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use {Poll, Async};
use stream::Stream;
/// A combinator used to flatten a stream-of-streams into one long stream of
/// elements.
///
/// This combinator is created by the `Stream::flatten` method.
#[derive(Debug)]
#[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> Flatten<S> {
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &S {
&self.stream
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut S {
&mut self.stream
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> S {
self.stream
}
}
// Forwarding impl of Sink from the underlying stream
impl<S> ::sink::Sink for Flatten<S>
where S: ::sink::Sink + Stream
{
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
fn start_send(&mut self, item: S::SinkItem) -> ::StartSend<S::SinkItem, S::SinkError> {
self.stream.start_send(item)
}
fn poll_complete(&mut self) -> Poll<(), S::SinkError> {
self.stream.poll_complete()
}
fn close(&mut self) -> Poll<(), S::SinkError> {
self.stream.close()
}
}
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,
}
}
}
}
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