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use core::fmt;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::ready;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
/// Future for the [`any`](super::StreamExt::any) method.
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Any<St, Fut, F> {
#[pin]
stream: St,
f: F,
accum: Option<bool>,
#[pin]
future: Option<Fut>,
}
}
impl<St, Fut, F> fmt::Debug for Any<St, Fut, F>
where
St: fmt::Debug,
Fut: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Any")
.field("stream", &self.stream)
.field("accum", &self.accum)
.field("future", &self.future)
.finish()
}
}
impl<St, Fut, F> Any<St, Fut, F>
where
St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = bool>,
{
pub(super) fn new(stream: St, f: F) -> Self {
Self { stream, f, accum: Some(false), future: None }
}
}
impl<St, Fut, F> FusedFuture for Any<St, Fut, F>
where
St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = bool>,
{
fn is_terminated(&self) -> bool {
self.accum.is_none() && self.future.is_none()
}
}
impl<St, Fut, F> Future for Any<St, Fut, F>
where
St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = bool>,
{
type Output = bool;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<bool> {
let mut this = self.project();
Poll::Ready(loop {
if let Some(fut) = this.future.as_mut().as_pin_mut() {
// we're currently processing a future to produce a new accum value
let acc = this.accum.unwrap() || ready!(fut.poll(cx));
if acc {
break true;
} // early exit
*this.accum = Some(acc);
this.future.set(None);
} else if this.accum.is_some() {
// we're waiting on a new item from the stream
match ready!(this.stream.as_mut().poll_next(cx)) {
Some(item) => {
this.future.set(Some((this.f)(item)));
}
None => {
break this.accum.take().unwrap();
}
}
} else {
panic!("Any polled after completion")
}
})
}
}
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