Fix constness of AudioBuffer accessors.

Don't return non-const pointers from const accessors and deal with the
spillover. Provide overloaded versions as needed.

Inspired by kwiberg:
https://webrtc-codereview.appspot.com/12379005/

R=bjornv@webrtc.org, kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/15379004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6030 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_processing/audio_buffer.cc b/webrtc/modules/audio_processing/audio_buffer.cc
index c53d4df..9160f69 100644
--- a/webrtc/modules/audio_processing/audio_buffer.cc
+++ b/webrtc/modules/audio_processing/audio_buffer.cc
@@ -228,7 +228,7 @@
   is_muted_ = false;
 }
 
-int16_t* AudioBuffer::data(int channel) const {
+const int16_t* AudioBuffer::data(int channel) const {
   assert(channel >= 0 && channel < num_proc_channels_);
   if (data_ != NULL) {
     return data_;
@@ -237,7 +237,12 @@
   return channels_->channel(channel);
 }
 
-int16_t* AudioBuffer::low_pass_split_data(int channel) const {
+int16_t* AudioBuffer::data(int channel) {
+  const AudioBuffer* t = this;
+  return const_cast<int16_t*>(t->data(channel));
+}
+
+const int16_t* AudioBuffer::low_pass_split_data(int channel) const {
   assert(channel >= 0 && channel < num_proc_channels_);
   if (split_channels_.get() == NULL) {
     return data(channel);
@@ -246,7 +251,12 @@
   return split_channels_->low_channel(channel);
 }
 
-int16_t* AudioBuffer::high_pass_split_data(int channel) const {
+int16_t* AudioBuffer::low_pass_split_data(int channel) {
+  const AudioBuffer* t = this;
+  return const_cast<int16_t*>(t->low_pass_split_data(channel));
+}
+
+const int16_t* AudioBuffer::high_pass_split_data(int channel) const {
   assert(channel >= 0 && channel < num_proc_channels_);
   if (split_channels_.get() == NULL) {
     return NULL;
@@ -255,19 +265,24 @@
   return split_channels_->high_channel(channel);
 }
 
-int16_t* AudioBuffer::mixed_data(int channel) const {
+int16_t* AudioBuffer::high_pass_split_data(int channel) {
+  const AudioBuffer* t = this;
+  return const_cast<int16_t*>(t->high_pass_split_data(channel));
+}
+
+const int16_t* AudioBuffer::mixed_data(int channel) const {
   assert(channel >= 0 && channel < num_mixed_channels_);
 
   return mixed_channels_->channel(channel);
 }
 
-int16_t* AudioBuffer::mixed_low_pass_data(int channel) const {
+const int16_t* AudioBuffer::mixed_low_pass_data(int channel) const {
   assert(channel >= 0 && channel < num_mixed_low_pass_channels_);
 
   return mixed_low_pass_channels_->channel(channel);
 }
 
-int16_t* AudioBuffer::low_pass_reference(int channel) const {
+const int16_t* AudioBuffer::low_pass_reference(int channel) const {
   assert(channel >= 0 && channel < num_proc_channels_);
   if (!reference_copied_) {
     return NULL;
@@ -280,7 +295,7 @@
   return keyboard_data_;
 }
 
-SplitFilterStates* AudioBuffer::filter_states(int channel) const {
+SplitFilterStates* AudioBuffer::filter_states(int channel) {
   assert(channel >= 0 && channel < num_proc_channels_);
   return &filter_states_[channel];
 }
diff --git a/webrtc/modules/audio_processing/audio_buffer.h b/webrtc/modules/audio_processing/audio_buffer.h
index eaf53eb..79f4689 100644
--- a/webrtc/modules/audio_processing/audio_buffer.h
+++ b/webrtc/modules/audio_processing/audio_buffer.h
@@ -55,15 +55,18 @@
   int samples_per_split_channel() const;
   int samples_per_keyboard_channel() const;
 
-  int16_t* data(int channel) const;
-  int16_t* low_pass_split_data(int channel) const;
-  int16_t* high_pass_split_data(int channel) const;
-  int16_t* mixed_data(int channel) const;
-  int16_t* mixed_low_pass_data(int channel) const;
-  int16_t* low_pass_reference(int channel) const;
+  int16_t* data(int channel);
+  const int16_t* data(int channel) const;
+  int16_t* low_pass_split_data(int channel);
+  const int16_t* low_pass_split_data(int channel) const;
+  int16_t* high_pass_split_data(int channel);
+  const int16_t* high_pass_split_data(int channel) const;
+  const int16_t* mixed_data(int channel) const;
+  const int16_t* mixed_low_pass_data(int channel) const;
+  const int16_t* low_pass_reference(int channel) const;
   const float* keyboard_data() const;
 
