sdl_rleaccel.c

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    if(!dest)
	return -1;
    df = dest->format;
    if(surface->format->BitsPerPixel != 32)
	return -1;		/* only 32bpp source supported */

    /* find out whether the destination is one we support,
       and determine the max size of the encoded result */
    masksum = df->Rmask | df->Gmask | df->Bmask;
    switch(df->BytesPerPixel) {
    case 2:
	/* 16bpp: only support 565 and 555 formats */
	switch(masksum) {
	case 0xffff:
	    if(df->Gmask == 0x07e0
	       || df->Rmask == 0x07e0 || df->Bmask == 0x07e0) {
		copy_opaque = copy_opaque_16;
		copy_transl = copy_transl_565;
	    } else
		return -1;
	    break;
	case 0x7fff:
	    if(df->Gmask == 0x03e0
	       || df->Rmask == 0x03e0 || df->Bmask == 0x03e0) {
		copy_opaque = copy_opaque_16;
		copy_transl = copy_transl_555;
	    } else
		return -1;
	    break;
	default:
	    return -1;
	}
	max_opaque_run = 255;	/* runs stored as bytes */

	/* worst case is alternating opaque and translucent pixels,
	   with room for alignment padding between lines */
	maxsize = surface->h * (2 + (4 + 2) * (surface->w + 1)) + 2;
	break;
    case 4:
	if(masksum != 0x00ffffff)
	    return -1;		/* requires unused high byte */
	copy_opaque = copy_32;
	copy_transl = copy_32;
	max_opaque_run = 255;	/* runs stored as short ints */

	/* worst case is alternating opaque and translucent pixels */
	maxsize = surface->h * 2 * 4 * (surface->w + 1) + 4;
	break;
    default:
	return -1;		/* anything else unsupported right now */
    }

    maxsize += sizeof(RLEDestFormat);
    rlebuf = (Uint8 *)malloc(maxsize);
    if(!rlebuf) {
	SDL_OutOfMemory();
	return -1;
    }
    {
	/* save the destination format so we can undo the encoding later */
	RLEDestFormat *r = (RLEDestFormat *)rlebuf;
	r->BytesPerPixel = df->BytesPerPixel;
	r->Rloss = df->Rloss;
	r->Gloss = df->Gloss;
	r->Bloss = df->Bloss;
	r->Rshift = df->Rshift;
	r->Gshift = df->Gshift;
	r->Bshift = df->Bshift;
	r->Ashift = df->Ashift;
	r->Rmask = df->Rmask;
	r->Gmask = df->Gmask;
	r->Bmask = df->Bmask;
	r->Amask = df->Amask;
    }
    dst = rlebuf + sizeof(RLEDestFormat);

    /* Do the actual encoding */
    {
	int x, y;
	int h = surface->h, w = surface->w;
	SDL_PixelFormat *sf = surface->format;
	Uint32 *src = (Uint32 *)((Uint8 *)surface->pixels + surface->offset);
	Uint8 *lastline = dst;	/* end of last non-blank line */

	/* opaque counts are 8 or 16 bits, depending on target depth */
#define ADD_OPAQUE_COUNTS(n, m)			\
	if(df->BytesPerPixel == 4) {		\
	    ((Uint16 *)dst)[0] = n;		\
	    ((Uint16 *)dst)[1] = m;		\
	    dst += 4;				\
	} else {				\
	    dst[0] = n;				\
	    dst[1] = m;				\
	    dst += 2;				\
	}

	/* translucent counts are always 16 bit */
#define ADD_TRANSL_COUNTS(n, m)		\
	(((Uint16 *)dst)[0] = n, ((Uint16 *)dst)[1] = m, dst += 4)

	for(y = 0; y < h; y++) {
	    int runstart, skipstart;
	    int blankline = 0;
	    /* First encode all opaque pixels of a scan line */
	    x = 0;
	    do {
		int run, skip, len;
		skipstart = x;
		while(x < w && !ISOPAQUE(src[x], sf))
		    x++;
		runstart = x;
		while(x < w && ISOPAQUE(src[x], sf))
		    x++;
		skip = runstart - skipstart;
		if(skip == w)
		    blankline = 1;
		run = x - runstart;
		while(skip > max_opaque_run) {
		    ADD_OPAQUE_COUNTS(max_opaque_run, 0);
		    skip -= max_opaque_run;
		}
		len = MIN(run, max_opaque_run);
		ADD_OPAQUE_COUNTS(skip, len);
		dst += copy_opaque(dst, src + runstart, len, sf, df);
		runstart += len;
		run -= len;
		while(run) {
		    len = MIN(run, max_opaque_run);
		    ADD_OPAQUE_COUNTS(0, len);
		    dst += copy_opaque(dst, src + runstart, len, sf, df);
		    runstart += len;
		    run -= len;
		}
	    } while(x < w);

