1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
use core::fmt::{Debug, Formatter, Result as FmtResult};
use core::pin::Pin;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_project_lite::pin_project;

pin_project! {
    /// Sink that clones incoming items and forwards them to two sinks at the same time.
    ///
    /// Backpressure from any downstream sink propagates up, which means that this sink
    /// can only process items as fast as its _slowest_ downstream sink.
    #[must_use = "sinks do nothing unless polled"]
    pub struct Fanout<Si1, Si2> {
        #[pin]
        sink1: Si1,
        #[pin]
        sink2: Si2
    }
}

impl<Si1, Si2> Fanout<Si1, Si2> {
    pub(super) fn new(sink1: Si1, sink2: Si2) -> Self {
        Self { sink1, sink2 }
    }

    /// Get a shared reference to the inner sinks.
    pub fn get_ref(&self) -> (&Si1, &Si2) {
        (&self.sink1, &self.sink2)
    }

    /// Get a mutable reference to the inner sinks.
    pub fn get_mut(&mut self) -> (&mut Si1, &mut Si2) {
        (&mut self.sink1, &mut self.sink2)
    }

    /// Get a pinned mutable reference to the inner sinks.
    pub fn get_pin_mut(self: Pin<&mut Self>) -> (Pin<&mut Si1>, Pin<&mut Si2>) {
        let this = self.project();
        (this.sink1, this.sink2)
    }

    /// Consumes this combinator, returning the underlying sinks.
    ///
    /// Note that this may discard intermediate state of this combinator,
    /// so care should be taken to avoid losing resources when this is called.
    pub fn into_inner(self) -> (Si1, Si2) {
        (self.sink1, self.sink2)
    }
}

impl<Si1: Debug, Si2: Debug> Debug for Fanout<Si1, Si2> {
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        f.debug_struct("Fanout")
            .field("sink1", &self.sink1)
            .field("sink2", &self.sink2)
            .finish()
    }
}

impl<Si1, Si2, Item> Sink<Item> for Fanout<Si1, Si2>
    where Si1: Sink<Item>,
          Item: Clone,
          Si2: Sink<Item, Error=Si1::Error>
{
    type Error = Si1::Error;

    fn poll_ready(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>> {
        let this = self.project();

        let sink1_ready = this.sink1.poll_ready(cx)?.is_ready();
        let sink2_ready = this.sink2.poll_ready(cx)?.is_ready();
        let ready = sink1_ready && sink2_ready;
        if ready { Poll::Ready(Ok(())) } else { Poll::Pending }
    }

    fn start_send(
        self: Pin<&mut Self>,
        item: Item,
    ) -> Result<(), Self::Error> {
        let this = self.project();

        this.sink1.start_send(item.clone())?;
        this.sink2.start_send(item)?;
        Ok(())
    }

    fn poll_flush(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>> {
        let this = self.project();

        let sink1_ready = this.sink1.poll_flush(cx)?.is_ready();
        let sink2_ready = this.sink2.poll_flush(cx)?.is_ready();
        let ready = sink1_ready && sink2_ready;
        if ready { Poll::Ready(Ok(())) } else { Poll::Pending }
    }

    fn poll_close(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>> {
        let this = self.project();

        let sink1_ready = this.sink1.poll_close(cx)?.is_ready();
        let sink2_ready = this.sink2.poll_close(cx)?.is_ready();
        let ready = sink1_ready && sink2_ready;
        if ready { Poll::Ready(Ok(())) } else { Poll::Pending }
    }
}