added MidiDriver_Emulated base class used by the adlib & ym2612 midi 'drivers'

svn-id: r15589

1 files changed, 96 insertions, 0 deletions

diff --git a/backends/midi/emumidi.h b/backends/midi/emumidi.h
new file mode 100644
index 0000000000..e5daa40647
--- /dev/null
+++ b/backends/midi/emumidi.h
@@ -0,0 +1,96 @@
+/* ScummVM - Scumm Interpreter
+ * Copyright (C) 2001-2004 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ * $Header$
+ */
+
+#include "stdafx.h"
+#include "sound/audiostream.h"
+#include "sound/mididrv.h"
+#include "sound/mixer.h"
+
+#define BASE_FREQ 250
+#define FIXP_SHIFT 16
+
+class MidiDriver_Emulated : public AudioStream, public MidiDriver {
+protected:
+	bool _isOpen;
+	SoundMixer *_mixer;
+
+private:
+	Timer::TimerProc _timer_proc;
+	void *_timer_param;
+
+	int _next_tick;
+	int _samples_per_tick;
+
+protected:
+	virtual void generate_samples(int16 *buf, int len) = 0;
+
+public:
+	MidiDriver_Emulated(SoundMixer *mixer) : _mixer(mixer) {
+		_isOpen = false;
+	
+		_timer_proc = 0;
+		_timer_param = 0;
+	
+		_next_tick = 0;
+		_samples_per_tick = 0;
+	}
+
+	int open() {
+		_isOpen = true;
+		_samples_per_tick = (getRate() << FIXP_SHIFT) / BASE_FREQ;
+	}
+
+	void setTimerCallback(void *timer_param, Timer::TimerProc timer_proc) {
+		_timer_proc = timer_proc;
+		_timer_param = timer_param;
+	}
+
+	uint32 getBaseTempo() { return 1000000 / BASE_FREQ; }
+
+
+	// 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 > (_next_tick >> FIXP_SHIFT))
+				step = (_next_tick >> FIXP_SHIFT);
+			generate_samples(data, step);
+	
+			_next_tick -= step << FIXP_SHIFT;
+			if (!(_next_tick >> FIXP_SHIFT)) {
+				if (_timer_proc)
+					(*_timer_proc)(_timer_param);
+				_next_tick += _samples_per_tick;
+			}
+			data += step * stereoFactor;
+			len -= step;
+		} while (len);
+
+		return numSamples;
+	}
+	int16 read() {
+		error("ProcInputStream::read not supported");
+	}
+	bool endOfData() const { return false; }
+};