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

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

content/media/AudioSampleFormat.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 -*- */
 /* 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 http://mozilla.org/MPL/2.0/. */
 #ifndef MOZILLA_AUDIOSAMPLEFORMAT_H_
 #define MOZILLA_AUDIOSAMPLEFORMAT_H_
 #include "nsAlgorithm.h"
 #include <algorithm>
 namespace mozilla {
 /**
  * Audio formats supported in MediaStreams and media elements.
  *
  * Only one of these is supported by AudioStream, and that is determined
  * at compile time (roughly, FLOAT32 on desktops, S16 on mobile). Media decoders
  * produce that format only; queued AudioData always uses that format.
  */
 enum AudioSampleFormat
 {
   // Native-endian signed 16-bit audio samples
   AUDIO_FORMAT_S16,
   // Signed 32-bit float samples
   AUDIO_FORMAT_FLOAT32,
   // Silence: format will be chosen later
   AUDIO_FORMAT_SILENCE,
   // The format used for output by AudioStream.
 #ifdef MOZ_SAMPLE_TYPE_S16
   AUDIO_OUTPUT_FORMAT = AUDIO_FORMAT_S16
 #else
   AUDIO_OUTPUT_FORMAT = AUDIO_FORMAT_FLOAT32
 #endif
 };
 enum {
   MAX_AUDIO_SAMPLE_SIZE = sizeof(float)
 };
 template <AudioSampleFormat Format> class AudioSampleTraits;
 template <> class AudioSampleTraits<AUDIO_FORMAT_FLOAT32> {
 public:
   typedef float Type;
 };
 template <> class AudioSampleTraits<AUDIO_FORMAT_S16> {
 public:
   typedef int16_t Type;
 };
 typedef AudioSampleTraits<AUDIO_OUTPUT_FORMAT>::Type AudioDataValue;
 template<typename T> class AudioSampleTypeToFormat;
 template <> class AudioSampleTypeToFormat<float> {
 public:
   static const AudioSampleFormat Format = AUDIO_FORMAT_FLOAT32;
 };
 template <> class AudioSampleTypeToFormat<short> {
 public:
   static const AudioSampleFormat Format = AUDIO_FORMAT_S16;
 };
 // Single-sample conversion
 /*
  * Use "2^N" conversion since it's simple, fast, "bit transparent", used by
  * many other libraries and apparently behaves reasonably.
  * http://blog.bjornroche.com/2009/12/int-float-int-its-jungle-out-there.html
  * http://blog.bjornroche.com/2009/12/linearity-and-dynamic-range-in-int.html
  */
 inline float
 AudioSampleToFloat(float aValue)
 {
   return aValue;
 }
 inline float
 AudioSampleToFloat(int16_t aValue)
 {
   return aValue/32768.0f;
 }
 template <typename T> T FloatToAudioSample(float aValue);
 template <> inline float
 FloatToAudioSample<float>(float aValue)
 {
   return aValue;
 }
 template <> inline int16_t
 FloatToAudioSample<int16_t>(float aValue)
 {
   float v = aValue*32768.0f;
   float clamped = std::max(-32768.0f, std::min(32767.0f, v));
   return int16_t(clamped);
 }
 // Sample buffer conversion
 template <typename From, typename To> inline void
 ConvertAudioSamples(const From* aFrom, To* aTo, int aCount)
 {
   for (int i = 0; i < aCount; ++i) {
     aTo[i] = FloatToAudioSample<To>(AudioSampleToFloat(aFrom[i]));
   }
 }
 inline void
 ConvertAudioSamples(const int16_t* aFrom, int16_t* aTo, int aCount)
 {
   memcpy(aTo, aFrom, sizeof(*aTo)*aCount);
 }
 inline void
 ConvertAudioSamples(const float* aFrom, float* aTo, int aCount)
 {
   memcpy(aTo, aFrom, sizeof(*aTo)*aCount);
 }
 // Sample buffer conversion with scale
 template <typename From, typename To> inline void
 ConvertAudioSamplesWithScale(const From* aFrom, To* aTo, int aCount, float aScale)
 {
   if (aScale == 1.0f) {
     ConvertAudioSamples(aFrom, aTo, aCount);
     return;
   }
   for (int i = 0; i < aCount; ++i) {
     aTo[i] = FloatToAudioSample<To>(AudioSampleToFloat(aFrom[i])*aScale);
   }
 }
 inline void
 ConvertAudioSamplesWithScale(const int16_t* aFrom, int16_t* aTo, int aCount, float aScale)
 {
   if (aScale == 1.0f) {
     ConvertAudioSamples(aFrom, aTo, aCount);
     return;
   }
   if (0.0f <= aScale && aScale < 1.0f) {
     int32_t scale = int32_t((1 << 16) * aScale);
     for (int i = 0; i < aCount; ++i) {
       aTo[i] = int16_t((int32_t(aFrom[i]) * scale) >> 16);
     }
     return;
   }
   for (int i = 0; i < aCount; ++i) {
     aTo[i] = FloatToAudioSample<int16_t>(AudioSampleToFloat(aFrom[i])*aScale);
   }
 }
 // In place audio sample scaling.
 inline void
 ScaleAudioSamples(float* aBuffer, int aCount, float aScale)
 {
   for (int32_t i = 0; i < aCount; ++i) {
     aBuffer[i] *= aScale;
   }
 }
 inline void
 ScaleAudioSamples(short* aBuffer, int aCount, float aScale)
 {
   int32_t volume = int32_t((1 << 16) * aScale);
   for (int32_t i = 0; i < aCount; ++i) {
     aBuffer[i] = short((int32_t(aBuffer[i]) * volume) >> 16);
   }
 }
 inline const void*
 AddAudioSampleOffset(const void* aBase, AudioSampleFormat aFormat,
                      int32_t aOffset)
 {
   static_assert(AUDIO_FORMAT_S16 == 0, "Bad constant");
   static_assert(AUDIO_FORMAT_FLOAT32 == 1, "Bad constant");
   NS_ASSERTION(aFormat == AUDIO_FORMAT_S16 || aFormat == AUDIO_FORMAT_FLOAT32,
                "Unknown format");
   return static_cast<const uint8_t*>(aBase) + (aFormat + 1)*2*aOffset;
 }
 } // namespace mozilla
 #endif /* MOZILLA_AUDIOSAMPLEFORMAT_H_ */

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

content/media/AudioSampleFormat.h