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
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
use core::fmt::{Debug, Formatter, Result as FmtResult};
use core::mem::replace;
use {Async, AsyncSink, Poll, Sink, StartSend};
/// 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.
pub struct Fanout<A: Sink, B: Sink> {
left: Downstream<A>,
right: Downstream<B>
}
impl<A: Sink, B: Sink> Fanout<A, B> {
/// 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) -> (A, B) {
(self.left.sink, self.right.sink)
}
}
impl<A: Sink + Debug, B: Sink + Debug> Debug for Fanout<A, B>
where A::SinkItem: Debug,
B::SinkItem: Debug
{
fn fmt(&self, f: &mut Formatter) -> FmtResult {
f.debug_struct("Fanout")
.field("left", &self.left)
.field("right", &self.right)
.finish()
}
}
pub fn new<A: Sink, B: Sink>(left: A, right: B) -> Fanout<A, B> {
Fanout {
left: Downstream::new(left),
right: Downstream::new(right)
}
}
impl<A, B> Sink for Fanout<A, B>
where A: Sink,
A::SinkItem: Clone,
B: Sink<SinkItem=A::SinkItem, SinkError=A::SinkError>
{
type SinkItem = A::SinkItem;
type SinkError = A::SinkError;
fn start_send(
&mut self,
item: Self::SinkItem
) -> StartSend<Self::SinkItem, Self::SinkError> {
// Attempt to complete processing any outstanding requests.
self.left.keep_flushing()?;
self.right.keep_flushing()?;
// Only if both downstream sinks are ready, start sending the next item.
if self.left.is_ready() && self.right.is_ready() {
self.left.state = self.left.sink.start_send(item.clone())?;
self.right.state = self.right.sink.start_send(item)?;
Ok(AsyncSink::Ready)
} else {
Ok(AsyncSink::NotReady(item))
}
}
fn poll_complete(&mut self) -> Poll<(), Self::SinkError> {
let left_async = self.left.poll_complete()?;
let right_async = self.right.poll_complete()?;
// Only if both downstream sinks are ready, signal readiness.
if left_async.is_ready() && right_async.is_ready() {
Ok(Async::Ready(()))
} else {
Ok(Async::NotReady)
}
}
fn close(&mut self) -> Poll<(), Self::SinkError> {
let left_async = self.left.close()?;
let right_async = self.right.close()?;
// Only if both downstream sinks are ready, signal readiness.
if left_async.is_ready() && right_async.is_ready() {
Ok(Async::Ready(()))
} else {
Ok(Async::NotReady)
}
}
}
#[derive(Debug)]
struct Downstream<S: Sink> {
sink: S,
state: AsyncSink<S::SinkItem>
}
impl<S: Sink> Downstream<S> {
fn new(sink: S) -> Self {
Downstream { sink: sink, state: AsyncSink::Ready }
}
fn is_ready(&self) -> bool {
self.state.is_ready()
}
fn keep_flushing(&mut self) -> Result<(), S::SinkError> {
if let AsyncSink::NotReady(item) = replace(&mut self.state, AsyncSink::Ready) {
self.state = self.sink.start_send(item)?;
}
Ok(())
}
fn poll_complete(&mut self) -> Poll<(), S::SinkError> {
self.keep_flushing()?;
let async = self.sink.poll_complete()?;
// Only if all values have been sent _and_ the underlying
// sink is completely flushed, signal readiness.
if self.state.is_ready() && async.is_ready() {
Ok(Async::Ready(()))
} else {
Ok(Async::NotReady)
}
}
fn close(&mut self) -> Poll<(), S::SinkError> {
self.keep_flushing()?;
// If all items have been flushed, initiate close.
if self.state.is_ready() {
self.sink.close()
} else {
Ok(Async::NotReady)
}
}
}
|
