components/speech/audio_buffer.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SPEECH_AUDIO_BUFFER_H_
#define COMPONENTS_SPEECH_AUDIO_BUFFER_H_

#include <stddef.h>
#include <stdint.h>

#include <string>

#include "base/compiler_specific.h"
#include "base/containers/circular_deque.h"
#include "base/memory/aligned_memory.h"
#include "base/memory/ref_counted.h"

// Models a chunk derived from an AudioBuffer.
class AudioChunk : public base::RefCountedThreadSafe<AudioChunk> {
 public:
  explicit AudioChunk(int bytes_per_sample);
  // Creates a chunk of |length| bytes, initialized to zeros.
  AudioChunk(size_t length, int bytes_per_sample);
  AudioChunk(const uint8_t* data, size_t length, int bytes_per_sample);
  AudioChunk(base::span<const uint8_t> data_span, int bytes_per_sample);

  AudioChunk(const AudioChunk&) = delete;
  AudioChunk& operator=(const AudioChunk&) = delete;

  bool IsEmpty() const;
  int bytes_per_sample() const { return bytes_per_sample_; }
  std::string_view AsStringView() const LIFETIME_BOUND;

  // DEPRECATED: Use AsStringView() or spanified accessors instead, as this
  // incurs a copy.
  // TODO(crbug.com/484089981): Internal code depends on this method to create a
  // copy of the returned string. Delete it once internal code has switched to
  // `AsStringView()` instead.
  std::string AsString();

  size_t NumSamples() const;
  int16_t GetSample16(size_t index) const;
  base::span<const int16_t> SamplesData16AsSpan() const;
  base::span<int16_t> SamplesData16AsWriteableSpan();

  // Guaranteed to be aligned to `bytes_per_sample_`.
  base::span<const uint8_t> data() const { return data_; }
  base::span<uint8_t> writable_data() { return data_; }

 private:
  friend class base::RefCountedThreadSafe<AudioChunk>;
  ~AudioChunk();

  base::AlignedHeapArray<uint8_t> data_;
  const int bytes_per_sample_;
};

// Models an audio buffer. The current implementation relies on on-demand
// allocations of AudioChunk(s) (which uses a string as storage).
class AudioBuffer {
 public:
  explicit AudioBuffer(int bytes_per_sample);

  AudioBuffer(const AudioBuffer&) = delete;
  AudioBuffer& operator=(const AudioBuffer&) = delete;

  ~AudioBuffer();

  // Enqueues a copy of |length| bytes of |data| buffer.
  void Enqueue(const uint8_t* data, size_t length);

  // Dequeues, in FIFO order, a single chunk respecting the length of the
  // corresponding Enqueue call (in a nutshell: multiple Enqueue calls followed
  // by DequeueSingleChunk calls will return the individual chunks without
  // merging them).
  scoped_refptr<AudioChunk> DequeueSingleChunk();

  // Dequeues all previously enqueued chunks, merging them in a single chunk.
  scoped_refptr<AudioChunk> DequeueAll();

  // Removes and frees all the enqueued chunks.
  void Clear();

  // Checks whether the buffer is empty.
  bool IsEmpty() const;

 private:
  using ChunksContainer = base::circular_deque<scoped_refptr<AudioChunk>>;
  ChunksContainer chunks_;
  const int bytes_per_sample_;
};

#endif  // COMPONENTS_SPEECH_AUDIO_BUFFER_H_