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use derive_new::new; use futures::{ready, Stream}; use pin_project::pin_project; use std::{ pin::Pin, task::{Context, Poll} }; use super::Pipe; #[pin_project] #[derive(new)] pub struct Filter<C, F> { #[pin] task: C, f: F, } impl<C: Stream, F> Stream for Filter<C, F> where F: FnMut(&C::Item) -> bool, { type Item = C::Item; fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> { let mut self_ = self.project(); let (mut task, f) = (self_.task, &mut self_.f); Poll::Ready(loop { match ready!(task.as_mut().poll_next(cx)) { Some(t) if f(&t) => break Some(t), Some(_) => (), None => break None, } }) } } impl<C: Pipe<Source>, F, Source> Pipe<Source> for Filter<C, F> where F: FnMut(&C::Item) -> bool, { type Item = C::Item; fn poll_next( self: Pin<&mut Self>, cx: &mut Context, mut stream: Pin<&mut impl Stream<Item = Source>>, ) -> Poll<Option<Self::Item>> { let mut self_ = self.project(); let (mut task, f) = (self_.task, &mut self_.f); Poll::Ready(loop { match ready!(task.as_mut().poll_next(cx, stream.as_mut())) { Some(t) if f(&t) => break Some(t), Some(_) => (), None => break None, } }) } }