forked from libp2p/rust-libp2p
/
interval.rs
209 lines (191 loc) · 6.93 KB
/
interval.rs
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// Copyright 2021 Oliver Wangler <oliver@wngr.de>
// Copyright 2019 Pierre Krieger
// Copyright (c) 2019 Tokio Contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
// OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// Initial version copied from
// https://github.com/tomaka/wasm-timer/blob/8964804eff980dd3eb115b711c57e481ba541708/src/timer/interval.rs
// and adapted.
use std::{
pin::Pin,
task::{Context, Poll},
time::Duration,
};
use futures::prelude::*;
use futures_timer::Delay;
use instant::Instant;
use pin_project::pin_project;
/// A stream representing notifications at fixed interval
///
/// Intervals are created through the `Interval::new` or
/// `Interval::new_intial` methods indicating when a first notification
/// should be triggered and when it will be repeated.
///
/// Note that intervals are not intended for high resolution timers, but rather
/// they will likely fire some granularity after the exact instant that they're
/// otherwise indicated to fire at.
#[pin_project]
#[derive(Debug)]
pub struct Interval {
#[pin]
delay: Delay,
interval: Duration,
fires_at: Instant,
}
impl Interval {
/// Creates a new interval which will fire at `dur` time into the future,
/// and will repeat every `dur` interval after
///
/// The returned object will be bound to the default timer for this thread.
/// The default timer will be spun up in a helper thread on first use.
pub fn new(dur: Duration) -> Interval {
Interval::new_initial(dur, dur)
}
/// Creates a new interval which will fire the first time after the specified `initial_delay`,
/// and then will repeat every `dur` interval after.
///
/// The returned object will be bound to the default timer for this thread.
/// The default timer will be spun up in a helper thread on first use.
pub fn new_initial(initial_delay: Duration, dur: Duration) -> Interval {
let fires_at = Instant::now() + initial_delay;
Interval {
delay: Delay::new(initial_delay),
interval: dur,
fires_at,
}
}
}
impl Stream for Interval {
type Item = ();
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
if self.as_mut().project().delay.poll(cx).is_pending() {
return Poll::Pending;
}
let next = next_interval(self.fires_at, Instant::now(), self.interval);
self.delay.reset(next);
self.fires_at += next;
Poll::Ready(Some(()))
}
}
/// Converts Duration object to raw nanoseconds if possible
///
/// This is useful to divide intervals.
///
/// While technically for large duration it's impossible to represent any
/// duration as nanoseconds, the largest duration we can represent is about
/// 427_000 years. Large enough for any interval we would use or calculate in
/// tokio.
fn duration_to_nanos(dur: Duration) -> Option<u64> {
let v = dur.as_secs().checked_mul(1_000_000_000)?;
v.checked_add(dur.subsec_nanos() as u64)
}
fn next_interval(prev: Instant, now: Instant, interval: Duration) -> Duration {
let new = prev + interval;
if new > now {
interval
} else {
let spent_ns =
duration_to_nanos(now.duration_since(prev)).expect("interval should be expired");
let interval_ns =
duration_to_nanos(interval).expect("interval is less that 427 thousand years");
let mult = spent_ns / interval_ns + 1;
assert!(
mult < (1 << 32),
"can't skip more than 4 billion intervals of {:?} \
(trying to skip {})",
interval,
mult
);
interval * mult as u32
}
}
#[cfg(test)]
mod test {
use super::next_interval;
use std::time::{Duration, Instant};
struct Timeline(Instant);
impl Timeline {
fn new() -> Timeline {
Timeline(Instant::now())
}
fn at(&self, millis: u64) -> Instant {
self.0 + Duration::from_millis(millis)
}
fn at_ns(&self, sec: u64, nanos: u32) -> Instant {
self.0 + Duration::new(sec, nanos)
}
}
fn dur(millis: u64) -> Duration {
Duration::from_millis(millis)
}
// The math around Instant/Duration isn't 100% precise due to rounding
// errors
fn almost_eq(a: Instant, b: Instant) -> bool {
let diff = match a.cmp(&b) {
std::cmp::Ordering::Less => b - a,
std::cmp::Ordering::Equal => return true,
std::cmp::Ordering::Greater => a - b,
};
diff < Duration::from_millis(1)
}
#[test]
fn norm_next() {
let tm = Timeline::new();
assert!(almost_eq(
tm.at(1) + next_interval(tm.at(1), tm.at(2), dur(10)),
tm.at(11)
));
assert!(almost_eq(
tm.at(7777) + next_interval(tm.at(7777), tm.at(7788), dur(100)),
tm.at(7877)
));
assert!(almost_eq(
tm.at(1) + next_interval(tm.at(1), tm.at(1000), dur(2100)),
tm.at(2101)
));
}
#[test]
fn fast_forward() {
let tm = Timeline::new();
assert!(almost_eq(
tm.at(1) + next_interval(tm.at(1), tm.at(1000), dur(10)),
tm.at(1001)
));
assert!(almost_eq(
tm.at(7777) + next_interval(tm.at(7777), tm.at(8888), dur(100)),
tm.at(8977)
));
assert!(almost_eq(
tm.at(1) + next_interval(tm.at(1), tm.at(10000), dur(2100)),
tm.at(10501)
));
}
/// TODO: this test actually should be successful, but since we can't
/// multiply Duration on anything larger than u32 easily we decided
/// to allow it to fail for now
#[test]
#[should_panic(expected = "can't skip more than 4 billion intervals")]
fn large_skip() {
let tm = Timeline::new();
assert_eq!(
tm.0 + next_interval(tm.at_ns(0, 1), tm.at_ns(25, 0), Duration::new(0, 2)),
tm.at_ns(25, 1)
);
}
}