C64 screen mode for DOSLIKE

example.c

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "dos.h"

#define VIC_IMPL
#include "vic.h"

unsigned char raster_colours[] = {
    0x6, 0x6, 0x6, 0xe, 0x6, 0xe, 
    0xe, 0x6, 0xe, 0xe, 0xe, 0x3, 
    0xe, 0x3, 0x3, 0xe, 0x3, 0x3, 
    0x3, 0x1, 0x3, 0x1, 0x1, 0x3, 
    0x1, 0x1, 0x1, 0x3, 0x1, 0x1, 
    0x3, 0x1, 0x3, 0x3, 0x3, 0xe, 
    0x3, 0x3, 0xe, 0x3, 0xe, 0xe, 
    0xe, 0x6, 0xe, 0xe, 0x6, 0xe, 
    0x6, 0x6, 0x6, 0x0, 0x0, 0x0
};

int main(int argc, char *argv[])
{
	float t=0;
  setvideomode( videomode_320x200 );
  setdoublebuffer(1);

  for (int q=0;q<1000;q++)
  {
    VIC.Colors[q]=(q/10)&0xf;
    VIC.Screen[q]=q&0xff;
  }

  VIC.horizontal_offset = VIC.vertical_offset = 0;  //  reset scroll
  VIC.Mode = 1;       //  text with MC 
  VIC.D021 = 0xb;     //  
  VIC.D022 = 0xf;     //
  VIC.D023 = 0x1;     //   
	VIC.D026 = 0;
	VIC.D027 = 1;

	VIC.SpriteMCM = 0b111111111;
	VIC.SpriteENA = 0b111111111;
  //  load charpad data
  //  from Saul Cross
  VIC.CharData=(unsigned char *)malloc(2048);
  VIC.SpriteData=(unsigned char *)malloc(16384);

	//	from CHARPAD
	//	REAL C64 data 
  FILE *fp = fopen("files/Bruce Lee Updated (1x1) - Chars.bin","rb");
  fread(&VIC.CharData[0],2048,1,fp);
  fclose(fp);

//	SPRITE's from SPRITEPAD 
//  fp = fopen("files/invaders - Sprites.bin","rb");
//  fread(&VIC.SpriteData[0],2048,1,fp);
//  fclose(fp);

  fp = fopen("files/Bruce Lee Updated (1x1) - Map (8bpc, 40x25).bin","rb");
  fread(&VIC.Screen[0],1000,1,fp);
  fclose(fp);

  unsigned char attribs[256];
  fp = fopen("files/Bruce Lee Updated (1x1) - CharAttribs_L1.bin","rb");
  fread(&attribs[0],256,1,fp);
  fclose(fp);
  //  set attribs 
  for (int q=0;q<1000;q++)
  {
    unsigned char c = VIC.Screen[q];
    VIC.Colors[q] = attribs[c];
  }

  unsigned char* buffer = screenbuffer();
  while(!shuttingdown())
  {
    waitvbl();

		for (int q=0;q<8;q++)
		{
			VIC.SpriteX[q] = 160+(sin(t+q)*140);
			VIC.SpriteY[q] = 100+(cos(t+q)*80);
			VIC.SpriteColor[q] = q + t;
			VIC.SpriteID[q] = q;
		}
		t+=0.01f;
		//	draw 200 scanlines 
		//	adjusting VIC.D021 as we go for raster effects 
		for (int y=0;y<200;y++)
		{
				VIC.D021 = raster_colours[(int)(y+(t*32)) % sizeof(raster_colours)];
				VIC_PaintScanline(buffer,y);
		}
		
		buffer = swapbuffers();
		if( keystate( KEY_ESCAPE ) ) {
				break;
		}
  }
	free(VIC.CharData);
	free(VIC.SpriteData);
  return(0);
}

vic.h

enum vic_mode_t {
  vic_hires,vic_mcm
};

struct
{
	unsigned char 	Screen[40*25];
	unsigned char 	Colors[40*25];

	unsigned char 	SpriteMCM;
	unsigned char 	SpriteENA;
	unsigned short 	SpriteX[8];
	unsigned char 	SpriteY[8];
	unsigned char 	SpriteColor[8];
	unsigned char 	SpriteID[8];

