Remove extra memcpys from AudioPullFifo.

media/base/audio_pull_fifo.cc

Index: media/base/audio_pull_fifo.cc
diff --git a/media/base/audio_pull_fifo.cc b/media/base/audio_pull_fifo.cc
index 4943591b7c2cdd30c1b499b17250a083eb3654f9..cf25142d904f588d11164db363df4d0568ef0757 100644
--- a/media/base/audio_pull_fifo.cc
+++ b/media/base/audio_pull_fifo.cc
@@ -7,53 +7,60 @@
 #include <algorithm>
 
 #include "base/logging.h"
+#include "media/base/audio_bus.h"
 
 namespace media {
 
 AudioPullFifo::AudioPullFifo(int channels, int frames, const ReadCB& read_cb)
-    : read_cb_(read_cb) {
-  fifo_.reset(new AudioFifo(channels, frames));
-  bus_ = AudioBus::Create(channels, frames);
-}
+    : read_cb_(read_cb),
+      fifo_(AudioBus::Create(channels, frames)),
+      fifo_index_(frames) {}
 
-AudioPullFifo::~AudioPullFifo() {
-  read_cb_.Reset();
-}
+AudioPullFifo::~AudioPullFifo() {}
 
 void AudioPullFifo::Consume(AudioBus* destination, int frames_to_consume) {
-  DCHECK(destination);
   DCHECK_LE(frames_to_consume, destination->frames());
 
-  int write_pos = 0;
   int remaining_frames_to_provide = frames_to_consume;
 
   // Try to fulfill the request using what's available in the FIFO.
-  ReadFromFifo(destination, &remaining_frames_to_provide, &write_pos);
+  int frames_read = ReadFromFifo(destination, remaining_frames_to_provide, 0);
+  int write_pos = frames_read;
+  remaining_frames_to_provide -= frames_read;
 
   // Get the remaining audio frames from the producer using the callback.
   while (remaining_frames_to_provide > 0) {
+    DCHECK_EQ(fifo_index_, fifo_->frames());
+    fifo_index_ = 0;
+
     // Fill up the FIFO by acquiring audio data from the producer.
-    read_cb_.Run(write_pos, bus_.get());
-    fifo_->Push(bus_.get());
+    read_cb_.Run(write_pos, fifo_.get());
 
     // Try to fulfill the request using what's available in the FIFO.
-    ReadFromFifo(destination, &remaining_frames_to_provide, &write_pos);
+    frames_read =
+        ReadFromFifo(destination, remaining_frames_to_provide, write_pos);
+    write_pos += frames_read;
+    remaining_frames_to_provide -= frames_read;
   }
 }
 
-void AudioPullFifo::Clear() {
-  fifo_->Clear();
-}
+void AudioPullFifo::Clear() { fifo_index_ = fifo_->frames(); }
+
+int AudioPullFifo::ReadFromFifo(AudioBus* destination,
+                                int frames_to_provide,
+                                int write_pos) {
+  int frames = std::min(frames_to_provide, fifo_->frames() - fifo_index_);
+  if (frames <= 0)
+    return 0;
+
+  for (int ch = 0; ch < fifo_->channels(); ++ch) {
+    const float* src = fifo_->channel(ch) + fifo_index_;
+    float* dest = destination->channel(ch) + write_pos;
+    memcpy(dest, src, frames * sizeof(*src));
+  }
 
-void AudioPullFifo::ReadFromFifo(AudioBus* destination,
-                                 int* frames_to_provide,
-                                 int* write_pos) {
-  DCHECK(frames_to_provide);
-  DCHECK(write_pos);
-  int frames = std::min(fifo_->frames(), *frames_to_provide);
-  fifo_->Consume(destination, *write_pos, frames);
-  *write_pos += frames;
-  *frames_to_provide -= frames;
+  fifo_index_ += frames;
+  return frames;
 }
 
 }  // namespace media