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use {Future, Poll, Async};
/// Do something with the item of a future, passing it on.
///
/// This is created by the `Future::inspect` method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Inspect<A, F> where A: Future {
future: A,
f: Option<F>,
}
pub fn new<A, F>(future: A, f: F) -> Inspect<A, F>
where A: Future,
F: FnOnce(&A::Item),
{
Inspect {
future: future,
f: Some(f),
}
}
impl<A, F> Future for Inspect<A, F>
where A: Future,
F: FnOnce(&A::Item),
{
type Item = A::Item;
type Error = A::Error;
fn poll(&mut self) -> Poll<A::Item, A::Error> {
match self.future.poll() {
Ok(Async::NotReady) => Ok(Async::NotReady),
Ok(Async::Ready(e)) => {
(self.f.take().expect("cannot poll Inspect twice"))(&e);
Ok(Async::Ready(e))
},
Err(e) => Err(e),
}
}
}
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