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use std::convert::From;
use std::io;
use futures;
use futures::Future;
use futures::Poll;
use futures::stream::Stream;
use tokio_oneshot;
enum State<S> {
Receiver(tokio_oneshot::Receiver<S>),
Ready(S),
}
#[allow(dead_code)]
pub struct Deferred<S>
where
S : Stream + Send + 'static,
S::Error : From<io::Error>,
{
state: State<S>,
}
#[allow(dead_code)]
pub struct DeferredInit<S>
where
S : Stream + Send + 'static,
S::Error : From<io::Error>,
{
sender: tokio_oneshot::Sender<S>,
}
#[allow(dead_code)]
pub fn stream_deferred<S>() -> (Deferred<S>, DeferredInit<S>)
where
S : Stream + Send + 'static,
S::Error : From<io::Error>,
{
let (tx, rx) = tokio_oneshot::oneshot();
(
Deferred { state: State::Receiver(rx) },
DeferredInit { sender: tx }
)
}
impl<S> DeferredInit<S>
where
S : Stream + Send + 'static,
S::Error : From<io::Error>,
{
pub fn init(self, stream: S) -> Result<(), futures::sync::mpsc::SendError<S>> {
self.sender.send(stream)
}
}
impl<S> Stream for Deferred<S>
where
S : Stream + Send + 'static,
S::Error : From<io::Error>,
{
type Item = S::Item;
type Error = S::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
let stream: S = match self.state {
State::Ready(ref mut s) => return s.poll(),
State::Receiver(ref mut receiver) => try_ready!(receiver.poll().map_err(|_| io::Error::new(io::ErrorKind::Other, "recv"))),
};
self.state = State::Ready(stream);
match self.state {
State::Ready(ref mut s) => s.poll(),
State::Receiver(..) => unreachable!(),
}
}
}