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doublebuffersdl-mixer.cpp

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL$
 * $Id$
 *
 */

#if defined(MACOSX) || defined(GP2X) || defined(CAANOO) || defined(GP2XWIZ)

#include "backends/mixer/doublebuffersdl/doublebuffersdl-mixer.h"

DoubleBufferSDLMixerManager::DoubleBufferSDLMixerManager()
      :
      _soundMutex(0), _soundCond(0), _soundThread(0),
      _soundThreadIsRunning(false), _soundThreadShouldQuit(false) {
      
}

DoubleBufferSDLMixerManager::~DoubleBufferSDLMixerManager() {
      deinitThreadedMixer();
}

void DoubleBufferSDLMixerManager::startAudio() {
      _soundThreadIsRunning = false;
      _soundThreadShouldQuit = false;

      // Create mutex and condition variable
      _soundMutex = SDL_CreateMutex();
      _soundCond = SDL_CreateCond();

      // Create two sound buffers
      _activeSoundBuf = 0;
      uint bufSize = _obtainedRate.samples * 4;
      _soundBufSize = bufSize;
      _soundBuffers[0] = (byte *)calloc(1, bufSize);
      _soundBuffers[1] = (byte *)calloc(1, bufSize);

      _soundThreadIsRunning = true;

      // Finally start the thread
      _soundThread = SDL_CreateThread(mixerProducerThreadEntry, this);

      SdlMixerManager::startAudio();
}

void DoubleBufferSDLMixerManager::mixerProducerThread() {
      byte nextSoundBuffer;

      SDL_LockMutex(_soundMutex);
      while (true) {
            // Wait till we are allowed to produce data
            SDL_CondWait(_soundCond, _soundMutex);

            if (_soundThreadShouldQuit)
                  break;

            // Generate samples and put them into the next buffer
            nextSoundBuffer = _activeSoundBuf ^ 1;
            _mixer->mixCallback(_soundBuffers[nextSoundBuffer], _soundBufSize);

            // Swap buffers
            _activeSoundBuf = nextSoundBuffer;
      }
      SDL_UnlockMutex(_soundMutex);
}

int SDLCALL DoubleBufferSDLMixerManager::mixerProducerThreadEntry(void *arg) {
      DoubleBufferSDLMixerManager *mixer = (DoubleBufferSDLMixerManager *)arg;
      assert(mixer);
      mixer->mixerProducerThread();
      return 0;
}

void DoubleBufferSDLMixerManager::deinitThreadedMixer() {
      // Kill thread?? _soundThread

      if (_soundThreadIsRunning) {
            // Signal the producer thread to end, and wait for it to actually finish.
            _soundThreadShouldQuit = true;
            SDL_CondBroadcast(_soundCond);
            SDL_WaitThread(_soundThread, NULL);

            // Kill the mutex & cond variables.
            // Attention: AT this point, the mixer callback must not be running
            // anymore, else we will crash!
            SDL_DestroyMutex(_soundMutex);
            SDL_DestroyCond(_soundCond);

            _soundThreadIsRunning = false;

            free(_soundBuffers[0]);
            free(_soundBuffers[1]);
      }
}

void DoubleBufferSDLMixerManager::callbackHandler(byte *samples, int len) {
      assert(_mixer);
      assert((int)_soundBufSize == len);

      // Lock mutex, to ensure our data is not overwritten by the producer thread
      SDL_LockMutex(_soundMutex);

      // Copy data from the current sound buffer
      memcpy(samples, _soundBuffers[_activeSoundBuf], len);

      // Unlock mutex and wake up the produced thread
      SDL_UnlockMutex(_soundMutex);
      SDL_CondSignal(_soundCond);
}

#endif

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