libcRSID.c

// cRSID lightweight (integer-only) RealSID library (with API-calls) by Hermit (Mihaly Horvath), Year 2022
// License: WTF - do what the fuck you want with the code, but please mention me as the original author

#include "libcRSID.h"

#include <stdlib.h>

#include "C64/C64.c"
#include "host/audio.c"
#include "host/file.c"

cRSID_C64instance cRSID_C64;

cRSID_C64instance *cRSID_init(unsigned short samplerate)
{
    static cRSID_C64instance *C64 = &cRSID_C64;

    C64->HighQualitySID   = 1;
    C64->Stereo           = 0;
    C64->SelectedSIDmodel = 0;
    C64->PlaybackSpeed    = 1; // default model and mode selections
    C64->MainVolume       = 255;

    C64 = cRSID_createC64(C64, samplerate);

    return C64;
}

void cRSID_initSIDtune(cRSID_C64instance *C64, cRSID_SIDheader *SIDheader, char subtune)
{                                        // subtune: 1..255
    static const unsigned char PowersOf2[] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};
    unsigned int InitTimeout = 10000000; // allowed instructions, value should be selected to allow for long-running
                                         // memory-copiers in init-routines (e.g. Synth Sample)

    if (subtune == 0)
        subtune = 1;
    else if (subtune > SIDheader->SubtuneAmount)
        subtune = SIDheader->SubtuneAmount;
    C64->SubTune   = subtune;
    C64->SecondCnt = C64->PlayTime = C64->Paused = 0;

    cRSID_setC64(C64);
    cRSID_initC64(C64); // cRSID_writeMemC64(C64,0xD418,0xF); //set C64 hardware and init (reset) it

    // determine init-address:
    C64->InitAddress =
        ((SIDheader->InitAddressH) << 8) + (SIDheader->InitAddressL); // get info from BASIC-startupcode for some tunes
    if (C64->RAMbank[1] == 0x37)
    { // are there SIDs with routine under IO area? some PSIDs don't set bank-registers themselves
        if ((0xA000 <= C64->InitAddress && C64->InitAddress < 0xC000) ||
            (C64->LoadAddress < 0xC000 && C64->EndAddress >= 0xA000))
            C64->RAMbank[1] = 0x36;
        else if (C64->InitAddress >= 0xE000 || C64->EndAddress >= 0xE000)
            C64->RAMbank[1] = 0x35;
    }
    cRSID_initCPU(&C64->CPU, C64->InitAddress); // prepare init-routine call
    C64->CPU.A = subtune - 1;

    if (!C64->RealSIDmode)
    {
        // call init-routine:
        for (InitTimeout = 10000000; InitTimeout > 0; InitTimeout--)
        {
            if (cRSID_emulateCPU() >= 0xFE)
                break;
        } // give error when timed out?
    }

    // determine timing-source, if CIA, replace FrameCycles previouisly set to VIC-timing
    if (subtune > 32)
        C64->TimerSource =
            C64->SIDheader->SubtuneTimeSources[0] & 0x80; // subtunes above 32 should use subtune32's timing
    else
        C64->TimerSource = C64->SIDheader->SubtuneTimeSources[(32 - subtune) >> 3] & PowersOf2[(subtune - 1) & 7];
    if (C64->TimerSource || C64->IObankWR[0xDC05] != 0x40 || C64->IObankWR[0xDC04] != 0x24)
    { // CIA1-timing (probably multispeed tune)
        C64->FrameCycles = ((C64->IObankWR[0xDC04] + (C64->IObankWR[0xDC05] << 8))); //<< 4) / C64->ClockRatio;
        C64->TimerSource = 1; // if init-routine changed DC04 or DC05, assume CIA-timing
    }

    // determine playaddress:
    C64->PlayAddress = (SIDheader->PlayAddressH << 8) + SIDheader->PlayAddressL;
    if (C64->PlayAddress)
    {     // normal play-address called with JSR
        if (C64->RAMbank[1] == 0x37)
        { // are there SIDs with routine under IO area?
            if (0xA000 <= C64->PlayAddress && C64->PlayAddress < 0xC000)
                C64->RAMbank[1] = 0x36;
        }
        else if (C64->PlayAddress >= 0xE000)
            C64->RAMbank[1] = 0x35; // player under KERNAL (e.g. Crystal Kingdom Dizzy)
    }
    else
    { // IRQ-playaddress for multispeed-tunes set by init-routine (some tunes turn off KERNAL ROM but doesn't set
      // IRQ-vector!)
        C64->PlayAddress = (C64->RAMbank[1] & 3) < 2
                               ? cRSID_readMemC64(C64, 0xFFFE) + (cRSID_readMemC64(C64, 0xFFFF) << 8) // for PSID
                               : cRSID_readMemC64(C64, 0x314) + (cRSID_readMemC64(C64, 0x315) << 8);
        if (C64->PlayAddress == 0)
        {                                               // if 0, still try with RSID-mode fallback
            cRSID_initCPU(&C64->CPU, C64->PlayAddress); // point CPU to play-routine
            C64->Finished = 1;
            C64->Returned = 1;
            return;
        }
    }

    if (!C64->RealSIDmode)
    {                                               // prepare (PSID) play-routine playback:
        cRSID_initCPU(&C64->CPU, C64->PlayAddress); // point CPU to play-routine
        C64->FrameCycleCnt  = 0;
        C64->Finished       = 1;
        C64->SampleCycleCnt = 0;                    // C64->CIAisSet=0;
    }
    else
    {
        C64->Finished = 0;
        C64->Returned = 0;
    }
}