/* The Graphics Interchange Format(c) is the Copyright property of
** CompuServe Incorporated.  GIF(sm) is a Service Mark property of
** CompuServe Incorporated.
*/

#include "gifread.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


/************************************************************************
	GIF File Reader
************************************************************************/
/* +-------------------------------------------------------------------+ */
/* | 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.           | */
/* +-------------------------------------------------------------------+ */

#define USE_GIF89	1

#define MAXIMAGE	256
#define	MAXCOLORMAPSIZE	256
#define CM_RED		0
#define CM_GREEN	1
#define CM_BLUE		2
#define CM_USED		3
#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))

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;
        unsigned int	Grayscale;
        unsigned int	Components;
} GifScreen;

#if USE_GIF89
static struct {
	int	transparent;
	int	delayTime;
	int	inputFlag;
	int	disposal;
} Gif89;
#endif

#define	TRUE		1
#define	FALSE		0


static int verbose = FALSE;
static int showComment = FALSE;
static int ZeroDataBlock = FALSE;

static int   ReadGIF ( FILE *fp, unsigned char *frame[] );
static int   ReadColorMap ( FILE *fd, int number, unsigned char buffer[3][MAXCOLORMAPSIZE], unsigned int *grayscale );
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 unsigned char* ReadImage ( FILE *fd, int len, int height, unsigned char cmap[3][MAXCOLORMAPSIZE], unsigned int grayscale, int interlace, int ignore );

static void pm_message(const char* format, ... );
static int pm_error(const char* format, ... );

static int error = FALSE;

unsigned char *gifread (FILE *fp, int *w, int *h, int *nc, int *nf,
			unsigned char ***frames)
{
  unsigned char* image[MAXIMAGE];
  int i;
  
  error = FALSE;

  *nf = ReadGIF(fp, image);

  /* Allocate and store frames */
  *frames = (unsigned char**)malloc(*nf * sizeof(unsigned char*));
  if (error || *frames == 0)
    {
      for (i=0; i<*nf; ++i)
	if (image[i]) free(image[i]);
      *nf = 0;
      return 0;
    }

  for (i=0; i<*nf; ++i)
    (*frames)[i] = image[i];

  *nc = GifScreen.Components;
  *w = GifScreen.Width;
  *h = GifScreen.Height;

  return image[0];
}

static int
ReadGIF( FILE *fd, unsigned char *frame[] )
{
	unsigned char	buf[16];
	unsigned char	c;
	int		useGlobalColormap;
	int		bitPixel;
	char		version[4];
	int i, j, p, nc, image_size;

	if (! ReadOK(fd,buf,6))
		return pm_error("error reading magic number" );

	if (strncmp((char*)buf,"GIF",3) != 0)
		return pm_error("not a GIF file" );

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

	if ((strcmp(version, "87a") != 0) && (strcmp(version, "89a") != 0))
		return pm_error("bad version number, not '87a' or '89a'" );

	if (! ReadOK(fd,buf,7))
		return pm_error("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 char)(buf[4]&0x70)>>3)+1);
	GifScreen.Background      = buf[5];
	GifScreen.AspectRatio     = buf[6];
        GifScreen.Grayscale	  = FALSE;
        GifScreen.Components	  = 0;

#if USE_GIF89
	Gif89.transparent = -1;
	Gif89.delayTime = -1;
	Gif89.inputFlag = -1;
	Gif89.disposal = 0;
#endif

	if (BitSet(buf[4], LOCALCOLORMAP)) {	/* Global Colormap */
		if (ReadColorMap(fd,GifScreen.BitPixel,GifScreen.ColorMap,
				 &GifScreen.Grayscale))
			return pm_error("error reading global colormap" );
	}

	if (GifScreen.AspectRatio != 0 && GifScreen.AspectRatio != 49) {
		double	r;
		r = ( GifScreen.AspectRatio + 15.0 ) / 64.0;
		pm_message("warning - non-square pixels; to fix do a 'pnmscale -%cscale %g'",
		    r < 1.0 ? 'x' : 'y',
		    r < 1.0 ? 1.0 / r : r );
	}

