text: //////////////////////////////////////////////////////////////////////////////
  //
  // Copyright (c) 2004-2019 musikcube team
  //
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are met:
  //
  //    * Redistributions of source code must retain the above copyright notice,
  //      this list of conditions and the following disclaimer.
  //
  //    * Redistributions in binary form must reproduce the above copyright
  //      notice, this list of conditions and the following disclaimer in the
  //      documentation and/or other materials provided with the distribution.
  //
  //    * Neither the name of the author nor the names of other contributors may
  //      be used to endorse or promote products derived from this software
  //      without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  // POSSIBILITY OF SUCH DAMAGE.
  //
  //////////////////////////////////////////////////////////////////////////////
  
  #include <core/musikcore_c.h>
  #include <core/runtime/MessageQueue.h>
  #include <core/library/LibraryFactory.h>
  #include <core/audio/PlaybackService.h>
  #include <core/library/LocalMetadataProxy.h>
  #include <core/library/IIndexer.h>
  
  #include <string>
  #include <thread>
  #include <set>
  
  using namespace musik;
  using namespace musik::core;
  using namespace musik::core::db::local;
  using namespace musik::core::audio;
  using namespace musik::core::sdk;
  using namespace musik::core::runtime;
  
  class mcsdk_context_message_queue: public MessageQueue {
      public:
          mcsdk_context_message_queue();
          virtual ~mcsdk_context_message_queue();
          void Quit();
          void Run();
      private:
          using LockT = std::unique_lock<std::mutex>;
          bool quit;
          std::mutex mutex;
  };
  
  struct mcsdk_context_internal {
      mcsdk_context_message_queue message_queue;
      std::thread thread;
      ILibraryPtr library;
      LocalMetadataProxy* metadata;
      PlaybackService* playback;
      std::shared_ptr<Preferences> preferences;
  };
  
  struct mcsdk_svc_indexer_callback_proxy;
  
  struct mcsdk_svc_indexer_context_internal {
      IIndexer* indexer;
      mcsdk_svc_indexer_callback_proxy* callback_proxy;
      std::set<mcsdk_svc_indexer_callbacks*> callbacks;
  };
  
  struct mcsdk_player_context_internal {
      Player::EventListener* event_listener;
      std::shared_ptr<IOutput> output;
      std::mutex event_mutex;
      std::condition_variable finished_condition;
      Player* player;
      bool player_finished;
  };