Add a block based Audio FIFO.

media/base/audio_fifo.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/audio_fifo.h"
 
 #include "base/logging.h"
 
 namespace media {
 
-// Given current position in the FIFO, the maximum number of elements in the
-// FIFO and the size of the input; this method provides two output results:
-// |size| and |wrap_size|. These two results can then be utilized for memcopy
-// operations to and from the FIFO.
-// Under "normal" circumstances, |size| will be equal to |in_size| and
-// |wrap_size| will be zero. This case corresponding to the non-wrapping case
-// where we have not yet reached the "edge" of the FIFO. If |pos| + |in_size|
-// exceeds the total size of the FIFO, we must wrap around and start reusing
-// a part the allocated memory. The size of this part is given by |wrap_size|.
-static void GetSizes(
-    int pos, int max_size, int in_size, int* size, int* wrap_size) {
+AudioFifo::AudioFifo(int channels, int frames)
+    : audio_bus_(AudioBus::Create(channels, frames)),
+      max_frames_(frames),
+      frames_pushed_(0),
+      frames_consumed_(0),
+      read_pos_(0),
+      write_pos_(0) {}
+
+AudioFifo::~AudioFifo() {}
+
+// static.
+void AudioFifo::GetSizes(int pos, int max_size, int in_size,
+                         int* size, int* wrap_size) {
   if (pos + in_size > max_size) {
     // Wrapping is required => derive size of each segment.
     *size = max_size - pos;
     *wrap_size = in_size - *size;
   } else {
     // Wrapping is not required.
     *size = in_size;
     *wrap_size = 0;
   }
 }
 
-// Updates the read/write position with |step| modulo the maximum number of
-// elements in the FIFO to ensure that the position counters wraps around at
-// the endpoint.
-static int UpdatePos(int pos, int step, int max_size) {
+// static.
+int AudioFifo::UpdatePos(int pos, int step, int max_size) {
   return ((pos + step) % max_size);
 }
 
-AudioFifo::AudioFifo(int channels, int frames)
-    : audio_bus_(AudioBus::Create(channels, frames)),
-      max_frames_(frames),
-      frames_pushed_(0),
-      frames_consumed_(0),
-      read_pos_(0),
-      write_pos_(0) {}
-
-AudioFifo::~AudioFifo() {}
-
 int AudioFifo::frames() const {
   int delta = frames_pushed_ - frames_consumed_;
   return delta;
 }
 
 void AudioFifo::Push(const AudioBus* source) {
   DCHECK(source);
   DCHECK_EQ(source->channels(), audio_bus_->channels());
 
   // Ensure that there is space for the new data in the FIFO.
@@ skipping 64 matching lines @@
 }
 
 void AudioFifo::Clear() {
   frames_pushed_ = 0;
   frames_consumed_ = 0;
   read_pos_ = 0;
   write_pos_ = 0;
 }
 
 }  // namespace media