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

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

content/media/StreamBuffer.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_STREAMBUFFER_H_
 #define MOZILLA_STREAMBUFFER_H_
 #include "MediaSegment.h"
 #include "nsAutoPtr.h"
 namespace mozilla {
 /**
  * Media time relative to the start of a StreamBuffer.
  */
 typedef MediaTime StreamTime;
 const StreamTime STREAM_TIME_MAX = MEDIA_TIME_MAX;
 /**
  * Track rate in Hz. Maximum 1 << MEDIA_TIME_FRAC_BITS Hz. This ensures
  * calculations below don't overflow.
  */
 typedef int32_t TrackRate;
 const TrackRate TRACK_RATE_MAX = 1 << MEDIA_TIME_FRAC_BITS;
 /**
  * Unique ID for track within a StreamBuffer. Tracks from different
  * StreamBuffers may have the same ID; this matters when appending StreamBuffers,
  * since tracks with the same ID are matched. Only IDs greater than 0 are allowed.
  */
 typedef int32_t TrackID;
 const TrackID TRACK_NONE = 0;
 inline TrackTicks TimeToTicksRoundUp(TrackRate aRate, StreamTime aTime)
 {
   NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Bad rate");
   NS_ASSERTION(0 <= aTime && aTime <= STREAM_TIME_MAX, "Bad time");
   return (aTime*aRate + (1 << MEDIA_TIME_FRAC_BITS) - 1) >> MEDIA_TIME_FRAC_BITS;
 }
 inline TrackTicks TimeToTicksRoundDown(TrackRate aRate, StreamTime aTime)
 {
   NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Bad rate");
   NS_ASSERTION(0 <= aTime && aTime <= STREAM_TIME_MAX, "Bad time");
   return (aTime*aRate) >> MEDIA_TIME_FRAC_BITS;
 }
 inline StreamTime TicksToTimeRoundUp(TrackRate aRate, TrackTicks aTicks)
 {
   NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Bad rate");
   NS_ASSERTION(0 <= aTicks && aTicks <= TRACK_TICKS_MAX, "Bad samples");
   return ((aTicks << MEDIA_TIME_FRAC_BITS) + aRate - 1)/aRate;
 }
 inline StreamTime TicksToTimeRound(TrackRate aRate, TrackTicks aTicks)
 {
   NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Bad rate");
   NS_ASSERTION(0 <= aTicks && aTicks <= TRACK_TICKS_MAX, "Bad samples");
   return ((aTicks << MEDIA_TIME_FRAC_BITS) + aRate/2)/aRate;
 }
 inline StreamTime TicksToTimeRoundDown(TrackRate aRate, TrackTicks aTicks)
 {
   NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Bad rate");
   NS_WARN_IF_FALSE(0 <= aTicks && aTicks <= TRACK_TICKS_MAX, "Bad samples");
   return (aTicks << MEDIA_TIME_FRAC_BITS)/aRate;
 }
 /**
  * This object contains the decoded data for a stream's tracks.
  * A StreamBuffer can be appended to. Logically a StreamBuffer only gets longer,
  * but we also have the ability to "forget" data before a certain time that
  * we know won't be used again. (We prune a whole number of seconds internally.)
  *
  * StreamBuffers should only be used from one thread at a time.
  *
  * A StreamBuffer has a set of tracks that can be of arbitrary types ---
  * the data for each track is a MediaSegment. The set of tracks can vary
  * over the timeline of the StreamBuffer.
  */
 class StreamBuffer {
 public:
   /**
    * Every track has a start time --- when it started in the StreamBuffer.
    * It has an end flag; when false, no end point is known; when true,
    * the track ends when the data we have for the track runs out.
    * Tracks have a unique ID assigned at creation. This allows us to identify
    * the same track across StreamBuffers. A StreamBuffer should never have
    * two tracks with the same ID (even if they don't overlap in time).
    * TODO Tracks can also be enabled and disabled over time.
    * TODO Add TimeVarying<TrackTicks,bool> mEnabled.
