| use core::fmt; |
| use core::marker::PhantomData; |
| use core::pin::Pin; |
| use futures_core::stream::{Stream, FusedStream}; |
| use futures_core::task::{Context, Poll}; |
| use futures_sink::Sink; |
| use pin_project::pin_project; |
| |
| /// Sink for the [`with_flat_map`](super::SinkExt::with_flat_map) method. |
| #[pin_project] |
| #[must_use = "sinks do nothing unless polled"] |
| pub struct WithFlatMap<Si, Item, U, St, F> { |
| #[pin] |
| sink: Si, |
| f: F, |
| #[pin] |
| stream: Option<St>, |
| buffer: Option<Item>, |
| _marker: PhantomData<fn(U)>, |
| } |
| |
| impl<Si, Item, U, St, F> fmt::Debug for WithFlatMap<Si, Item, U, St, F> |
| where |
| Si: fmt::Debug, |
| St: fmt::Debug, |
| Item: fmt::Debug, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("WithFlatMap") |
| .field("sink", &self.sink) |
| .field("stream", &self.stream) |
| .field("buffer", &self.buffer) |
| .finish() |
| } |
| } |
| |
| 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::Error>>, |
| { |
| pub(super) fn new(sink: Si, f: F) -> Self { |
| WithFlatMap { |
| sink, |
| f, |
| stream: None, |
| buffer: None, |
| _marker: PhantomData, |
| } |
| } |
| |
| delegate_access_inner!(sink, Si, ()); |
| |
| fn try_empty_stream( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Si::Error>> { |
| let mut this = self.project(); |
| |
| if this.buffer.is_some() { |
| ready!(this.sink.as_mut().poll_ready(cx))?; |
| let item = this.buffer.take().unwrap(); |
| this.sink.as_mut().start_send(item)?; |
| } |
| if let Some(mut some_stream) = this.stream.as_mut().as_pin_mut() { |
| while let Some(item) = ready!(some_stream.as_mut().poll_next(cx)?) { |
| match this.sink.as_mut().poll_ready(cx)? { |
| Poll::Ready(()) => this.sink.as_mut().start_send(item)?, |
| Poll::Pending => { |
| *this.buffer = Some(item); |
| return Poll::Pending; |
| } |
| }; |
| } |
| } |
| this.stream.set(None); |
| Poll::Ready(Ok(())) |
| } |
| } |
| |
| // Forwarding impl of Stream from the underlying sink |
| 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::Error>>, |
| { |
| type Item = S::Item; |
| |
| delegate_stream!(sink); |
| } |
| |
| impl<S, Item, U, St, F> FusedStream for WithFlatMap<S, Item, U, St, F> |
| where |
| S: FusedStream + Sink<Item>, |
| F: FnMut(U) -> St, |
| St: Stream<Item = Result<Item, S::Error>>, |
| { |
| fn is_terminated(&self) -> bool { |
| self.sink.is_terminated() |
| } |
| } |
| |
| 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::Error>>, |
| { |
| type Error = Si::Error; |
| |
| fn poll_ready( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::Error>> { |
| self.try_empty_stream(cx) |
| } |
| |
| fn start_send( |
| self: Pin<&mut Self>, |
| item: U, |
| ) -> Result<(), Self::Error> { |
| let mut this = self.project(); |
| |
| assert!(this.stream.is_none()); |
| this.stream.set(Some((this.f)(item))); |
| Ok(()) |
| } |
| |
| fn poll_flush( |
| mut self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::Error>> { |
| ready!(self.as_mut().try_empty_stream(cx)?); |
| self.project().sink.poll_flush(cx) |
| } |
| |
| fn poll_close( |
| mut self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Result<(), Self::Error>> { |
| ready!(self.as_mut().try_empty_stream(cx)?); |
| self.project().sink.poll_close(cx) |
| } |
| } |