diff -r 000000000000 -r 6474c204b198 content/media/AudioEventTimeline.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/AudioEventTimeline.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,577 @@
+/* -*- 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 AudioEventTimeline_h_
+#define AudioEventTimeline_h_
+
+#include <algorithm>
+#include "mozilla/Assertions.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/TypedEnum.h"
+#include "mozilla/PodOperations.h"
+
+#include "nsTArray.h"
+#include "math.h"
+
+namespace mozilla {
+
+namespace dom {
+
+// This is an internal helper class and should not be used outside of this header.
+struct AudioTimelineEvent {
+  enum Type MOZ_ENUM_TYPE(uint32_t) {
+    SetValue,
+    LinearRamp,
+    ExponentialRamp,
+    SetTarget,
+    SetValueCurve
+  };
+
+  AudioTimelineEvent(Type aType, double aTime, float aValue, double aTimeConstant = 0.0,
+                     float aDuration = 0.0, const float* aCurve = nullptr, uint32_t aCurveLength = 0)
+    : mType(aType)
+    , mTimeConstant(aTimeConstant)
+    , mDuration(aDuration)
+#ifdef DEBUG
+    , mTimeIsInTicks(false)
+#endif
+  {
+    mTime = aTime;
+    if (aType == AudioTimelineEvent::SetValueCurve) {
+      SetCurveParams(aCurve, aCurveLength);
+    } else {
+      mValue = aValue;
+    }
+  }
+
+  AudioTimelineEvent(const AudioTimelineEvent& rhs)
+  {
+    PodCopy(this, &rhs, 1);
+    if (rhs.mType == AudioTimelineEvent::SetValueCurve) {
+      SetCurveParams(rhs.mCurve, rhs.mCurveLength);
+    }
+  }
+
+  ~AudioTimelineEvent()
+  {
+    if (mType == AudioTimelineEvent::SetValueCurve) {
+      delete[] mCurve;
+    }
+  }
+
+  bool IsValid() const
+  {
+    if (mType == AudioTimelineEvent::SetValueCurve) {
+      if (!mCurve || !mCurveLength) {
+        return false;
+      }
+      for (uint32_t i = 0; i < mCurveLength; ++i) {
+        if (!IsValid(mCurve[i])) {
+          return false;
+        }
+      }
+    }
+
+    return IsValid(mTime) &&
+           IsValid(mValue) &&
+           IsValid(mTimeConstant) &&
+           IsValid(mDuration);
+  }
+
+  template <class TimeType>
+  TimeType Time() const;
+
+  void SetTimeInTicks(int64_t aTimeInTicks)
+  {
+    mTimeInTicks = aTimeInTicks;
+#ifdef DEBUG
+    mTimeIsInTicks = true;
+#endif
+  }
+
+  void SetCurveParams(const float* aCurve, uint32_t aCurveLength) {
+    mCurveLength = aCurveLength;
+    if (aCurveLength) {
+      mCurve = new float[aCurveLength];
+      PodCopy(mCurve, aCurve, aCurveLength);
+    } else {
+      mCurve = nullptr;
+    }
+  }
+
+  Type mType;
+  union {
+    float mValue;
+    uint32_t mCurveLength;
+  };
+  // The time for an event can either be in absolute value or in ticks.
+  // Initially the time of the event is always in absolute value.
+  // In order to convert it to ticks, call SetTimeInTicks.  Once this
+  // method has been called for an event, the time cannot be converted
+  // back to absolute value.
+  union {
+    double mTime;
+    int64_t mTimeInTicks;
+  };
+  // mCurve contains a buffer of SetValueCurve samples.  We sample the
+  // values in the buffer depending on how far along we are in time.
+  // If we're at time T and the event has started as time T0 and has a
+  // duration of D, we sample the buffer at floor(mCurveLength*(T-T0)/D)
+  // if T<T0+D, and just take the last sample in the buffer otherwise.
