1use core::fmt::{Debug, Formatter, Result as FmtResult};
2use core::pin::Pin;
3use futures_core::task::{Context, Poll};
4use futures_sink::Sink;
5use pin_project_lite::pin_project;
6
7pin_project! {
8 /// Sink that clones incoming items and forwards them to two sinks at the same time.
9 ///
10 /// Backpressure from any downstream sink propagates up, which means that this sink
11 /// can only process items as fast as its _slowest_ downstream sink.
12 #[must_use = "sinks do nothing unless polled"]
13 pub struct Fanout<Si1, Si2> {
14 #[pin]
15 sink1: Si1,
16 #[pin]
17 sink2: Si2
18 }
19}
20
21impl<Si1, Si2> Fanout<Si1, Si2> {
22 pub(super) fn new(sink1: Si1, sink2: Si2) -> Self {
23 Self { sink1, sink2 }
24 }
25
26 /// Get a shared reference to the inner sinks.
27 pub fn get_ref(&self) -> (&Si1, &Si2) {
28 (&self.sink1, &self.sink2)
29 }
30
31 /// Get a mutable reference to the inner sinks.
32 pub fn get_mut(&mut self) -> (&mut Si1, &mut Si2) {
33 (&mut self.sink1, &mut self.sink2)
34 }
35
36 /// Get a pinned mutable reference to the inner sinks.
37 pub fn get_pin_mut(self: Pin<&mut Self>) -> (Pin<&mut Si1>, Pin<&mut Si2>) {
38 let this = self.project();
39 (this.sink1, this.sink2)
40 }
41
42 /// Consumes this combinator, returning the underlying sinks.
43 ///
44 /// Note that this may discard intermediate state of this combinator,
45 /// so care should be taken to avoid losing resources when this is called.
46 pub fn into_inner(self) -> (Si1, Si2) {
47 (self.sink1, self.sink2)
48 }
49}
50
51impl<Si1: Debug, Si2: Debug> Debug for Fanout<Si1, Si2> {
52 fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
53 f.debug_struct("Fanout").field("sink1", &self.sink1).field(name:"sink2", &self.sink2).finish()
54 }
55}
56
57impl<Si1, Si2, Item> Sink<Item> for Fanout<Si1, Si2>
58where
59 Si1: Sink<Item>,
60 Item: Clone,
61 Si2: Sink<Item, Error = Si1::Error>,
62{
63 type Error = Si1::Error;
64
65 fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
66 let this = self.project();
67
68 let sink1_ready = this.sink1.poll_ready(cx)?.is_ready();
69 let sink2_ready = this.sink2.poll_ready(cx)?.is_ready();
70 let ready = sink1_ready && sink2_ready;
71 if ready {
72 Poll::Ready(Ok(()))
73 } else {
74 Poll::Pending
75 }
76 }
77
78 fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error> {
79 let this = self.project();
80
81 this.sink1.start_send(item.clone())?;
82 this.sink2.start_send(item)?;
83 Ok(())
84 }
85
86 fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
87 let this = self.project();
88
89 let sink1_ready = this.sink1.poll_flush(cx)?.is_ready();
90 let sink2_ready = this.sink2.poll_flush(cx)?.is_ready();
91 let ready = sink1_ready && sink2_ready;
92 if ready {
93 Poll::Ready(Ok(()))
94 } else {
95 Poll::Pending
96 }
97 }
98
99 fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
100 let this = self.project();
101
102 let sink1_ready = this.sink1.poll_close(cx)?.is_ready();
103 let sink2_ready = this.sink2.poll_close(cx)?.is_ready();
104 let ready = sink1_ready && sink2_ready;
105 if ready {
106 Poll::Ready(Ok(()))
107 } else {
108 Poll::Pending
109 }
110 }
111}
112