| use core::pin::Pin; |
| use futures_core::stream::{FusedStream, Stream}; |
| use futures_core::task::{Context, Poll}; |
| #[cfg(feature = "sink")] |
| use futures_sink::Sink; |
| use pin_project::pin_project; |
| |
| /// Stream for the [`enumerate`](super::StreamExt::enumerate) method. |
| #[pin_project] |
| #[derive(Debug)] |
| #[must_use = "streams do nothing unless polled"] |
| pub struct Enumerate<St> { |
| #[pin] |
| stream: St, |
| count: usize, |
| } |
| |
| impl<St: Stream> Enumerate<St> { |
| pub(super) fn new(stream: St) -> Enumerate<St> { |
| Enumerate { |
| stream, |
| count: 0, |
| } |
| } |
| |
| delegate_access_inner!(stream, St, ()); |
| } |
| |
| impl<St: Stream + FusedStream> FusedStream for Enumerate<St> { |
| fn is_terminated(&self) -> bool { |
| self.stream.is_terminated() |
| } |
| } |
| |
| impl<St: Stream> Stream for Enumerate<St> { |
| type Item = (usize, St::Item); |
| |
| fn poll_next( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Option<Self::Item>> { |
| let this = self.project(); |
| |
| match ready!(this.stream.poll_next(cx)) { |
| Some(item) => { |
| let prev_count = *this.count; |
| *this.count += 1; |
| Poll::Ready(Some((prev_count, item))) |
| } |
| None => Poll::Ready(None), |
| } |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.stream.size_hint() |
| } |
| } |
| |
| // Forwarding impl of Sink from the underlying stream |
| #[cfg(feature = "sink")] |
| impl<S, Item> Sink<Item> for Enumerate<S> |
| where |
| S: Stream + Sink<Item>, |
| { |
| type Error = S::Error; |
| |
| delegate_sink!(stream, Item); |
| } |