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use core::pin::Pin;
use pin_project_lite::pin_project;
use crate::stream::Stream;
use crate::task::{Context, Poll};
pin_project! {
#[derive(Debug)]
pub struct Filter<S, P> {
#[pin]
stream: S,
predicate: P,
}
}
impl<S, P> Filter<S, P> {
pub(super) fn new(stream: S, predicate: P) -> Self {
Self {
stream,
predicate,
}
}
}
impl<S, P> Stream for Filter<S, P>
where
S: Stream,
P: FnMut(&S::Item) -> bool,
{
type Item = S::Item;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
let this = self.project();
let next = futures_core::ready!(this.stream.poll_next(cx));
match next {
Some(v) if (this.predicate)(&v) => Poll::Ready(Some(v)),
Some(_) => {
cx.waker().wake_by_ref();
Poll::Pending
}
None => Poll::Ready(None),
}
}
}