1 use core::pin::Pin; 2 use futures_core::future::Future; 3 use futures_core::ready; 4 use futures_core::task::{Context, Poll}; 5 use futures_sink::Sink; 6 7 /// Future for the [`feed`](super::SinkExt::feed) method. 8 #[derive(Debug)] 9 #[must_use = "futures do nothing unless you `.await` or poll them"] 10 pub struct Feed<'a, Si: ?Sized, Item> { 11 sink: &'a mut Si, 12 item: Option<Item>, 13 } 14 15 // Pinning is never projected to children 16 impl<Si: Unpin + ?Sized, Item> Unpin for Feed<'_, Si, Item> {} 17 18 impl<'a, Si: Sink<Item> + Unpin + ?Sized, Item> Feed<'a, Si, Item> { new(sink: &'a mut Si, item: Item) -> Self19 pub(super) fn new(sink: &'a mut Si, item: Item) -> Self { 20 Feed { 21 sink, 22 item: Some(item), 23 } 24 } 25 sink_pin_mut(&mut self) -> Pin<&mut Si>26 pub(super) fn sink_pin_mut(&mut self) -> Pin<&mut Si> { 27 Pin::new(self.sink) 28 } 29 is_item_pending(&self) -> bool30 pub(super) fn is_item_pending(&self) -> bool { 31 self.item.is_some() 32 } 33 } 34 35 impl<Si: Sink<Item> + Unpin + ?Sized, Item> Future for Feed<'_, Si, Item> { 36 type Output = Result<(), Si::Error>; 37 poll( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Self::Output>38 fn poll( 39 self: Pin<&mut Self>, 40 cx: &mut Context<'_>, 41 ) -> Poll<Self::Output> { 42 let this = self.get_mut(); 43 let mut sink = Pin::new(&mut this.sink); 44 ready!(sink.as_mut().poll_ready(cx))?; 45 let item = this.item.take().expect("polled Feed after completion"); 46 sink.as_mut().start_send(item)?; 47 Poll::Ready(Ok(())) 48 } 49 } 50