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//! Timer event source
//!
//! The [`Timer`] is an event source that will fire its event after a certain amount of time
//! specified at creation. Its timing is tracked directly by the event loop core logic, and it does
//! not consume any system resource.
//!
//! The timer precision depends on whether the loop was initialized in high-precision mode. If not,
//! you can expect precision of order of 1 millisecond, if you need sub-millisecond precision,
//! make sure you initialize the [`EventLoop`](crate::EventLoop) using
//! [`EventLoop::try_new_high_precision()`](crate::EventLoop::try_new_high_precision). Note also
//! that if you need to rely on good precision timers in general, you may need to enable realtime
//! features of your OS to ensure your thread is quickly woken up by the system scheduler.
//!
//! The provided event is an [`Instant`] representing the deadline for which this timer has fired
//! (which can be earlier than the current time depending on the event loop congestion).
//!
//! The callback associated with this event source is expected to return a [`TimeoutAction`], which
//! can be used to implement self-repeating timers by telling calloop to reprogram the same timer
//! for a later timeout after it has fired.
/*
* This module provides two main types:
*
* - `Timer` is the user-facing type that represents a timer event source
* - `TimerWheel` is an internal data structure for tracking registered timeouts, it is used by
* the polling logic in sys/mod.rs
*/
use std::{
cell::RefCell,
collections::BinaryHeap,
rc::Rc,
task::Waker,
time::{Duration, Instant},
};
use crate::{EventSource, LoopHandle, Poll, PostAction, Readiness, Token, TokenFactory};
#[derive(Debug)]
struct Registration {
token: Token,
wheel: Rc<RefCell<TimerWheel>>,
counter: u32,
}
/// A timer event source
///
/// When registered to the event loop, it will trigger an event once its deadline is reached.
/// If the deadline is in the past relative to the moment of its insertion in the event loop,
/// the `TImer` will trigger an event as soon as the event loop is dispatched.
#[derive(Debug)]
pub struct Timer {
registration: Option<Registration>,
deadline: Instant,
}
impl Timer {
/// Create a timer that will fire immediately when inserted in the event loop
pub fn immediate() -> Timer {
Self::from_deadline(Instant::now())
}
/// Create a timer that will fire after a given duration from now
pub fn from_duration(duration: Duration) -> Timer {
Self::from_deadline(Instant::now() + duration)
}
/// Create a timer that will fire at a given instant
pub fn from_deadline(deadline: Instant) -> Timer {
Timer {
registration: None,
deadline,
}
}
/// Changes the deadline of this timer to an [`Instant`]
///
/// If the `Timer` is currently registered in the event loop, it needs to be
/// re-registered for this change to take effect.
pub fn set_deadline(&mut self, deadline: Instant) {
self.deadline = deadline;
}
/// Changes the deadline of this timer to a [`Duration`] from now
///
/// If the `Timer` is currently registered in the event loop, it needs to be
/// re-registered for this change to take effect.
pub fn set_duration(&mut self, duration: Duration) {
self.set_deadline(Instant::now() + duration)
}
/// Get the current deadline of this `Timer`
pub fn current_deadline(&self) -> Instant {
self.deadline
}
}
impl EventSource for Timer {
type Event = Instant;
type Metadata = ();
type Ret = TimeoutAction;
type Error = std::io::Error;
fn process_events<F>(
&mut self,
_: Readiness,
token: Token,
mut callback: F,
) -> Result<PostAction, Self::Error>
where
F: FnMut(Self::Event, &mut Self::Metadata) -> Self::Ret,
{
if let Some(ref registration) = self.registration {
if registration.token != token {
return Ok(PostAction::Continue);
}
let new_deadline = match callback(self.deadline, &mut ()) {
TimeoutAction::Drop => return Ok(PostAction::Remove),
TimeoutAction::ToInstant(instant) => instant,
TimeoutAction::ToDuration(duration) => Instant::now() + duration,
};
// If we received an event, we MUST have a valid counter value
registration.wheel.borrow_mut().insert_reuse(
registration.counter,
new_deadline,
registration.token,
);
self.deadline = new_deadline;
}
Ok(PostAction::Continue)
}
fn register(&mut self, poll: &mut Poll, token_factory: &mut TokenFactory) -> crate::Result<()> {
let wheel = poll.timers.clone();
let token = token_factory.token();
