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use crate::Stream;
use pin_project_lite::pin_project;
use std::pin::Pin;
use std::task::{Context, Poll};
pin_project! {
/// Stream returned by [`fuse()`][super::StreamExt::fuse].
#[derive(Debug)]
pub struct Fuse<T> {
#[pin]
stream: Option<T>,
}
}
impl<T> Fuse<T>
where
T: Stream,
{
pub(crate) fn new(stream: T) -> Fuse<T> {
Fuse {
stream: Some(stream),
}
}
}
impl<T> Stream for Fuse<T>
where
T: Stream,
{
type Item = T::Item;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
let res = match Option::as_pin_mut(self.as_mut().project().stream) {
Some(stream) => ready!(stream.poll_next(cx)),
None => return Poll::Ready(None),
};
if res.is_none() {
// Do not poll the stream anymore
self.as_mut().project().stream.set(None);
}
Poll::Ready(res)
}
fn size_hint(&self) -> (usize, Option<usize>) {
match self.stream {
Some(ref stream) => stream.size_hint(),
None => (0, Some(0)),
}
}
}