+  float* mCurve;
+  double mTimeConstant;
+  double mDuration;
+#ifdef DEBUG
+  bool mTimeIsInTicks;
+#endif
+
+private:
+  static bool IsValid(double value)
+  {
+    return mozilla::IsFinite(value);
+  }
+};
+
+template <>
+inline double AudioTimelineEvent::Time<double>() const
+{
+  MOZ_ASSERT(!mTimeIsInTicks);
+  return mTime;
+}
+
+template <>
+inline int64_t AudioTimelineEvent::Time<int64_t>() const
+{
+  MOZ_ASSERT(mTimeIsInTicks);
+  return mTimeInTicks;
+}
+
+/**
+ * This class will be instantiated with different template arguments for testing and
+ * production code.
+ *
+ * ErrorResult is a type which satisfies the following:
+ *  - Implements a Throw() method taking an nsresult argument, representing an error code.
+ */
+template <class ErrorResult>
+class AudioEventTimeline
+{
+public:
+  explicit AudioEventTimeline(float aDefaultValue)
+    : mValue(aDefaultValue),
+      mComputedValue(aDefaultValue),
+      mLastComputedValue(aDefaultValue)
+  {
+  }
+
+  bool HasSimpleValue() const
+  {
+    return mEvents.IsEmpty();
+  }
+
+  float GetValue() const
+  {
+    // This method should only be called if HasSimpleValue() returns true
+    MOZ_ASSERT(HasSimpleValue());
+    return mValue;
+  }
+
+  float Value() const
+  {
+    // TODO: Return the current value based on the timeline of the AudioContext
+    return mValue;
+  }
+
+  void SetValue(float aValue)
+  {
+    // Silently don't change anything if there are any events
+    if (mEvents.IsEmpty()) {
+      mLastComputedValue = mComputedValue = mValue = aValue;
+    }
+  }
+
+  void SetValueAtTime(float aValue, double aStartTime, ErrorResult& aRv)
+  {
+    InsertEvent(AudioTimelineEvent(AudioTimelineEvent::SetValue, aStartTime, aValue), aRv);
+  }
+
+  void LinearRampToValueAtTime(float aValue, double aEndTime, ErrorResult& aRv)
+  {
+    InsertEvent(AudioTimelineEvent(AudioTimelineEvent::LinearRamp, aEndTime, aValue), aRv);
+  }
+
+  void ExponentialRampToValueAtTime(float aValue, double aEndTime, ErrorResult& aRv)
+  {
+    InsertEvent(AudioTimelineEvent(AudioTimelineEvent::ExponentialRamp, aEndTime, aValue), aRv);
+  }
+
+  void SetTargetAtTime(float aTarget, double aStartTime, double aTimeConstant, ErrorResult& aRv)
+  {
+    InsertEvent(AudioTimelineEvent(AudioTimelineEvent::SetTarget, aStartTime, aTarget, aTimeConstant), aRv);
+  }
+
+  void SetValueCurveAtTime(const float* aValues, uint32_t aValuesLength, double aStartTime, double aDuration, ErrorResult& aRv)
+  {
+    InsertEvent(AudioTimelineEvent(AudioTimelineEvent::SetValueCurve, aStartTime, 0.0f, 0.0f, aDuration, aValues, aValuesLength), aRv);
+  }
+
+  void CancelScheduledValues(double aStartTime)
+  {
+    for (unsigned i = 0; i < mEvents.Length(); ++i) {
+      if (mEvents[i].mTime >= aStartTime) {
+#ifdef DEBUG
+        // Sanity check: the array should be sorted, so all of the following
+        // events should have a time greater than aStartTime too.
+        for (unsigned j = i + 1; j < mEvents.Length(); ++j) {
+          MOZ_ASSERT(mEvents[j].mTime >= aStartTime);
+        }
+#endif
+        mEvents.TruncateLength(i);
+        break;
+      }
+    }
+  }
+
+  void CancelAllEvents()
+  {
+    mEvents.Clear();
+  }
+
+  static bool TimesEqual(int64_t aLhs, int64_t aRhs)
+  {
+    return aLhs == aRhs;
+  }
+
+  // Since we are going to accumulate error by adding 0.01 multiple time in a
+  // loop, we want to fuzz the equality check in GetValueAtTime.
