futures_util/sink/
send_all.rs

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1use crate::stream::{Fuse, StreamExt, TryStreamExt};
2use core::fmt;
3use core::pin::Pin;
4use futures_core::future::Future;
5use futures_core::ready;
6use futures_core::stream::{Stream, TryStream};
7use futures_core::task::{Context, Poll};
8use futures_sink::Sink;
9
10/// Future for the [`send_all`](super::SinkExt::send_all) method.
11#[allow(explicit_outlives_requirements)] // https://github.com/rust-lang/rust/issues/60993
12#[must_use = "futures do nothing unless you `.await` or poll them"]
13pub struct SendAll<'a, Si, St>
14where
15    Si: ?Sized,
16    St: ?Sized + TryStream,
17{
18    sink: &'a mut Si,
19    stream: Fuse<&'a mut St>,
20    buffered: Option<St::Ok>,
21}
22
23impl<Si, St> fmt::Debug for SendAll<'_, Si, St>
24where
25    Si: fmt::Debug + ?Sized,
26    St: fmt::Debug + ?Sized + TryStream,
27    St::Ok: fmt::Debug,
28{
29    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
30        f.debug_struct("SendAll")
31            .field("sink", &self.sink)
32            .field("stream", &self.stream)
33            .field("buffered", &self.buffered)
34            .finish()
35    }
36}
37
38// Pinning is never projected to any fields
39impl<Si, St> Unpin for SendAll<'_, Si, St>
40where
41    Si: Unpin + ?Sized,
42    St: TryStream + Unpin + ?Sized,
43{
44}
45
46impl<'a, Si, St, Ok, Error> SendAll<'a, Si, St>
47where
48    Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
49    St: TryStream<Ok = Ok, Error = Error> + Stream + Unpin + ?Sized,
50{
51    pub(super) fn new(sink: &'a mut Si, stream: &'a mut St) -> Self {
52        Self { sink, stream: stream.fuse(), buffered: None }
53    }
54
55    fn try_start_send(
56        &mut self,
57        cx: &mut Context<'_>,
58        item: St::Ok,
59    ) -> Poll<Result<(), Si::Error>> {
60        debug_assert!(self.buffered.is_none());
61        match Pin::new(&mut self.sink).poll_ready(cx)? {
62            Poll::Ready(()) => Poll::Ready(Pin::new(&mut self.sink).start_send(item)),
63            Poll::Pending => {
64                self.buffered = Some(item);
65                Poll::Pending
66            }
67        }
68    }
69}
70
71impl<Si, St, Ok, Error> Future for SendAll<'_, Si, St>
72where
73    Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
74    St: Stream<Item = Result<Ok, Error>> + Unpin + ?Sized,
75{
76    type Output = Result<(), Error>;
77
78    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
79        let this = &mut *self;
80        // If we've got an item buffered already, we need to write it to the
81        // sink before we can do anything else
82        if let Some(item) = this.buffered.take() {
83            ready!(this.try_start_send(cx, item))?
84        }
85
86        loop {
87            match this.stream.try_poll_next_unpin(cx)? {
88                Poll::Ready(Some(item)) => ready!(this.try_start_send(cx, item))?,
89                Poll::Ready(None) => {
90                    ready!(Pin::new(&mut this.sink).poll_flush(cx))?;
91                    return Poll::Ready(Ok(()));
92                }
93                Poll::Pending => {
94                    ready!(Pin::new(&mut this.sink).poll_flush(cx))?;
95                    return Poll::Pending;
96                }
97            }
98        }
99    }
100}
futures_util/sink/send_all.rs

futures_util/sink/
send_all.rs
