mirror of
https://github.com/libretro/scummvm.git
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112 lines
2.7 KiB
C++
112 lines
2.7 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*/
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#include "sound/audiostream.h"
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#include "sound/mididrv.h"
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#include "sound/mixer.h"
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#define FIXP_SHIFT 16
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class MidiDriver_Emulated : public Audio::AudioStream, public MidiDriver {
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protected:
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bool _isOpen;
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Audio::Mixer *_mixer;
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Audio::SoundHandle _mixerSoundHandle;
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private:
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Common::TimerManager::TimerProc _timerProc;
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void *_timerParam;
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int _nextTick;
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int _samplesPerTick;
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protected:
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virtual void generateSamples(int16 *buf, int len) = 0;
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virtual void onTimer() {}
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int _baseFreq;
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public:
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MidiDriver_Emulated(Audio::Mixer *mixer) : _mixer(mixer) {
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_isOpen = false;
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_timerProc = 0;
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_timerParam = 0;
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_nextTick = 0;
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_samplesPerTick = 0;
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_baseFreq = 250;
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}
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int open() {
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_isOpen = true;
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int d = getRate() / _baseFreq;
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int r = getRate() % _baseFreq;
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// This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
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// but less prone to arithmetic overflow.
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_samplesPerTick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / _baseFreq;
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return 0;
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}
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void setTimerCallback(void *timer_param, Common::TimerManager::TimerProc timer_proc) {
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_timerProc = timer_proc;
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_timerParam = timer_param;
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}
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uint32 getBaseTempo() { return 1000000 / _baseFreq; }
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// AudioStream API
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int readBuffer(int16 *data, const int numSamples) {
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const int stereoFactor = isStereo() ? 2 : 1;
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int len = numSamples / stereoFactor;
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int step;
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do {
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step = len;
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if (step > (_nextTick >> FIXP_SHIFT))
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step = (_nextTick >> FIXP_SHIFT);
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generateSamples(data, step);
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_nextTick -= step << FIXP_SHIFT;
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if (!(_nextTick >> FIXP_SHIFT)) {
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if (_timerProc)
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(*_timerProc)(_timerParam);
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onTimer();
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_nextTick += _samplesPerTick;
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}
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data += step * stereoFactor;
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len -= step;
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} while (len);
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return numSamples;
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}
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bool endOfData() const { return false; }
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};
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