let counter = wheel.borrow_mut().insert(self.deadline, token);
self.registration = Some(Registration {
token,
wheel,
counter,
});
Ok(())
}
fn reregister(
&mut self,
poll: &mut Poll,
token_factory: &mut TokenFactory,
) -> crate::Result<()> {
self.unregister(poll)?;
self.register(poll, token_factory)
}
fn unregister(&mut self, poll: &mut Poll) -> crate::Result<()> {
if let Some(registration) = self.registration.take() {
poll.timers.borrow_mut().cancel(registration.counter);
}
Ok(())
}
}
/// Action to reschedule a timeout if necessary
#[derive(Debug)]
pub enum TimeoutAction {
/// Don't reschedule this timer
Drop,
/// Reschedule this timer to a given [`Instant`]
ToInstant(Instant),
/// Reschedule this timer to a given [`Duration`] in the future
ToDuration(Duration),
}
// Internal representation of a timeout registered in the TimerWheel
#[derive(Debug)]
struct TimeoutData {
deadline: Instant,
token: RefCell<Option<Token>>,
counter: u32,
}
// A data structure for tracking registered timeouts
#[derive(Debug)]
pub(crate) struct TimerWheel {
heap: BinaryHeap<TimeoutData>,
counter: u32,
}
impl TimerWheel {
pub(crate) fn new() -> TimerWheel {
TimerWheel {
heap: BinaryHeap::new(),
counter: 0,
}
}
pub(crate) fn insert(&mut self, deadline: Instant, token: Token) -> u32 {
self.heap.push(TimeoutData {
deadline,
token: RefCell::new(Some(token)),
counter: self.counter,
});
let ret = self.counter;
self.counter += 1;
ret
}
pub(crate) fn insert_reuse(&mut self, counter: u32, deadline: Instant, token: Token) {
self.heap.push(TimeoutData {
deadline,
token: RefCell::new(Some(token)),
counter,
});
}
pub(crate) fn cancel(&mut self, counter: u32) {
self.heap
.iter()
.find(|data| data.counter == counter)
.map(|data| data.token.take());
}
pub(crate) fn next_expired(&mut self, now: Instant) -> Option<(u32, Token)> {
loop {
// check if there is an expired item
if let Some(data) = self.heap.peek() {
if data.deadline > now {
return None;
}
// there is an expired timeout, continue the
// loop body
} else {
return None;
}
// There is an item in the heap, this unwrap cannot blow
let data = self.heap.pop().unwrap();
if let Some(token) = data.token.into_inner() {
return Some((data.counter, token));
}
// otherwise this timeout was cancelled, continue looping
}
}
pub(crate) fn next_deadline(&self) -> Option<std::time::Instant> {
self.heap.peek().map(|data| data.deadline)
}
}
// trait implementations for TimeoutData
impl std::cmp::Ord for TimeoutData {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
// earlier values have priority
self.deadline.cmp(&other.deadline).reverse()
}
}
impl std::cmp::PartialOrd for TimeoutData {
fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
Some(self.cmp(other))
}
}
// This impl is required for PartialOrd but actually never used
// and the type is private, so ignore its coverage
impl std::cmp::PartialEq for TimeoutData {
#[cfg_attr(coverage, no_coverage)]
fn eq(&self, other: &Self) -> bool {
self.deadline == other.deadline
}
}
impl std::cmp::Eq for TimeoutData {}
// Logic for timer futures
/// A future that resolves once a certain timeout is expired
pub struct TimeoutFuture {
deadline: Instant,
waker: Rc<RefCell<Option<Waker>>>,
}
impl std::fmt::Debug for TimeoutFuture {
#[cfg_attr(coverage, no_coverage)]
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("TimeoutFuture")
.field("deadline", &self.deadline)
.finish_non_exhaustive()
}
}
impl TimeoutFuture {
/// Create a future that resolves after a given duration
pub fn from_duration<Data>(handle: &LoopHandle<'_, Data>, duration: Duration) -> TimeoutFuture {
Self::from_deadline(handle, Instant::now() + duration)
}
/// Create a future that resolves at a given instant
pub fn from_deadline<Data>(handle: &LoopHandle<'_, Data>, deadline: Instant) -> TimeoutFuture {
let timer = Timer::from_deadline(deadline);
let waker = Rc::new(RefCell::new(None::<Waker>));
let waker2 = waker.clone();
handle
.insert_source(timer, move |_, &mut (), _| {
if let Some(waker) = waker2.borrow_mut().clone() {
waker.wake()
}
TimeoutAction::Drop
})
.unwrap();
TimeoutFuture { deadline, waker }
}
}
impl std::future::Future for TimeoutFuture {
type Output = ();
fn poll(
self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Self::Output> {
if std::time::Instant::now() >= self.deadline {
return std::task::Poll::Ready(());
}
*self.waker.borrow_mut() = Some(cx.waker().clone());
std::task::Poll::Pending
