/* +-------------------------------------------------------------------+ */
/* | 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.	       | */
/* +-------------------------------------------------------------------+ */

/* $Id: readGIF.c,v 1.21 2005/03/20 20:15:34 demailly Exp $ */

#include <stdio.h>
#include <string.h>
#include <X11/Xlib.h>
#include <X11/Intrinsic.h>
#include "xpaint.h"
#include "image.h"
#include "rwTable.h"

#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)	(fread(buffer, len, 1, file) != 0)

#define LM_to_uint(a,b)			(((b)<<8)|(a))

extern int file_isSpecialImage;
extern int file_transparent;
extern int file_numpages;

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 GrayColorScheme;
} GifScreen;

static struct {
    int transparent;
    int index;
    int delayTime;
    int inputFlag;
    int disposal;
} Gif89 = {
    0, -1, -1, -1, 0
};

static int ReadColorMap(FILE * fd, int number,
			unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);
static int DoExtension(FILE * fd, int label);
static int GetDataBlock(FILE * fd, unsigned char *buf);
static int GetCode(FILE * fd, int code_size, int flag);
static int LWZReadByte(FILE * fd, int flag, int input_code_size);
static Image *ReadImage(FILE * fd, int width, int height, int cmapSize,
			unsigned char cmap[3][MAXCOLORMAPSIZE],
			int gray, int interlace, int ignore);

int
TestGIF(char *file)
{
    FILE *fd = fopen(file, "r");
    char buf[10];
    int ret = 0;

    if (fd == NULL)
	return 0;

    if (ReadOK(fd, buf, 6)) {
	if ((strncmp(buf, "GIF", 3) == 0) &&
	    ((strcmp(buf + 3, "87a") != 0) ||
	     (strcmp(buf + 3, "89a") != 0)))
	    ret = 1;
    }
    fclose(fd);

    return ret;
}

Image *
ReadGIF(char *file)
{
    unsigned char buf[16];
    unsigned char c;
    unsigned char transp_index = 0;
    unsigned char localColorMap[3][MAXCOLORMAPSIZE];
    int i, transparent = 0, numpage;
    int grayScale;
    int useGlobalColormap;
    int bitPixel;
    int imageCount = 0;
    char version[4];
    FILE *fd = fopen(file, "r");
    Image *image, *output = NULL;

    if (fd == NULL)
	return NULL;

    if (!ReadOK(fd, buf, 6)) {
	RWSetMsg("error reading magic number");
	fclose(fd);
	return NULL;
    }
    if (strncmp((char *) buf, "GIF", 3) != 0) {
	RWSetMsg("not a GIF file");
	fclose(fd);
	return NULL;
    }
    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'");
	fclose(fd);
	return NULL;
    }
    if (!ReadOK(fd, buf, 7)) {
	RWSetMsg("failed to read screen descriptor");
	fclose(fd);
	return NULL;
    }
    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(fd, GifScreen.BitPixel, GifScreen.ColorMap,
			 &GifScreen.GrayColorScheme)) {
	    RWSetMsg("error reading global colormap");
	    fclose(fd);
	    return NULL;
	}
    }

    numpage = Global.numpage;

    while (1) {
	if (!ReadOK(fd, &c, 1)) {
	    if (!output) RWSetMsg("EOF / read error on image data");
	    fclose(fd);
	    goto the_end;
	}
	if (c == ';') {		/* GIF terminator */
	    if (imageCount < numpage) {
		RWSetMsg("only %d image%s found in file",
			 imageCount, imageCount > 1 ? "s" : "");
		fclose(fd);
		return NULL;
	    }
            goto the_end;
	}
	if (c == '!') {		/* Extension */
	    if (!ReadOK(fd, &c, 1)) {
		RWSetMsg("EOF / read error on extension function code");
		goto the_end;
	    }
	    DoExtension(fd, c);
            transparent = Gif89.transparent;
            if (transparent)
                transp_index = Gif89.index;
	    continue;
	}
	if (c != ',') {		/* Not a valid start character */
	    continue;
	}
	++imageCount;