+  static bool TimesEqual(double aLhs, double aRhs)
+  {
+    const float kEpsilon = 0.0000000001f;
+    return fabs(aLhs - aRhs) < kEpsilon;
+  }
+
+  template<class TimeType>
+  float GetValueAtTime(TimeType aTime)
+  {
+    mComputedValue = GetValueAtTimeHelper(aTime);
+    return mComputedValue;
+  }
+
+  // This method computes the AudioParam value at a given time based on the event timeline
+  template<class TimeType>
+  float GetValueAtTimeHelper(TimeType aTime)
+  {
+    const AudioTimelineEvent* previous = nullptr;
+    const AudioTimelineEvent* next = nullptr;
+
+    bool bailOut = false;
+    for (unsigned i = 0; !bailOut && i < mEvents.Length(); ++i) {
+      switch (mEvents[i].mType) {
+      case AudioTimelineEvent::SetValue:
+      case AudioTimelineEvent::SetTarget:
+      case AudioTimelineEvent::LinearRamp:
+      case AudioTimelineEvent::ExponentialRamp:
+      case AudioTimelineEvent::SetValueCurve:
+        if (TimesEqual(aTime, mEvents[i].template Time<TimeType>())) {
+          mLastComputedValue = mComputedValue;
+          // Find the last event with the same time
+          do {
+            ++i;
+          } while (i < mEvents.Length() &&
+                   aTime == mEvents[i].template Time<TimeType>());
+
+          // SetTarget nodes can be handled no matter what their next node is (if they have one)
+          if (mEvents[i - 1].mType == AudioTimelineEvent::SetTarget) {
+            // Follow the curve, without regard to the next event, starting at
+            // the last value of the last event.
+            return ExponentialApproach(mEvents[i - 1].template Time<TimeType>(),
+                                       mLastComputedValue, mEvents[i - 1].mValue,
+                                       mEvents[i - 1].mTimeConstant, aTime);
+          }
+
+          // SetValueCurve events can be handled no matter what their event node is (if they have one)
+          if (mEvents[i - 1].mType == AudioTimelineEvent::SetValueCurve) {
+            return ExtractValueFromCurve(mEvents[i - 1].template Time<TimeType>(),
+                                         mEvents[i - 1].mCurve,
+                                         mEvents[i - 1].mCurveLength,
+                                         mEvents[i - 1].mDuration, aTime);
+          }
+
+          // For other event types
+          return mEvents[i - 1].mValue;
+        }
+        previous = next;
+        next = &mEvents[i];
+        if (aTime < mEvents[i].template Time<TimeType>()) {
+          bailOut = true;
+        }
+        break;
+      default:
+        MOZ_ASSERT(false, "unreached");
+      }
+    }
+    // Handle the case where the time is past all of the events
+    if (!bailOut) {
+      previous = next;
+      next = nullptr;
+    }
+
+    // Just return the default value if we did not find anything
+    if (!previous && !next) {
+      return mValue;
+    }
+
+    // If the requested time is before all of the existing events
+    if (!previous) {
+      return mValue;
+    }
+
+    // SetTarget nodes can be handled no matter what their next node is (if they have one)
+    if (previous->mType == AudioTimelineEvent::SetTarget) {
+      return ExponentialApproach(previous->template Time<TimeType>(),
+                                 mLastComputedValue, previous->mValue,
+                                 previous->mTimeConstant, aTime);
+    }
+
+    // SetValueCurve events can be handled no mattar what their next node is (if they have one)
+    if (previous->mType == AudioTimelineEvent::SetValueCurve) {
+      return ExtractValueFromCurve(previous->template Time<TimeType>(),
+                                   previous->mCurve, previous->mCurveLength,
+                                   previous->mDuration, aTime);
+    }
+
+    // If the requested time is after all of the existing events
+    if (!next) {
+      switch (previous->mType) {
+      case AudioTimelineEvent::SetValue:
+      case AudioTimelineEvent::LinearRamp:
+      case AudioTimelineEvent::ExponentialRamp:
+        // The value will be constant after the last event
+        return previous->mValue;
+      case AudioTimelineEvent::SetValueCurve:
+        return ExtractValueFromCurve(previous->template Time<TimeType>(),
+                                     previous->mCurve, previous->mCurveLength,
+                                     previous->mDuration, aTime);
+      case AudioTimelineEvent::SetTarget:
+        MOZ_ASSERT(false, "unreached");
