path: root/source/dsp2emu.c

#include "../copyright"

uint16_t DSP2Op09Word1 = 0;
uint16_t DSP2Op09Word2 = 0;
bool DSP2Op05HasLen = false;
int DSP2Op05Len = 0;
bool DSP2Op06HasLen = false;
int DSP2Op06Len = 0;
uint8_t DSP2Op05Transparent = 0;

void DSP2_Op05()
{
   uint8_t color;
   // Overlay bitmap with transparency.
   // Input:
   //
   //   Bitmap 1:  i[0] <=> i[size-1]
   //   Bitmap 2:  i[size] <=> i[2*size-1]
   //
   // Output:
   //
   //   Bitmap 3:  o[0] <=> o[size-1]
   //
   // Processing:
   //
   //   Process all 4-bit pixels (nibbles) in the bitmap
   //
   //   if ( BM2_pixel == transparent_color )
   //      pixelout = BM1_pixel
   //   else
   //      pixelout = BM2_pixel

   // The max size bitmap is limited to 255 because the size parameter is a byte
   // I think size=0 is an error.  The behavior of the chip on size=0 is to
   // return the last value written to DR if you read DR on Op05 with
   // size = 0.  I don't think it's worth implementing this quirk unless it's
   // proven necessary.

   int n;
   unsigned char c1;
   unsigned char c2;
   unsigned char* p1 = DSP1.parameters;
   unsigned char* p2 = &DSP1.parameters[DSP2Op05Len];
   unsigned char* p3 = DSP1.output;

   color = DSP2Op05Transparent & 0x0f;

   for (n = 0; n < DSP2Op05Len; n++)
   {
      c1 = *p1++;
      c2 = *p2++;
      *p3++ = (((c2 >> 4) == color) ? c1 & 0xf0 : c2 & 0xf0) |
              (((c2 & 0x0f) == color) ? c1 & 0x0f : c2 & 0x0f);
   }
}

void DSP2_Op01()
{
   // Op01 size is always 32 bytes input and output.
   // The hardware does strange things if you vary the size.

   int j;
   unsigned char c0, c1, c2, c3;
   unsigned char* p1 = DSP1.parameters;
   unsigned char* p2a = DSP1.output;
   unsigned char* p2b = &DSP1.output[16]; // halfway

   // Process 8 blocks of 4 bytes each

   for (j = 0; j < 8; j++)
   {
      c0 = *p1++;
      c1 = *p1++;
      c2 = *p1++;
      c3 = *p1++;

      *p2a++ = (c0 & 0x10) << 3 |
               (c0 & 0x01) << 6 |
               (c1 & 0x10) << 1 |
               (c1 & 0x01) << 4 |
               (c2 & 0x10) >> 1 |
               (c2 & 0x01) << 2 |
               (c3 & 0x10) >> 3 |
               (c3 & 0x01);

      *p2a++ = (c0 & 0x20) << 2 |
               (c0 & 0x02) << 5 |
               (c1 & 0x20)      |
               (c1 & 0x02) << 3 |
               (c2 & 0x20) >> 2 |
               (c2 & 0x02) << 1 |
               (c3 & 0x20) >> 4 |
               (c3 & 0x02) >> 1;

      *p2b++ = (c0 & 0x40) << 1 |
               (c0 & 0x04) << 4 |
               (c1 & 0x40) >> 1 |
               (c1 & 0x04) << 2 |
               (c2 & 0x40) >> 3 |
               (c2 & 0x04)      |
               (c3 & 0x40) >> 5 |
               (c3 & 0x04) >> 2;


      *p2b++ = (c0 & 0x80)      |
               (c0 & 0x08) << 3 |
               (c1 & 0x80) >> 2 |
               (c1 & 0x08) << 1 |
               (c2 & 0x80) >> 4 |
               (c2 & 0x08) >> 1 |
               (c3 & 0x80) >> 6 |
               (c3 & 0x08) >> 3;
   }
   return;
}

void DSP2_Op06()
{
   // Input:
   //    size
   //    bitmap

   int   i, j;

   for (i = 0, j = DSP2Op06Len - 1; i < DSP2Op06Len; i++, j--)
      DSP1.output[j] = (DSP1.parameters[i] << 4) | (DSP1.parameters[i] >> 4);
}

bool DSP2Op0DHasLen = false;
int DSP2Op0DOutLen = 0;
int DSP2Op0DInLen = 0;

