/*

 * GUSEMU32 - mixing engine (similar to Interwave GF1 compatibility)

 *

 * Copyright (C) 2000-2007 Tibor "TS" Schütz

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "gusemu.h"

#include "gustate.h"

#define GUSregb(position)  (*            (gusptr+(position)))

#define GUSregw(position)  (*(GUSword *) (gusptr+(position)))

#define GUSregd(position)  (*(GUSdword *)(gusptr+(position)))

#define GUSvoice(position) (*(GUSword *)(voiceptr+(position)))

/* samples are always 16bit stereo (4 bytes each, first right then left interleaved) */

void gus_mixvoices(GUSEmuState * state, unsigned int playback_freq, unsigned int numsamples,

                   GUSsample *bufferpos)

{

    /* note that byte registers are stored in the upper half of each voice register! */

    GUSbyte        *gusptr;

    int             Voice;

    GUSword        *voiceptr;

    unsigned int    count;

    for (count = 0; count < numsamples * 2; count++)

        *(bufferpos + count) = 0;       /* clear */

    gusptr = state->gusdatapos;

    voiceptr = (GUSword *) gusptr;

    if (!(GUSregb(GUS4cReset) & 0x01))  /* reset flag active? */

        return;

    for (Voice = 0; Voice <= (GUSregb(NumVoices) & 31); Voice++)

    {

        if (GUSvoice(wVSRControl)        &  0x200)

            GUSvoice(wVSRControl)        |= 0x100; /* voice stop request */

        if (GUSvoice(wVSRVolRampControl) &  0x200)

            GUSvoice(wVSRVolRampControl) |= 0x100; /* Volume ramp stop request */

        if (!(GUSvoice(wVSRControl) & GUSvoice(wVSRVolRampControl) & 0x100)) /* neither voice nor volume calculation active - save some time here ;) */

        {

            unsigned int    sample;

            unsigned int    LoopStart = (GUSvoice(wVSRLoopStartHi) << 16) | GUSvoice(wVSRLoopStartLo); /* 23.9 format */

            unsigned int    LoopEnd   = (GUSvoice(wVSRLoopEndHi)   << 16) | GUSvoice(wVSRLoopEndLo);   /* 23.9 format */

            unsigned int    CurrPos   = (GUSvoice(wVSRCurrPosHi)   << 16) | GUSvoice(wVSRCurrPosLo);   /* 23.9 format */

            int             VoiceIncrement = ((((unsigned long) GUSvoice(wVSRFreq) * 44100) / playback_freq) * (14 >> 1)) /

                                             ((GUSregb(NumVoices) & 31) + 1); /* 6.10 increment/frame to 23.9 increment/sample */

            int             PanningPos = (GUSvoice(wVSRPanning) >> 8) & 0xf;

            unsigned int    Volume32   = 32 * GUSvoice(wVSRCurrVol); /* 32 times larger than original gus for maintaining precision while ramping */

            unsigned int    StartVol32 = (GUSvoice(wVSRVolRampStartVol) & 0xff00) * 32;

            unsigned int    EndVol32   = (GUSvoice(wVSRVolRampEndVol)   & 0xff00) * 32;

            int             VolumeIncrement32 = (32 * 16 * (GUSvoice(wVSRVolRampRate) & 0x3f00) >> 8) >> ((((GUSvoice(wVSRVolRampRate) & 0xc000) >> 8) >> 6) * 3); /* including 1/8/64/512 volume speed divisor */

            VolumeIncrement32 = (((VolumeIncrement32 * 44100 / 2) / playback_freq) * 14) / ((GUSregb(NumVoices) & 31) + 1); /* adjust ramping speed to playback speed */

            if (GUSvoice(wVSRControl) & 0x4000)

                VoiceIncrement    = -VoiceIncrement;    /* reverse playback */

            if (GUSvoice(wVSRVolRampControl) & 0x4000)

                VolumeIncrement32 = -VolumeIncrement32; /* reverse ramping */

            for (sample = 0; sample < numsamples; sample++)

