Struct Cancel

pub(crate) struct Cancel<F> {
    inner: Arc<Mutex<Inner>>,
    fut: F,
}

A cancellable future type, loosely influenced by RemoteHandle.

This type is useful for cases when we can’t cancel a future simply by dropping it, because the future is owned by some other object (like a FuturesUnordered) that won’t give it up.

Limitations

Do not try to cancel a future from inside a cancellable future, including the future itself: this may cause a panic or deadlock.

In arti-rpcserver, we prevent this happening by ensuring that every method that calls cancel() is itself uncancellable.

Fields

inner: Arc<Mutex<Inner>>

Shared state between the Cancel and the CancelHandle.

fut: F

The inner future.

TODO: Possibly we should move this into inner, so that we can make sure that we don’t execute the future without holding the lock, and so we can drop the future immediately when it’s cancelled. But that would take some fairly tricky type erasure, so maybe it isn’t worth it?

Implementations

impl<F> Cancel<F>

pub(crate) fn project<'pin>( self: Pin<&'pin mut Self>, ) -> __CancelProjection<'pin, F>

pub(crate) fn project_ref<'pin>( self: Pin<&'pin Self>, ) -> __CancelProjectionRef<'pin, F>

impl<F> Cancel<F>

pub(crate) fn new(fut: F) -> (CancelHandle, Cancel<F>)

Wrap fut in a new future that can be cancelled.

Returns a handle to cancel the future, and the cancellable future.

Trait Implementations

impl<F: Future> Future for Cancel<F>

type Output = Result<<F as Future>::Output, Cancelled>

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

Attempts to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.

impl<'pin, F> Unpin for Cancel<F>

where PinnedFieldsOf<__Cancel<'pin, F>>: Unpin,