tvmode.cpp

著名SFC模拟器Snes9x的源代码。

/*
 * Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
 *
 * (c) Copyright 1996 - 2001 Gary Henderson ([e-mail]) and
 *                           Jerremy Koot ([e-mail])
 *
 * Super FX C emulator code 
 * (c) Copyright 1997 - 1999 Ivar ([e-mail]) and
 *                           Gary Henderson.
 * Super FX assembler emulator code (c) Copyright 1998 zsKnight and _Demo_.
 *
 * DSP1 emulator code (c) Copyright 1998 Ivar, _Demo_ and Gary Henderson.
 * C4 asm and some C emulation code (c) Copyright 2000 zsKnight and _Demo_.
 * C4 C code (c) Copyright 2001 Gary Henderson ([e-mail]).
 *
 * DOS port code contains the works of other authors. See headers in
 * individual files.
 *
 * Snes9x homepage: www.snes9x.com
 *
 * Permission to use, copy, modify and distribute Snes9x in both binary and
 * source form, for non-commercial purposes, is hereby granted without fee,
 * providing that this license information and copyright notice appear with
 * all copies and any derived work.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event shall the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Snes9x is freeware for PERSONAL USE only. Commercial users should
 * seek permission of the copyright holders first. Commercial use includes
 * charging money for Snes9x or software derived from Snes9x.
 *
 * The copyright holders request that bug fixes and improvements to the code
 * should be forwarded to them so everyone can benefit from the modifications
 * in future versions.
 *
 * Super NES and Super Nintendo Entertainment System are trademarks of
 * Nintendo Co., Limited and its subsidiary companies.
 */
#include <sys/farptr.h>

#include "snes9x.h"
#include "port.h"
#include "gfx.h"

#include <allegro.h>

extern uint32 screen_width;
extern uint32 screen_height;

void TVMode (uint8 *srcPtr, uint32 srcPitch,
	     uint8 *deltaPtr,
	     BITMAP *dstBitmap, int width, int height)
{
    uint8 *finish;
    uint32 dstPitch = dstBitmap->w * 2;
    uint32 line;
    uint32 x_offset;
    uint32 fraction;
    uint32 error = 0;
    uint32 colorMask = ~(RGB_LOW_BITS_MASK | (RGB_LOW_BITS_MASK << 16));
    uint32 lowPixelMask = RGB_LOW_BITS_MASK;

    if (height * 2 <= screen_height)
    {
	line = (screen_height - height * 2) >> 1;
	fraction = 0x10000;
    }
    else
    {
	line = 0;
	fraction = ((screen_height - height) * 0x10000) / height;
    }

    _farsetsel (dstBitmap->seg);
    
    if (width == 512)
    {
	// Offset into scanline in bytes, since each pixel takes two bytes,
	// no divide by two.
	x_offset = screen_width - width;

	do
	{
	    uint32 *bP = (uint32 *) srcPtr;
	    uint32 *xP = (uint32 *) deltaPtr;
	    uint32 dP = bmp_write_line (dstBitmap, line) + x_offset;
	    uint32 currentPixel;
	    uint32 currentDelta;

	    finish = (uint8 *) bP + ((width + 2) << 1);
	    if ((error += fraction) >= 0x10000)
	    {
		error -= 0x10000;
		do
		{
		    currentPixel = *bP++;

		    if (currentPixel != *xP++)
		    {
			uint32 product, darkened;

			*(xP - 1) = currentPixel;
			_farnspokel (dP, currentPixel);

			darkened = (product = ((currentPixel & colorMask) >> 1));
			darkened += (product = ((product & colorMask) >> 1));
			darkened += (product & colorMask) >> 1;
			_farnspokel (dP + dstPitch, darkened);
		    }

		    dP += 4;
		} while ((uint8 *) bP < finish);
		line += 2;
	    }
	    else
	    {
		do
		{
		    currentPixel = *bP++;

		    if (currentPixel != *xP++)
		    {
			*(xP - 1) = currentPixel;
			_farnspokel (dP, currentPixel);
		    }
		    dP += 4;
		} while ((uint8 *) bP < finish);
		line++;
	    }

	    deltaPtr += srcPitch;
	    srcPtr += srcPitch;
	} while (--height);
    }
    else
    {
	x_offset = (screen_width - width * 2);
	do
	{
	    uint32 *bP = (uint32 *) srcPtr;
	    uint32 *xP = (uint32 *) deltaPtr;
	    uint32 dP = bmp_write_line (dstBitmap, line) + x_offset;
	    uint32 currentPixel;
	    uint32 nextPixel;
	    uint32 currentDelta;
	    uint32 nextDelta;

	    finish = (uint8 *) bP + ((width + 2) << 1);
	    nextPixel = *bP++;
	    nextDelta = *xP++;
	    if ((error += fraction) >= 0x10000)
	    {
		error -= 0x10000;
		do
		{
		    currentPixel = nextPixel;
		    currentDelta = nextDelta;
		    nextPixel = *bP++;
		    nextDelta = *xP++;

		    if ((nextPixel != nextDelta) || (currentPixel != currentDelta))
		    {
			uint32 colorA, colorB, product, darkened;

			*(xP - 2) = currentPixel;
			colorA = currentPixel & 0xffff;

			colorB = (currentPixel & 0xffff0000) >> 16;
			product = colorA |
				  ((((colorA & colorMask) >> 1) +
				    ((colorB & colorMask) >> 1) +
				    (colorA & colorB & lowPixelMask)) << 16);
			_farnspokel (dP, product);

			darkened = (product = ((product & colorMask) >> 1));
			darkened += (product = ((product & colorMask) >> 1));
			darkened += (product & colorMask) >> 1;
			_farnspokel (dP + dstPitch, darkened);

			colorA = nextPixel & 0xffff;
			product = colorB |
				  ((((colorA & colorMask) >> 1) +
				    ((colorB & colorMask) >> 1) +
				    (colorA & colorB & lowPixelMask)) << 16);
			_farnspokel (dP + 4, product);

			darkened = (product = ((product & colorMask) >> 1));
			darkened += (product = ((product & colorMask) >> 1));
			darkened += (product & colorMask) >> 1;
			_farnspokel (dP + dstPitch + 4, darkened);
		    }

		    dP += 8;
		} while ((uint8 *) bP < finish);
		line += 2;
	    }
	    else
	    {
		do
		{
		    currentPixel = nextPixel;
		    currentDelta = nextDelta;
		    nextPixel = *bP++;
		    nextDelta = *xP++;

		    if ((nextPixel != nextDelta) || (currentPixel != currentDelta))
		    {
			uint32 colorA, colorB, product;

			*(xP - 2) = currentPixel;
			colorA = currentPixel & 0xffff;

			colorB = (currentPixel & 0xffff0000) >> 16;
			product = colorA |
				  ((((colorA & colorMask) >> 1) +
				    ((colorB & colorMask) >> 1) +
				    (colorA & colorB & lowPixelMask)) << 16);
			_farnspokel (dP, product);

			colorA = nextPixel & 0xffff;
			product = colorB |
				  ((((colorA & colorMask) >> 1) +
				    ((colorB & colorMask) >> 1) +
				    (colorA & colorB & lowPixelMask)) << 16);
			_farnspokel (dP + 4, product);
		    }
		    dP += 8;
		} while ((uint8 *) bP < finish);
		line++;
	    }

	    deltaPtr += srcPitch;
	    srcPtr += srcPitch;
	} while (--height);
    }
}