-  SplitFilterStates* filter_states(int channel) const;
+  SplitFilterStates* filter_states(int channel);
 
   void set_activity(AudioFrame::VADActivity activity);
   AudioFrame::VADActivity activity() const;
diff --git a/webrtc/modules/audio_processing/echo_control_mobile_impl.cc b/webrtc/modules/audio_processing/echo_control_mobile_impl.cc
index 1dce403..a03adc5 100644
--- a/webrtc/modules/audio_processing/echo_control_mobile_impl.cc
+++ b/webrtc/modules/audio_processing/echo_control_mobile_impl.cc
@@ -128,7 +128,7 @@
   for (int i = 0; i < audio->num_channels(); i++) {
     // TODO(ajm): improve how this works, possibly inside AECM.
     //            This is kind of hacked up.
-    int16_t* noisy = audio->low_pass_reference(i);
+    const int16_t* noisy = audio->low_pass_reference(i);
     int16_t* clean = audio->low_pass_split_data(i);
     if (noisy == NULL) {
       noisy = clean;
diff --git a/webrtc/modules/audio_processing/gain_control_impl.cc b/webrtc/modules/audio_processing/gain_control_impl.cc
index e859044..a67b67e 100644
--- a/webrtc/modules/audio_processing/gain_control_impl.cc
+++ b/webrtc/modules/audio_processing/gain_control_impl.cc
@@ -59,7 +59,7 @@
 
   assert(audio->samples_per_split_channel() <= 160);
 
-  int16_t* mixed_data = audio->low_pass_split_data(0);
+  const int16_t* mixed_data = audio->low_pass_split_data(0);
   if (audio->num_channels() > 1) {
     audio->CopyAndMixLowPass(1);
     mixed_data = audio->mixed_low_pass_data(0);
diff --git a/webrtc/modules/audio_processing/level_estimator_impl.cc b/webrtc/modules/audio_processing/level_estimator_impl.cc
index c5985ce..a91e963 100644
--- a/webrtc/modules/audio_processing/level_estimator_impl.cc
+++ b/webrtc/modules/audio_processing/level_estimator_impl.cc
@@ -20,7 +20,15 @@
 namespace webrtc {
 namespace {
 
-const double kMaxSquaredLevel = 32768.0 * 32768.0;
+const float kMaxSquaredLevel = 32768.0 * 32768.0;
+
+float SumSquare(const int16_t* data, int length) {
+  float sum_square = 0.f;
+  for (int i = 0; i < length; ++i) {
+    sum_square += data[i] * data[i];
+  }
+  return sum_square;
+}
 
 class Level {
  public:
@@ -36,7 +44,7 @@
     sample_count_ = 0;
   }
 
-  void Process(int16_t* data, int length) {
+  void Process(const int16_t* data, int length) {
     assert(data != NULL);
     assert(length > 0);
     sum_square_ += SumSquare(data, length);
@@ -55,7 +63,7 @@
     }
 
     // Normalize by the max level.
-    double rms = sum_square_ / (sample_count_ * kMaxSquaredLevel);
+    float rms = sum_square_ / (sample_count_ * kMaxSquaredLevel);
     // 20log_10(x^0.5) = 10log_10(x)
     rms = 10 * log10(rms);
     if (rms > 0)
@@ -69,18 +77,10 @@
   }
 
  private:
-  static double SumSquare(int16_t* data, int length) {
-    double sum_square = 0.0;
-    for (int i = 0; i < length; ++i) {
-      double data_d = static_cast<double>(data[i]);
-      sum_square += data_d * data_d;
-    }
-    return sum_square;
-  }
-
-  double sum_square_;
+  float sum_square_;
   int sample_count_;
 };
+
 }  // namespace
 
 LevelEstimatorImpl::LevelEstimatorImpl(const AudioProcessing* apm,
@@ -102,7 +102,7 @@
     return apm_->kNoError;
   }
 
-  int16_t* mixed_data = audio->data(0);
+  const int16_t* mixed_data = audio->data(0);
   if (audio->num_channels() > 1) {
     audio->CopyAndMix(1);
     mixed_data = audio->mixed_data(0);
diff --git a/webrtc/modules/audio_processing/voice_detection_impl.cc b/webrtc/modules/audio_processing/voice_detection_impl.cc
index 1d3d124..c6e497f 100644
--- a/webrtc/modules/audio_processing/voice_detection_impl.cc
+++ b/webrtc/modules/audio_processing/voice_detection_impl.cc
@@ -61,7 +61,7 @@
   }
   assert(audio->samples_per_split_channel() <= 160);
 
-  int16_t* mixed_data = audio->low_pass_split_data(0);
+  const int16_t* mixed_data = audio->low_pass_split_data(0);
   if (audio->num_channels() > 1) {
     audio->CopyAndMixLowPass(1);
     mixed_data = audio->mixed_low_pass_data(0);