Initial commit

audio/softsynth/emumidi.h

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+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef AUDIO_SOFTSYNTH_EMUMIDI_H
+#define AUDIO_SOFTSYNTH_EMUMIDI_H
+
+#include "audio/audiostream.h"
+#include "audio/mididrv.h"
+#include "audio/mixer.h"
+
+class MidiDriver_Emulated : public Audio::AudioStream, public MidiDriver {
+protected:
+	bool _isOpen;
+	Audio::Mixer *_mixer;
+	Audio::SoundHandle _mixerSoundHandle;
+
+private:
+	Common::TimerManager::TimerProc _timerProc;
+	void *_timerParam;
+
+	enum {
+		FIXP_SHIFT = 16
+	};
+
+	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
+	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;
+	}
+
+	bool isOpen() const { return _isOpen; }
+
+	virtual void setTimerCallback(void *timer_param, Common::TimerManager::TimerProc timer_proc) {
+		_timerProc = timer_proc;
+		_timerParam = timer_param;
+	}
+
+	virtual uint32 getBaseTempo() {
+		return 1000000 / _baseFreq;
+	}
+
+	// AudioStream API
+	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;
+	}
+
+	virtual bool endOfData() const {
+		return false;
+	}
+};
+
+#endif