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use timer::{HandlePriv, Registration};
use Error;
use futures::{Future, Poll};
use std::time::{Duration, Instant};
/// A future that completes at a specified instant in time.
///
/// Instances of `Delay` perform no work and complete with `()` once the
/// specified deadline has been reached.
///
/// `Delay` has a resolution of one millisecond and should not be used for tasks
/// that require high-resolution timers.
///
/// # Cancellation
///
/// Canceling a `Delay` is done by dropping the value. No additional cleanup or
/// other work is required.
///
/// [`new`]: #method.new
#[derive(Debug)]
pub struct Delay {
/// The link between the `Delay` instance at the timer that drives it.
///
/// This also stores the `deadline` value.
registration: Registration,
}
impl Delay {
/// Create a new `Delay` instance that elapses at `deadline`.
///
/// Only millisecond level resolution is guaranteed. There is no guarantee
/// as to how the sub-millisecond portion of `deadline` will be handled.
/// `Delay` should not be used for high-resolution timer use cases.
pub fn new(deadline: Instant) -> Delay {
let registration = Registration::new(deadline, Duration::from_millis(0));
Delay { registration }
}
pub(crate) fn new_timeout(deadline: Instant, duration: Duration) -> Delay {
let registration = Registration::new(deadline, duration);
Delay { registration }
}
pub(crate) fn new_with_handle(deadline: Instant, handle: HandlePriv) -> Delay {
let mut registration = Registration::new(deadline, Duration::from_millis(0));
registration.register_with(handle);
Delay { registration }
}
/// Returns the instant at which the future will complete.
pub fn deadline(&self) -> Instant {
self.registration.deadline()
}
/// Returns true if the `Delay` has elapsed
///
/// A `Delay` is elapsed when the requested duration has elapsed.
pub fn is_elapsed(&self) -> bool {
self.registration.is_elapsed()
}
/// Reset the `Delay` instance to a new deadline.
///
/// Calling this function allows changing the instant at which the `Delay`
/// future completes without having to create new associated state.
///
/// This function can be called both before and after the future has
/// completed.
pub fn reset(&mut self, deadline: Instant) {
self.registration.reset(deadline);
}
pub(crate) fn reset_timeout(&mut self) {
self.registration.reset_timeout();
}
/// Register the delay with the timer instance for the current execution
/// context.
fn register(&mut self) {
self.registration.register();
}
}
impl Future for Delay {
type Item = ();
type Error = Error;
fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
// Ensure the `Delay` instance is associated with a timer.
self.register();
self.registration.poll_elapsed()
}
}
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