| use core::fmt; |
| use core::pin::Pin; |
| use futures_core::future::Future; |
| use futures_core::stream::{FusedStream, Stream}; |
| use futures_core::task::{Context, Poll}; |
| #[cfg(feature = "sink")] |
| use futures_sink::Sink; |
| use pin_utils::{unsafe_pinned, unsafe_unpinned}; |
| |
| /// Stream for the [`skip_while`](super::StreamExt::skip_while) method. |
| #[must_use = "streams do nothing unless polled"] |
| pub struct SkipWhile<St, Fut, F> where St: Stream { |
| stream: St, |
| f: F, |
| pending_fut: Option<Fut>, |
| pending_item: Option<St::Item>, |
| done_skipping: bool, |
| } |
| |
| impl<St: Unpin + Stream, Fut: Unpin, F> Unpin for SkipWhile<St, Fut, F> {} |
| |
| impl<St, Fut, F> fmt::Debug for SkipWhile<St, Fut, F> |
| where |
| St: Stream + fmt::Debug, |
| St::Item: fmt::Debug, |
| Fut: fmt::Debug, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("SkipWhile") |
| .field("stream", &self.stream) |
| .field("pending_fut", &self.pending_fut) |
| .field("pending_item", &self.pending_item) |
| .field("done_skipping", &self.done_skipping) |
| .finish() |
| } |
| } |
| |
| impl<St, Fut, F> SkipWhile<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>); |
| unsafe_unpinned!(done_skipping: bool); |
| |
| pub(super) fn new(stream: St, f: F) -> SkipWhile<St, Fut, F> { |
| SkipWhile { |
| stream, |
| f, |
| pending_fut: None, |
| pending_item: None, |
| done_skipping: false, |
| } |
| } |
| |
| /// 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 |
| } |
| |
| /// Acquires a pinned 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_pin_mut(self: Pin<&mut Self>) -> Pin<&mut St> { |
| 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> FusedStream for SkipWhile<St, Fut, F> |
| where St: FusedStream, |
| F: FnMut(&St::Item) -> Fut, |
| Fut: Future<Output = bool>, |
| { |
| fn is_terminated(&self) -> bool { |
| self.pending_item.is_none() && self.stream.is_terminated() |
| } |
| } |
| |
| impl<St, Fut, F> Stream for SkipWhile<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>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Option<St::Item>> { |
| if self.done_skipping { |
| return self.as_mut().stream().poll_next(cx); |
| } |
| |
| loop { |
| if self.pending_item.is_none() { |
| let item = match ready!(self.as_mut().stream().poll_next(cx)) { |
| 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 skipped = ready!(self.as_mut().pending_fut().as_pin_mut().unwrap().poll(cx)); |
| let item = self.as_mut().pending_item().take().unwrap(); |
| self.as_mut().pending_fut().set(None); |
| |
| if !skipped { |
| *self.as_mut().done_skipping() = true; |
| return Poll::Ready(Some(item)) |
| } |
| } |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let pending_len = if self.pending_item.is_some() { 1 } else { 0 }; |
| let (_, upper) = self.stream.size_hint(); |
| let upper = match upper { |
| Some(x) => x.checked_add(pending_len), |
| None => None, |
| }; |
| (0, upper) // can't know a lower bound, due to the predicate |
| } |
| } |
| |
| // Forwarding impl of Sink from the underlying stream |
| #[cfg(feature = "sink")] |
| impl<S, Fut, F, Item> Sink<Item> for SkipWhile<S, Fut, F> |
| where S: Stream + Sink<Item>, |
| F: FnMut(&S::Item) -> Fut, |
| Fut: Future<Output = bool>, |
| { |
| type Error = S::Error; |
| |
| delegate_sink!(stream, Item); |
| } |