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use core::fmt;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
use pin_project::{pin_project, project};
#[pin_project]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct ForEach<St, Fut, F> {
#[pin]
stream: St,
f: F,
#[pin]
future: Option<Fut>,
}
impl<St, Fut, F> fmt::Debug for ForEach<St, Fut, F>
where
St: fmt::Debug,
Fut: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ForEach")
.field("stream", &self.stream)
.field("future", &self.future)
.finish()
}
}
impl<St, Fut, F> ForEach<St, Fut, F>
where St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
pub(super) fn new(stream: St, f: F) -> ForEach<St, Fut, F> {
ForEach {
stream,
f,
future: None,
}
}
}
impl<St, Fut, F> FusedFuture for ForEach<St, Fut, F>
where St: FusedStream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
fn is_terminated(&self) -> bool {
self.future.is_none() && self.stream.is_terminated()
}
}
impl<St, Fut, F> Future for ForEach<St, Fut, F>
where St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
type Output = ();
#[project]
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
#[project]
let ForEach { mut stream, f, mut future } = self.project();
loop {
if let Some(fut) = future.as_mut().as_pin_mut() {
ready!(fut.poll(cx));
future.set(None);
} else if let Some(item) = ready!(stream.as_mut().poll_next(cx)) {
future.set(Some(f(item)));
} else {
break;
}
}
Poll::Ready(())
}
}