Line data    Source code

       1             : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim:set ts=2 sw=2 sts=2 et cindent: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #if !defined(MediaTimer_h_)
       8             : #define MediaTimer_h_
       9             : 
      10             : #include "mozilla/AbstractThread.h"
      11             : #include "mozilla/IntegerPrintfMacros.h"
      12             : #include "mozilla/Monitor.h"
      13             : #include "mozilla/MozPromise.h"
      14             : #include "mozilla/RefPtr.h"
      15             : #include "mozilla/TimeStamp.h"
      16             : #include "nsITimer.h"
      17             : #include <queue>
      18             : 
      19             : namespace mozilla {
      20             : 
      21             : extern LazyLogModule gMediaTimerLog;
      22             : 
      23             : #define TIMER_LOG(x, ...) \
      24             :   MOZ_ASSERT(gMediaTimerLog); \
      25             :   MOZ_LOG(gMediaTimerLog, LogLevel::Debug, ("[MediaTimer=%p relative_t=%" PRId64 "]" x, this, \
      26             :                                         RelativeMicroseconds(TimeStamp::Now()), ##__VA_ARGS__))
      27             : 
      28             : // This promise type is only exclusive because so far there isn't a reason for
      29             : // it not to be. Feel free to change that.
      30             : typedef MozPromise<bool, bool, /* IsExclusive = */ true> MediaTimerPromise;
      31             : 
      32             : // Timers only know how to fire at a given thread, which creates an impedence
      33             : // mismatch with code that operates with TaskQueues. This class solves
      34             : // that mismatch with a dedicated (but shared) thread and a nice MozPromise-y
      35             : // interface.
      36             : class MediaTimer
      37             : {
      38             : public:
      39             :   MediaTimer();
      40             : 
      41             :   // We use a release with a custom Destroy().
      42             :   NS_IMETHOD_(MozExternalRefCountType) AddRef(void);
      43             :   NS_IMETHOD_(MozExternalRefCountType) Release(void);
      44             : 
      45             :   RefPtr<MediaTimerPromise> WaitUntil(const TimeStamp& aTimeStamp, const char* aCallSite);
      46             : 
      47             : private:
      48           0 :   virtual ~MediaTimer() { MOZ_ASSERT(OnMediaTimerThread()); }
      49             : 
      50             :   void DispatchDestroy(); // Invoked by Release on an arbitrary thread.
      51             :   void Destroy(); // Runs on the timer thread.
      52             : 
      53             :   bool OnMediaTimerThread();
      54             :   void ScheduleUpdate();
      55             :   void Update();
      56             :   void UpdateLocked();
      57             : 
      58             :   static void TimerCallback(nsITimer* aTimer, void* aClosure);
      59             :   void TimerFired();
      60             :   void ArmTimer(const TimeStamp& aTarget, const TimeStamp& aNow);
      61             : 
      62           0 :   bool TimerIsArmed()
      63             :   {
      64           0 :     return !mCurrentTimerTarget.IsNull();
      65             :   }
      66             : 
      67           0 :   void CancelTimerIfArmed()
      68             :   {
      69           0 :     MOZ_ASSERT(OnMediaTimerThread());
      70           0 :     if (TimerIsArmed()) {
      71           0 :       TIMER_LOG("MediaTimer::CancelTimerIfArmed canceling timer");
      72           0 :       mTimer->Cancel();
      73           0 :       mCurrentTimerTarget = TimeStamp();
      74             :     }
      75           0 :   }
      76             : 
      77             : 
      78           0 :   struct Entry
      79             :   {
      80             :     TimeStamp mTimeStamp;
      81             :     RefPtr<MediaTimerPromise::Private> mPromise;
      82             : 
      83           0 :     explicit Entry(const TimeStamp& aTimeStamp, const char* aCallSite)
      84           0 :       : mTimeStamp(aTimeStamp)
      85           0 :       , mPromise(new MediaTimerPromise::Private(aCallSite))
      86           0 :     {}
      87             : 
      88             :     // Define a < overload that reverses ordering because std::priority_queue
      89             :     // provides access to the largest element, and we want the smallest
      90             :     // (i.e. the soonest).