+      }
+      MOZ_ASSERT(false, "unreached");
+    }
+
+    // Finally, handle the case where we have both a previous and a next event
+
+    // First, handle the case where our range ends up in a ramp event
+    switch (next->mType) {
+    case AudioTimelineEvent::LinearRamp:
+      return LinearInterpolate(previous->template Time<TimeType>(), previous->mValue, next->template Time<TimeType>(), next->mValue, aTime);
+    case AudioTimelineEvent::ExponentialRamp:
+      return ExponentialInterpolate(previous->template Time<TimeType>(), previous->mValue, next->template Time<TimeType>(), next->mValue, aTime);
+    case AudioTimelineEvent::SetValue:
+    case AudioTimelineEvent::SetTarget:
+    case AudioTimelineEvent::SetValueCurve:
+      break;
+    }
+
+    // Now handle all other cases
+    switch (previous->mType) {
+    case AudioTimelineEvent::SetValue:
+    case AudioTimelineEvent::LinearRamp:
+    case AudioTimelineEvent::ExponentialRamp:
+      // If the next event type is neither linear or exponential ramp, the
+      // value is constant.
+      return previous->mValue;
+    case AudioTimelineEvent::SetValueCurve:
+      return ExtractValueFromCurve(previous->template Time<TimeType>(),
+                                   previous->mCurve, previous->mCurveLength,
+                                   previous->mDuration, aTime);
+    case AudioTimelineEvent::SetTarget:
+      MOZ_ASSERT(false, "unreached");
+    }
+
+    MOZ_ASSERT(false, "unreached");
+    return 0.0f;
+  }
+
+  // Return the number of events scheduled
+  uint32_t GetEventCount() const
+  {
+    return mEvents.Length();
+  }
+
+  static float LinearInterpolate(double t0, float v0, double t1, float v1, double t)
+  {
+    return v0 + (v1 - v0) * ((t - t0) / (t1 - t0));
+  }
+
+  static float ExponentialInterpolate(double t0, float v0, double t1, float v1, double t)
+  {
+    return v0 * powf(v1 / v0, (t - t0) / (t1 - t0));
+  }
+
+  static float ExponentialApproach(double t0, double v0, float v1, double timeConstant, double t)
+  {
+    return v1 + (v0 - v1) * expf(-(t - t0) / timeConstant);
+  }
+
+  static float ExtractValueFromCurve(double startTime, float* aCurve, uint32_t aCurveLength, double duration, double t)
+  {
+    if (t >= startTime + duration) {
+      // After the duration, return the last curve value
+      return aCurve[aCurveLength - 1];
+    }
+    double ratio = std::max((t - startTime) / duration, 0.0);
+    if (ratio >= 1.0) {
+      return aCurve[aCurveLength - 1];
+    }
+    return aCurve[uint32_t(aCurveLength * ratio)];
+  }
+
+  void ConvertEventTimesToTicks(int64_t (*aConvertor)(double aTime, void* aClosure), void* aClosure,
+                                int32_t aSampleRate)
+  {
+    for (unsigned i = 0; i < mEvents.Length(); ++i) {
+      mEvents[i].SetTimeInTicks(aConvertor(mEvents[i].template Time<double>(), aClosure));
+      mEvents[i].mTimeConstant *= aSampleRate;
+      mEvents[i].mDuration *= aSampleRate;
+    }
+  }
+
+private:
+  const AudioTimelineEvent* GetPreviousEvent(double aTime) const
+  {
+    const AudioTimelineEvent* previous = nullptr;
+    const AudioTimelineEvent* next = nullptr;
+
+    bool bailOut = false;
+    for (unsigned i = 0; !bailOut && i < mEvents.Length(); ++i) {
+      switch (mEvents[i].mType) {
+      case AudioTimelineEvent::SetValue:
+      case AudioTimelineEvent::SetTarget:
+      case AudioTimelineEvent::LinearRamp:
+      case AudioTimelineEvent::ExponentialRamp:
+      case AudioTimelineEvent::SetValueCurve:
+        if (aTime == mEvents[i].mTime) {
+          // Find the last event with the same time
+          do {
+            ++i;
+          } while (i < mEvents.Length() &&
+                   aTime == mEvents[i].mTime);
+          return &mEvents[i - 1];
+        }
+        previous = next;
+        next = &mEvents[i];
+        if (aTime < mEvents[i].mTime) {
+          bailOut = true;
+        }
+        break;
+      default:
+        MOZ_ASSERT(false, "unreached");
+      }
+    }
+    // Handle the case where the time is past all of the events
+    if (!bailOut) {
+      previous = next;
+    }
+
+    return previous;
+  }
+
+  void InsertEvent(const AudioTimelineEvent& aEvent, ErrorResult& aRv)
+  {
+    if (!aEvent.IsValid()) {
+      aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+      return;
+    }
+
+    // Make sure that non-curve events don't fall within the duration of a
+    // curve event.
