async_sink/ext/
fanout.rs

1use crate::Sink;
2use core::fmt::{Debug, Formatter, Result as FmtResult};
3use core::pin::Pin;
4use core::task::{Context, Poll};
5
6/// Sink that clones incoming items and forwards them to two sinks at the same time.
7///
8/// Backpressure from any downstream sink propagates up, which means that this sink
9/// can only process items as fast as its _slowest_ downstream sink.
10#[must_use = "sinks do nothing unless polled"]
11pub struct Fanout<Si1, Si2> {
12    sink1: Si1,
13    sink2: Si2,
14}
15
16impl<Si1, Si2> Unpin for Fanout<Si1, Si2>
17where
18    Si1: Unpin,
19    Si2: Unpin,
20{
21}
22
23impl<Si1, Si2> Fanout<Si1, Si2> {
24    pub(super) fn new(sink1: Si1, sink2: Si2) -> Self {
25        Self { sink1, sink2 }
26    }
27
28    /// Get a shared reference to the inner sinks.
29    pub fn get_ref(&self) -> (&Si1, &Si2) {
30        (&self.sink1, &self.sink2)
31    }
32
33    /// Get a mutable reference to the inner sinks.
34    pub fn get_mut(&mut self) -> (&mut Si1, &mut Si2) {
35        (&mut self.sink1, &mut self.sink2)
36    }
37
38    /// Get a pinned mutable reference to the inner sinks.
39    pub fn get_pin_mut(self: Pin<&mut Self>) -> (Pin<&mut Si1>, Pin<&mut Si2>) {
40        unsafe {
41            let this = self.get_unchecked_mut();
42            (
43                Pin::new_unchecked(&mut this.sink1),
44                Pin::new_unchecked(&mut this.sink2),
45            )
46        }
47    }
48
49    /// Consumes this combinator, returning the underlying sinks.
50    ///
51    /// Note that this may discard intermediate state of this combinator,
52    /// so care should be taken to avoid losing resources when this is called.
53    pub fn into_inner(self) -> (Si1, Si2) {
54        (self.sink1, self.sink2)
55    }
56}
57
58impl<Si1: Debug, Si2: Debug> Debug for Fanout<Si1, Si2> {
59    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
60        f.debug_struct("Fanout")
61            .field("sink1", &self.sink1)
62            .field("sink2", &self.sink2)
63            .finish()
64    }
65}
66
67impl<Si1, Si2, Item> Sink<Item> for Fanout<Si1, Si2>
68where
69    Si1: Sink<Item>,
70    Item: Clone,
71    Si2: Sink<Item, Error = Si1::Error>,
72{
73    type Error = Si1::Error;
74
75    fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
76        let (sink1, sink2) = self.get_pin_mut();
77
78        match (sink2.poll_ready(cx), sink1.poll_ready(cx)) {
79            (Poll::Ready(Ok(())), Poll::Ready(Ok(()))) => Poll::Ready(Ok(())),
80            (Poll::Ready(Err(e)), _) | (_, Poll::Ready(Err(e))) => Poll::Ready(Err(e)),
81            (_, Poll::Pending) | (Poll::Pending, _) => Poll::Pending,
82        }
83    }
84
85    fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error> {
86        let (sink1, sink2) = self.get_pin_mut();
87
88        match (sink1.start_send(item.clone()), sink2.start_send(item)) {
89            (Ok(()), Ok(())) => Ok(()),
90            (Err(e), _) | (_, Err(e)) => Err(e),
91        }
92    }
93
94    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
95        let (sink1, sink2) = self.get_pin_mut();
96
97        match (sink2.poll_flush(cx), sink1.poll_flush(cx)) {
98            (Poll::Ready(Ok(())), Poll::Ready(Ok(()))) => Poll::Ready(Ok(())),
99            (Poll::Ready(Err(e)), _) | (_, Poll::Ready(Err(e))) => Poll::Ready(Err(e)),
100            (_, Poll::Pending) | (Poll::Pending, _) => Poll::Pending,
101        }
102    }
103
104    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
105        let (sink1, sink2) = self.get_pin_mut();
106
107        match (sink2.poll_close(cx), sink1.poll_close(cx)) {
108            (Poll::Ready(Ok(())), Poll::Ready(Ok(()))) => Poll::Ready(Ok(())),
109            (Poll::Ready(Err(e)), _) | (_, Poll::Ready(Err(e))) => Poll::Ready(Err(e)),
110            (_, Poll::Pending) | (Poll::Pending, _) => Poll::Pending,
111        }
112    }
113}
async_sink/ext/fanout.rs

async_sink/ext/
fanout.rs
