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use core::pin::Pin;
use futures_core::future::Future;
use futures_core::stream::{FusedStream, 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 Filter<St, Fut, F>
where St: Stream,
F: FnMut(&St::Item) -> Fut,
Fut: Future<Output = bool>,
{
stream: St,
f: F,
pending_fut: Option<Fut>,
pending_item: Option<St::Item>,
}
impl<St, Fut, F> Filter<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>);
pub(super) fn new(stream: St, f: F) -> Filter<St, Fut, F> {
Filter {
stream,
f,
pending_fut: None,
pending_item: None,
}
}
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> Unpin for Filter<St, Fut, F>
where St: Stream + Unpin,
F: FnMut(&St::Item) -> Fut,
Fut: Future<Output = bool> + Unpin,
{}
impl<St, Fut, F> FusedStream for Filter<St, Fut, F>
where St: Stream + FusedStream,
F: FnMut(&St::Item) -> Fut,
Fut: Future<Output = bool>,
{
fn is_terminated(&self) -> bool {
self.pending_fut.is_none() && self.stream.is_terminated()
}
}
impl<St, Fut, F> Stream for Filter<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>> {
loop {
if self.as_mut().pending_fut().as_pin_mut().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 yield_item = 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 yield_item {
return Poll::Ready(Some(item));
}
}
}
}
impl<S, Fut, F, Item> Sink<Item> for Filter<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);
}