/*    SDL_image:  An example image loading library for use with SDL    Copyright (C) 1997-2006 Sam Lantinga    This library is free software; you can redistribute it and/or    modify it under the terms of the GNU Lesser General Public    License as published by the Free Software Foundation; either    version 2.1 of the License, or (at your option) any later version.    This library is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU    Lesser General Public License for more details.    You should have received a copy of the GNU Lesser General Public    License along with this library; if not, write to the Free Software    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA    Sam Lantinga    slouken@libsdl.org*//* This is a GIF image file loading framework */#include <stdio.h>#include <string.h>#include "SDL_image.h"#ifdef LOAD_GIF/* See if an image is contained in a data source */int IMG_isGIF(SDL_RWops *src){	int start;	int is_GIF;	char magic[6];	if ( !src )		return 0;	start = SDL_RWtell(src);	is_GIF = 0;	if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {		if ( (strncmp(magic, "GIF", 3) == 0) &&		     ((memcmp(magic + 3, "87a", 3) == 0) ||		      (memcmp(magic + 3, "89a", 3) == 0)) ) {			is_GIF = 1;		}	}	SDL_RWseek(src, start, SEEK_SET);	return(is_GIF);}/* Code from here to end of file has been adapted from XPaint:           *//* +-------------------------------------------------------------------+ *//* | Copyright 1990, 1991, 1993 David Koblas.			       | *//* | Copyright 1996 Torsten Martinsen.				       | *//* |   Permission to use, copy, modify, and distribute this software   | *//* |   and its documentation for any purpose and without fee is hereby | *//* |   granted, provided that the above copyright notice appear in all | *//* |   copies and that both that copyright notice and this permission  | *//* |   notice appear in supporting documentation.  This software is    | *//* |   provided "as is" without express or implied warranty.	       | *//* +-------------------------------------------------------------------+ *//* Adapted for use in SDL by Sam Lantinga -- 7/20/98 */#define USED_BY_SDL#include <stdio.h>#include <string.h>#ifdef USED_BY_SDL/* Changes to work with SDL:   Include SDL header file   Use SDL_Surface rather than xpaint Image structure   Define SDL versions of RWSetMsg(), ImageNewCmap() and ImageSetCmap()*/#include "SDL.h"#define Image			SDL_Surface#define RWSetMsg		IMG_SetError#define ImageNewCmap(w, h, s)	SDL_AllocSurface(SDL_SWSURFACE,w,h,8,0,0,0,0)#define ImageSetCmap(s, i, R, G, B) do { \				s->format->palette->colors[i].r = R; \				s->format->palette->colors[i].g = G; \				s->format->palette->colors[i].b = B; \			} while (0)/* * * * * */#else/* Original XPaint sources */#include "image.h"#include "rwTable.h"#define SDL_RWops	FILE#define SDL_RWclose	fclose#endif /* USED_BY_SDL */#define	MAXCOLORMAPSIZE		256#define	TRUE	1#define	FALSE	0#define CM_RED		0#define CM_GREEN	1#define CM_BLUE		2#define	MAX_LWZ_BITS		12#define INTERLACE		0x40#define LOCALCOLORMAP	0x80#define BitSet(byte, bit)	(((byte) & (bit)) == (bit))#define	ReadOK(file,buffer,len)	SDL_RWread(file, buffer, len, 1)#define LM_to_uint(a,b)			(((b)<<8)|(a))static struct {    unsigned int Width;    unsigned int Height;    unsigned char ColorMap[3][MAXCOLORMAPSIZE];    unsigned int BitPixel;    unsigned int ColorResolution;    unsigned int Background;    unsigned int AspectRatio;    int GrayScale;} GifScreen;static struct {    int transparent;    