Make AudioVector::operator[] inline and modify index calculation

webrtc/modules/audio_coding/neteq/audio_vector.h

Index: webrtc/modules/audio_coding/neteq/audio_vector.h
diff --git a/webrtc/modules/audio_coding/neteq/audio_vector.h b/webrtc/modules/audio_coding/neteq/audio_vector.h
index 756292aa783aabd0449bfd76d61a20ade77dca85..c8722517dd604a598abb6f6b3a5f4454720c78df 100644
--- a/webrtc/modules/audio_coding/neteq/audio_vector.h
+++ b/webrtc/modules/audio_coding/neteq/audio_vector.h
@@ -110,8 +110,13 @@ class AudioVector {
   virtual bool Empty() const;
 
   // Accesses and modifies an element of AudioVector.
-  const int16_t& operator[](size_t index) const;
-  int16_t& operator[](size_t index);
+  inline const int16_t& operator[](size_t index) const {

[kwiberg-webrtc, 2017/02/07 14:04:15]

The "inline" keyword isn't necessary---functions defined (as opposed to
declared) in a class definition are inline by default.

+    return array_[(begin_index_ + index) % capacity_];

[the sun, 2017/02/02 19:29:55]

Integer division is still surprisingly expensive on some platforms. Are we
certain it is needed here? Can we make the capacity a power of two and use
bitwise AND instead?

[kwiberg-webrtc, 2017/02/07 14:04:15]

Alternatively, can we be sure that 0 <= begin_index_ + index < 2 * capacity_?
Conditionally subtracting capacity_ is probably cheaper than modulus.

[hlundin-webrtc, 2017/02/13 14:21:13]

I did something along those lines.

+  }
+
+  inline int16_t& operator[](size_t index) {
+    return array_[(begin_index_ + index) % capacity_];
+  }
 
  private:
   static const size_t kDefaultInitialSize = 10;