	if (!ReadOK(fd, buf, 9)) {
	    RWSetMsg("couldn't read left/top/width/height");
	    fclose(fd);
	    goto the_end;
	}
	useGlobalColormap = !BitSet(buf[8], LOCALCOLORMAP);

	bitPixel = 1 << ((buf[8] & 0x07) + 1);

	if (!useGlobalColormap) {
	    if (ReadColorMap(fd, bitPixel, localColorMap, &grayScale)) {
		RWSetMsg("error reading local colormap");
		return NULL;
	    }
	    image = ReadImage(fd, LM_to_uint(buf[4], buf[5]),
		 	      LM_to_uint(buf[6], buf[7]),
			      bitPixel, localColorMap, grayScale,
			      BitSet(buf[8], INTERLACE),
			      imageCount != numpage);
	} else {
	    image = ReadImage(fd, LM_to_uint(buf[4], buf[5]),
			      LM_to_uint(buf[6], buf[7]),
			      GifScreen.BitPixel, GifScreen.ColorMap,
			      GifScreen.GrayColorScheme, 
                              BitSet(buf[8], INTERLACE),
			      imageCount != numpage);
	}
        if (image) output = image;
        file_numpages = imageCount;
        file_isSpecialImage = (file_numpages>1);
    }

 the_end :
    if (transparent && output) {
        file_transparent = 1;
        ImageMakeMask(output); 
	for (i=0; i<output->width*output->height; i++)
	    output->alpha[i] = ((output->data[i]==transp_index)? 0:255);
    }
    return output;
}

static int
ReadColorMap(FILE *fd, 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(fd, 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 int
DoExtension(FILE *fd, int label)
{
    static 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(fd, (unsigned char *) buf) != 0);
	return FALSE;
    case 0xf9:			/* Graphic Control Extension */
	str = "Graphic Control Extension";
	(void) GetDataBlock(fd, (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 = 1;
	    Gif89.index = buf[3];
	}

	while (GetDataBlock(fd, (unsigned char *) buf) != 0);
	return FALSE;
    default:
	str = buf;
	sprintf(buf, "UNKNOWN (0x%02x)", label);
	break;
    }

    while (GetDataBlock(fd, (unsigned char *) buf) != 0);

    return FALSE;
}

static int ZeroDataBlock = FALSE;

static int
GetDataBlock(FILE *fd, unsigned char *buf)
{
    unsigned char count;

    if (!ReadOK(fd, &count, 1)) {
	/* pm_message("error in getting DataBlock size" ); */
	return -1;
    }
    ZeroDataBlock = count == 0;

    if ((count != 0) && (!ReadOK(fd, buf, count))) {
	/* pm_message("error in reading DataBlock" ); */
	return -1;
    }
    return count;
}

static int
GetCode(FILE *fd, 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(fd, &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 int
LWZReadByte(FILE *fd, 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;

    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(fd, 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(fd, code_size, FALSE);
	} while (firstcode == clear_code);
	return firstcode;
    }
    if (sp > stack)
	return *--sp;

    while ((code = GetCode(fd, 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(fd, code_size, FALSE);
	    return firstcode;
	} else if (code == end_code) {
	    int count;
	    unsigned char buf[260];

	    if (ZeroDataBlock)
		return -2;

	    while ((count = GetDataBlock(fd, 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(FILE * fd, int width, 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(fd, &c, 1)) {
	RWSetMsg("EOF / read error on image data");
	return NULL;
    }
    if (LWZReadByte(fd, TRUE, c) < 0) {
	RWSetMsg("error reading image");
	return NULL;
    }
    /*
    **	If this is an "uninteresting picture" ignore it.
     */
    if (ignore) {
	while (LWZReadByte(fd, FALSE, c) >= 0);
	return NULL;
    }
    image = ImageNewCmap(width, 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(fd, FALSE, c)) >= 0) {
	image->data[xpos + ypos * width] = v;

	++xpos;
	if (xpos == width) {
	    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 finished;
		    }
		}
	    } else {
		++ypos;
	    }
	}
	if (ypos >= height)
	    break;
    }

  finished:

    return image;
}
