| use crate::Stream; |
| |
| use core::fmt; |
| use core::pin::Pin; |
| use core::task::{Context, Poll}; |
| use pin_project_lite::pin_project; |
| |
| pin_project! { |
| /// Stream for the [`map_while`](super::StreamExt::map_while) method. |
| #[must_use = "streams do nothing unless polled"] |
| pub struct MapWhile<St, F> { |
| #[pin] |
| stream: St, |
| f: F, |
| } |
| } |
| |
| impl<St, F> fmt::Debug for MapWhile<St, F> |
| where |
| St: fmt::Debug, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("MapWhile") |
| .field("stream", &self.stream) |
| .finish() |
| } |
| } |
| |
| impl<St, F> MapWhile<St, F> { |
| pub(super) fn new(stream: St, f: F) -> Self { |
| MapWhile { stream, f } |
| } |
| } |
| |
| impl<St, F, T> Stream for MapWhile<St, F> |
| where |
| St: Stream, |
| F: FnMut(St::Item) -> Option<T>, |
| { |
| type Item = T; |
| |
| fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> { |
| let me = self.project(); |
| let f = me.f; |
| me.stream.poll_next(cx).map(|opt| opt.and_then(f)) |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let (_, upper) = self.stream.size_hint(); |
| (0, upper) |
| } |
| } |