    * Takes ownership of aSegment.
    */
   class Track {
   public:
     Track(TrackID aID, TrackRate aRate, TrackTicks aStart, MediaSegment* aSegment)
       : mStart(aStart),
         mSegment(aSegment),
         mRate(aRate),
         mID(aID),
         mEnded(false)
     {
       MOZ_COUNT_CTOR(Track);
       NS_ASSERTION(aID > TRACK_NONE, "Bad track ID");
       NS_ASSERTION(0 < aRate && aRate <= TRACK_RATE_MAX, "Invalid rate");
       NS_ASSERTION(0 <= aStart && aStart <= aSegment->GetDuration(), "Bad start position");
     }
     ~Track()
     {
       MOZ_COUNT_DTOR(Track);
     }
     template <class T> T* Get() const
     {
       if (mSegment->GetType() == T::StaticType()) {
         return static_cast<T*>(mSegment.get());
       }
       return nullptr;
     }
     MediaSegment* GetSegment() const { return mSegment; }
     TrackRate GetRate() const { return mRate; }
     TrackID GetID() const { return mID; }
     bool IsEnded() const { return mEnded; }
     TrackTicks GetStart() const { return mStart; }
     TrackTicks GetEnd() const { return mSegment->GetDuration(); }
     StreamTime GetEndTimeRoundDown() const
     {
       return mozilla::TicksToTimeRoundDown(mRate, mSegment->GetDuration());
     }
     StreamTime GetStartTimeRoundDown() const
     {
       return mozilla::TicksToTimeRoundDown(mRate, mStart);
     }
     TrackTicks TimeToTicksRoundDown(StreamTime aTime) const
     {
       return mozilla::TimeToTicksRoundDown(mRate, aTime);
     }
     StreamTime TicksToTimeRoundDown(TrackTicks aTicks) const
     {
       return mozilla::TicksToTimeRoundDown(mRate, aTicks);
     }
     MediaSegment::Type GetType() const { return mSegment->GetType(); }
     void SetEnded() { mEnded = true; }
     void AppendFrom(Track* aTrack)
     {
       NS_ASSERTION(!mEnded, "Can't append to ended track");
       NS_ASSERTION(aTrack->mID == mID, "IDs must match");
       NS_ASSERTION(aTrack->mStart == 0, "Source track must start at zero");
       NS_ASSERTION(aTrack->mSegment->GetType() == GetType(), "Track types must match");
       NS_ASSERTION(aTrack->mRate == mRate, "Track rates must match");
       mSegment->AppendFrom(aTrack->mSegment);
       mEnded = aTrack->mEnded;
     }
     MediaSegment* RemoveSegment()
     {
       return mSegment.forget();
     }
     void ForgetUpTo(TrackTicks aTime)
     {
       mSegment->ForgetUpTo(aTime);
     }
     size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
     {
       size_t amount = aMallocSizeOf(this);
       if (mSegment) {
         amount += mSegment->SizeOfIncludingThis(aMallocSizeOf);
       }
       return amount;
     }
   protected:
     friend class StreamBuffer;
     // Start offset is in ticks at rate mRate
     TrackTicks mStart;
     // The segment data starts at the start of the owning StreamBuffer, i.e.,
     // there's mStart silence/no video at the beginning.
     nsAutoPtr<MediaSegment> mSegment;
     TrackRate mRate; // rate in ticks per second
     // Unique ID
     TrackID mID;
     // True when the track ends with the data in mSegment
     bool mEnded;
   };
   class CompareTracksByID {
   public:
     bool Equals(Track* aA, Track* aB) const {
       return aA->GetID() == aB->GetID();
     }
     bool LessThan(Track* aA, Track* aB) const {
       return aA->GetID() < aB->GetID();
     }
   };
   StreamBuffer()
     : mTracksKnownTime(0), mForgottenTime(0)
   {
     MOZ_COUNT_CTOR(StreamBuffer);
   }
   ~StreamBuffer()
   {
     MOZ_COUNT_DTOR(StreamBuffer);
   }
   size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
   {
     size_t amount = 0;