      91           0 :     bool operator<(const Entry& aOther) const
      92             :     {
      93           0 :       return mTimeStamp > aOther.mTimeStamp;
      94             :     }
      95             :   };
      96             : 
      97             :   ThreadSafeAutoRefCnt mRefCnt;
      98             :   NS_DECL_OWNINGTHREAD
      99             :   nsCOMPtr<nsIEventTarget> mThread;
     100             :   std::priority_queue<Entry> mEntries;
     101             :   Monitor mMonitor;
     102             :   nsCOMPtr<nsITimer> mTimer;
     103             :   TimeStamp mCurrentTimerTarget;
     104             : 
     105             :   // Timestamps only have relative meaning, so we need a base timestamp for
     106             :   // logging purposes.
     107             :   TimeStamp mCreationTimeStamp;
     108           0 :   int64_t RelativeMicroseconds(const TimeStamp& aTimeStamp)
     109             :   {
     110           0 :     return (int64_t) (aTimeStamp - mCreationTimeStamp).ToMicroseconds();
     111             :   }
     112             : 
     113             :   bool mUpdateScheduled;
     114             : };
     115             : 
     116             : // Class for managing delayed dispatches on target thread.
     117           0 : class DelayedScheduler {
     118             : public:
     119           0 :   explicit DelayedScheduler(AbstractThread* aTargetThread)
     120           0 :     : mTargetThread(aTargetThread), mMediaTimer(new MediaTimer())
     121             :   {
     122           0 :     MOZ_ASSERT(mTargetThread);
     123           0 :   }
     124             : 
     125           0 :   bool IsScheduled() const { return !mTarget.IsNull(); }
     126             : 
     127           0 :   void Reset()
     128             :   {
     129           0 :     MOZ_ASSERT(mTargetThread->IsCurrentThreadIn(),
     130             :       "Must be on target thread to disconnect");
     131           0 :     if (IsScheduled()) {
     132           0 :       mRequest.Disconnect();
     133           0 :       mTarget = TimeStamp();
     134             :     }
     135           0 :   }
     136             : 
     137             :   template <typename ResolveFunc, typename RejectFunc>
     138           0 :   void Ensure(mozilla::TimeStamp& aTarget,
     139             :               ResolveFunc&& aResolver,
     140             :               RejectFunc&& aRejector)
     141             :   {
     142           0 :     MOZ_ASSERT(mTargetThread->IsCurrentThreadIn());
     143           0 :     if (IsScheduled() && mTarget <= aTarget) {
     144           0 :       return;
     145             :     }
     146           0 :     Reset();
     147           0 :     mTarget = aTarget;
     148           0 :     mMediaTimer->WaitUntil(mTarget, __func__)->Then(
     149             :       mTargetThread, __func__,
     150             :       Forward<ResolveFunc>(aResolver),
     151             :       Forward<RejectFunc>(aRejector))
     152             :     ->Track(mRequest);
     153             :   }
     154             : 
     155           0 :   void CompleteRequest()
     156             :   {
     157           0 :     MOZ_ASSERT(mTargetThread->IsCurrentThreadIn());
     158           0 :     mRequest.Complete();
     159           0 :     mTarget = TimeStamp();
     160           0 :   }
     161             : 
     162             : private:
     163             :   RefPtr<AbstractThread> mTargetThread;
     164             :   RefPtr<MediaTimer> mMediaTimer;
     165             :   MozPromiseRequestHolder<mozilla::MediaTimerPromise> mRequest;
     166             :   TimeStamp mTarget;
     167             : };
     168             : 
     169             : } // namespace mozilla
     170             : 
     171             : #endif