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use {Poll, Async};
use stream::Stream;
#[must_use = "streams do nothing unless polled"]
pub struct Flatten<S>
where S: Stream,
{
stream: S,
next: Option<S::Item>,
}
pub fn new<S>(s: S) -> Flatten<S>
where S: Stream,
S::Item: Stream,
<S::Item as Stream>::Error: From<S::Error>,
{
Flatten {
stream: s,
next: None,
}
}
impl<S> Stream for Flatten<S>
where S: Stream,
S::Item: Stream,
<S::Item as Stream>::Error: From<S::Error>,
{
type Item = <S::Item as Stream>::Item;
type Error = <S::Item as Stream>::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
loop {
if self.next.is_none() {
match try_ready!(self.stream.poll()) {
Some(e) => self.next = Some(e),
None => return Ok(Async::Ready(None)),
}
}
assert!(self.next.is_some());
match self.next.as_mut().unwrap().poll() {
Ok(Async::Ready(None)) => self.next = None,
other => return other,
}
}
}
}