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use core::pin::Pin;
use futures_core::future::Future;
use futures_core::task::{LocalWaker, Poll};
use pin_utils::unsafe_pinned;
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Fuse<Fut: Future> {
future: Option<Fut>,
}
impl<Fut: Future> Fuse<Fut> {
unsafe_pinned!(future: Option<Fut>);
pub(super) fn new(f: Fut) -> Fuse<Fut> {
Fuse {
future: Some(f),
}
}
}
impl<Fut: Future> Future for Fuse<Fut> {
type Output = Fut::Output;
fn poll(mut self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<Fut::Output> {
let v = match self.future().as_pin_mut() {
Some(fut) => {
match fut.poll(lw) {
Poll::Pending => return Poll::Pending,
Poll::Ready(v) => v
}
}
None => return Poll::Pending,
};
Pin::set(self.future(), None);
Poll::Ready(v)
}
}