rustics/
time.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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
//
//  This code is available under the Berkeley 2-Clause, Berkely 2-clause,
//  and MIT licenses.  It is also available as public domain source where
//  permitted by law.
//

use std::time::Instant;

//  A Timer is an abstraction of a clock to be used for performance
//  monitoring.  It is intended to allow for many implementations.
//  The underlying clock implementation determines the meaning of an
//  interval value.  For example, a DurationTimer uses the standard
//  Rust Duration type, which returns wall-clock time.
//
//  The start method starts a timing interval.  It may be called
//  multiple times on a single structure.  The last invocation of
//  the start method overrides any previous calls.
//
//  The finish routine is used at the end of a sample interval.  It
//  returns the interval time in nanoseconds and also starts a new
//  interval, since the restart cost is nearly zero.  Thus, "finish"
//  can be called multiple times after a "start" invocation to return
//  the times for a sequence of events.  If a more precise timing is
//  required, "start" will start an interval.
//
//  hz returns the herz of the underlying clock.

pub trait Timer {
    fn start(&mut self);            // start or restart a timer
    fn finish(&mut self) -> u128;   // get the elapsed time and set a new start time
    fn hz(&self) -> u128;           // get the clock hz
}


//  DurationTimer uses the Rust standard time function "Duration" to
//  measure time intervals.  This timer thus returns wall-clock time.

pub struct DurationTimer {
    start:      Instant,
    previous:   u128,
}

impl Timer for DurationTimer {
    fn start(&mut self) {
        self.start = Instant::now();
        self.previous = 0;
    }

    fn finish(&mut self) -> u128 {
        let end_time = self.start.elapsed().as_nanos();
        let result = end_time - self.previous;
        self.previous = end_time;
        result
    }

    fn hz(&self) -> u128 {
        1_000_000_000
    }
}

impl DurationTimer {
    pub fn new() -> DurationTimer {
        let start = Instant::now();
        let previous = 0;

        DurationTimer { start, previous }
    }
}

impl Default for DurationTimer {
    fn default() -> Self {
        Self::new()
    }
}

//  This trait can be implemented for platform-specific clocks.
//  The structures can then be wrapped in a ClockTimer struct.
//  See the test routine "simple_test_clock" for an example.

pub trait SimpleClock {
    fn get_time(&mut self) -> u128;
    fn hz(&self) -> u128;
}

//  This is a wrapper class for platform-specific clocks that
//  would be useful to support.
//
//  For efficiency, using 64-bit math internally might be useful.
//  On the other hand, using femtoseconds might be useful for
//  particularly hostile hz ratings.

pub struct ClockTimer {
    start:      u128,
    clock:      Box<dyn SimpleClock>,
}

impl Timer for ClockTimer {
    fn start(&mut self) {
        self.start = self.clock.get_time();
    }

    fn finish(&mut self) -> u128 {
        let end_time = self.clock.get_time();
        let ticks = end_time - self.start;
        self.start = end_time;
        ticks
    }

    fn hz(&self) -> u128 {
        self.clock.hz()
    }
}

impl ClockTimer {
    pub fn new(mut clock: Box<dyn SimpleClock>) -> ClockTimer {
        let start = clock.get_time();

        ClockTimer { start, clock }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::thread::sleep;
    use std::time::Duration;

    pub fn simple_test_duration() {
        let mut clock = DurationTimer::new();
        clock.start();
        let seconds = 1;
        let sleep_time = Duration::new(seconds, 0);
        let base_interval = seconds as u128 * clock.hz() as u128;

        for i in 1..10 {
            sleep(sleep_time);
            let interval = clock.finish();
            println!(" interval {} = {}", i, interval);
            assert!(interval >= base_interval);
            assert!(interval < base_interval + (base_interval / 20));
        }
    }

    struct TestSimpleClock {
        pub current:    u128,
        pub increment:  u128,
    }

    impl SimpleClock for TestSimpleClock {
        fn get_time(&mut self) -> u128 {
            let result = self.current;
            self.current = self.current + self.increment;
            self.increment = self.increment * 2;
            result
        }

        fn hz(&self) -> u128 {
            1_000_000_000
        }
    }

    pub fn simple_test_clock() {
        let current = 0;
        let mut increment = 1500;
        let simple_clock = Box::new(TestSimpleClock { current, increment });
        let mut clock = ClockTimer::new(simple_clock);

        // Creating the clock invokes get_time, so the increment in the
        // test clock increases.  Keep ours in sync with it.

        increment = increment * 2;

        assert!(clock.hz() == 1_000_000_000);

        clock.start();

        for _i in 1..5 {
            let interval = clock.finish();
            println!("  result {} == predict {}", interval, increment);
            assert!(interval == increment);

            // Keep our increment in sync with the test clock.
            increment = increment * 2;
        }
    }

    #[test]
    pub fn simple_tests() {
        simple_test_duration();
        simple_test_clock();
    }
}