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use {Poll, Async, Future, AsyncSink};
use stream::{Stream, Fuse};
use sink::Sink;
/// Future for the `Stream::forward` combinator, which sends a stream of values
/// to a sink and then waits until the sink has fully flushed those values.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Forward<T: Stream, U> {
sink: Option<U>,
stream: Option<Fuse<T>>,
buffered: Option<T::Item>,
}
pub fn new<T, U>(stream: T, sink: U) -> Forward<T, U>
where U: Sink<SinkItem=T::Item>,
T: Stream,
T::Error: From<U::SinkError>,
{
Forward {
sink: Some(sink),
stream: Some(stream.fuse()),
buffered: None,
}
}
impl<T, U> Forward<T, U>
where U: Sink<SinkItem=T::Item>,
T: Stream,
T::Error: From<U::SinkError>,
{
/// Get a shared reference to the inner sink.
/// If this combinator has already been polled to completion, None will be returned.
pub fn sink_ref(&self) -> Option<&U> {
self.sink.as_ref()
}
/// Get a mutable reference to the inner sink.
/// If this combinator has already been polled to completion, None will be returned.
pub fn sink_mut(&mut self) -> Option<&mut U> {
self.sink.as_mut()
}
/// Get a shared reference to the inner stream.
/// If this combinator has already been polled to completion, None will be returned.
pub fn stream_ref(&self) -> Option<&T> {
self.stream.as_ref().map(|x| x.get_ref())
}
/// Get a mutable reference to the inner stream.
/// If this combinator has already been polled to completion, None will be returned.
pub fn stream_mut(&mut self) -> Option<&mut T> {
self.stream.as_mut().map(|x| x.get_mut())
}
fn take_result(&mut self) -> (T, U) {
let sink = self.sink.take()
.expect("Attempted to poll Forward after completion");
let fuse = self.stream.take()
.expect("Attempted to poll Forward after completion");
(fuse.into_inner(), sink)
}
fn try_start_send(&mut self, item: T::Item) -> Poll<(), U::SinkError> {
debug_assert!(self.buffered.is_none());
if let AsyncSink::NotReady(item) = self.sink_mut()
.expect("Attempted to poll Forward after completion")
.start_send(item)?
{
self.buffered = Some(item);
return Ok(Async::NotReady)
}
Ok(Async::Ready(()))
}
}
impl<T, U> Future for Forward<T, U>
where U: Sink<SinkItem=T::Item>,
T: Stream,
T::Error: From<U::SinkError>,
{
type Item = (T, U);
type Error = T::Error;
fn poll(&mut self) -> Poll<(T, U), T::Error> {
// If we've got an item buffered already, we need to write it to the
// sink before we can do anything else
if let Some(item) = self.buffered.take() {
try_ready!(self.try_start_send(item))
}
loop {
match self.stream.as_mut()
.expect("Attempted to poll Forward after completion")
.poll()?
{
Async::Ready(Some(item)) => try_ready!(self.try_start_send(item)),
Async::Ready(None) => {
try_ready!(self.sink_mut().expect("Attempted to poll Forward after completion").close());
return Ok(Async::Ready(self.take_result()))
}
Async::NotReady => {
try_ready!(self.sink_mut().expect("Attempted to poll Forward after completion").poll_complete());
return Ok(Async::NotReady)
}
}
}
}
}
|
