vertigo/
future_box.rs

1use std::{
2    cell::Cell,
3    future::Future,
4    pin::Pin,
5    rc::Rc,
6    task::{Context, Poll, Waker},
7};
8
9// https://users.rust-lang.org/t/how-to-receive-a-async-callback/40110/3
10// https://users.rust-lang.org/t/can-you-turn-a-callback-into-a-future-into-async-await/49378/16
11// https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=10cd4b012f678705c9d78fed5ca81857
12
13#[derive(Default)]
14pub struct CallbackFutureInner<T> {
15    waker: Cell<Option<Waker>>,
16    result: Cell<Option<T>>,
17}
18
19impl<T> CallbackFutureInner<T> {
20    fn new() -> Rc<CallbackFutureInner<T>> {
21        Rc::new(CallbackFutureInner {
22            waker: Cell::new(None),
23            result: Cell::new(None),
24        })
25    }
26}
27
28#[derive(Default, Clone)]
29pub struct FutureBoxSend<T> {
30    inner: Rc<CallbackFutureInner<T>>,
31}
32
33impl<T> FutureBoxSend<T> {
34    fn new(inner: Rc<CallbackFutureInner<T>>) -> FutureBoxSend<T> {
35        FutureBoxSend { inner }
36    }
37
38    pub fn publish(&self, result: T) {
39        self.inner.result.set(Some(result));
40        if let Some(w) = self.inner.waker.take() {
41            w.wake()
42        }
43    }
44}
45
46#[derive(Default, Clone)]
47pub struct FutureBox<T> {
48    inner: Rc<CallbackFutureInner<T>>,
49}
50
51impl<T> FutureBox<T> {
52    pub fn new() -> (FutureBoxSend<T>, FutureBox<T>) {
53        let inner = CallbackFutureInner::new();
54        let sender = FutureBoxSend::new(inner.clone());
55        let future = FutureBox { inner };
56        (sender, future)
57    }
58}
59
60impl<T> Future for FutureBox<T> {
61    type Output = T;
62    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
63        match self.inner.result.take() {
64            Some(x) => Poll::Ready(x),
65            None => {
66                self.inner.waker.set(Some(cx.waker().clone()));
67                Poll::Pending
68            }
69        }
70    }
71}
vertigo/future_box.rs

vertigo/
future_box.rs
