Introduce AudioBus to replace std::vector<float*>.

media/base/audio_bus.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_bus.h"
+
+#include <limits>
+
+#include "base/logging.h"
+#include "media/audio/audio_parameters.h"
+#include "media/base/limits.h"
+
+namespace media {
+
+// Ensure each channel is 16-byte aligned for easy SSE optimizations.
+static const int kChannelAlignment = 16;
+
+static inline bool IsAligned(void* ptr) {

[scherkus (not reviewing), 2012/08/07 02:51:16]

don't needlessly inline -- this is for a DCHECK() in run-once code and
furthermore only in the wrapping case

[DaleCurtis, 2012/08/07 18:29:45]

Done.

+  return (reinterpret_cast<uintptr_t>(ptr) & (kChannelAlignment - 1)) == 0U;
+}
+
+AudioBus::AudioBus(int channels, int frames)
+    : frames_(frames) {
+  // Sanity check values, use CHECK to prevent any overflow attempts.

[scherkus (not reviewing), 2012/08/07 02:51:16]

comment ain't needed

[DaleCurtis, 2012/08/07 18:29:45]

Done.

+  CHECK_GT(frames, 0);
+  CHECK_LE(frames, limits::kMaxSamplesPerPacket);
+  CHECK_GT(channels, 0);
+  CHECK_LE(channels, limits::kMaxChannels);
+  CHECK_LT(limits::kMaxSamplesPerPacket * limits::kMaxChannels,

[scherkus (not reviewing), 2012/08/07 02:51:16]

this CHECK seems redundant given:
 * kMaxSamplesPerPacket = 192000
 * kMaxChannels = 32

That brings us to 6144000, which is well under 2147483648!

[DaleCurtis, 2012/08/07 18:29:45]

Correct, but this part of the code doesn't know that; i.e., not checking this
means we assume those values will always multiply out to be less than INT_MAX.

No reason for it to be a CHECK vs DCHECK though.

+           std::numeric_limits<int>::max());
+
+  // Choose a size such that each channel is aligned by kChannelAlignment.
+  int aligned_frames =
+      (frames_ + kChannelAlignment - 1) & ~(kChannelAlignment - 1);
+  data_size_ = sizeof(float) * channels * aligned_frames;
+
+  data_.reset(static_cast<float*>(base::AlignedAlloc(
+      data_size_, kChannelAlignment)));
+
+  // Separate audio data out into channels for easy lookup later.
+  channel_data_.reserve(channels);
+  for (int i = 0; i < channels; ++i)
+    channel_data_.push_back(data_.get() + i * aligned_frames);
+}
+
+AudioBus::AudioBus(int frames, const std::vector<float*>& channel_data)
+    : data_size_(0),
+      channel_data_(channel_data),
+      frames_(frames) {
+  // Sanity check wrapped vector for alignment and channel count.
+  for (size_t i = 0; i < channel_data_.size(); ++i)
+    DCHECK(IsAligned(channel_data_[i]));
+}
+
+AudioBus::~AudioBus() {}
+
+scoped_ptr<AudioBus> AudioBus::Create(int channels, int frames) {
+  return scoped_ptr<AudioBus>(new AudioBus(channels, frames));
+}
+
+scoped_ptr<AudioBus> AudioBus::Create(const AudioParameters& params) {
+  return scoped_ptr<AudioBus>(new AudioBus(
+      params.channels(), params.frames_per_buffer()));
+}
+
+scoped_ptr<AudioBus> AudioBus::WrapVector(
+    int frames, const std::vector<float*>& channel_data) {
+  return scoped_ptr<AudioBus>(new AudioBus(frames, channel_data));
+}
+
+void* AudioBus::data() const {
+  DCHECK(data_.get());
+  return data_.get();
+}
+
+int AudioBus::data_size() const {
+  DCHECK(data_.get());
+  return data_size_;
+}
+
+void AudioBus::ZeroFrames(int frames) const {
+  DCHECK_LE(frames, frames_);
+  for (size_t i = 0; i < channel_data_.size(); ++i)
+    memset(channel_data_[i], 0, frames * sizeof(*channel_data_[i]));
+}
+
+}  // namespace media