1 /* ScummVM - Graphic Adventure Engine
2  *
3  * ScummVM is the legal property of its developers, whose names
4  * are too numerous to list here. Please refer to the COPYRIGHT
5  * file distributed with this source distribution.
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version 2
10  * of the License, or (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20  *
21  */
22 
23 #ifndef AUDIO_SOFTSYNTH_EMUMIDI_H
24 #define AUDIO_SOFTSYNTH_EMUMIDI_H
25 
26 #include "audio/audiostream.h"
27 #include "audio/mididrv.h"
28 #include "audio/mixer.h"
29 
30 class MidiDriver_Emulated : public Audio::AudioStream, public MidiDriver {
31 protected:
32 	bool _isOpen;
33 	Audio::Mixer *_mixer;
34 	Audio::SoundHandle _mixerSoundHandle;
35 
36 private:
37 	Common::TimerManager::TimerProc _timerProc;
38 	void *_timerParam;
39 
40 	enum {
41 		FIXP_SHIFT = 16
42 	};
43 
44 	int _nextTick;
45 	int _samplesPerTick;
46 
47 protected:
48 	int _baseFreq;
49 
50 	virtual void generateSamples(int16 *buf, int len) = 0;
onTimer()51 	virtual void onTimer() {}
52 
53 public:
MidiDriver_Emulated(Audio::Mixer * mixer)54 	MidiDriver_Emulated(Audio::Mixer *mixer) :
55 		_mixer(mixer),
56 		_isOpen(false),
57 		_timerProc(0),
58 		_timerParam(0),
59 		_nextTick(0),
60 		_samplesPerTick(0),
61 		_baseFreq(250) {
62 	}
63 
64 	// MidiDriver API
open()65 	virtual int open() {
66 		_isOpen = true;
67 
68 		int d = getRate() / _baseFreq;
69 		int r = getRate() % _baseFreq;
70 
71 		// This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
72 		// but less prone to arithmetic overflow.
73 
74 		_samplesPerTick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / _baseFreq;
75 
76 		return 0;
77 	}
78 
isOpen()79 	bool isOpen() const { return _isOpen; }
80 
setTimerCallback(void * timer_param,Common::TimerManager::TimerProc timer_proc)81 	virtual void setTimerCallback(void *timer_param, Common::TimerManager::TimerProc timer_proc) {
82 		_timerProc = timer_proc;
83 		_timerParam = timer_param;
84 	}
85 
getBaseTempo()86 	virtual uint32 getBaseTempo() {
87 		return 1000000 / _baseFreq;
88 	}
89 
90 	// AudioStream API
readBuffer(int16 * data,const int numSamples)91 	virtual int readBuffer(int16 *data, const int numSamples) {
92 		const int stereoFactor = isStereo() ? 2 : 1;
93 		int len = numSamples / stereoFactor;
94 		int step;
95 
96 		do {
97 			step = len;
98 			if (step > (_nextTick >> FIXP_SHIFT))
99 				step = (_nextTick >> FIXP_SHIFT);
100 
101 			generateSamples(data, step);
102 
103 			_nextTick -= step << FIXP_SHIFT;
104 			if (!(_nextTick >> FIXP_SHIFT)) {
105 				if (_timerProc)
106 					(*_timerProc)(_timerParam);
107 
108 				onTimer();
109 
110 				_nextTick += _samplesPerTick;
111 			}
112 
113 			data += step * stereoFactor;
114 			len -= step;
115 		} while (len);
116 
117 		return numSamples;
118 	}
119 
endOfData()120 	virtual bool endOfData() const {
121 		return false;
122 	}
123 };
124 
125 #endif
126