text: // 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.
  
  #ifndef MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_
  #define MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_
  
  #include <stdint.h>
  
  #include <memory>
  #include <set>
  #include <vector>
  
  #include "base/callback.h"
  #include "base/macros.h"
  #include "media/base/audio_decoder_config.h"
  #include "media/base/audio_timestamp_helper.h"
  #include "media/base/bit_reader.h"
  #include "media/base/byte_queue.h"
  #include "media/base/media_export.h"
  #include "media/base/stream_parser.h"
  
  namespace media {
  
  class MEDIA_EXPORT MPEGAudioStreamParserBase : public StreamParser {
   public:
    // |start_code_mask| is used to find the start of each frame header.  Also
    // referred to as the sync code in the MP3 and ADTS header specifications.
    // |codec_delay| is the number of samples the decoder will output before the
    // first real frame.
    MPEGAudioStreamParserBase(uint32_t start_code_mask,
                              AudioCodec audio_codec,
                              int codec_delay);
    ~MPEGAudioStreamParserBase() override;
  
    // StreamParser implementation.
    void Init(const InitCB& init_cb,
              const NewConfigCB& config_cb,
              const NewBuffersCB& new_buffers_cb,
              bool ignore_text_tracks,
              const EncryptedMediaInitDataCB& encrypted_media_init_data_cb,
              const NewMediaSegmentCB& new_segment_cb,
              const EndMediaSegmentCB& end_of_segment_cb,
              const scoped_refptr<MediaLog>& media_log) override;
    void Flush() override;
    bool Parse(const uint8_t* buf, int size) override;
  
   protected:
    // Subclasses implement this method to parse format specific frame headers.
    // |data| & |size| describe the data available for parsing.
    //
    // Implementations are expected to consume an entire frame header.  It should
    // only return a value greater than 0 when |data| has enough bytes to
    // successfully parse & consume the entire frame header.
    //
    // |frame_size| - Required parameter that is set to the size of the frame, in
    // bytes, including the frame header if the function returns a value > 0.
    // |sample_rate| - Optional parameter that is set to the sample rate
    // of the frame if this function returns a value > 0.
    // |channel_layout| - Optional parameter that is set to the channel_layout
    // of the frame if this function returns a value > 0.
    // |sample_count| - Optional parameter that is set to the number of samples
    // in the frame if this function returns a value > 0.
    // |metadata_frame| - Optional parameter that is set to true if the frame has
    // valid values for the above parameters, but no usable encoded data; only set
    // to true if this function returns a value > 0.
    //
    // |sample_rate|, |channel_layout|, |sample_count|, |metadata_frame| may be
    // NULL if the caller is not interested in receiving these values from the
    // frame header.
    //
    // If |metadata_frame| is true, the MPEGAudioStreamParserBase will discard the
    // frame after consuming the metadata values above.
    //
    // Returns:
    // > 0 : The number of bytes parsed.
    //   0 : If more data is needed to parse the entire frame header.
    // < 0 : An error was encountered during parsing.
    virtual int ParseFrameHeader(const uint8_t* data,
                                 int size,
                                 int* frame_size,
                                 int* sample_rate,
                                 ChannelLayout* channel_layout,
                                 int* sample_count,
                                 bool* metadata_frame) const = 0;
  
    const scoped_refptr<MediaLog>& media_log() const { return media_log_; }
  
   private:
    enum State {
      UNINITIALIZED,
      INITIALIZED,
      PARSE_ERROR
    };
  
    void ChangeState(State state);
  
    // Parsing functions for various byte stream elements.  |data| & |size|
    // describe the data available for parsing.
    //
    // Returns:
    // > 0 : The number of bytes parsed.
    //   0 : If more data is needed to parse the entire element.
    // < 0 : An error was encountered during parsing.
    int ParseFrame(const uint8_t* data, int size, BufferQueue* buffers);
    int ParseIcecastHeader(const uint8_t* data, int size);
    int ParseID3v1(const uint8_t* data, int size);
    int ParseID3v2(const uint8_t* data, int size);
  
    // Parses an ID3v2 "sync safe" integer.
    // |reader| - A BitReader to read from.
    // |value| - Set to the integer value read, if true is returned.
    //
    // Returns true if the integer was successfully parsed and |value|
    // was set.
    // Returns false if an error was encountered. The state of |value| is
    // undefined when false is returned.
    bool ParseSyncSafeInt(BitReader* reader, int32_t* value);
  
    // Scans |data| for the next valid start code.
    // Returns:
    // > 0 : The number of bytes that should be skipped to reach the
    //       next start code..
    //   0 : If a valid start code was not found and more data is needed.
    // < 0 : An error was encountered during parsing.
    int FindNextValidStartCode(const uint8_t* data, int size) const;
  
    // Sends the buffers in |buffers| to |new_buffers_cb_| and then clears
    // |buffers|.
    // If |end_of_segment| is set to true, then |end_of_segment_cb_| is called
    // after |new_buffers_cb_| to signal that these buffers represent the end of a
    // media segment.
    // Returns true if the buffers are sent successfully.
    bool SendBuffers(BufferQueue* buffers, bool end_of_segment);
  
    State state_;
  
    InitCB init_cb_;
    NewConfigCB config_cb_;
    NewBuffersCB new_buffers_cb_;
    NewMediaSegmentCB new_segment_cb_;
    EndMediaSegmentCB end_of_segment_cb_;
    scoped_refptr<MediaLog> media_log_;
  
    ByteQueue queue_;
  
    AudioDecoderConfig config_;
    std::unique_ptr<AudioTimestampHelper> timestamp_helper_;
    bool in_media_segment_;
    const uint32_t start_code_mask_;
    const AudioCodec audio_codec_;
    const int codec_delay_;
  
    DISALLOW_COPY_AND_ASSIGN(MPEGAudioStreamParserBase);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_
  