Add a block based Audio FIFO.

media/base/audio_block_fifo.cc

Index: media/base/audio_block_fifo.cc
diff --git a/media/base/audio_block_fifo.cc b/media/base/audio_block_fifo.cc
new file mode 100644
index 0000000000000000000000000000000000000000..311a7d50e7578d69d87d3a4521ed44aea52f04f6
--- /dev/null
+++ b/media/base/audio_block_fifo.cc
@@ -0,0 +1,81 @@
+// Copyright 2014 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_block_fifo.h"
+
+#include "base/logging.h"
+
+namespace media {
+
+AudioBlockFifo::AudioBlockFifo(int channels, int frames, int blocks)
+    : block_frames_(frames),
+      write_pos_(0) {
+  // Create |blocks| of audio buses and push them to the containers.

[DaleCurtis, 2014/07/14 20:14:27]

Since you know the capacity, call audio_blocks_.reserve(blocks) here to avoid
unnecessary growth of the vector.

[no longer working on chromium, 2014/07/15 21:43:13]

Done.

+  for (int i = 0; i < blocks; ++i) {
+    scoped_ptr<AudioBus> audio_bus = AudioBus::Create(channels, frames);
+    audio_blocks_.push_back(audio_bus.release());
+    unfilled_blocks_.push(audio_blocks_.back());
+  }
+}
+
+AudioBlockFifo::~AudioBlockFifo() {}
+
+void AudioBlockFifo::Push(const void* source, int frames,

[DaleCurtis, 2014/07/14 20:14:27]

Is this actually allowed clang-format style? I thought only one parameter per
line.

[no longer working on chromium, 2014/07/15 21:43:13]

I saw both in the current chromium code, so I guess it is allowed.
Anyway, I changed it one param per line.

+                          int bytes_per_sample) {
+  DCHECK(source);
+  DCHECK_GT(frames, 0);
+  DCHECK_GT(bytes_per_sample, 0);
+
+  const uint8* source_ptr = static_cast<const uint8*>(source);
+  int frames_to_push = frames;
+  while (frames_to_push) {
+    // Get the current write block.
+    AudioBus* current_block = unfilled_blocks_.front();
+    CHECK(current_block);

[DaleCurtis, 2014/07/14 20:14:27]

Seems unnecessary?  Just add a DCHECK(!unfilled_blocks_.empty()) above.

[no longer working on chromium, 2014/07/15 21:43:13]

Done.

+    DCHECK_EQ(current_block->frames(), block_frames_);
+
+    // Figure out what segment sizes we need when adding the new content to
+    // the FIFO.
+    const int push_frames =
+        std::min(block_frames_ - write_pos_, frames_to_push);
+
+    // Deinterleave the content to the FIFO and update the |write_pos_|.
+    current_block->FromInterleaved(source_ptr, push_frames, bytes_per_sample);
+    write_pos_ = (write_pos_ + push_frames) % block_frames_;
+    if (!write_pos_) {
+      // The current block is completely filled, move it from |empety_blocks_|

[DaleCurtis, 2014/07/14 20:14:27]

empty_blocks_

[no longer working on chromium, 2014/07/15 21:43:12]

comment was updated.

+      // to |filled_blocks_|.
+      filled_blocks_.push(current_block);
+      unfilled_blocks_.pop();
+    }
+
+    source_ptr += push_frames * bytes_per_sample * current_block->channels();
+    frames_to_push -= push_frames;
+  }
+}
+
+const AudioBus* AudioBlockFifo::Consume() {
+  DCHECK(available_blocks());
+  AudioBus* audio_bus = filled_blocks_.front();
+  unfilled_blocks_.push(audio_bus);
+  filled_blocks_.pop();
+  return audio_bus;
+}
+
+void AudioBlockFifo::Clear() {
+  write_pos_ = 0;
+  while (!filled_blocks_.empty()) {
+    AudioBus* audio_bus = filled_blocks_.front();
+    unfilled_blocks_.push(audio_bus);
+    filled_blocks_.pop();
+  }
+}
+
+int AudioBlockFifo::unfilled_frames() const {
+  DCHECK_GE(static_cast<int>(unfilled_blocks_.size() * block_frames_),

[DaleCurtis, 2014/07/14 20:14:27]

Since you're making calculations here, this can't be a hacker_style method.  How
about GetUnfilledFrames or GetAvailableFrames()?

[no longer working on chromium, 2014/07/15 21:43:13]

GetUnfilledFrames() sounds good since available_blocks() is used to tell the
available blocks of data for consumption.

FYI, it seems frames() in audio_fifo.h is hacker_style but has implementation in
.cc:
https://code.google.com/p/chromium/codesearch#chromium/src/media/base/audio_f...

Do you want me to fix it as well?

+            write_pos_);
+  return unfilled_blocks_.size() * block_frames_ - write_pos_;
+}
+
+}  // namespace media