The Tor Browser: content/media/MediaSegment.h@97036ab72558 (annotated)

content/media/MediaSegment.h@97036ab72558 (annotated)

content/media/MediaSegment.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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 http://mozilla.org/MPL/2.0/. */
 #ifndef MOZILLA_MEDIASEGMENT_H_
 #define MOZILLA_MEDIASEGMENT_H_
 #include "nsTArray.h"
 #ifdef MOZILLA_INTERNAL_API
 #include "mozilla/TimeStamp.h"
 #endif
 #include <algorithm>
 #include "Latency.h"
 namespace mozilla {
 /**
  * We represent media times in 64-bit fixed point. So 1 MediaTime is
  * 1/(2^MEDIA_TIME_FRAC_BITS) seconds.
  */
 typedef int64_t MediaTime;
 const int64_t MEDIA_TIME_FRAC_BITS = 20;
 const int64_t MEDIA_TIME_MAX = INT64_MAX;
 inline MediaTime MillisecondsToMediaTime(int32_t aMS)
 {
   return (MediaTime(aMS) << MEDIA_TIME_FRAC_BITS)/1000;
 }
 inline MediaTime SecondsToMediaTime(double aS)
 {
   NS_ASSERTION(aS <= (MEDIA_TIME_MAX >> MEDIA_TIME_FRAC_BITS),
                "Out of range");
   return MediaTime(aS * (1 << MEDIA_TIME_FRAC_BITS));
 }
 inline double MediaTimeToSeconds(MediaTime aTime)
 {
   return aTime*(1.0/(1 << MEDIA_TIME_FRAC_BITS));
 }
 inline int64_t MediaTimeToMicroseconds(MediaTime aTime)
 {
   return aTime*(1000000.0/(1 << MEDIA_TIME_FRAC_BITS));
 }
 /**
  * A number of ticks at a rate determined by some underlying track (e.g.
  * audio sample rate). We want to make sure that multiplying TrackTicks by
  * 2^MEDIA_TIME_FRAC_BITS doesn't overflow, so we set its max accordingly.
  */
 typedef int64_t TrackTicks;
 const int64_t TRACK_TICKS_MAX = INT64_MAX >> MEDIA_TIME_FRAC_BITS;
 /**
  * A MediaSegment is a chunk of media data sequential in time. Different
  * types of data have different subclasses of MediaSegment, all inheriting
  * from MediaSegmentBase.
  * All MediaSegment data is timed using TrackTicks. The actual tick rate
  * is defined on a per-track basis. For some track types, this can be
  * a fixed constant for all tracks of that type (e.g. 1MHz for video).
  *
  * Each media segment defines a concept of "null media data" (e.g. silence
  * for audio or "no video frame" for video), which can be efficiently
  * represented. This is used for padding.
  */
 class MediaSegment {
 public:
   virtual ~MediaSegment()
   {
     MOZ_COUNT_DTOR(MediaSegment);
   }
   enum Type {
     AUDIO,
     VIDEO,
     TYPE_COUNT
   };
   /**
    * Gets the total duration of the segment.
    */
   TrackTicks GetDuration() const { return mDuration; }
   Type GetType() const { return mType; }
   /**
    * Create a MediaSegment of the same type.
    */
   virtual MediaSegment* CreateEmptyClone() const = 0;
   /**
    * Moves contents of aSource to the end of this segment.
    */
   virtual void AppendFrom(MediaSegment* aSource) = 0;
   /**
    * Append a slice of aSource to this segment.
    */
   virtual void AppendSlice(const MediaSegment& aSource,
                            TrackTicks aStart, TrackTicks aEnd) = 0;
   /**
    * Replace all contents up to aDuration with null data.
    */
   virtual void ForgetUpTo(TrackTicks aDuration) = 0;
   /**
    * Insert aDuration of null data at the start of the segment.
    */
   virtual void InsertNullDataAtStart(TrackTicks aDuration) = 0;
   /**
    * Insert aDuration of null data at the end of the segment.
    */
   virtual void AppendNullData(TrackTicks aDuration) = 0;
   /**
    * Replace contents with disabled data of the same duration
    */
   virtual void ReplaceWithDisabled() = 0;
   /**
    * Remove all contents, setting duration to 0.
    */
   virtual void Clear() = 0;
   virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
