text: // 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.
  
  #ifndef MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
  #define MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
  
  #include <memory>
  
  #include "base/callback.h"
  #include "base/macros.h"
  #include "base/memory/ref_counted.h"
  #include "base/memory/weak_ptr.h"
  #include "base/time/time.h"
  #include "media/base/audio_decoder.h"
  #include "media/base/cdm_context.h"
  #include "media/base/decryptor.h"
  #include "media/base/demuxer_stream.h"
  
  namespace base {
  class SingleThreadTaskRunner;
  }
  
  namespace media {
  
  class AudioTimestampHelper;
  class DecoderBuffer;
  class Decryptor;
  class MediaLog;
  
  // Decryptor-based AudioDecoder implementation that can decrypt and decode
  // encrypted audio buffers and return decrypted and decompressed audio frames.
  // All public APIs and callbacks are trampolined to the |task_runner_| so
  // that no locks are required for thread safety.
  class MEDIA_EXPORT DecryptingAudioDecoder : public AudioDecoder {
   public:
    DecryptingAudioDecoder(
        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
        const scoped_refptr<MediaLog>& media_log,
        const base::Closure& waiting_for_decryption_key_cb);
    ~DecryptingAudioDecoder() override;
  
    // AudioDecoder implementation.
    std::string GetDisplayName() const override;
    void Initialize(const AudioDecoderConfig& config,
                    CdmContext* cdm_context,
                    const InitCB& init_cb,
                    const OutputCB& output_cb) override;
    void Decode(const scoped_refptr<DecoderBuffer>& buffer,
                const DecodeCB& decode_cb) override;
    void Reset(const base::Closure& closure) override;
  
   private:
    // For a detailed state diagram please see this link: http://goo.gl/8jAok
    // TODO(xhwang): Add a ASCII state diagram in this file after this class
    // stabilizes.
    // TODO(xhwang): Update this diagram for DecryptingAudioDecoder.
    enum State {
      kUninitialized = 0,
      kPendingDecoderInit,
      kIdle,
      kPendingDecode,
      kWaitingForKey,
      kDecodeFinished,
      kError
    };
  
    // Initializes the audio decoder on the |decryptor_| with |config_|.
    void InitializeDecoder();
  
    // Callback for Decryptor::InitializeAudioDecoder() during initialization.
    void FinishInitialization(bool success);
  
    void DecodePendingBuffer();
  
    // Callback for Decryptor::DecryptAndDecodeAudio().
    void DeliverFrame(int buffer_size,
                      Decryptor::Status status,
                      const Decryptor::AudioFrames& frames);
  
    // Callback for the |decryptor_| to notify this object that a new key has been
    // added.
    void OnKeyAdded();
  
    // Resets decoder and calls |reset_cb_|.
    void DoReset();
  
    // Sets timestamps for |frames| and then passes them to |output_cb_|.
    void ProcessDecodedFrames(const Decryptor::AudioFrames& frames);
  
    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  
    scoped_refptr<MediaLog> media_log_;
  
    State state_;
  
    InitCB init_cb_;
    OutputCB output_cb_;
    DecodeCB decode_cb_;
    base::Closure reset_cb_;
    base::Closure waiting_for_decryption_key_cb_;
  
    // The current decoder configuration.
    AudioDecoderConfig config_;
  
    Decryptor* decryptor_;
  
    // The buffer that needs decrypting/decoding.
    scoped_refptr<media::DecoderBuffer> pending_buffer_to_decode_;
  
    // Indicates the situation where new key is added during pending decode
    // (in other words, this variable can only be set in state kPendingDecode).
    // If this variable is true and kNoKey is returned then we need to try
    // decrypting/decoding again in case the newly added key is the correct
    // decryption key.
    bool key_added_while_decode_pending_;
  
    std::unique_ptr<AudioTimestampHelper> timestamp_helper_;
  
    base::WeakPtr<DecryptingAudioDecoder> weak_this_;
    base::WeakPtrFactory<DecryptingAudioDecoder> weak_factory_;
  
    DISALLOW_COPY_AND_ASSIGN(DecryptingAudioDecoder);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
  