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emumidi.h

/* 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.
 *
 * $URL$
 * $Id$
 */

#ifndef SOUND_SOFTSYNTH_EMUMIDI_H
#define SOUND_SOFTSYNTH_EMUMIDI_H

#include "audio/audiostream.h"
#include "audio/mididrv.h"
#include "audio/mixer.h"

#define FIXP_SHIFT 16

00034 class MidiDriver_Emulated : public Audio::AudioStream, public MidiDriver {
protected:
      bool _isOpen;
      Audio::Mixer *_mixer;
      Audio::SoundHandle _mixerSoundHandle;

private:
      Common::TimerManager::TimerProc _timerProc;
      void *_timerParam;

      int _nextTick;
      int _samplesPerTick;

protected:
      int _baseFreq;

      virtual void generateSamples(int16 *buf, int len) = 0;
      virtual void onTimer() {}

public:
      MidiDriver_Emulated(Audio::Mixer *mixer) :
            _mixer(mixer),
            _isOpen(false),
            _timerProc(0),
            _timerParam(0),
            _nextTick(0),
            _samplesPerTick(0),
            _baseFreq(250) {
      }

      // MidiDriver API
00065       virtual int open() {
            _isOpen = true;

            int d = getRate() / _baseFreq;
            int r = getRate() % _baseFreq;

            // This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
            // but less prone to arithmetic overflow.

            _samplesPerTick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / _baseFreq;

            return 0;
      }

00079       bool isOpen() const { return _isOpen; }

      virtual void setTimerCallback(void *timer_param, Common::TimerManager::TimerProc timer_proc) {
            _timerProc = timer_proc;
            _timerParam = timer_param;
      }

00086       virtual uint32 getBaseTempo() {
            return 1000000 / _baseFreq;
      }

      // AudioStream API
00091       virtual int readBuffer(int16 *data, const int numSamples) {
            const int stereoFactor = isStereo() ? 2 : 1;
            int len = numSamples / stereoFactor;
            int step;

            do {
                  step = len;
                  if (step > (_nextTick >> FIXP_SHIFT))
                        step = (_nextTick >> FIXP_SHIFT);

                  generateSamples(data, step);

                  _nextTick -= step << FIXP_SHIFT;
                  if (!(_nextTick >> FIXP_SHIFT)) {
                        if (_timerProc)
                              (*_timerProc)(_timerParam);

                        onTimer();

                        _nextTick += _samplesPerTick;
                  }

                  data += step * stereoFactor;
                  len -= step;
            } while (len);

            return numSamples;
      }

00120       virtual bool endOfData() const {
            return false;
      }
};

#endif

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