   {
     return 0;
   }
   virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
   {
     return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
   }
 protected:
   MediaSegment(Type aType) : mDuration(0), mType(aType)
   {
     MOZ_COUNT_CTOR(MediaSegment);
   }
   TrackTicks mDuration; // total of mDurations of all chunks
   Type mType;
 };
 /**
  * C is the implementation class subclassed from MediaSegmentBase.
  * C must contain a Chunk class.
  */
 template <class C, class Chunk> class MediaSegmentBase : public MediaSegment {
 public:
   virtual MediaSegment* CreateEmptyClone() const
   {
     return new C();
   }
   virtual void AppendFrom(MediaSegment* aSource)
   {
     NS_ASSERTION(aSource->GetType() == C::StaticType(), "Wrong type");
     AppendFromInternal(static_cast<C*>(aSource));
   }
   void AppendFrom(C* aSource)
   {
     AppendFromInternal(aSource);
   }
   virtual void AppendSlice(const MediaSegment& aSource,
                            TrackTicks aStart, TrackTicks aEnd)
   {
     NS_ASSERTION(aSource.GetType() == C::StaticType(), "Wrong type");
     AppendSliceInternal(static_cast<const C&>(aSource), aStart, aEnd);
   }
   void AppendSlice(const C& aOther, TrackTicks aStart, TrackTicks aEnd)
   {
     AppendSliceInternal(aOther, aStart, aEnd);
   }
   /**
    * Replace the first aDuration ticks with null media data, because the data
    * will not be required again.
    */
   virtual void ForgetUpTo(TrackTicks aDuration)
   {
     if (mChunks.IsEmpty() || aDuration <= 0) {
       return;
     }
     if (mChunks[0].IsNull()) {
       TrackTicks extraToForget = std::min(aDuration, mDuration) - mChunks[0].GetDuration();
       if (extraToForget > 0) {
         RemoveLeading(extraToForget, 1);
         mChunks[0].mDuration += extraToForget;
         mDuration += extraToForget;
       }
       return;
     }
     RemoveLeading(aDuration, 0);
     mChunks.InsertElementAt(0)->SetNull(aDuration);
     mDuration += aDuration;
   }
   virtual void InsertNullDataAtStart(TrackTicks aDuration)
   {
     if (aDuration <= 0) {
       return;
     }
     if (!mChunks.IsEmpty() && mChunks[0].IsNull()) {
       mChunks[0].mDuration += aDuration;
     } else {
       mChunks.InsertElementAt(0)->SetNull(aDuration);
     }
 #ifdef MOZILLA_INTERNAL_API
     mChunks[0].mTimeStamp = mozilla::TimeStamp::Now();
 #endif
     mDuration += aDuration;
   }
   virtual void AppendNullData(TrackTicks aDuration)
   {
     if (aDuration <= 0) {
       return;
     }
     if (!mChunks.IsEmpty() && mChunks[mChunks.Length() - 1].IsNull()) {
       mChunks[mChunks.Length() - 1].mDuration += aDuration;
     } else {
       mChunks.AppendElement()->SetNull(aDuration);
     }
     mDuration += aDuration;
   }
   virtual void ReplaceWithDisabled()
   {
     if (GetType() != AUDIO) {
       MOZ_CRASH("Disabling unknown segment type");
     }
     TrackTicks duration = GetDuration();
     Clear();
     AppendNullData(duration);
   }
   virtual void Clear()
   {
     mDuration = 0;
     mChunks.Clear();
   }
   class ChunkIterator {
   public:
     ChunkIterator(MediaSegmentBase<C, Chunk>& aSegment)
       : mSegment(aSegment), mIndex(0) {}
     bool IsEnded() { return mIndex >= mSegment.mChunks.Length(); }
     void Next() { ++mIndex; }
     Chunk& operator*() { return mSegment.mChunks[mIndex]; }
     Chunk* operator->() { return &mSegment.mChunks[mIndex]; }
   private:
     MediaSegmentBase<C, Chunk>& mSegment;
     uint32_t mIndex;
   };
   void RemoveLeading(TrackTicks aDuration)
   {
     RemoveLeading(aDuration, 0);
   }
 #ifdef MOZILLA_INTERNAL_API
   void GetStartTime(TimeStamp &aTime) {
