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
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
use super::assert_future;
use crate::future::TryFutureExt;
use core::iter::FromIterator;
use core::mem;
use core::pin::Pin;
use alloc::vec::Vec;
use futures_core::future::{Future, TryFuture};
use futures_core::task::{Context, Poll};
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct SelectOk<Fut> {
inner: Vec<Fut>,
}
impl<Fut: Unpin> Unpin for SelectOk<Fut> {}
pub fn select_ok<I>(iter: I) -> SelectOk<I::Item>
where I: IntoIterator,
I::Item: TryFuture + Unpin,
{
let ret = SelectOk {
inner: iter.into_iter().collect()
};
assert!(!ret.inner.is_empty(), "iterator provided to select_ok was empty");
assert_future::<Result<(<I::Item as TryFuture>::Ok, Vec<I::Item>), <I::Item as TryFuture>::Error>, _>(ret)
}
impl<Fut: TryFuture + Unpin> Future for SelectOk<Fut> {
type Output = Result<(Fut::Ok, Vec<Fut>), Fut::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
loop {
let item = self.inner.iter_mut().enumerate().find_map(|(i, f)| {
match f.try_poll_unpin(cx) {
Poll::Pending => None,
Poll::Ready(e) => Some((i, e)),
}
});
match item {
Some((idx, res)) => {
drop(self.inner.remove(idx));
match res {
Ok(e) => {
let rest = mem::replace(&mut self.inner, Vec::new());
return Poll::Ready(Ok((e, rest)))
}
Err(e) => {
if self.inner.is_empty() {
return Poll::Ready(Err(e))
}
}
}
}
None => {
return Poll::Pending
}
}
}
}
}
impl<Fut: TryFuture + Unpin> FromIterator<Fut> for SelectOk<Fut> {
fn from_iter<T: IntoIterator<Item = Fut>>(iter: T) -> Self {
select_ok(iter)
}
}