
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I propose 01fbd7d (it should be possible to fast-forward to that commit if no further adjustments to it are necessary)
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Is it worth looking at some benchmarks to see if the referenced version is even necessary? Would the performance hit for using a cloned receiver be that bad? |
No matter what an atomic operation is going to be slower than one that doesn't use atomics. Still, benchmarks would be nice |
Added
Receiver::recv_ownedas well as supporting typesRecvOwnedandRecvOwnedInner.