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/* ScummVM - Scumm Interpreter
* Copyright (C) 2001-2006 The ScummVM project
*
* 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.
*
* $Header$
*/
#include "common/stdafx.h"
#include "sound/audiostream.h"
#include "sound/mididrv.h"
#include "sound/mixer.h"
#define FIXP_SHIFT 16
class MidiDriver_Emulated : public AudioStream, public MidiDriver {
protected:
bool _isOpen;
Audio::Mixer *_mixer;
private:
Common::Timer::TimerProc _timerProc;
void *_timerParam;
int _nextTick;
int _samplesPerTick;
protected:
virtual void generateSamples(int16 *buf, int len) = 0;
virtual void onTimer() {}
int _baseFreq;
public:
MidiDriver_Emulated(Audio::Mixer *mixer) : _mixer(mixer) {
_isOpen = false;
_timerProc = 0;
_timerParam = 0;
_nextTick = 0;
_samplesPerTick = 0;
_baseFreq = 250;
}
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;
}
void setTimerCallback(void *timer_param, Common::Timer::TimerProc timer_proc) {
_timerProc = timer_proc;
_timerParam = timer_param;
}
uint32 getBaseTempo() { return 1000000 / _baseFreq; }
// AudioStream API
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;
}
bool endOfData() const { return false; }
};
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