+    for (unsigned i = 0; i < mEvents.Length(); ++i) {
+      if (mEvents[i].mType == AudioTimelineEvent::SetValueCurve &&
+          mEvents[i].mTime <= aEvent.mTime &&
+          (mEvents[i].mTime + mEvents[i].mDuration) >= aEvent.mTime) {
+        aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+        return;
+      }
+    }
+
+    // Make sure that curve events don't fall in a range which includes other
+    // events.
+    if (aEvent.mType == AudioTimelineEvent::SetValueCurve) {
+      for (unsigned i = 0; i < mEvents.Length(); ++i) {
+        if (mEvents[i].mTime > aEvent.mTime &&
+            mEvents[i].mTime < (aEvent.mTime + aEvent.mDuration)) {
+          aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+          return;
+        }
+      }
+    }
+
+    // Make sure that invalid values are not used for exponential curves
+    if (aEvent.mType == AudioTimelineEvent::ExponentialRamp) {
+      if (aEvent.mValue <= 0.f) {
+        aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+        return;
+      }
+      const AudioTimelineEvent* previousEvent = GetPreviousEvent(aEvent.mTime);
+      if (previousEvent) {
+        if (previousEvent->mValue <= 0.f) {
+          aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+          return;
+        }
+      } else {
+        if (mValue <= 0.f) {
+          aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+          return;
+        }
+      }
+    }
+
+    for (unsigned i = 0; i < mEvents.Length(); ++i) {
+      if (aEvent.mTime == mEvents[i].mTime) {
+        if (aEvent.mType == mEvents[i].mType) {
+          // If times and types are equal, replace the event
+          mEvents.ReplaceElementAt(i, aEvent);
+        } else {
+          // Otherwise, place the element after the last event of another type
+          do {
+            ++i;
+          } while (i < mEvents.Length() &&
+                   aEvent.mType != mEvents[i].mType &&
+                   aEvent.mTime == mEvents[i].mTime);
+          mEvents.InsertElementAt(i, aEvent);
+        }
+        return;
+      }
+      // Otherwise, place the event right after the latest existing event
+      if (aEvent.mTime < mEvents[i].mTime) {
+        mEvents.InsertElementAt(i, aEvent);
+        return;
+      }
+    }
+
+    // If we couldn't find a place for the event, just append it to the list
+    mEvents.AppendElement(aEvent);
+  }
+
+private:
+  // This is a sorted array of the events in the timeline.  Queries of this
+  // data structure should probably be more frequent than modifications to it,
+  // and that is the reason why we're using a simple array as the data structure.
+  // We can optimize this in the future if the performance of the array ends up
+  // being a bottleneck.
+  nsTArray<AudioTimelineEvent> mEvents;
+  float mValue;
+  // This is the value of this AudioParam we computed at the last call.
+  float mComputedValue;
+  // This is the value of this AudioParam at the last tick of the previous event.
+  float mLastComputedValue;
+};
+
+}
+}
+
+#endif
+