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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#if !defined(MediaTimer_h_)
# define MediaTimer_h_
# include <queue>
# include "mozilla/AbstractThread.h"
# include "mozilla/IntegerPrintfMacros.h"
# include "mozilla/Monitor.h"
# include "mozilla/MozPromise.h"
# include "mozilla/RefPtr.h"
# include "mozilla/TimeStamp.h"
# include "mozilla/Unused.h"
# include "nsITimer.h"
namespace mozilla {
extern LazyLogModule gMediaTimerLog;
# define TIMER_LOG(x, ...) \
MOZ_ASSERT(gMediaTimerLog); \
MOZ_LOG(gMediaTimerLog, LogLevel::Debug, \
("[MediaTimer=%p relative_t=%" PRId64 "]" x, this, \
RelativeMicroseconds(TimeStamp::Now()), ##__VA_ARGS__))
// This promise type is only exclusive because so far there isn't a reason for
// it not to be. Feel free to change that.
typedef MozPromise<bool, bool, /* IsExclusive = */ true> MediaTimerPromise;
// Timers only know how to fire at a given thread, which creates an impedence
// mismatch with code that operates with TaskQueues. This class solves
// that mismatch with a dedicated (but shared) thread and a nice MozPromise-y
// interface.
class MediaTimer {
explicit MediaTimer(bool aFuzzy = false);
RefPtr<MediaTimerPromise> WaitFor(const TimeDuration& aDuration,
const char* aCallSite);
RefPtr<MediaTimerPromise> WaitUntil(const TimeStamp& aTimeStamp,
const char* aCallSite);
void Cancel(); // Cancel and reject any unresolved promises with false.
virtual ~MediaTimer() { MOZ_ASSERT(OnMediaTimerThread()); }
void DispatchDestroy(); // Invoked by Release on an arbitrary thread.
void Destroy(); // Runs on the timer thread.
bool OnMediaTimerThread();
void ScheduleUpdate();
void Update();
void UpdateLocked();
bool IsExpired(const TimeStamp& aTarget, const TimeStamp& aNow);
void Reject();
static void TimerCallback(nsITimer* aTimer, void* aClosure);
void TimerFired();
void ArmTimer(const TimeStamp& aTarget, const TimeStamp& aNow);
bool TimerIsArmed() { return !mCurrentTimerTarget.IsNull(); }
void CancelTimerIfArmed() {
if (TimerIsArmed()) {
TIMER_LOG("MediaTimer::CancelTimerIfArmed canceling timer");
mCurrentTimerTarget = TimeStamp();
struct Entry {
TimeStamp mTimeStamp;
RefPtr<MediaTimerPromise::Private> mPromise;
explicit Entry(const TimeStamp& aTimeStamp, const char* aCallSite)
: mTimeStamp(aTimeStamp),
mPromise(new MediaTimerPromise::Private(aCallSite)) {}
// Define a < overload that reverses ordering because std::priority_queue
// provides access to the largest element, and we want the smallest
// (i.e. the soonest).
bool operator<(const Entry& aOther) const {
return mTimeStamp > aOther.mTimeStamp;
nsCOMPtr<nsIEventTarget> mThread;
std::priority_queue<Entry> mEntries;
Monitor mMonitor;
nsCOMPtr<nsITimer> mTimer;
TimeStamp mCurrentTimerTarget;
// Timestamps only have relative meaning, so we need a base timestamp for
// logging purposes.
TimeStamp mCreationTimeStamp;
int64_t RelativeMicroseconds(const TimeStamp& aTimeStamp) {
return (int64_t)(aTimeStamp - mCreationTimeStamp).ToMicroseconds();
bool mUpdateScheduled;
const bool mFuzzy;
// Class for managing delayed dispatches on target thread.
class DelayedScheduler {
explicit DelayedScheduler(nsISerialEventTarget* aTargetThread,
bool aFuzzy = false)
: mTargetThread(aTargetThread), mMediaTimer(new MediaTimer(aFuzzy)) {
bool IsScheduled() const { return !mTarget.IsNull(); }
void Reset() {
"Must be on target thread to disconnect");
mTarget = TimeStamp();
template <typename ResolveFunc, typename RejectFunc>
void Ensure(mozilla::TimeStamp& aTarget, ResolveFunc&& aResolver,
RejectFunc&& aRejector) {
if (IsScheduled() && mTarget <= aTarget) {
mTarget = aTarget;
mMediaTimer->WaitUntil(mTarget, __func__)
->Then(mTargetThread, __func__, std::forward<ResolveFunc>(aResolver),
void CompleteRequest() {
mTarget = TimeStamp();
nsCOMPtr<nsISerialEventTarget> mTargetThread;
RefPtr<MediaTimer> mMediaTimer;
MozPromiseRequestHolder<mozilla::MediaTimerPromise> mRequest;
TimeStamp mTarget;
} // namespace mozilla