blob: b4c8647bdbf8ee564dfe9b4495d74857b5d7cb94 [file] [log] [blame]
use core::marker::Unpin;
use core::pin::Pin;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{LocalWaker, Poll};
use pin_utils::unsafe_pinned;
/// 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<St>
where St: Stream,
{
stream: St,
next: Option<St::Item>,
}
impl<St: Stream> Unpin for Flatten<St>
where St: Stream + Unpin,
St::Item: Stream + Unpin,
{}
impl<St: Stream> Flatten<St>
where St: Stream,
St::Item: Stream,
{
unsafe_pinned!(stream: St);
unsafe_pinned!(next: Option<St::Item>);
pub(super) fn new(stream: St) -> Flatten<St>{
Flatten { stream, next: None, }
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
&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 St {
&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) -> St {
self.stream
}
}
impl<St: Stream + FusedStream> FusedStream for Flatten<St> {
fn is_terminated(&self) -> bool {
self.next.is_none() && self.stream.is_terminated()
}
}
impl<St> Stream for Flatten<St>
where St: Stream,
St::Item: Stream,
{
type Item = <St::Item as Stream>::Item;
fn poll_next(
mut self: Pin<&mut Self>,
lw: &LocalWaker,
) -> Poll<Option<Self::Item>> {
loop {
if self.as_mut().next().as_pin_mut().is_none() {
match ready!(self.as_mut().stream().poll_next(lw)) {
Some(e) => self.as_mut().next().set(Some(e)),
None => return Poll::Ready(None),
}
}
let item = ready!(self.as_mut().next().as_pin_mut().unwrap().poll_next(lw));
if item.is_some() {
return Poll::Ready(item);
} else {
self.as_mut().next().set(None);
}
}
}
}
/* TODO
// Forwarding impl of Sink from the underlying stream
impl<S> Sink for Flatten<S>
where S: Sink + Stream
{
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
delegate_sink!(stream);
}
*/