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use core::pin::Pin;
use futures_core::stream::{FusedStream, Stream, TryStream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_utils::unsafe_pinned;
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TryFlatten<St>
where
St: TryStream,
{
stream: St,
next: Option<St::Ok>,
}
impl<St> Unpin for TryFlatten<St>
where
St: TryStream + Unpin,
St::Ok: Unpin,
{
}
impl<St> TryFlatten<St>
where
St: TryStream,
{
unsafe_pinned!(stream: St);
unsafe_pinned!(next: Option<St::Ok>);
}
impl<St> TryFlatten<St>
where
St: TryStream,
St::Ok: TryStream,
<St::Ok as TryStream>::Error: From<St::Error>,
{
pub(super) fn new(stream: St) -> Self {
Self { stream, next: None }
}
pub fn get_ref(&self) -> &St {
&self.stream
}
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut St> {
self.stream()
}
pub fn into_inner(self) -> St {
self.stream
}
}
impl<St> FusedStream for TryFlatten<St>
where
St: TryStream + FusedStream,
St::Ok: TryStream,
<St::Ok as TryStream>::Error: From<St::Error>,
{
fn is_terminated(&self) -> bool {
self.next.is_none() && self.stream.is_terminated()
}
}
impl<St> Stream for TryFlatten<St>
where
St: TryStream,
St::Ok: TryStream,
<St::Ok as TryStream>::Error: From<St::Error>,
{
type Item = Result<<St::Ok as TryStream>::Ok, <St::Ok as TryStream>::Error>;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
loop {
if self.next.is_none() {
match ready!(self.as_mut().stream().try_poll_next(cx)?) {
Some(e) => self.as_mut().next().set(Some(e)),
None => return Poll::Ready(None),
}
}
if let Some(item) = ready!(self
.as_mut()
.next()
.as_pin_mut()
.unwrap()
.try_poll_next(cx)?)
{
return Poll::Ready(Some(Ok(item)));
} else {
self.as_mut().next().set(None);
}
}
}
}
#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for TryFlatten<S>
where
S: TryStream + Sink<Item>,
{
type Error = <S as Sink<Item>>::Error;
delegate_sink!(stream, Item);
}