| use core::marker::PhantomData; |
| use core::pin::Pin; |
| use futures_core::stream::Stream; |
| use futures_core::task::{Context, Poll}; |
| use futures_sink::Sink; |
| use pin_utils::{unsafe_pinned, unsafe_unpinned}; |
| |
| /// Sink for the [`with_flat_map`](super::SinkExt::with_flat_map) method. |
| #[derive(Debug)] |
| #[must_use = "sinks do nothing unless polled"] |
| pub struct WithFlatMap<Si, Item, U, St, F> |
| where |
| Si: Sink<Item>, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, Si::SinkError>>, |
| { |
| sink: Si, |
| f: F, |
| stream: Option<St>, |
| buffer: Option<Item>, |
| _marker: PhantomData<fn(U)>, |
| } |
| |
| impl<Si, Item, U, St, F> Unpin for WithFlatMap<Si, Item, U, St, F> |
| where |
| Si: Sink<Item> + Unpin, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, Si::SinkError>> + Unpin, |
| {} |
| |
| impl<Si, Item, U, St, F> WithFlatMap<Si, Item, U, St, F> |
| where |
| Si: Sink<Item>, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, Si::SinkError>>, |
| { |
| unsafe_pinned!(sink: Si); |
| unsafe_unpinned!(f: F); |
| unsafe_pinned!(stream: Option<St>); |
| |
| pub(super) fn new(sink: Si, f: F) -> Self { |
| WithFlatMap { |
| sink, |
| f, |
| stream: None, |
| buffer: None, |
| _marker: PhantomData, |
| } |
| } |
| |
| /// Get a shared reference to the inner sink. |
| pub fn get_ref(&self) -> &Si { |
| &self.sink |
| } |
| |
| /// Get a mutable reference to the inner sink. |
| pub fn get_mut(&mut self) -> &mut Si { |
| &mut self.sink |
| } |
| |
| /// Get a pinned mutable reference to the inner sink. |
| pub fn get_pin_mut<'a>(self: Pin<&'a mut Self>) -> Pin<&'a mut Si> { |
| self.sink() |
| } |
| |
| /// Consumes this combinator, returning the underlying sink. |
| /// |
| /// 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) -> Si { |
| self.sink |
| } |
| |
| fn try_empty_stream( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Si::SinkError>> { |
| let WithFlatMap { sink, stream, buffer, .. } = |
| unsafe { Pin::get_unchecked_mut(self) }; |
| let mut sink = unsafe { Pin::new_unchecked(sink) }; |
| let mut stream = unsafe { Pin::new_unchecked(stream) }; |
| |
| if buffer.is_some() { |
| try_ready!(sink.as_mut().poll_ready(cx)); |
| let item = buffer.take().unwrap(); |
| try_ready!(Poll::Ready(sink.as_mut().start_send(item))); |
| } |
| if let Some(mut some_stream) = stream.as_mut().as_pin_mut() { |
| while let Some(x) = ready!(some_stream.as_mut().poll_next(cx)) { |
| let item = try_ready!(Poll::Ready(x)); |
| match sink.as_mut().poll_ready(cx)? { |
| Poll::Ready(()) => sink.as_mut().start_send(item)?, |
| Poll::Pending => { |
| *buffer = Some(item); |
| return Poll::Pending; |
| } |
| }; |
| } |
| } |
| stream.set(None); |
| Poll::Ready(Ok(())) |
| } |
| } |
| |
| impl<S, Item, U, St, F> Stream for WithFlatMap<S, Item, U, St, F> |
| where |
| S: Stream + Sink<Item>, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, S::SinkError>>, |
| { |
| type Item = S::Item; |
| fn poll_next( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Option<S::Item>> { |
| self.sink().poll_next(cx) |
| } |
| } |
| |
| impl<Si, Item, U, St, F> Sink<U> for WithFlatMap<Si, Item, U, St, F> |
| where |
| Si: Sink<Item>, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, Si::SinkError>>, |
| { |
| type SinkError = Si::SinkError; |
| |
| fn poll_ready( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::SinkError>> { |
| self.try_empty_stream(cx) |
| } |
| |
| fn start_send( |
| mut self: Pin<&mut Self>, |
| item: U, |
| ) -> Result<(), Self::SinkError> { |
| assert!(self.stream.is_none()); |
| let stream = (self.as_mut().f())(item); |
| self.stream().set(Some(stream)); |
| Ok(()) |
| } |
| |
| fn poll_flush( |
| mut self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::SinkError>> { |
| match self.as_mut().try_empty_stream(cx) { |
| Poll::Pending => Poll::Pending, |
| Poll::Ready(Ok(())) => self.as_mut().sink().poll_flush(cx), |
| Poll::Ready(Err(e)) => Poll::Ready(Err(e)), |
| } |
| } |
| |
| fn poll_close( |
| mut self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::SinkError>> { |
| match self.as_mut().try_empty_stream(cx) { |
| Poll::Pending => Poll::Pending, |
| Poll::Ready(Ok(())) => self.as_mut().sink().poll_close(cx), |
| Poll::Ready(Err(e)) => Poll::Ready(Err(e)), |
| } |
| } |
| } |