futures_rx/stream_ext/
timing.rs

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
use std::{
    pin::Pin,
    task::{Context, Poll},
    time::{Duration, Instant},
};

use futures::{
    stream::{Fuse, FusedStream},
    Stream, StreamExt,
};
use pin_project_lite::pin_project;

pin_project! {
    /// Stream for the [`timing`](RxStreamExt::timing) method.
    #[must_use = "streams do nothing unless polled"]
    pub struct Timing<S: Stream> {
        #[pin]
        stream: Fuse<S>,
        last_time: Option<Instant>,
    }
}

impl<S: Stream> Timing<S> {
    pub(crate) fn new(stream: S) -> Self {
        Self {
            stream: stream.fuse(),
            last_time: None,
        }
    }
}

impl<S: Stream> FusedStream for Timing<S> {
    fn is_terminated(&self) -> bool {
        self.stream.is_terminated()
    }
}

impl<S: Stream> Stream for Timing<S> {
    type Item = Timed<S::Item>;

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

        match this.stream.poll_next(cx) {
            Poll::Ready(Some(event)) => {
                let timestamp = Instant::now();
                let interval = this.last_time.map(|it| timestamp.duration_since(it));

                *this.last_time = Some(timestamp);

                Poll::Ready(Some(Timed {
                    event,
                    timestamp,
                    interval,
                }))
            }
            Poll::Ready(None) => Poll::Ready(None),
            Poll::Pending => Poll::Pending,
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.stream.size_hint()
    }
}

#[derive(Debug, Clone)]
pub struct Timed<T> {
    pub event: T,
    pub timestamp: Instant,
    pub interval: Option<Duration>,
}

#[cfg(test)]
mod test {
    use std::time::Instant;

    use futures::{executor::block_on, stream, Stream, StreamExt};
    use futures_time::{future::FutureExt, time::Duration};

    use crate::RxExt;

    #[test]
    fn smoke() {
        let stream = create_stream();

        block_on(async {
            let start = Instant::now();
            let all_events = stream.timing().collect::<Vec<_>>().await;
            let timestamps = all_events
                .iter()
                .map(|it| it.timestamp)
                .enumerate()
                .collect::<Vec<_>>();
            let intervals = all_events
                .iter()
                .map(|it| it.interval)
                .enumerate()
                .collect::<Vec<_>>();

            for (index, timestamp) in timestamps {
                assert!(
                    timestamp.duration_since(start).as_millis() >= (50 * index).try_into().unwrap()
                );
            }

            for (index, interval) in intervals {
                if index == 0 {
                    assert!(interval.is_none());
                } else {
                    assert!(interval.expect("interval is None!").as_millis() >= 50);
                }
            }
        });
    }

    fn create_stream() -> impl Stream<Item = usize> {
        stream::unfold(0, move |count| async move {
            if count < 10 {
                async { true }.delay(Duration::from_millis(50)).await;

                Some((count, count + 1))
            } else {
                None
            }
        })
    }
}