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hatari 1.4.0

/*
  Hatari - spec640x16.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[5]; /* Workspace to store pixels to so can print in right order for Spec512 */
	int y, x, Screen4BytesPerLine;

	/* on x86, unaligned access macro touches also
	 * next byte, zero it for code checkers
	 */
	pixelspace[4] = 0;

	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 colors */
		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;
#else
			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;
#endif
			/* 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 = GET_SPEC512_OFFSET_PIXELS(pixelspace, 1);
				PLOT_SPEC512_MID_640_16BIT(1);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 5);
				PLOT_SPEC512_MID_640_16BIT(5);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 9);
				PLOT_SPEC512_MID_640_16BIT(9);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_FINAL_PIXELS(pixelspace);
				PLOT_SPEC512_END_LOW_640_16BIT(13);
			}
			else
			{
				ecx = pixelspace[0];
				PLOT_SPEC512_LEFT_LOW_640_16BIT_DOUBLE_Y(0);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 1);
				PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(1);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 5);
				PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(5);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_PIXELS(pixelspace, 9);
				PLOT_SPEC512_MID_640_16BIT_DOUBLE_Y(9);
				Spec512_UpdatePaletteSpan();

				ecx = GET_SPEC512_OFFSET_FINAL_PIXELS(pixelspace);
				PLOT_SPEC512_END_LOW_640_16BIT_DOUBLE_Y(13);
			}

			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;
}

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