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use core::pin::Pin;
use futures_core::future::Future;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TakeWhile<St: Stream , Fut, F> {
stream: St,
f: F,
pending_fut: Option<Fut>,
pending_item: Option<St::Item>,
done_taking: bool,
}
impl<St: Unpin + Stream, Fut: Unpin, F> Unpin for TakeWhile<St, Fut, F> {}
impl<St, Fut, F> TakeWhile<St, Fut, F>
where St: Stream,
F: FnMut(&St::Item) -> Fut,
Fut: Future<Output = bool>,
{
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
unsafe_pinned!(pending_fut: Option<Fut>);
unsafe_unpinned!(pending_item: Option<St::Item>);
unsafe_unpinned!(done_taking: bool);
pub(super) fn new(stream: St, f: F) -> TakeWhile<St, Fut, F> {
TakeWhile {
stream,
f,
pending_fut: None,
pending_item: None,
done_taking: false,
}
}
pub fn get_ref(&self) -> &St {
&self.stream
}
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
pub fn into_inner(self) -> St {
self.stream
}
}
impl<St, Fut, F> Stream for TakeWhile<St, Fut, F>
where St: Stream,
F: FnMut(&St::Item) -> Fut,
Fut: Future<Output = bool>,
{
type Item = St::Item;
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<St::Item>> {
if self.done_taking {
return Poll::Ready(None);
}
if self.pending_item.is_none() {
let item = match ready!(self.as_mut().stream().poll_next(cx)) {
Some(e) => e,
None => return Poll::Ready(None),
};
let fut = (self.as_mut().f())(&item);
self.as_mut().pending_fut().set(Some(fut));
*self.as_mut().pending_item() = Some(item);
}
let take = ready!(self.as_mut().pending_fut().as_pin_mut().unwrap().poll(cx));
self.as_mut().pending_fut().set(None);
let item = self.as_mut().pending_item().take().unwrap();
if take {
Poll::Ready(Some(item))
} else {
*self.as_mut().done_taking() = true;
Poll::Ready(None)
}
}
}
impl<S, Fut, F, Item> Sink<Item> for TakeWhile<S, Fut, F>
where S: Stream + Sink<Item>,
F: FnMut(&S::Item) -> Fut,
Fut: Future<Output = bool>,
{
type SinkError = S::SinkError;
delegate_sink!(stream, Item);
}