     aTime = mChunks[0].mTimeStamp;
   }
 #endif
   virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const MOZ_OVERRIDE
   {
     size_t amount = mChunks.SizeOfExcludingThis(aMallocSizeOf);
     for (size_t i = 0; i < mChunks.Length(); i++) {
       amount += mChunks[i].SizeOfExcludingThisIfUnshared(aMallocSizeOf);
     }
     return amount;
   }
   virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const MOZ_OVERRIDE
   {
     return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
   }
 protected:
   MediaSegmentBase(Type aType) : MediaSegment(aType) {}
   /**
    * Appends the contents of aSource to this segment, clearing aSource.
    */
   void AppendFromInternal(MediaSegmentBase<C, Chunk>* aSource)
   {
     MOZ_ASSERT(aSource->mDuration >= 0);
     mDuration += aSource->mDuration;
     aSource->mDuration = 0;
     if (!mChunks.IsEmpty() && !aSource->mChunks.IsEmpty() &&
         mChunks[mChunks.Length() - 1].CanCombineWithFollowing(aSource->mChunks[0])) {
       mChunks[mChunks.Length() - 1].mDuration += aSource->mChunks[0].mDuration;
       aSource->mChunks.RemoveElementAt(0);
     }
     mChunks.MoveElementsFrom(aSource->mChunks);
   }
   void AppendSliceInternal(const MediaSegmentBase<C, Chunk>& aSource,
                            TrackTicks aStart, TrackTicks aEnd)
   {
     MOZ_ASSERT(aStart <= aEnd, "Endpoints inverted");
     NS_WARN_IF_FALSE(aStart >= 0 && aEnd <= aSource.mDuration, "Slice out of range");
     mDuration += aEnd - aStart;
     TrackTicks offset = 0;
     for (uint32_t i = 0; i < aSource.mChunks.Length() && offset < aEnd; ++i) {
       const Chunk& c = aSource.mChunks[i];
       TrackTicks start = std::max(aStart, offset);
       TrackTicks nextOffset = offset + c.GetDuration();
       TrackTicks end = std::min(aEnd, nextOffset);
       if (start < end) {
         mChunks.AppendElement(c)->SliceTo(start - offset, end - offset);
       }
       offset = nextOffset;
     }
   }
   Chunk* AppendChunk(TrackTicks aDuration)
   {
     MOZ_ASSERT(aDuration >= 0);
     Chunk* c = mChunks.AppendElement();
     c->mDuration = aDuration;
     mDuration += aDuration;
     return c;
   }
   Chunk* FindChunkContaining(TrackTicks aOffset, TrackTicks* aStart = nullptr)
   {
     if (aOffset < 0) {
       return nullptr;
     }
     TrackTicks offset = 0;
     for (uint32_t i = 0; i < mChunks.Length(); ++i) {
       Chunk& c = mChunks[i];
       TrackTicks nextOffset = offset + c.GetDuration();
       if (aOffset < nextOffset) {
         if (aStart) {
           *aStart = offset;
         }
         return &c;
       }
       offset = nextOffset;
     }
     return nullptr;
   }
   Chunk* GetLastChunk()
   {
     if (mChunks.IsEmpty()) {
       return nullptr;
     }
     return &mChunks[mChunks.Length() - 1];
   }
   void RemoveLeading(TrackTicks aDuration, uint32_t aStartIndex)
   {
     NS_ASSERTION(aDuration >= 0, "Can't remove negative duration");
     TrackTicks t = aDuration;
     uint32_t chunksToRemove = 0;
     for (uint32_t i = aStartIndex; i < mChunks.Length() && t > 0; ++i) {
       Chunk* c = &mChunks[i];
       if (c->GetDuration() > t) {
         c->SliceTo(t, c->GetDuration());
         t = 0;
         break;
       }
       t -= c->GetDuration();
       chunksToRemove = i + 1 - aStartIndex;
     }
     mChunks.RemoveElementsAt(aStartIndex, chunksToRemove);
     mDuration -= aDuration - t;
   }
   nsTArray<Chunk> mChunks;
 #ifdef MOZILLA_INTERNAL_API
   mozilla::TimeStamp mTimeStamp;
 #endif
 };
 }
 #endif /* MOZILLA_MEDIASEGMENT_H_ */

The Tor Browser / annotate

content/media/MediaSegment.h@97036ab72558 (annotated)

content/media/MediaSegment.h