tokio_timer/
delay.rs

1use timer::{HandlePriv, Registration};
2use Error;
3
4use futures::{Future, Poll};
5
6use std::time::{Duration, Instant};
7
8/// A future that completes at a specified instant in time.
9///
10/// Instances of `Delay` perform no work and complete with `()` once the
11/// specified deadline has been reached.
12///
13/// `Delay` has a resolution of one millisecond and should not be used for tasks
14/// that require high-resolution timers.
15///
16/// # Cancellation
17///
18/// Canceling a `Delay` is done by dropping the value. No additional cleanup or
19/// other work is required.
20///
21/// [`new`]: #method.new
22#[derive(Debug)]
23pub struct Delay {
24    /// The link between the `Delay` instance at the timer that drives it.
25    ///
26    /// This also stores the `deadline` value.
27    registration: Registration,
28}
29
30impl Delay {
31    /// Create a new `Delay` instance that elapses at `deadline`.
32    ///
33    /// Only millisecond level resolution is guaranteed. There is no guarantee
34    /// as to how the sub-millisecond portion of `deadline` will be handled.
35    /// `Delay` should not be used for high-resolution timer use cases.
36    pub fn new(deadline: Instant) -> Delay {
37        let registration = Registration::new(deadline, Duration::from_millis(0));
38
39        Delay { registration }
40    }
41
42    pub(crate) fn new_timeout(deadline: Instant, duration: Duration) -> Delay {
43        let registration = Registration::new(deadline, duration);
44        Delay { registration }
45    }
46
47    pub(crate) fn new_with_handle(deadline: Instant, handle: HandlePriv) -> Delay {
48        let mut registration = Registration::new(deadline, Duration::from_millis(0));
49        registration.register_with(handle);
50
51        Delay { registration }
52    }
53
54    /// Returns the instant at which the future will complete.
55    pub fn deadline(&self) -> Instant {
56        self.registration.deadline()
57    }
58
59    /// Returns true if the `Delay` has elapsed
60    ///
61    /// A `Delay` is elapsed when the requested duration has elapsed.
62    pub fn is_elapsed(&self) -> bool {
63        self.registration.is_elapsed()
64    }
65
66    /// Reset the `Delay` instance to a new deadline.
67    ///
68    /// Calling this function allows changing the instant at which the `Delay`
69    /// future completes without having to create new associated state.
70    ///
71    /// This function can be called both before and after the future has
72    /// completed.
73    pub fn reset(&mut self, deadline: Instant) {
74        self.registration.reset(deadline);
75    }
76
77    pub(crate) fn reset_timeout(&mut self) {
78        self.registration.reset_timeout();
79    }
80
81    /// Register the delay with the timer instance for the current execution
82    /// context.
83    fn register(&mut self) {
84        self.registration.register();
85    }
86}
87
88impl Future for Delay {
89    type Item = ();
90    type Error = Error;
91
92    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
93        // Ensure the `Delay` instance is associated with a timer.
94        self.register();
95
96        self.registration.poll_elapsed()
97    }
98}
tokio_timer/delay.rs

tokio_timer/
delay.rs
