Struct maitake::sync::wait_map::Wait

pub struct Wait<'a, K, V, Lock = DefaultMutex>
where
    K: PartialEq,
    Lock: ScopedRawMutex,
{ /* private fields */ }

Future returned from WaitMap::wait().

This future is fused, so once it has completed, any future calls to poll will immediately return Poll::Ready.

Notes

This future is !Unpin, as it is unsafe to core::mem::forget a Wait future once it has been polled. For instance, the following code must not compile:

 use maitake_sync::wait_map::Wait;

 // Calls to this function should only compile if `T` is `Unpin`.
 fn assert_unpin<T: Unpin>() {}

 assert_unpin::<Wait<'_, usize, ()>>();

Implementations

impl<'map, 'wait, K, V, Lock> Wait<'map, K, V, Lock>

where K: PartialEq, Lock: ScopedRawMutex,

pub fn subscribe( self: Pin<&'wait mut Wait<'map, K, V, Lock>> ) -> Subscribe<'wait, 'map, K, V, Lock>

Returns a future that completes when the Wait item has been added to the WaitMap, and is ready to receive data

This is useful for ensuring that a receiver is ready before sending a message that will elicit the expected response.

Example

use std::sync::Arc;
use maitake::scheduler;
use maitake_sync::wait_map::{WaitMap, WakeOutcome};
use futures_util::pin_mut;

let scheduler = Scheduler::new();
let q = Arc::new(WaitMap::new());

let q2 = q.clone();
scheduler.spawn(async move {
    let wait = q2.wait(0);

    // At this point, we have created the future, but it has not yet
    // been added to the queue. We could immediately await 'wait',
    // but then we would be unable to progress further. We must
    // first pin the `wait` future, to ensure that it does not move
    // until it has been completed.
    pin_mut!(wait);
    wait.as_mut().subscribe().await.unwrap();

    // We now know the waiter has been enqueued, at this point we could
    // send a message that will cause key == 0 to be returned, without
    // worrying about racing with the expected response, e.g:
    //
    // sender.send_with_id(0, SomeMessage).await?;
    //
    let val = wait.await.unwrap();
    assert_eq!(val, 10);
});

assert!(matches!(q.wake(&0, 100), WakeOutcome::NoMatch(_)));

let tick = scheduler.tick();

assert!(matches!(q.wake(&0, 100), WakeOutcome::Woke));

pub fn enqueue( self: Pin<&'wait mut Wait<'map, K, V, Lock>> ) -> Subscribe<'wait, 'map, K, V, Lock>

👎Deprecated since 0.1.3: renamed to subscribe for consistency, use that instead

Deprecated alias for Wait::subscribe. See that method for details.

Trait Implementations

impl<'a, K, V, Lock> Debug for Wait<'a, K, V, Lock>

where K: Debug + PartialEq, V: Debug, Lock: Debug + ScopedRawMutex,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a, K, V, Lock> Drop for Wait<'a, K, V, Lock>

where K: PartialEq, Lock: ScopedRawMutex,

fn drop(&mut self)

Executes the destructor for this type.

impl<K, V> Future for Wait<'_, K, V>

where K: PartialEq,

type Output = Result<V, WaitError>

The type of value produced on completion.

fn poll( self: Pin<&mut Wait<'_, K, V>>, cx: &mut Context<'_> ) -> Poll<<Wait<'_, K, V> as Future>::Output>

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

impl<'pin, 'a, K, V, Lock> Unpin for Wait<'a, K, V, Lock>

where K: PartialEq, Lock: ScopedRawMutex, __Wait<'pin, 'a, K, V, Lock>: Unpin,