| use crate::Stream; |
| |
| use core::fmt; |
| use core::pin::Pin; |
| use core::task::{Context, Poll}; |
| use pin_project_lite::pin_project; |
| |
| pin_project! { |
| /// Stream returned by the [`filter_map`](super::StreamExt::filter_map) method. |
| #[must_use = "streams do nothing unless polled"] |
| pub struct FilterMap<St, F> { |
| #[pin] |
| stream: St, |
| f: F, |
| } |
| } |
| |
| impl<St, F> fmt::Debug for FilterMap<St, F> |
| where |
| St: fmt::Debug, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("FilterMap") |
| .field("stream", &self.stream) |
| .finish() |
| } |
| } |
| |
| impl<St, F> FilterMap<St, F> { |
| pub(super) fn new(stream: St, f: F) -> Self { |
| Self { stream, f } |
| } |
| } |
| |
| impl<St, F, T> Stream for FilterMap<St, F> |
| where |
| St: Stream, |
| F: FnMut(St::Item) -> Option<T>, |
| { |
| type Item = T; |
| |
| fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> { |
| loop { |
| match ready!(self.as_mut().project().stream.poll_next(cx)) { |
| Some(e) => { |
| if let Some(e) = (self.as_mut().project().f)(e) { |
| return Poll::Ready(Some(e)); |
| } |
| } |
| None => return Poll::Ready(None), |
| } |
| } |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| (0, self.stream.size_hint().1) // can't know a lower bound, due to the predicate |
| } |
| } |