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

use clock::Now;
use timer;

use tokio_executor::Enter;

use std::cell::Cell;
use std::fmt;
use std::sync::Arc;
use std::time::Instant;

/// A handle to a source of time.
///
/// `Clock` instances return `Instant` values corresponding to "now". The source
/// of these values is configurable. The default source is `Instant::now()`.
#[derive(Default, Clone)]
pub struct Clock {
    now: Option<Arc<Now>>,
}

/// Thread-local tracking the current clock
thread_local!(static CLOCK: Cell<Option<*const Clock>> = Cell::new(None));

/// Returns an `Instant` corresponding to "now".
///
/// This function delegates to the source of time configured for the current
/// execution context. By default, this is `Instant::now()`.
///
/// Note that, because the source of time is configurable, it is possible to
/// observe non-monotonic behavior when calling `now` from different
/// executors.
///
/// See [module](index.html) level documentation for more details.
///
/// # Examples
///
/// ```
/// # use tokio_timer::clock;
/// let now = clock::now();
/// ```
pub fn now() -> Instant {
    CLOCK.with(|current| {
        match current.get() {
            Some(ptr) => {
                unsafe { (*ptr).now() }
            }
            None => Instant::now(),
        }
    })
}

impl Clock {
    /// Return a new `Clock` instance that uses the current execution context's
    /// source of time.
    pub fn new() -> Clock {
        CLOCK.with(|current| {
            match current.get() {
                Some(ptr) => {
                    unsafe { (*ptr).clone() }
                }
                None => Clock::system(),
            }
        })
    }

    /// Return a new `Clock` instance that uses `now` as the source of time.
    pub fn new_with_now<T: Now>(now: T) -> Clock {
        Clock {
            now: Some(Arc::new(now)),
        }
    }

    /// Return a new `Clock` instance that uses `Instant::now()` as the source
    /// of time.
    pub fn system() -> Clock {
        Clock {
            now: None,
        }
    }

    /// Returns an instant corresponding to "now" by using the instance's source
    /// of time.
    pub fn now(&self) -> Instant {
        match self.now {
            Some(ref now) => now.now(),
            None => Instant::now(),
        }
    }
}

#[allow(deprecated)]
impl timer::Now for Clock {
    fn now(&mut self) -> Instant {
        Clock::now(self)
    }
}

impl fmt::Debug for Clock {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.debug_struct("Clock")
            .field("now", {
                if self.now.is_some() {
                    &"Some(Arc<Now>)"
                } else {
                    &"None"
                }
            })
            .finish()
    }
}

/// Set the default clock for the duration of the closure.
///
/// # Panics
///
/// This function panics if there already is a default clock set.
pub fn with_default<F, R>(clock: &Clock, enter: &mut Enter, f: F) -> R
where F: FnOnce(&mut Enter) -> R
{
    CLOCK.with(|cell| {
        assert!(cell.get().is_none(), "default clock already set for execution context");

        // Ensure that the clock is removed from the thread-local context
        // when leaving the scope. This handles cases that involve panicking.
        struct Reset<'a>(&'a Cell<Option<*const Clock>>);

        impl<'a> Drop for Reset<'a> {
            fn drop(&mut self) {
                self.0.set(None);
            }
        }

        let _reset = Reset(cell);

        cell.set(Some(clock as *const Clock));

        f(enter)
    })
}