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
#![cfg_attr(not(feature = "rt"), allow(dead_code))]

//! Source of time abstraction.
//!
//! By default, `std::time::Instant::now()` is used. However, when the
//! `test-util` feature flag is enabled, the values returned for `now()` are
//! configurable.

cfg_not_test_util! {
    use crate::time::{Duration, Instant};

    #[derive(Debug, Clone)]
    pub(crate) struct Clock {}

    pub(crate) fn now() -> Instant {
        Instant::from_std(std::time::Instant::now())
    }

    impl Clock {
        pub(crate) fn new() -> Clock {
            Clock {}
        }

        pub(crate) fn now(&self) -> Instant {
            now()
        }

        pub(crate) fn is_paused(&self) -> bool {
            false
        }

        pub(crate) fn advance(&self, _dur: Duration) {
            unreachable!();
        }
    }
}

cfg_test_util! {
    use crate::time::{Duration, Instant};
    use std::sync::{Arc, Mutex};

    cfg_rt! {
        fn clock() -> Option<Clock> {
            crate::runtime::context::clock()
        }
    }

    cfg_not_rt! {
        fn clock() -> Option<Clock> {
            None
        }
    }

    /// A handle to a source of time.
    #[derive(Debug, Clone)]
    pub(crate) struct Clock {
        inner: Arc<Mutex<Inner>>,
    }

    #[derive(Debug)]
    struct Inner {
        /// Instant to use as the clock's base instant.
        base: std::time::Instant,

        /// Instant at which the clock was last unfrozen
        unfrozen: Option<std::time::Instant>,
    }

    /// Pause time
    ///
    /// The current value of `Instant::now()` is saved and all subsequent calls
    /// to `Instant::now()` until the timer wheel is checked again will return the saved value.
    /// Once the timer wheel is checked, time will immediately advance to the next registered
    /// `Sleep`. This is useful for running tests that depend on time.
    ///
    /// # Panics
    ///
    /// Panics if time is already frozen or if called from outside of the Tokio
    /// runtime.
    pub fn pause() {
        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
        clock.pause();
    }

    /// Resume time
    ///
    /// Clears the saved `Instant::now()` value. Subsequent calls to
    /// `Instant::now()` will return the value returned by the system call.
    ///
    /// # Panics
    ///
    /// Panics if time is not frozen or if called from outside of the Tokio
    /// runtime.
    pub fn resume() {
        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
        let mut inner = clock.inner.lock().unwrap();

        if inner.unfrozen.is_some() {
            panic!("time is not frozen");
        }

        inner.unfrozen = Some(std::time::Instant::now());
    }

    /// Advance time
    ///
    /// Increments the saved `Instant::now()` value by `duration`. Subsequent
    /// calls to `Instant::now()` will return the result of the increment.
    ///
    /// # Panics
    ///
    /// Panics if time is not frozen or if called from outside of the Tokio
    /// runtime.
    pub async fn advance(duration: Duration) {
        use crate::future::poll_fn;
        use std::task::Poll;

        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
        clock.advance(duration);

        let mut yielded = false;
        poll_fn(|cx| {
            if yielded {
                Poll::Ready(())
            } else {
                yielded = true;
                cx.waker().wake_by_ref();
                Poll::Pending
            }
        }).await;
    }

    /// Return the current instant, factoring in frozen time.
    pub(crate) fn now() -> Instant {
        if let Some(clock) = clock() {
            clock.now()
        } else {
            Instant::from_std(std::time::Instant::now())
        }
    }

    impl Clock {
        /// Return a new `Clock` instance that uses the current execution context's
        /// source of time.
        pub(crate) fn new() -> Clock {
            let now = std::time::Instant::now();

            Clock {
                inner: Arc::new(Mutex::new(Inner {
                    base: now,
                    unfrozen: Some(now),
                })),
            }
        }

        pub(crate) fn pause(&self) {
            let mut inner = self.inner.lock().unwrap();

            let elapsed = inner.unfrozen.as_ref().expect("time is already frozen").elapsed();
            inner.base += elapsed;
            inner.unfrozen = None;
        }

        pub(crate) fn is_paused(&self) -> bool {
            let inner = self.inner.lock().unwrap();
            inner.unfrozen.is_none()
        }

        pub(crate) fn advance(&self, duration: Duration) {
            let mut inner = self.inner.lock().unwrap();

            if inner.unfrozen.is_some() {
                panic!("time is not frozen");
            }

            inner.base += duration;
        }

        pub(crate) fn now(&self) -> Instant {
            let inner = self.inner.lock().unwrap();

            let mut ret = inner.base;

            if let Some(unfrozen) = inner.unfrozen {
                ret += unfrozen.elapsed();
            }

            Instant::from_std(ret)
        }
    }
}