await_values 0.1.0

Primitives for subscribing to / notifying about changes to values
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61

//SPDX-License-Identifier: MIT OR Apache-2.0
use crate::ObserverError;
use atomic_waker::AtomicWaker;
use std::sync::Arc;
use std::sync::atomic::AtomicBool;

#[derive(Debug, Clone)]
pub struct ActiveObservation {
    shared: Arc<Shared>,
}

impl Drop for ActiveObservation {
    fn drop(&mut self) {
        // When the ActiveObservation is dropped, we set the notified flag to true
        // to indicate that the observation is no longer active.
        self.shared
            .ready
            .store(true, std::sync::atomic::Ordering::Relaxed);
        self.shared.waker.wake();
    }
}

#[derive(Debug)]
struct Shared {
    waker: AtomicWaker,
    ready: AtomicBool,
}

pub(crate) struct ActiveObservationFuture {
    shared: Arc<Shared>,
}

impl Future for ActiveObservationFuture {
    type Output = Result<(), ObserverError>;

    fn poll(
        self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Self::Output> {
        // Polling logic to check for changes and notify observers
        self.shared.waker.register(cx.waker());
        if self.shared.ready.load(std::sync::atomic::Ordering::Relaxed) {
            return std::task::Poll::Ready(Ok(()));
        }
        std::task::Poll::Pending
    }
}

pub fn observation() -> (ActiveObservation, ActiveObservationFuture) {
    let shared = Arc::new(Shared {
        waker: AtomicWaker::new(),
        ready: AtomicBool::new(false),
    });

    (
        ActiveObservation {
            shared: shared.clone(),
        },
        ActiveObservationFuture { shared },
    )
}