async_sink/ext/
feed.rs

1use super::Sink;
2use core::future::Future;
3use core::pin::Pin;
4use core::task::{Context, Poll};
5
6/// Future for the [`feed`](super::SinkExt::feed) method.
7#[derive(Debug)]
8#[must_use = "futures do nothing unless you `.await` or poll them"]
9pub struct Feed<'a, Si: ?Sized, Item> {
10    sink: &'a mut Si,
11    item: Option<Item>,
12}
13
14// `Feed` is `Unpin` because it only contains a mutable reference to the sink,
15// not the sink itself.
16impl<Si: ?Sized, Item> Unpin for Feed<'_, Si, Item> {}
17
18impl<'a, Si: Sink<Item> + Unpin + ?Sized, Item> Feed<'a, Si, Item> {
19    pub(super) fn new(sink: &'a mut Si, item: Item) -> Self {
20        Feed {
21            sink,
22            item: Some(item),
23        }
24    }
25
26    pub(super) fn sink_pin_mut(&mut self) -> Pin<&mut Si> {
27        Pin::new(self.sink)
28    }
29
30    pub(super) fn is_item_pending(&self) -> bool {
31        self.item.is_some()
32    }
33}
34
35impl<Si: Sink<Item> + Unpin + ?Sized, Item> Future for Feed<'_, Si, Item> {
36    type Output = Result<(), Si::Error>;
37
38    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
39        let this = self.get_mut();
40        let mut sink = Pin::new(&mut *this.sink);
41        match sink.as_mut().poll_ready(cx) {
42            Poll::Ready(Ok(())) => {
43                let item = this.item.take().expect("polled Feed after completion");
44                Poll::Ready(sink.as_mut().start_send(item))
45            }
46            Poll::Ready(Err(e)) => Poll::Ready(Err(e)),
47            Poll::Pending => Poll::Pending,
48        }
49    }
50}
async_sink/ext/feed.rs

async_sink/ext/
feed.rs
