1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "media/base/audio_pull_fifo.h"
6
7#include <algorithm>
8
9#include "base/logging.h"
10#include "media/base/audio_bus.h"
11
12namespace media {
13
14AudioPullFifo::AudioPullFifo(int channels, int frames, const ReadCB& read_cb)
15    : read_cb_(read_cb),
16      fifo_(AudioBus::Create(channels, frames)),
17      fifo_index_(frames) {}
18
19AudioPullFifo::~AudioPullFifo() {}
20
21void AudioPullFifo::Consume(AudioBus* destination, int frames_to_consume) {
22  DCHECK_LE(frames_to_consume, destination->frames());
23
24  int remaining_frames_to_provide = frames_to_consume;
25
26  // Try to fulfill the request using what's available in the FIFO.
27  int frames_read = ReadFromFifo(destination, remaining_frames_to_provide, 0);
28  int write_pos = frames_read;
29  remaining_frames_to_provide -= frames_read;
30
31  // Get the remaining audio frames from the producer using the callback.
32  while (remaining_frames_to_provide > 0) {
33    DCHECK_EQ(fifo_index_, fifo_->frames());
34    fifo_index_ = 0;
35
36    // Fill up the FIFO by acquiring audio data from the producer.
37    read_cb_.Run(write_pos, fifo_.get());
38
39    // Try to fulfill the request using what's available in the FIFO.
40    frames_read =
41        ReadFromFifo(destination, remaining_frames_to_provide, write_pos);
42    write_pos += frames_read;
43    remaining_frames_to_provide -= frames_read;
44  }
45}
46
47void AudioPullFifo::Clear() { fifo_index_ = fifo_->frames(); }
48
49int AudioPullFifo::ReadFromFifo(AudioBus* destination,
50                                int frames_to_provide,
51                                int write_pos) {
52  int frames = std::min(frames_to_provide, fifo_->frames() - fifo_index_);
53  if (frames <= 0)
54    return 0;
55
56  for (int ch = 0; ch < fifo_->channels(); ++ch) {
57    const float* src = fifo_->channel(ch) + fifo_index_;
58    float* dest = destination->channel(ch) + write_pos;
59    memcpy(dest, src, frames * sizeof(*src));
60  }
61
62  fifo_index_ += frames;
63  return frames;
64}
65
66}  // namespace media
67