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|
use core::marker::PhantomData;
use {Poll, Async, StartSend, AsyncSink};
use sink::Sink;
use stream::Stream;
/// Sink for the `Sink::with_flat_map` combinator, chaining a computation that returns an iterator
/// to run prior to pushing a value into the underlying sink
#[derive(Debug)]
#[must_use = "sinks do nothing unless polled"]
pub struct WithFlatMap<S, U, F, St>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
sink: S,
f: F,
stream: Option<St>,
buffer: Option<S::SinkItem>,
_phantom: PhantomData<fn(U)>,
}
pub fn new<S, U, F, St>(sink: S, f: F) -> WithFlatMap<S, U, F, St>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
WithFlatMap {
sink: sink,
f: f,
stream: None,
buffer: None,
_phantom: PhantomData,
}
}
impl<S, U, F, St> WithFlatMap<S, U, F, St>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
/// Get a shared reference to the inner sink.
pub fn get_ref(&self) -> &S {
&self.sink
}
/// Get a mutable reference to the inner sink.
pub fn get_mut(&mut self) -> &mut S {
&mut self.sink
}
/// Consumes this combinator, returning the underlying sink.
///
/// 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.sink
}
fn try_empty_stream(&mut self) -> Poll<(), S::SinkError> {
if let Some(x) = self.buffer.take() {
if let AsyncSink::NotReady(x) = self.sink.start_send(x)? {
self.buffer = Some(x);
return Ok(Async::NotReady);
}
}
if let Some(mut stream) = self.stream.take() {
while let Some(x) = try_ready!(stream.poll()) {
if let AsyncSink::NotReady(x) = self.sink.start_send(x)? {
self.stream = Some(stream);
self.buffer = Some(x);
return Ok(Async::NotReady);
}
}
}
Ok(Async::Ready(()))
}
}
impl<S, U, F, St> Stream for WithFlatMap<S, U, F, St>
where
S: Stream + Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
type Item = S::Item;
type Error = S::Error;
fn poll(&mut self) -> Poll<Option<S::Item>, S::Error> {
self.sink.poll()
}
}
impl<S, U, F, St> Sink for WithFlatMap<S, U, F, St>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
type SinkItem = U;
type SinkError = S::SinkError;
fn start_send(&mut self, i: Self::SinkItem) -> StartSend<Self::SinkItem, Self::SinkError> {
if self.try_empty_stream()?.is_not_ready() {
return Ok(AsyncSink::NotReady(i));
}
assert!(self.stream.is_none());
self.stream = Some((self.f)(i));
self.try_empty_stream()?;
Ok(AsyncSink::Ready)
}
fn poll_complete(&mut self) -> Poll<(), Self::SinkError> {
if self.try_empty_stream()?.is_not_ready() {
return Ok(Async::NotReady);
}
self.sink.poll_complete()
}
fn close(&mut self) -> Poll<(), Self::SinkError> {
if self.try_empty_stream()?.is_not_ready() {
return Ok(Async::NotReady);
}
assert!(self.stream.is_none());
self.sink.close()
}
}
|
