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use {Async, Future, Poll};
use core::fmt;
use stream::Stream;
#[must_use = "streams do nothing unless polled"]
pub struct FlattenStream<F>
where F: Future,
<F as Future>::Item: Stream<Error=F::Error>,
{
state: State<F>
}
impl<F> fmt::Debug for FlattenStream<F>
where F: Future + fmt::Debug,
<F as Future>::Item: Stream<Error=F::Error> + fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("FlattenStream")
.field("state", &self.state)
.finish()
}
}
pub fn new<F>(f: F) -> FlattenStream<F>
where F: Future,
<F as Future>::Item: Stream<Error=F::Error>,
{
FlattenStream {
state: State::Future(f)
}
}
#[derive(Debug)]
enum State<F>
where F: Future,
<F as Future>::Item: Stream<Error=F::Error>,
{
Future(F),
Stream(F::Item),
Eof,
Done,
}
impl<F> Stream for FlattenStream<F>
where F: Future,
<F as Future>::Item: Stream<Error=F::Error>,
{
type Item = <F::Item as Stream>::Item;
type Error = <F::Item as Stream>::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
loop {
let (next_state, ret_opt) = match self.state {
State::Future(ref mut f) => {
match f.poll() {
Ok(Async::NotReady) => {
return Ok(Async::NotReady)
},
Ok(Async::Ready(stream)) => {
(State::Stream(stream), None)
}
Err(e) => {
(State::Eof, Some(Err(e)))
}
}
}
State::Stream(ref mut s) => {
return s.poll();
}
State::Eof => {
(State::Done, Some(Ok(Async::Ready(None))))
}
State::Done => {
panic!("poll called after eof");
}
};
self.state = next_state;
if let Some(ret) = ret_opt {
return ret;
}
}
}
}