/* The following code is extracted from giftoppm.c, from the pbmplus package */

/* +-------------------------------------------------------------------+ */
/* | Copyright 1990, David Koblas.                                     | */
/* |   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.           | */
/* +-------------------------------------------------------------------+ */

#include <stdio.h>
#include "fig2dev.h"
#include "object.h"

extern	FILE	*open_picfile();
extern	void	close_picfile();

#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))

struct {
	unsigned int	Width;
	unsigned int	Height;
	unsigned int	BitPixel;
	unsigned int	ColorResolution;
	unsigned int	Background;
	unsigned int	AspectRatio;
} GifScreen;

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

static	int	verbose;
int	showComment;

static Boolean ReadColorMap();
static Boolean DoExtension();
static int GetDataBlock();
static int GetCode();
static int LWZReadByte();
static Boolean ReadGIFImage();

int
read_gif(pic)
  F_pic *pic;
{
	FILE		*fd;
	unsigned char	buf[16];
	unsigned char	c;
	int		useGlobalColormap;
	int		bitPixel;
	char		version[4];
	int		filtype;		/* file (0) or pipe (1) */

	if ((fd=open_picfile(pic->file, &filtype)) == NULL)
	    return 0;

	if (! ReadOK(fd,buf,6)) {
		close_picfile(fd,filtype);
		return 0;
	}

	if (strncmp((char *) buf,"GIF",3) != 0) {
		close_picfile(fd,filtype);
		return -1;
	}

	strncpy(version, (char *) (buf + 3), 3);
	version[3] = '\0';

	if ((strcmp(version, "87a") != 0) && (strcmp(version, "89a") != 0)) {
		fprintf(stderr,"Unknown GIF version %s\n",version);
		close_picfile(fd,filtype);
		return -1;
	}

	if (! ReadOK(fd,buf,7)) {
		close_picfile(fd,filtype);
		return 0;		/* failed to read screen descriptor */
	}

	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 = (((unsigned int)(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,pic->cmap)) {
			close_picfile(fd,filtype);
			return 0;		/* error reading global colormap */
		}
	}

	if (GifScreen.AspectRatio != 0 && GifScreen.AspectRatio != 49) {
		fprintf(stderr,"GIF: warning - non-square pixels\n");
	}

	for (;;) {
		if (! ReadOK(fd,&c,1)) {
			close_picfile(fd,filtype);	/* EOF / read error on image data */
			return 0;
		}

		if (c == ';') {		/* GIF terminator */
			close_picfile(fd,filtype);
			return 1;
		}

		if (c == '!') { 	/* Extension */
			if (! ReadOK(fd,&c,1))
				fprintf(stderr,"GIF read error on extention function code\n");
			(void) DoExtension(fd, c);
			continue;
		}

		if (c != ',') {		/* Not a valid start character */
			continue;
		}

		if (! ReadOK(fd,buf,9)) {
			close_picfile(fd,filtype);
			return 0;	/* couldn't read left/top/width/height */
		}

		useGlobalColormap = ! BitSet(buf[8], LOCALCOLORMAP);

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

		if (! useGlobalColormap) {
			if (!ReadColorMap(fd, bitPixel, pic->cmap)) {
				close_picfile(fd,filtype);
				fprintf(stderr,"error reading local GIF colormap\n" );
				return 0;
			}
			pic->numcols = bitPixel;
			if (!ReadGIFImage(pic, fd, LM_to_uint(buf[4],buf[5]),
				  LM_to_uint(buf[6],buf[7]),
				  BitSet(buf[8], INTERLACE)))
			    return 0;
		} else {
			if (!ReadGIFImage(pic, fd, LM_to_uint(buf[4],buf[5]),
				  LM_to_uint(buf[6],buf[7]),
				  BitSet(buf[8], INTERLACE)))
			    return 0;
			pic->numcols = GifScreen.BitPixel;
		}
	}
}

static Boolean
ReadColorMap(fd,number,cmap)
FILE	*fd;
int	number;
unsigned char cmap[3][MAXCOLORMAPSIZE];
{
	int		i;
	unsigned char	rgb[3];

	for (i = 0; i < number; ++i) {
		if (! ReadOK(fd, rgb, sizeof(rgb))) {
			fprintf(stderr,"bad GIF colormap\n" );
			return FALSE;
		}
		cmap[0][i] = rgb[0];
		cmap[1][i] = rgb[1];
		cmap[2][i] = rgb[2];
	}
	return TRUE;
}

static Boolean
DoExtension(fd, label)
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) {
			; /* GIF comment */
		}
		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 = 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;
}

int	ZeroDataBlock = FALSE;

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

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

	ZeroDataBlock = count == 0;

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

	return count;
}

static int
GetCode(fd, code_size, flag)
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) then ran off the end of 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(fd, flag, input_code_size)
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) {
				fprintf(stderr,"LWZReadByte: missing EOD in data stream (common occurence)\n");
			}
			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]) {
				fprintf(stderr,"LWZReadByte: circular table entry BIG ERROR\n");
			}
			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 Boolean
ReadGIFImage(pic, fd, len, height, interlace)
F_pic	*pic;
FILE	*fd;
int	len, height;
int	interlace;
{
	unsigned char	c;	
	int		v;
	int		xpos = 0, ypos = 0, pass = 0;
	unsigned char	*image;

	/*
	**  Initialize the Compression routines
	*/
	if (! ReadOK(fd,&c,1))
		return FALSE;		/* EOF / read error on image data */

	if (LWZReadByte(fd, TRUE, c) < 0)
		return FALSE;		/* error reading image */

	if ((image = (unsigned char*) malloc(len* height* sizeof(char))) == NULL)
		return FALSE;		/* couldn't alloc space for image */

	while ((v = LWZReadByte(fd,FALSE,c)) >= 0 ) {
		image[ypos*len+xpos] = (unsigned char) v;
		++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:
	pic->subtype = P_GIF;
	pic->bitmap = image;	/* save the pixel data */
	pic->hw_ratio = (float) height / len;
	pic->bit_size.x = len;
	pic->bit_size.y = height;
	return TRUE;
}