| use core::marker::Unpin; |
| use core::pin::Pin; |
| use futures_core::future::Future; |
| use futures_core::stream::{FusedStream, Stream}; |
| use futures_core::task::{LocalWaker, Poll}; |
| use pin_utils::{unsafe_pinned, unsafe_unpinned}; |
| |
| /// A stream combinator used to filter the results of a stream and only yield |
| /// some values. |
| /// |
| /// This structure is produced by the `Stream::filter` method. |
| #[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, |
| } |
| } |
| |
| /// Acquires a reference to the underlying stream that this combinator is |
| /// pulling from. |
| pub fn get_ref(&self) -> &St { |
| &self.stream |
| } |
| |
| /// Acquires a mutable reference to the underlying stream that this |
| /// combinator is pulling from. |
| /// |
| /// Note that care must be taken to avoid tampering with the state of the |
| /// stream which may otherwise confuse this combinator. |
| pub fn get_mut(&mut self) -> &mut St { |
| &mut self.stream |
| } |
| |
| /// Consumes this combinator, returning the underlying stream. |
| /// |
| /// Note that this may discard intermediate state of this combinator, so |
| /// care should be taken to avoid losing resources when this is called. |
| 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>, |
| lw: &LocalWaker, |
| ) -> 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(lw)) { |
| 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(lw)); |
| self.as_mut().pending_fut().set(None); |
| let item = self.as_mut().pending_item().take().unwrap(); |
| |
| if yield_item { |
| return Poll::Ready(Some(item)); |
| } |
| } |
| } |
| } |
| |
| /* TODO |
| // Forwarding impl of Sink from the underlying stream |
| impl<S, R, P> Sink for Filter<S, R, P> |
| where S: Stream, |
| P: FnMut(&S::Item) -> R, |
| R: Future<Item = bool>, |
| S: Sink, |
| { |
| type SinkItem = S::SinkItem; |
| type SinkError = S::SinkError; |
| |
| delegate_sink!(stream); |
| } |
| */ |