            {

                int             sample1, sample2, Volume;

                if (GUSvoice(wVSRControl) & 0x400)      /* 16bit */

                {

                    int offset = ((CurrPos >> 9) & 0xc0000) + (((CurrPos >> 9) & 0x1ffff) << 1);

                    GUSchar *adr;

                    adr = (GUSchar *) state->himemaddr + offset;

                    sample1 = (*adr & 0xff) + (*(adr + 1) * 256);

                    sample2 = (*(adr + 2) & 0xff) + (*(adr + 2 + 1) * 256);

                }

                else            /* 8bit */

                {

                    int offset = (CurrPos >> 9) & 0xfffff;

                    GUSchar *adr;

                    adr = (GUSchar *) state->himemaddr + offset;

                    sample1 = (*adr) * 256;

                    sample2 = (*(adr + 1)) * 256;

                }

                Volume = ((((Volume32 >> (4 + 5)) & 0xff) + 256) << (Volume32 >> ((4 + 8) + 5))) / 512; /* semi-logarithmic volume, +5 due to additional precision */

                sample1 = (((sample1 * Volume) >> 16) * (512 - (CurrPos % 512))) / 512;

                sample2 = (((sample2 * Volume) >> 16) * (CurrPos % 512)) / 512;

                sample1 += sample2;

                if (!(GUSvoice(wVSRVolRampControl) & 0x100))

                {

                    Volume32 += VolumeIncrement32;

                    if ((GUSvoice(wVSRVolRampControl) & 0x4000) ? (Volume32 <= StartVol32) : (Volume32 >= EndVol32)) /* ramp up boundary cross */

                    {

                        if (GUSvoice(wVSRVolRampControl) & 0x2000)

                            GUSvoice(wVSRVolRampControl) |= 0x8000;     /* volramp IRQ enabled? -> IRQ wait flag */

                        if (GUSvoice(wVSRVolRampControl) & 0x800)       /* loop enabled */

                        {

                            if (GUSvoice(wVSRVolRampControl) & 0x1000)  /* bidir. loop */

                            {

                                GUSvoice(wVSRVolRampControl) ^= 0x4000; /* toggle dir */

                                VolumeIncrement32 = -VolumeIncrement32;

                            }

                            else

                                Volume32 = (GUSvoice(wVSRVolRampControl) & 0x4000) ? EndVol32 : StartVol32; /* unidir. loop ramp */

                        }

                        else

                        {

                            GUSvoice(wVSRVolRampControl) |= 0x100;

                            Volume32 =

                                (GUSvoice(wVSRVolRampControl) & 0x4000) ? StartVol32 : EndVol32;

                        }

                    }

                }

                if ((GUSvoice(wVSRVolRampControl) & 0xa000) == 0xa000)  /* volramp IRQ set and enabled? */

                {

                    GUSregd(voicevolrampirq) |= 1 << Voice;             /* set irq slot */

                }

                else

                {

                    GUSregd(voicevolrampirq) &= (~(1 << Voice));        /* clear irq slot */

                    GUSvoice(wVSRVolRampControl) &= 0x7f00;

                }

                if (!(GUSvoice(wVSRControl) & 0x100))

                {

                    CurrPos += VoiceIncrement;

                    if ((GUSvoice(wVSRControl) & 0x4000) ? (CurrPos <= LoopStart) : (CurrPos >= LoopEnd)) /* playback boundary cross */

                    {

                        if (GUSvoice(wVSRControl) & 0x2000)

                            GUSvoice(wVSRControl) |= 0x8000;       /* voice IRQ enabled -> IRQ wait flag */

                        if (GUSvoice(wVSRControl) & 0x800)         /* loop enabled */

                        {

                            if (GUSvoice(wVSRControl) & 0x1000)    /* pingpong loop */

                            {

                                GUSvoice(wVSRControl) ^= 0x4000;   /* toggle dir */

                                VoiceIncrement = -VoiceIncrement;

                            }

                            else

                                CurrPos = (GUSvoice(wVSRControl) & 0x4000) ? LoopEnd : LoopStart; /* unidir. loop */

                        }

                        else if (!(GUSvoice(wVSRVolRampControl) & 0x400))

