/*
  Hatari - spec640x18.c
 
  This file is distributed under the GNU Public License, version 2 or at your
  option any later version. Read the file gpl.txt for details.

  Screen conversion, Spec512 to 640x16Bit
*/


static void ConvertSpec512_640x16Bit(void)
{
  Uint32 *edi, *ebp;
  Uint32 *esi;
  Uint32 eax, ebx, ecx, edx;
  Uint32 pixelspace[4]; /* Workspace to store pixels to so can print in right order for Spec512 */
  int y, x, Screen4BytesPerLine;

  Spec512_StartFrame();                 /* Start frame, track palettes */
  Screen4BytesPerLine = PCScreenBytesPerLine/4;
  edx = 0;                              /* Clear index for loop */

  for (y = STScreenStartHorizLine; y < STScreenEndHorizLine; y++) {

    Spec512_StartScanLine();            /* Build up palettes for every 4 pixels, store in 'ScanLinePalettes' */
    edx = 0;                            /* Clear index for loop */

    /* Get screen addresses, 'edi'-ST screen, 'ebp'-Previous ST screen, 'esi'-PC screen */
    eax = STScreenLineOffset[y] + STScreenLeftSkipBytes;  /* Offset for this line + Amount to skip on left hand side */
    edi = (Uint32 *)((Uint8 *)pSTScreen + eax);        /* ST format screen 4-plane 16 colours */
    ebp = (Uint32 *)((Uint8 *)pSTScreenCopy + eax);    /* Previous ST format screen */
    esi = (Uint32 *)pPCScreenDest;                     /* PC format screen */

    x = STScreenWidthBytes>>3;       /* Amount to draw across in 16-pixels (8 bytes) */

    do    /* x-loop */
    {
      ebx = *edi;                       /* Do 16 pixels at one time */
      ecx = *(edi+1);

#if SDL_BYTEORDER == SDL_LIL_ENDIAN

      /* Convert planes to byte indices - as works in wrong order store to workspace so can read back in order! */
      LOW_BUILD_PIXELS_0 ;              /* Generate 'ecx' as pixels [4,5,6,7] */
      pixelspace[1] = ecx;
      LOW_BUILD_PIXELS_1 ;              /* Generate 'ecx' as pixels [12,13,14,15] */
      pixelspace[3] = ecx;
      LOW_BUILD_PIXELS_2 ;              /* Generate 'ecx' as pixels [0,1,2,3] */
      pixelspace[0] = ecx;
      LOW_BUILD_PIXELS_3 ;              /* Generate 'ecx' as pixels [8,9,10,11] */
      pixelspace[2] = ecx;

      /* And plot, the Spec512 is offset by 1 pixel and works on 'chunks' of 4 pixels */
      /* So, we plot 1_4_4_3 to give 16 pixels, changing palette between */
      /* (last one is used for first of next 16-pixels) */
      if(!bScrDoubleY)                  /* Double on Y? */
      {
        ecx = pixelspace[0];
        PLOT_SPEC512_LEFT_LOW_640_16BIT(0) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+1 );
        PLOT_SPEC512_MID_640_16BIT(1) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+5 );
        PLOT_SPEC512_MID_640_16BIT(5) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+9 );
        PLOT_SPEC512_MID_640_16BIT(9) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+13 );
        PLOT_SPEC512_END_LOW_640_16BIT(13) ;
      }
      else
      {
        ecx = pixelspace[0];
        PLOT_SPEC512_LEFT_LOW_640_16BIT_DOUBLE_Y(0) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+1 );
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(1) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+5 );
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(5) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+9 );
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(9) ;
        Spec512_UpdatePaletteSpan();

        ecx = *(Uint32 *)( ((Uint8 *)pixelspace)+13 );
        PLOT_SPEC512_END_LOW_640_16BIT_DOUBLE_Y(13) ;
      }

#else
      /* Well, I didn't get the code above working on big-endian  machines, too,
         But I hope the following lines are good enough to do the job... */

      LOW_BUILD_PIXELS_0 ;
      pixelspace[3] = ecx;
      LOW_BUILD_PIXELS_1 ;
      pixelspace[1] = ecx;
      LOW_BUILD_PIXELS_2 ;
      pixelspace[2] = ecx;
      LOW_BUILD_PIXELS_3 ;
      pixelspace[0] = ecx;

      if(!bScrDoubleY)                  /* Double on Y? */
      {
        ecx = pixelspace[0];
        PLOT_SPEC512_MID_640_16BIT(0) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[1];
        PLOT_SPEC512_MID_640_16BIT(4) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[2];
        PLOT_SPEC512_MID_640_16BIT(8) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[3];
        PLOT_SPEC512_MID_640_16BIT(12) ;
        Spec512_UpdatePaletteSpan();
      }
      else
      {
        ecx = pixelspace[0];
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(0) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[1];
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(4) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[2];
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(8) ;
        Spec512_UpdatePaletteSpan();

        ecx = pixelspace[3];
        PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(12) ;
        Spec512_UpdatePaletteSpan();
      }

#endif

      esi += 16;                        /* Next PC pixels */
      edi += 2;                         /* Next ST pixels */
      ebp += 2;                         /* Next ST copy pixels */
    }
    while(--x);                      /* Loop on X */

    Spec512_EndScanLine();

    /* Offset to next line: */
    pPCScreenDest = (((Uint8 *)pPCScreenDest)+2*PCScreenBytesPerLine);
  }

  bScreenContentsChanged = TRUE;
}