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
use core::marker::PhantomData;
use futures_core::{Poll, Async, Stream};
use futures_core::task;
use futures_sink::Sink;
#[derive(Debug)]
#[must_use = "sinks do nothing unless polled"]
pub struct WithFlatMap<S, U, St, F>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
sink: S,
f: F,
stream: Option<St>,
buffer: Option<S::SinkItem>,
_phantom: PhantomData<fn(U)>,
}
pub fn new<S, U, St, F>(sink: S, f: F) -> WithFlatMap<S, U, St, F>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
WithFlatMap {
sink: sink,
f: f,
stream: None,
buffer: None,
_phantom: PhantomData,
}
}
impl<S, U, St, F> WithFlatMap<S, U, St, F>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
pub fn get_ref(&self) -> &S {
&self.sink
}
pub fn get_mut(&mut self) -> &mut S {
&mut self.sink
}
pub fn into_inner(self) -> S {
self.sink
}
fn try_empty_stream(&mut self, cx: &mut task::Context) -> Poll<(), S::SinkError> {
if let Some(x) = self.buffer.take() {
match self.sink.poll_ready(cx)? {
Async::Ready(()) => self.sink.start_send(x)?,
Async::Pending => {
self.buffer = Some(x);
return Ok(Async::Pending);
}
}
}
if let Some(mut stream) = self.stream.take() {
while let Some(x) = try_ready!(stream.poll_next(cx)) {
match self.sink.poll_ready(cx)? {
Async::Ready(()) => self.sink.start_send(x)?,
Async::Pending => {
self.stream = Some(stream);
self.buffer = Some(x);
return Ok(Async::Pending);
}
}
}
}
Ok(Async::Ready(()))
}
}
impl<S, U, St, F> Stream for WithFlatMap<S, U, St, F>
where
S: Stream + Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
type Item = S::Item;
type Error = S::Error;
fn poll_next(&mut self, cx: &mut task::Context) -> Poll<Option<S::Item>, S::Error> {
self.sink.poll_next(cx)
}
}
impl<S, U, St, F> Sink for WithFlatMap<S, U, St, F>
where
S: Sink,
F: FnMut(U) -> St,
St: Stream<Item = S::SinkItem, Error=S::SinkError>,
{
type SinkItem = U;
type SinkError = S::SinkError;
fn poll_ready(&mut self, cx: &mut task::Context) -> Poll<(), Self::SinkError> {
self.try_empty_stream(cx)
}
fn start_send(&mut self, i: Self::SinkItem) -> Result<(), Self::SinkError> {
assert!(self.stream.is_none());
self.stream = Some((self.f)(i));
Ok(())
}
fn poll_flush(&mut self, cx: &mut task::Context) -> Poll<(), Self::SinkError> {
if self.try_empty_stream(cx)?.is_pending() {
return Ok(Async::Pending);
}
self.sink.poll_flush(cx)
}
fn poll_close(&mut self, cx: &mut task::Context) -> Poll<(), Self::SinkError> {
if self.try_empty_stream(cx)?.is_pending() {
return Ok(Async::Pending);
}
self.sink.poll_close(cx)
}
}