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
use core::pin::Pin;
use futures_core::future::Future;
use futures_core::task::{LocalWaker, Poll};
use pin_utils::unsafe_pinned;
#[derive(Debug, Clone)]
#[must_use = "futures do nothing unless polled"]
pub struct OptionFuture<F> {
option: Option<F>,
}
impl<F> OptionFuture<F> {
unsafe_pinned!(option: Option<F>);
}
impl<F: Future> Future for OptionFuture<F> {
type Output = Option<F::Output>;
fn poll(
mut self: Pin<&mut Self>,
lw: &LocalWaker
) -> Poll<Self::Output> {
match self.option().as_pin_mut() {
Some(x) => x.poll(lw).map(Some),
None => Poll::Ready(None),
}
}
}
impl<T> From<Option<T>> for OptionFuture<T> {
fn from(option: Option<T>) -> Self {
OptionFuture { option }
}
}