	    /* Make sure the next output address is 32-bit aligned */
	    dst += (unsigned long)dst & 2;

	    /* Next, encode all translucent pixels of the same scan line */
	    x = 0;
	    do {
		int run, skip, len;
		skipstart = x;
		while(x < w && !ISTRANSL(src[x], sf))
		    x++;
		runstart = x;
		while(x < w && ISTRANSL(src[x], sf))
		    x++;
		skip = runstart - skipstart;
		blankline &= (skip == w);
		run = x - runstart;
		while(skip > max_transl_run) {
		    ADD_TRANSL_COUNTS(max_transl_run, 0);
		    skip -= max_transl_run;
		}
		len = MIN(run, max_transl_run);
		ADD_TRANSL_COUNTS(skip, len);
		dst += copy_transl(dst, src + runstart, len, sf, df);
		runstart += len;
		run -= len;
		while(run) {
		    len = MIN(run, max_transl_run);
		    ADD_TRANSL_COUNTS(0, len);
		    dst += copy_transl(dst, src + runstart, len, sf, df);
		    runstart += len;
		    run -= len;
		}
		if(!blankline)
		    lastline = dst;
	    } while(x < w);

	    src += surface->pitch >> 2;
	}
	dst = lastline;		/* back up past trailing blank lines */
	ADD_OPAQUE_COUNTS(0, 0);
    }

#undef ADD_OPAQUE_COUNTS
#undef ADD_TRANSL_COUNTS

    /* Now that we have it encoded, release the original pixels */
    if((surface->flags & SDL_PREALLOC) != SDL_PREALLOC
       && (surface->flags & SDL_HWSURFACE) != SDL_HWSURFACE) {
	free( surface->pixels );
	surface->pixels = NULL;
    }

    /* realloc the buffer to release unused memory */
    {
	Uint8 *p = realloc(rlebuf, dst - rlebuf);
	if(!p)
	    p = rlebuf;
	surface->map->sw_data->aux_data = p;
    }

    return 0;
}

static Uint32 getpix_8(Uint8 *srcbuf)
{
    return *srcbuf;
}

static Uint32 getpix_16(Uint8 *srcbuf)
{
    return *(Uint16 *)srcbuf;
}

static Uint32 getpix_24(Uint8 *srcbuf)
{
    if(SDL_BYTEORDER == SDL_LIL_ENDIAN)
	return srcbuf[0] + (srcbuf[1] << 8) + (srcbuf[2] << 16);
    else
	return (srcbuf[0] << 16) + (srcbuf[1] << 8) + srcbuf[2];
}

static Uint32 getpix_32(Uint8 *srcbuf)
{
    return *(Uint32 *)srcbuf;
}

typedef Uint32 (*getpix_func)(Uint8 *);

static getpix_func getpixes[4] = {
    getpix_8, getpix_16, getpix_24, getpix_32
};

static int RLEColorkeySurface(SDL_Surface *surface)
{
        Uint8 *rlebuf, *dst;
	int maxn;
	int y;
	Uint8 *srcbuf, *curbuf, *lastline;
	int maxsize = 0;
	int skip, run;
	int bpp = surface->format->BytesPerPixel;
	getpix_func getpix;
	Uint32 ckey, rgbmask;
	int w, h;

	/* calculate the worst case size for the compressed surface */
	switch(bpp) {
	case 1:
	    /* worst case is alternating opaque and transparent pixels,
	       starting with an opaque pixel */
	    maxsize = surface->h * 3 * (surface->w / 2 + 1) + 2;
	    break;
	case 2:
	case 3:
	    /* worst case is solid runs, at most 255 pixels wide */
	    maxsize = surface->h * (2 * (surface->w / 255 + 1)
				    + surface->w * bpp) + 2;
	    break;
	case 4:
	    /* worst case is solid runs, at most 65535 pixels wide */
	    maxsize = surface->h * (4 * (surface->w / 65535 + 1)
				    + surface->w * 4) + 4;
	    break;
	}

	rlebuf = (Uint8 *)malloc(maxsize);
	if ( rlebuf == NULL ) {
		SDL_OutOfMemory();
		return(-1);
	}