int delayTime;    int inputFlag;    int disposal;} Gif89;static int ReadColorMap(SDL_RWops * src, int number,			unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);static int DoExtension(SDL_RWops * src, int label);static int GetDataBlock(SDL_RWops * src, unsigned char *buf);static int GetCode(SDL_RWops * src, int code_size, int flag);static int LWZReadByte(SDL_RWops * src, int flag, int input_code_size);static Image *ReadImage(SDL_RWops * src, int len, int height, int,			unsigned char cmap[3][MAXCOLORMAPSIZE],			int gray, int interlace, int ignore);Image *IMG_LoadGIF_RW(SDL_RWops *src){    int start;    unsigned char buf[16];    unsigned char c;    unsigned char localColorMap[3][MAXCOLORMAPSIZE];    int grayScale;    int useGlobalColormap;    int bitPixel;    int imageCount = 0;    char version[4];    int imageNumber = 1;    Image *image = NULL;    if ( src == NULL ) {	return NULL;    }    start = SDL_RWtell(src);    if (!ReadOK(src, buf, 6)) {	RWSetMsg("error reading magic number");        goto done;    }    if (strncmp((char *) buf, "GIF", 3) != 0) {	RWSetMsg("not a GIF file");        goto done;    }    strncpy(version, (char *) buf + 3, 3);    version[3] = '\0';    if ((strcmp(version, "87a") != 0) && (strcmp(version, "89a") != 0)) {	RWSetMsg("bad version number, not '87a' or '89a'");        goto done;    }    Gif89.transparent = -1;    Gif89.delayTime = -1;    Gif89.inputFlag = -1;    Gif89.disposal = 0;    if (!ReadOK(src, buf, 7)) {	RWSetMsg("failed to read screen descriptor");        goto done;    }    GifScreen.Width = LM_to_uint(buf[0], buf[1]);    GifScreen.Height = LM_to_uint(buf[2], buf[3]);    GifScreen.BitPixel = 2 << (buf[4] & 0x07);    GifScreen.ColorResolution = (((buf[4] & 0x70) >> 3) + 1);    GifScreen.Background = buf[5];    GifScreen.AspectRatio = buf[6];    if (BitSet(buf[4], LOCALCOLORMAP)) {	/* Global Colormap */	if (ReadColorMap(src, GifScreen.BitPixel, GifScreen.ColorMap,			 &GifScreen.GrayScale)) {	    RWSetMsg("error reading global colormap");            goto done;	}    }    do {	if (!ReadOK(src, &c, 1)) {	    RWSetMsg("EOF / read error on image data");            goto done;	}	if (c == ';') {		/* GIF terminator */	    if (imageCount < imageNumber) {		RWSetMsg("only %d image%s found in file",			 imageCount, imageCount > 1 ? "s" : "");                goto done;	    }	}	if (c == '!') {		/* Extension */	    if (!ReadOK(src, &c, 1)) {		RWSetMsg("EOF / read error on extention function code");                goto done;	    }	    DoExtension(src, c);	    continue;	}	if (c != ',') {		/* Not a valid start character */	    continue;	}	++imageCount;	if (!ReadOK(src, buf, 9)) {	    RWSetMsg("couldn't read left/top/width/height");            goto done;	}	useGlobalColormap = !BitSet(buf[8], LOCALCOLORMAP);	bitPixel = 1 << ((buf[8] & 0x07) + 1);	if (!useGlobalColormap) {	    if (ReadColorMap(src, bitPixel, localColorMap, &grayScale)) {		RWSetMsg("error reading local colormap");                goto done;	    }	    image = ReadImage(src, LM_to_uint(buf[4], buf[5]),			      LM_to_uint(buf[6], buf[7]),			      bitPixel, localColorMap, grayScale,			      BitSet(buf[8], INTERLACE),			      imageCount != imageNumber);	} else {	    image = ReadImage(src, LM_to_uint(buf[4], buf[5]),			      LM_to_uint(buf[6], buf[7]),			      GifScreen.BitPixel, GifScreen.ColorMap,			      GifScreen.GrayScale, BitSet(buf[8], INTERLACE),			      imageCount != imageNumber);	}    } while (image == NULL);#ifdef USED_BY_SDL    if ( Gif89.transparent >= 0 ) {        SDL_SetColorKey(image, SDL_SRCCOLORKEY, Gif89.transparent);    }#endifdone:    if ( image == NULL ) {        SDL_RWseek(src, start, SEEK_SET);    }    return image;}static intReadColorMap(SDL_RWops *src, int number,             unsigned char buffer[3][MAXCOLORMAPSIZE], int *gray){    int i;    unsigned char rgb[3];    int flag;    flag = TRUE;    for (i = 0; i < number; ++i) {	if (!ReadOK(src, rgb, sizeof(rgb))) {	    RWSetMsg("bad colormap");	    return 1;	}	buffer[CM_RED][i] = rgb[0];	buffer[CM_GREEN][i] = rgb[1];	buffer[CM_BLUE][i] = rgb[2];	flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);    }#if 0    if (flag)	*gray = (number == 2) ? PBM_TYPE : PGM_TYPE;    else	*gray = PPM_TYPE;#else    *gray = 0;#endif    return FALSE;}static intDoExtension(SDL_RWops *src, int label){    static unsigned char buf[256];    char *str;    switch (label) {    case 0x01:			/* Plain Text Extension */	str = "Plain Text Extension";	break;    case 0xff:			/* Application Extension */	str = "Application Extension";	break;    case 0xfe:			/* Comment Extension */	str = "Comment Extension";	while (GetDataBlock(src, (unsigned char *) buf) != 0)	    ;	return FALSE;    case 0xf9:			/* Graphic Control Extension */	str = "Graphic Control Extension";	(void) GetDataBlock(src, (unsigned char *) buf);	Gif89.disposal = (buf[0] >> 2) & 0x7;	Gif89.inputFlag = (buf[0] >> 1) & 0x1;	Gif89.delayTime = LM_to_uint(buf[1], buf[2]);	if ((buf[0] & 0x1) != 0)	    Gif89.transparent = buf[3];	while (GetDataBlock(src, (unsigned char *) buf) != 0)	    ;	return FALSE;    default:	str = (char *)buf;	sprintf(str, "UNKNOWN (0x%02x)", label);	break;    }    while (GetDataBlock(src, (unsigned char *) buf) != 0)	;    return FALSE;}static int ZeroDataBlock = FALSE;static intGetDataBlock(SDL_RWops *src, unsigned char *buf){    unsigned char count;    if (!ReadOK(src, &count, 1)) {	/* pm_message("error in getting DataBlock size" ); */	return -1;    }    ZeroDataBlock = count == 0;    if ((count != 0) && (!ReadOK(src, buf, count))) {	/* pm_message("error in reading DataBlock" ); */	return -1;    }    return count;}static intGetCode(SDL_RWops *src, int code_size, int flag){    static unsigned char buf[280];    static int curbit, lastbit, done, last_byte;    int i, j, ret;    unsigned char count;    if (flag) {	curbit = 0;	lastbit = 0;	done = FALSE;	return 0;    }    if ((curbit + code_size) >= lastbit) {	if (done) {	    if (curbit >= lastbit)		RWSetMsg("ran off the end of my bits");	    return -1;	}	buf[0] = buf[last_byte - 2];	buf[1] = buf[last_byte - 1];	if ((count = GetDataBlock(src, &buf[2])) == 0)	    done = TRUE;	last_byte = 2 + count;	curbit = (curbit - lastbit) + 16;	lastbit = (2 + count) * 8;    }    ret = 0;    for (i = curbit, j = 0; j < code_size; ++i, ++j)	ret |= ((buf[i / 8] & (1 << (i % 8))) != 0) << j;    curbit += code_size;    return ret;}static intLWZReadByte(SDL_RWops *src, int flag, int input_code_size){    static int fresh = FALSE;    int code, incode;    static int code_size, set_code_size;    static int max_code, max_code_size;    static int firstcode, oldcode;    static int clear_code, end_code;    static int table[2][(1 << MAX_LWZ_BITS)];    static int stack[(1 << (MAX_LWZ_BITS)) * 2], *sp;    register int i;    /* Fixed buffer overflow found by Michael Skladnikiewicz */    if (input_code_size > MAX_LWZ_BITS)        return -1;    if (flag) {	set_code_size = input_code_size;	code_size = set_code_size + 1;	clear_code = 1 << set_code_size;	