blob: f14957f119a570baaed33a145ed8520939e1e733 [file] [log] [blame]
use core::marker::Unpin;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{LocalWaker, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// A stream combinator which executes a unit closure over each item on a
/// stream.
///
/// This structure is returned by the `Stream::for_each` method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct ForEach<St, Fut, F> {
stream: St,
f: F,
future: Option<Fut>,
}
impl<St, Fut, F> Unpin for ForEach<St, Fut, F>
where St: Stream + Unpin,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()> + Unpin,
{}
impl<St, Fut, F> ForEach<St, Fut, F>
where St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
unsafe_pinned!(future: Option<Fut>);
pub(super) fn new(stream: St, f: F) -> ForEach<St, Fut, F> {
ForEach {
stream,
f,
future: None,
}
}
}
impl<St: FusedStream, Fut, F> FusedFuture for ForEach<St, Fut, F> {
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 = ();
fn poll(mut self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<()> {
loop {
if let Some(future) = self.as_mut().future().as_pin_mut() {
ready!(future.poll(lw));
}
self.as_mut().future().as_mut().set(None);
match ready!(self.as_mut().stream().poll_next(lw)) {
Some(e) => {
let future = (self.as_mut().f())(e);
self.as_mut().future().set(Some(future));
}
None => {
return Poll::Ready(());
}
}
}
}
}