	/* Set up the conversion */
	srcbuf = (Uint8 *)surface->pixels+surface->offset;
	curbuf = srcbuf;
	maxn = bpp == 4 ? 65535 : 255;
	skip = run = 0;
	dst = rlebuf;
	rgbmask = ~surface->format->Amask;
	ckey = surface->format->colorkey & rgbmask;
	lastline = dst;
	getpix = getpixes[bpp - 1];
	w = surface->w;
	h = surface->h;

#define ADD_COUNTS(n, m)			\
	if(bpp == 4) {				\
	    ((Uint16 *)dst)[0] = n;		\
	    ((Uint16 *)dst)[1] = m;		\
	    dst += 4;				\
	} else {				\
	    dst[0] = n;				\
	    dst[1] = m;				\
	    dst += 2;				\
	}

	for(y = 0; y < h; y++) {
	    int x = 0;
	    int blankline = 0;
	    do {
		int run, skip, len;
		int runstart;
		int skipstart = x;

		/* find run of transparent, then opaque pixels */
		while(x < w && (getpix(srcbuf + x * bpp) & rgbmask) == ckey)
		    x++;
		runstart = x;
		while(x < w && (getpix(srcbuf + x * bpp) & rgbmask) != ckey)
		    x++;
		skip = runstart - skipstart;
		if(skip == w)
		    blankline = 1;
		run = x - runstart;

		/* encode segment */
		while(skip > maxn) {
		    ADD_COUNTS(maxn, 0);
		    skip -= maxn;
		}
		len = MIN(run, maxn);
		ADD_COUNTS(skip, len);
		memcpy(dst, srcbuf + runstart * bpp, len * bpp);
		dst += len * bpp;
		run -= len;
		runstart += len;
		while(run) {
		    len = MIN(run, maxn);
		    ADD_COUNTS(0, len);
		    memcpy(dst, srcbuf + runstart * bpp, len * bpp);
		    dst += len * bpp;
		    runstart += len;
		    run -= len;
		}
		if(!blankline)
		    lastline = dst;
	    } while(x < w);

	    srcbuf += surface->pitch;
	}
	dst = lastline;		/* back up bast trailing blank lines */
	ADD_COUNTS(0, 0);

#undef ADD_COUNTS

	/* Now that we have it encoded, release the original pixels */
	if((surface->flags & SDL_PREALLOC) != SDL_PREALLOC
	   && (surface->flags & SDL_HWSURFACE) != SDL_HWSURFACE) {
	    free( surface->pixels );
	    surface->pixels = NULL;
	}

	/* realloc the buffer to release unused memory */
	{
	    /* If realloc returns NULL, the original block is left intact */
	    Uint8 *p = realloc(rlebuf, dst - rlebuf);
	    if(!p)
		p = rlebuf;
	    surface->map->sw_data->aux_data = p;
	}

	return(0);
}

int SDL_RLESurface(SDL_Surface *surface)
{
	int retcode;

	/* Clear any previous RLE conversion */
	if ( (surface->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
		SDL_UnRLESurface(surface, 1);
	}

	/* We don't support RLE encoding of bitmaps */
	if ( surface->format->BitsPerPixel < 8 ) {
		return(-1);
	}

	/* Lock the surface if it's in hardware */
	if ( surface->flags & (SDL_HWSURFACE|SDL_ASYNCBLIT) ) {
		SDL_VideoDevice *video = current_video;
		SDL_VideoDevice *this  = current_video;
		if ( video->LockHWSurface(this, surface) < 0 ) {
			return(-1);
		}
	}

	/* Encode */
	if((surface->flags & SDL_SRCCOLORKEY) == SDL_SRCCOLORKEY) {
	    retcode = RLEColorkeySurface(surface);
	} else {
	    if((surface->flags & SDL_SRCALPHA) == SDL_SRCALPHA
	       && surface->format->Amask != 0)
		retcode = RLEAlphaSurface(surface);
	    else
		retcode = -1;	/* no RLE for per-surface alpha sans ckey */
	}

