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use {Future, Poll, Async};
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Fuse<A: Future> {
future: Option<A>,
}
pub fn new<A: Future>(f: A) -> Fuse<A> {
Fuse {
future: Some(f),
}
}
impl<A: Future> Future for Fuse<A> {
type Item = A::Item;
type Error = A::Error;
fn poll(&mut self) -> Poll<A::Item, A::Error> {
let res = self.future.as_mut().map(|f| f.poll());
match res.unwrap_or(Ok(Async::NotReady)) {
res @ Ok(Async::Ready(_)) |
res @ Err(_) => {
self.future = None;
res
}
Ok(Async::NotReady) => Ok(Async::NotReady)
}
}
}