	unsigned char 	*CharData;
	unsigned char 	*SpriteData;
	unsigned char 	D020;	
	unsigned char 	D021;	
	unsigned char 	D022;	
	unsigned char 	D023;
	unsigned char 	D026;	
	unsigned char 	D027;	
	unsigned char 	Mode,horizontal_offset,vertical_offset;
} VIC;

static unsigned int VIC_Palette[16] = 
{
	0x000000, 0xFFFFFF, 0x813338,
	0x75cec8, 0x8e3c97, 0x56ac4d,
	0x2e2c9b, 0xedf171, 0x8e5029,
	0x553800, 0xc46c71, 0x4a4a4a,
	0x7b7b7b, 0xa9ff9f, 0x706deb,
	0xb2b2b2
};

#ifdef VIC_IMPL
void VIC_PaintScanline(unsigned char *buffer,unsigned char scanline)
{
  unsigned char *ptr = &buffer[0];

  if (VIC.CharData==NULL) return;
  //  clamp scroll
  VIC.horizontal_offset&=7;
  VIC.vertical_offset&=7;
  //  update pal 
  for (int q=0;q<16;q++)
    setpal( q, (VIC_Palette[q]>>18)&0xff,(VIC_Palette[q]>>10)&0xff,(VIC_Palette[q]>>2)&0xff);
  //  
  {
    int ay = scanline + VIC.vertical_offset;
    unsigned char py = ay&7;
    for (int x=0;x<320;x++)
    {
      int ax = x + VIC.horizontal_offset;
      unsigned char px = ax&7;
      unsigned char color = VIC.Colors[(ax>>3)+((ay>>3)*40)]; //  color memory
      unsigned char cell = VIC.Screen[(ax>>3)+((ay>>3)*40)];//  screen memory
      unsigned char chr = VIC.CharData[(cell<<3)+py];         //  tile memory
      //  set background pixel 
      buffer[x+(scanline*320)]=VIC.D021;                  
      //  depends on mode 
      switch(VIC.Mode)
      {
        case vic_hires:
        {
          if ((chr>>(7-px))&1)
            buffer[x+(scanline*320)]=color;
        }
        break;
        case vic_mcm:                       //  multi color mode
        {
          if ((color&0x8)==0)               //  bottom 8 colors is hires
          {
            if ((chr>>(7-px))&1)
              buffer[x+(scanline*320)]=color;
          }
          else                              //  top 8 is 2 bits per pixel 
          {
            unsigned char mask = (7-px)&6;
            unsigned char cc = (chr>>mask)&3;
            if (cc==1)  buffer[x+(scanline*320)]=VIC.D022;
            if (cc==2)  buffer[x+(scanline*320)]=VIC.D023;
            if (cc==3)  buffer[x+(scanline*320)]=color&7;
          }
        }
        break;
      }
    }
		//	sprites
		for (int sid=0;sid<8;sid++)
		{
			unsigned char mode = (VIC.SpriteMCM>>(sid))&1;
			unsigned char enabled = (VIC.SpriteENA>>(sid))&1;
			if (enabled==1)
			{
				if ((scanline>=VIC.SpriteY[sid]) && (scanline<VIC.SpriteY[sid]+21))
				{
					unsigned char yoff = (scanline-VIC.SpriteY[sid])*3;
					unsigned char *ptr = &VIC.SpriteData[(VIC.SpriteID[sid]*64)+yoff];
					for (int x=0;x<24;x++)
					{
						unsigned char px = x&7;
						unsigned char chr = ptr[x>>3];         //  tile memory

						if (mode==0)
						{
							if ((chr>>(7-px))&1)
								buffer[VIC.SpriteX[sid]+x+(scanline*320)]=VIC.SpriteColor[sid];
						}
						else 
						{
							unsigned char mask = (7-px)&6;
							unsigned char cc = (chr>>mask)&3;
							if (cc==1)  buffer[VIC.SpriteX[sid]+x+(scanline*320)]=VIC.D026;
							if (cc==3)  buffer[VIC.SpriteX[sid]+x+(scanline*320)]=VIC.D027;
							if (cc==2)  buffer[VIC.SpriteX[sid]+x+(scanline*320)]=VIC.SpriteColor[sid];
						}
					}				
				}
			}
		}
  }
}
#else
void VIC_PaintScanline(unsigned char *buffer,unsigned char scanline);
#endif