	/* Unlock the surface if it's in hardware */
	if ( surface->flags & (SDL_HWSURFACE|SDL_ASYNCBLIT) ) {
		SDL_VideoDevice *video = current_video;
		SDL_VideoDevice *this  = current_video;
		video->UnlockHWSurface(this, surface);
	}

	if(retcode < 0)
	    return -1;

	/* The surface is now accelerated */
	surface->flags |= SDL_RLEACCEL;

	return(0);
}

/*
 * Un-RLE a surface with pixel alpha
 * This may not give back exactly the image before RLE-encoding; all
 * completely transparent pixels will be lost, and colour and alpha depth
 * may have been reduced (when encoding for 16bpp targets).
 */
static void UnRLEAlpha(SDL_Surface *surface)
{
    Uint8 *srcbuf;
    Uint32 *dst;
    SDL_PixelFormat *sf = surface->format;
    RLEDestFormat *df = surface->map->sw_data->aux_data;
    int (*uncopy_opaque)(Uint32 *, void *, int,
			 RLEDestFormat *, SDL_PixelFormat *);
    int (*uncopy_transl)(Uint32 *, void *, int,
			 RLEDestFormat *, SDL_PixelFormat *);
    int w = surface->w;
    int bpp = df->BytesPerPixel;

    if(bpp == 2) {
	uncopy_opaque = uncopy_opaque_16;
	uncopy_transl = uncopy_transl_16;
    } else {
	uncopy_opaque = uncopy_transl = uncopy_32;
    }

    surface->pixels = malloc(surface->h * surface->pitch);
    /* fill background with transparent pixels */
    memset(surface->pixels, 0, surface->h * surface->pitch);

    dst = surface->pixels;
    srcbuf = (Uint8 *)(df + 1);
    for(;;) {
	/* copy opaque pixels */
	int ofs = 0;
	do {
	    unsigned run;
	    if(bpp == 2) {
		ofs += srcbuf[0];
		run = srcbuf[1];
		srcbuf += 2;
	    } else {
		ofs += ((Uint16 *)srcbuf)[0];
		run = ((Uint16 *)srcbuf)[1];
		srcbuf += 4;
	    }
	    if(run) {
		srcbuf += uncopy_opaque(dst + ofs, srcbuf, run, df, sf);
		ofs += run;
	    } else if(!ofs)
		return;
	} while(ofs < w);

	/* skip padding if needed */
	if(bpp == 2)
	    srcbuf += (unsigned long)srcbuf & 2;
	
	/* copy translucent pixels */
	ofs = 0;
	do {
	    unsigned run;
	    ofs += ((Uint16 *)srcbuf)[0];
	    run = ((Uint16 *)srcbuf)[1];
	    srcbuf += 4;
	    if(run) {
		srcbuf += uncopy_transl(dst + ofs, srcbuf, run, df, sf);
		ofs += run;
	    }
	} while(ofs < w);
	dst += surface->pitch >> 2;
    }
}

void SDL_UnRLESurface(SDL_Surface *surface, int recode)
{
    if ( (surface->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
	surface->flags &= ~SDL_RLEACCEL;

	if(recode && (surface->flags & SDL_PREALLOC) != SDL_PREALLOC
	   && (surface->flags & SDL_HWSURFACE) != SDL_HWSURFACE) {
	    if((surface->flags & SDL_SRCCOLORKEY) == SDL_SRCCOLORKEY) {
		SDL_Rect full;
		unsigned alpha_flag;

		/* re-create the original surface */
		surface->pixels = malloc(surface->h * surface->pitch);

		/* fill it with the background colour */
		SDL_FillRect(surface, NULL, surface->format->colorkey);

		/* now render the encoded surface */
		full.x = full.y = 0;
		full.w = surface->w;
		full.h = surface->h;
		alpha_flag = surface->flags & SDL_SRCALPHA;
		surface->flags &= ~SDL_SRCALPHA; /* opaque blit */
		SDL_RLEBlit(surface, &full, surface, &full);
		surface->flags |= alpha_flag;
	    } else
		UnRLEAlpha(surface);
	}

	if ( surface->map && surface->map->sw_data->aux_data ) {
	    free(surface->map->sw_data->aux_data);
	    surface->map->sw_data->aux_data = NULL;
	}
    }
}