     amount += mTracks.SizeOfExcludingThis(aMallocSizeOf);
     for (size_t i = 0; i < mTracks.Length(); i++) {
       amount += mTracks[i]->SizeOfIncludingThis(aMallocSizeOf);
     }
     return amount;
   }
   /**
    * Takes ownership of aSegment. Don't do this while iterating, or while
    * holding a Track reference.
    * aSegment must have aStart worth of null data.
    */
   Track& AddTrack(TrackID aID, TrackRate aRate, TrackTicks aStart, MediaSegment* aSegment)
   {
     NS_ASSERTION(TimeToTicksRoundDown(aRate, mTracksKnownTime) <= aStart,
                  "Start time too early");
     NS_ASSERTION(!FindTrack(aID), "Track with this ID already exists");
     return **mTracks.InsertElementSorted(new Track(aID, aRate, aStart, aSegment),
                                          CompareTracksByID());
   }
   void AdvanceKnownTracksTime(StreamTime aKnownTime)
   {
     NS_ASSERTION(aKnownTime >= mTracksKnownTime, "Can't move tracks-known time earlier");
     mTracksKnownTime = aKnownTime;
   }
   /**
    * The end time for the StreamBuffer is the latest time for which we have
    * data for all tracks that haven't ended by that time.
    */
   StreamTime GetEnd() const;
   /**
    * Returns the earliest time >= 0 at which all tracks have ended
    * and all their data has been played out and no new tracks can be added,
    * or STREAM_TIME_MAX if there is no such time.
    */
   StreamTime GetAllTracksEnd() const;
 #ifdef DEBUG
   void DumpTrackInfo() const;
 #endif
   Track* FindTrack(TrackID aID);
   class TrackIter {
   public:
     /**
      * Iterate through the tracks of aBuffer in order of ID.
      */
     TrackIter(const StreamBuffer& aBuffer) :
       mBuffer(&aBuffer.mTracks), mIndex(0), mMatchType(false) {}
     /**
      * Iterate through the tracks of aBuffer with type aType, in order of ID.
      */
     TrackIter(const StreamBuffer& aBuffer, MediaSegment::Type aType) :
       mBuffer(&aBuffer.mTracks), mIndex(0), mType(aType), mMatchType(true) { FindMatch(); }
     bool IsEnded() { return mIndex >= mBuffer->Length(); }
     void Next()
     {
       ++mIndex;
       FindMatch();
     }
     Track* get() { return mBuffer->ElementAt(mIndex); }
     Track& operator*() { return *mBuffer->ElementAt(mIndex); }
     Track* operator->() { return mBuffer->ElementAt(mIndex); }
   private:
     void FindMatch()
     {
       if (!mMatchType)
         return;
       while (mIndex < mBuffer->Length() &&
              mBuffer->ElementAt(mIndex)->GetType() != mType) {
         ++mIndex;
       }
     }
     const nsTArray<nsAutoPtr<Track> >* mBuffer;
     uint32_t mIndex;
     MediaSegment::Type mType;
     bool mMatchType;
   };
   friend class TrackIter;
   /**
    * Forget stream data before aTime; they will no longer be needed.
    * Also can forget entire tracks that have ended at or before aTime.
    * Can't be used to forget beyond GetEnd().
    */
   void ForgetUpTo(StreamTime aTime);
   /**
    * Returns the latest time passed to ForgetUpTo.
    */
   StreamTime GetForgottenDuration()
   {
     return mForgottenTime;
   }
 protected:
   // Any new tracks added will start at or after this time. In other words, the track
   // list is complete and correct for all times less than this time.
   StreamTime mTracksKnownTime;
   StreamTime mForgottenTime;
   // All known tracks for this StreamBuffer
   nsTArray<nsAutoPtr<Track> > mTracks;
 };
 }
 #endif /* MOZILLA_STREAMBUFFER_H_ */

The Tor Browser / annotate

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

content/media/StreamBuffer.h