/* fire.c (comment5.c) - Don Yang (uguu.org)

   DOS only, runs under windowed DOS box but fullscreen highly recommended.
   Compiles with MSC 6.0 or TC 3.0

   11/29/98: main
                                                                           */

/* Includes */
#include<conio.h>
#include<stdlib.h>

/* Macros */
#define Rnd()              \
   (RndTable[RndIndex = (RndIndex + 1) & 0x7fff])

/* Globals (all data are global) */
int Palette[] = {
   0x0400, 0x02b0, 0x0ab0, 0x0ab1,
   0x2ab2, 0x2bb0, 0x3fb0, 0x2fb1,
   0x3fb1, 0x2fb2, 0x3fb2, 0x7fb0,
   0x7fb1, 0x7fb2, 0x4fdb, 0x4fdb, 0x4fdb};
int *AltPalette;

int OldImage[80 * 25], Image[80 * 25], Fire[80 * 27 + 2];

int shift = 0, dir = 1, skip = 0, spark1 = 20, spark2 = 60;
unsigned i, RndIndex;

int _far *Screen = (int _far *)0xb8000000L;
char *Text;
unsigned char RndTable[0x8000];

/* Main */
void cdecl main(void)
{
   /* Save image */
   for(i = 0; i < 80 * 25; i++)
      OldImage[i] = Screen[i];

   /* Generate random numbers */
   for(i = 0; i < 0x8000; i++)
      RndTable[i] = (unsigned char)(rand() & 0x3f);

   /* Initialize dithering palette */
   AltPalette = Palette + 1;

   Text = (char *)&Image[12 * 80 + 32];


   /* Loop until keypress */
   while( !kbhit() )
   {

      /* Burn */

      /* Generate random pixels (heat source) */
      for(i = 0; i < 162; i++)
         Fire[80 * 25 + i] = Rnd() + shift;

      /* Add sparks */
      Fire[80 * 25 + spark1] = 255;
      Fire[80 * 25 + spark2] = 0;
      if( Rnd() & 1 )   spark1++;
      else              spark1 += 79;
      if( Rnd() & 1 )   spark2++;
      else              spark2 += 79;

      spark1 %= 80;
      spark2 %= 80;

      skip = (skip + 1) % 4;
      if( !skip )
      {
         shift += dir;
         if( !shift || shift == 0xc0 )
            dir = -dir;
      }

      /* Update pixels */
      for(i = 0; i < 80 * 25; i++)
      {
         Fire[i] = (Fire[i + 80] * 16 + Fire[i + 160] * 14
                  + Fire[i + 161] + Fire[i + 162]) >> 5;
      }


      /* Render */
      for(i = 0; i < 80 * 25; i++)
      {
         Image[i] = (Fire[i] & 0xf > Rnd() & 0xf) ?
                    Palette[Fire[i] >> 4] : AltPalette[Fire[i] >> 4];
      }
      Text[0] = 'D';
      Text[4] = 'O';
      Text[8] = 'N';
      Text[16] = 'Y';
      Text[20] = 'A';
      Text[24] = 'N';
      Text[28] = 'G';


      /* Blit */

      /* Wait for vertical synchronization */
      while( inp(0x3da) & 8 );
      while( !(inp(0x3da) & 8) );

      for(i = 0; i < 80 * 25; i++)
         Screen[i] = Image[i];
   }


   /* Clear keystroke */
   if( !getch() )
      getch();

   /* Restore screen */
   for(i = 0; i < 80 * 25; i++)
      Screen[i] = OldImage[i];

} /* main() */