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::*;
use std::time::Duration;
#[test]
fn simple_timer() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = false;
event_loop
.handle()
.insert_source(
Timer::from_duration(Duration::from_millis(100)),
|_, &mut (), dispatched| {
*dispatched = true;
TimeoutAction::Drop
},
)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
// not yet dispatched
assert!(!dispatched);
event_loop
.dispatch(Some(Duration::from_millis(150)), &mut dispatched)
.unwrap();
// now dispatched
assert!(dispatched);
}
#[test]
fn simple_timer_instant() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = false;
event_loop
.handle()
.insert_source(
Timer::from_duration(Duration::from_millis(100)),
|_, &mut (), dispatched| {
*dispatched = true;
TimeoutAction::Drop
},
)
.unwrap();
event_loop
.dispatch(Some(Duration::from_millis(150)), &mut dispatched)
.unwrap();
// now dispatched
assert!(dispatched);
}
#[test]
fn immediate_timer() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = false;
event_loop
.handle()
.insert_source(Timer::immediate(), |_, &mut (), dispatched| {
*dispatched = true;
TimeoutAction::Drop
})
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
// now dispatched
assert!(dispatched);
}
// We cannot actually test high precision timers, as they are only high precision in release mode
// This test is here to ensure that the high-precision codepath are executed and work as intended
// even if we cannot test if they are actually high precision
#[test]
fn high_precision_timer() {
let mut event_loop = EventLoop::try_new_high_precision().unwrap();
let mut dispatched = false;
event_loop
.handle()
.insert_source(
Timer::from_duration(Duration::from_millis(100)),
|_, &mut (), dispatched| {
*dispatched = true;
TimeoutAction::Drop
},
)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
// not yet dispatched
assert!(!dispatched);
event_loop
.dispatch(Some(Duration::from_micros(10200)), &mut dispatched)
.unwrap();
// yet not dispatched
assert!(!dispatched);
event_loop
.dispatch(Some(Duration::from_millis(100)), &mut dispatched)
.unwrap();
// now dispatched
assert!(dispatched);
}
#[test]
fn cancel_timer() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = false;
let token = event_loop
.handle()
.insert_source(
Timer::from_duration(Duration::from_millis(100)),
|_, &mut (), dispatched| {
*dispatched = true;
TimeoutAction::Drop
},
)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
// not yet dispatched
assert!(!dispatched);
event_loop.handle().remove(token);
event_loop
.dispatch(Some(Duration::from_millis(150)), &mut dispatched)
.unwrap();
// still not dispatched
assert!(!dispatched);
}
#[test]
fn repeating_timer() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = 0;
event_loop
.handle()
.insert_source(
Timer::from_duration(Duration::from_millis(500)),
|_, &mut (), dispatched| {
*dispatched += 1;
TimeoutAction::ToDuration(Duration::from_millis(500))
},
)
.unwrap();
event_loop
.dispatch(Some(Duration::from_millis(250)), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 0);
event_loop
.dispatch(Some(Duration::from_millis(510)), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 1);
event_loop
.dispatch(Some(Duration::from_millis(510)), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 2);
event_loop
.dispatch(Some(Duration::from_millis(510)), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 3);
}
#[cfg(feature = "executor")]
#[test]
fn timeout_future() {
let mut event_loop = EventLoop::try_new().unwrap();
let mut dispatched = 0;
let timeout_1 =
TimeoutFuture::from_duration(&event_loop.handle(), Duration::from_millis(500));
let timeout_2 =
TimeoutFuture::from_duration(&event_loop.handle(), Duration::from_millis(1500));
let (exec, sched) = crate::sources::futures::executor().unwrap();
event_loop
.handle()
.insert_source(exec, move |(), &mut (), got| {
*got += 1;
})
.unwrap();
sched.schedule(timeout_1).unwrap();
sched.schedule(timeout_2).unwrap();
// We do a 0-timeout dispatch after every regular dispatch to let the timeout triggers
// flow back to the executor
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 0);
event_loop
.dispatch(Some(Duration::from_millis(1000)), &mut dispatched)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 1);
event_loop
.dispatch(Some(Duration::from_millis(1100)), &mut dispatched)
.unwrap();
event_loop
.dispatch(Some(Duration::ZERO), &mut dispatched)
.unwrap();
assert_eq!(dispatched, 2);
}
}