emumidi.h

/* 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