                            GUSvoice(wVSRControl) |= 0x100;        /* loop disabled, rollover check */

                    }

                }

                if ((GUSvoice(wVSRControl) & 0xa000) == 0xa000)    /* wavetable IRQ set and enabled? */

                {

                    GUSregd(voicewavetableirq) |= 1 << Voice;      /* set irq slot */

                }

                else

                {

                    GUSregd(voicewavetableirq) &= (~(1 << Voice)); /* clear irq slot */

                    GUSvoice(wVSRControl) &= 0x7f00;

                }

                /* mix samples into buffer */

                *(bufferpos + 2 * sample)     += (GUSsample) ((sample1 * PanningPos) >> 4);        /* right */

                *(bufferpos + 2 * sample + 1) += (GUSsample) ((sample1 * (15 - PanningPos)) >> 4); /* left */

            }

            /* write back voice and volume */

            GUSvoice(wVSRCurrVol)   = Volume32 / 32;

            GUSvoice(wVSRCurrPosHi) = CurrPos >> 16;

            GUSvoice(wVSRCurrPosLo) = CurrPos & 0xffff;

        }

        voiceptr += 16; /* next voice */

    }

}

void gus_irqgen(GUSEmuState * state, unsigned int elapsed_time)

/* time given in microseconds */

{

    int             requestedIRQs = 0;

    GUSbyte        *gusptr;

    gusptr = state->gusdatapos;

    if (GUSregb(TimerDataReg2x9) & 1) /* start timer 1 (80us decrement rate) */

    {

        unsigned int    timer1fraction = state->timer1fraction;

        int             newtimerirqs;

        newtimerirqs          = (elapsed_time + timer1fraction) / (80 * (256 - GUSregb(GUS46Counter1)));

        state->timer1fraction = (elapsed_time + timer1fraction) % (80 * (256 - GUSregb(GUS46Counter1)));

        if (newtimerirqs)

        {

            if (!(GUSregb(TimerDataReg2x9) & 0x40))

                GUSregb(TimerStatus2x8) |= 0xc0; /* maskable bits */

            if (GUSregb(GUS45TimerCtrl) & 4)     /* timer1 irq enable */

            {

                GUSregb(TimerStatus2x8) |= 4;    /* nonmaskable bit */

                GUSregb(IRQStatReg2x6)  |= 4;    /* timer 1 irq pending */

                GUSregw(TimerIRQs) += newtimerirqs;

                requestedIRQs += newtimerirqs;

            }

        }

    }

    if (GUSregb(TimerDataReg2x9) & 2) /* start timer 2 (320us decrement rate) */

    {

        unsigned int timer2fraction = state->timer2fraction;

        int             newtimerirqs;

        newtimerirqs          = (elapsed_time + timer2fraction) / (320 * (256 - GUSregb(GUS47Counter2)));

        state->timer2fraction = (elapsed_time + timer2fraction) % (320 * (256 - GUSregb(GUS47Counter2)));

        if (newtimerirqs)

        {

            if (!(GUSregb(TimerDataReg2x9) & 0x20))

                GUSregb(TimerStatus2x8) |= 0xa0; /* maskable bits */

            if (GUSregb(GUS45TimerCtrl) & 8)     /* timer2 irq enable */

            {

                GUSregb(TimerStatus2x8) |= 2;    /* nonmaskable bit */

                GUSregb(IRQStatReg2x6)  |= 8;    /* timer 2 irq pending */

                GUSregw(TimerIRQs) += newtimerirqs;

                requestedIRQs += newtimerirqs;

            }

        }

    }

    if (GUSregb(GUS4cReset) & 0x4) /* synth IRQ enable */

    {

        if (GUSregd(voicewavetableirq))

            GUSregb(IRQStatReg2x6) |= 0x20;

        if (GUSregd(voicevolrampirq))

            GUSregb(IRQStatReg2x6) |= 0x40;

    }

    if ((!requestedIRQs) && GUSregb(IRQStatReg2x6))

        requestedIRQs++;

    if (GUSregb(IRQStatReg2x6))

        GUSregw(BusyTimerIRQs) = GUS_irqrequest(state, state->gusirq, requestedIRQs);

}