end_code = clear_code + 1;	max_code_size = 2 * clear_code;	max_code = clear_code + 2;	GetCode(src, 0, TRUE);	fresh = TRUE;	for (i = 0; i < clear_code; ++i) {	    table[0][i] = 0;	    table[1][i] = i;	}	for (; i < (1 << MAX_LWZ_BITS); ++i)	    table[0][i] = table[1][0] = 0;	sp = stack;	return 0;    } else if (fresh) {	fresh = FALSE;	do {	    firstcode = oldcode = GetCode(src, code_size, FALSE);	} while (firstcode == clear_code);	return firstcode;    }    if (sp > stack)	return *--sp;    while ((code = GetCode(src, code_size, FALSE)) >= 0) {	if (code == clear_code) {	    for (i = 0; i < clear_code; ++i) {		table[0][i] = 0;		table[1][i] = i;	    }	    for (; i < (1 << MAX_LWZ_BITS); ++i)		table[0][i] = table[1][i] = 0;	    code_size = set_code_size + 1;	    max_code_size = 2 * clear_code;	    max_code = clear_code + 2;	    sp = stack;	    firstcode = oldcode = GetCode(src, code_size, FALSE);	    return firstcode;	} else if (code == end_code) {	    int count;	    unsigned char buf[260];	    if (ZeroDataBlock)		return -2;	    while ((count = GetDataBlock(src, buf)) > 0)		;	    if (count != 0) {		/*		 * pm_message("missing EOD in data stream (common occurence)");		 */	    }	    return -2;	}	incode = code;	if (code >= max_code) {	    *sp++ = firstcode;	    code = oldcode;	}	while (code >= clear_code) {	    *sp++ = table[1][code];	    if (code == table[0][code])		RWSetMsg("circular table entry BIG ERROR");	    code = table[0][code];	}	*sp++ = firstcode = table[1][code];	if ((code = max_code) < (1 << MAX_LWZ_BITS)) {	    table[0][code] = oldcode;	    table[1][code] = firstcode;	    ++max_code;	    if ((max_code >= max_code_size) &&		(max_code_size < (1 << MAX_LWZ_BITS))) {		max_code_size *= 2;		++code_size;	    }	}	oldcode = incode;	if (sp > stack)	    return *--sp;    }    return code;}static Image *ReadImage(SDL_RWops * src, int len, int height, int cmapSize,	  unsigned char cmap[3][MAXCOLORMAPSIZE],	  int gray, int interlace, int ignore){    Image *image;    unsigned char c;    int i, v;    int xpos = 0, ypos = 0, pass = 0;    /*    **	Initialize the compression routines     */    if (!ReadOK(src, &c, 1)) {	RWSetMsg("EOF / read error on image data");	return NULL;    }    if (LWZReadByte(src, TRUE, c) < 0) {	RWSetMsg("error reading image");	return NULL;    }    /*    **	If this is an "uninteresting picture" ignore it.     */    if (ignore) {	while (LWZReadByte(src, FALSE, c) >= 0)	    ;	return NULL;    }    image = ImageNewCmap(len, height, cmapSize);    for (i = 0; i < cmapSize; i++)	ImageSetCmap(image, i, cmap[CM_RED][i],		     cmap[CM_GREEN][i], cmap[CM_BLUE][i]);    while ((v = LWZReadByte(src, FALSE, c)) >= 0) {#ifdef USED_BY_SDL	((Uint8 *)image->pixels)[xpos + ypos * image->pitch] = v;#else	image->data[xpos + ypos * len] = v;#endif	++xpos;	if (xpos == len) {	    xpos = 0;	    if (interlace) {		switch (pass) {		case 0:		case 1:		    ypos += 8;		    break;		case 2:		    ypos += 4;		    break;		case 3:		    ypos += 2;		    break;		}		if (ypos >= height) {		    ++pass;		    switch (pass) {		    case 1:			ypos = 4;			break;		    case 2:			ypos = 2;			break;		    case 3:			ypos = 1;			break;		    default:			goto fini;		    }		}	    } else {		++ypos;	    }	}	if (ypos >= height)	    break;    }  fini:    return image;}#else/* See if an image is contained in a data source */int IMG_isGIF(SDL_RWops *src){	return(0);}/* Load a GIF type image from an SDL datasource */SDL_Surface *IMG_LoadGIF_RW(SDL_RWops *src){	return(NULL);}#endif /* LOAD_GIF */