#ifndef DSP2_BIT_ACCURRATE_CODE

// Scale bitmap based on input length out output length

void DSP2_Op0D()
{
   // Overload's algorithm - use this unless doing hardware testing

   // One note:  the HW can do odd byte scaling but since we divide
   // by two to get the count of bytes this won't work well for
   // odd byte scaling (in any of the current algorithm implementations).
   // So far I haven't seen Dungeon Master use it.
   // If it does we can adjust the parameters and code to work with it

   int i;
   int pixel_offset;
   uint8_t pixelarray[512];

   for (i = 0; i < DSP2Op0DOutLen * 2; i++)
   {
      pixel_offset = (i * DSP2Op0DInLen) / DSP2Op0DOutLen;
      if ((pixel_offset & 1) == 0)
         pixelarray[i] = DSP1.parameters[pixel_offset >> 1] >> 4;
      else
         pixelarray[i] = DSP1.parameters[pixel_offset >> 1] & 0x0f;
   }

   for (i = 0; i < DSP2Op0DOutLen; i++)
      DSP1.output[i] = (pixelarray[i << 1] << 4) | pixelarray[(i << 1) + 1];
}

#else

void DSP2_Op0D()
{
   // Bit accurate hardware algorithm - uses fixed point math
   // This should match the DSP2 Op0D output exactly
   // I wouldn't recommend using this unless you're doing hardware debug.
   // In some situations it has small visual artifacts that
   // are not readily apparent on a TV screen but show up clearly
   // on a monitor.  Use Overload's scaling instead.
   // This is for hardware verification testing.
   //
   // One note:  the HW can do odd byte scaling but since we divide
   // by two to get the count of bytes this won't work well for
   // odd byte scaling (in any of the current algorithm implementations).
   // So far I haven't seen Dungeon Master use it.
   // If it does we can adjust the parameters and code to work with it


   uint32_t multiplier;   // Any size int >= 32-bits
   uint32_t pixloc;    // match size of multiplier
   int   i, j;
   uint8_t pixelarray[512];

   if (DSP2Op0DInLen <= DSP2Op0DOutLen)
      multiplier = 0x10000;   // In our self defined fixed point 0x10000 == 1
   else
      multiplier = (DSP2Op0DInLen << 17) / ((DSP2Op0DOutLen << 1) + 1);

   pixloc = 0;
   for (i = 0; i < DSP2Op0DOutLen * 2; i++)
   {
      j = pixloc >> 16;

      if (j & 1)
         pixelarray[i] = DSP1.parameters[j >> 1] & 0x0f;
      else
         pixelarray[i] = (DSP1.parameters[j >> 1] & 0xf0) >> 4;

      pixloc += multiplier;
   }

   for (i = 0; i < DSP2Op0DOutLen; i++)
      DSP1.output[i] = (pixelarray[i << 1] << 4) | pixelarray[(i << 1) + 1];
}

#endif

#if 0 // Probably no reason to use this code - it's not quite bit accurate and it doesn't look as good as Overload's algorithm

void DSP2_Op0D()
{
   // Float implementation of Neviksti's algorithm
   // This is the right algorithm to match the DSP2 bits but the precision
   // of the PC float does not match the precision of the fixed point math
   // on the DSP2 causing occasional one off data mismatches (which should
   // be no problem because its just a one pixel difference in a scaled image
   // to be displayed).

   float multiplier;
   float pixloc;
   int   i, j;
   uint8_t pixelarray[512];

   if (DSP2Op0DInLen <= DSP2Op0DOutLen)
      multiplier = (float) 1.0;
   else
      multiplier = (float)((DSP2Op0DInLen * 2.0) / (DSP2Op0DOutLen * 2.0 + 1.0));

   pixloc = 0.0;
   for (i = 0; i < DSP2Op0DOutLen * 2; i++)
   {
      // j = (int)(i * multiplier);
      j = (int) pixloc;

      if (j & 1)
         pixelarray[i] = DSP1.parameters[j >> 1] & 0x0f;
      else
         pixelarray[i] = (DSP1.parameters[j >> 1] & 0xf0) >> 4;

      pixloc += multiplier;   // use an add in the loop instead of multiply to increase loop speed
   }

   for (i = 0; i < DSP2Op0DOutLen; i++)
      DSP1.output[i] = (pixelarray[i << 1] << 4) | pixelarray[(i << 1) + 1];
}

#endif