	for (i=0; i<MAXIMAGE; ) {
		if (! ReadOK(fd,&c,1))
			return pm_error("EOF / read error on image data" );

		if (c == ';') {		/* GIF terminator */
			return i;
		}

		if (c == '!') { 	/* Extension */
			if (! ReadOK(fd,&c,1))
				return pm_error("OF / read error on extention function code");
			DoExtension(fd, c);
			continue;
		}

		if (c != ',') {		/* Not a valid start character */
			pm_message("bogus character 0x%02x, ignoring", (int) c );
			continue;
		}

		if (! ReadOK(fd,buf,9))
			return pm_error("couldn't read left/top/width/height");

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

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

		if (! useGlobalColormap)
			if (ReadColorMap(fd, bitPixel, GifScreen.ColorMap,
					 &GifScreen.Grayscale))
				return pm_error("error reading local colormap" );

		nc = GifScreen.Grayscale ? 1 : 3;
		if (Gif89.transparent >= 0) ++nc;
		if (GifScreen.Components != 0 &&
		    GifScreen.Components != (unsigned) nc)
		  {
		    pm_message("multiple colormap formats encounted at frame %d",
			       i);
		    return i;
		  }
		GifScreen.Components = nc;
		frame[i] = ReadImage(fd, LM_to_uint(buf[4],buf[5]),
				     LM_to_uint(buf[6],buf[7]),
				     GifScreen.ColorMap,
				     GifScreen.Grayscale,
				     BitSet(buf[8], INTERLACE), 0 );

		/* Convert to I, IA, RGB, or RGBA. */
		image_size = GifScreen.Width * GifScreen.Height;
		switch (nc) {
		case 4:		/* RGBA */
		  for (p = image_size - 1; p >= 0; --p) {
		    j = frame[i][p];
		    frame[i][p*4  ] = GifScreen.ColorMap[CM_RED][j];
		    frame[i][p*4+1] = GifScreen.ColorMap[CM_GREEN][j];
		    frame[i][p*4+2] = GifScreen.ColorMap[CM_BLUE][j];
		    frame[i][p*4+3] = (j == Gif89.transparent) ? 0 : 255;
		  }
		  break;
		case 3:		/* RGB */
		  for (p = image_size - 1; p >= 0; --p) {
		    j = frame[i][p];
		    frame[i][p*3  ] = GifScreen.ColorMap[CM_RED][j];
		    frame[i][p*3+1] = GifScreen.ColorMap[CM_GREEN][j];
		    frame[i][p*3+2] = GifScreen.ColorMap[CM_BLUE][j];
		  }
		  break;
		case 2:		/* IA (Intensity, Alpha) */
		  for (p = image_size - 1; p >= 0; --p) {
		    j = frame[i][p];
		    frame[i][p*2  ] = GifScreen.ColorMap[CM_RED][j];
		    frame[i][p*2+1] = (j == Gif89.transparent) ? 0 : 255;
		  }
		  break;
		case 1:		/* I (Intensity) */
		  for (p = image_size - 1; p >= 0; --p) {
		    frame[i][p] = GifScreen.ColorMap[CM_RED][frame[i][p]];
		  }
		  break;
		}
		++i;
	}
	return MAXIMAGE;
}

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

	*grayscale = TRUE;
	for (i = 0; i < number; ++i) {
		if (! ReadOK(fd, rgb, sizeof(rgb)))
			return pm_error("bad colormap" );

		buffer[CM_RED][i] = rgb[0];
		buffer[CM_GREEN][i] = rgb[1];
		buffer[CM_BLUE][i] = rgb[2];
		if (rgb[0] != rgb[1] || rgb[1] != rgb[2])
		  *grayscale = FALSE;
	}

	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"; */
#ifdef notdef
		if (GetDataBlock(fd, (unsigned char*) buf) == 0);

		lpos   = LM_to_uint(buf[0], buf[1]);
		tpos   = LM_to_uint(buf[2], buf[3]);
		width  = LM_to_uint(buf[4], buf[5]);
		height = LM_to_uint(buf[6], buf[7]);
		cellw  = buf[8];
		cellh  = buf[9];
		foreground = buf[10];
		background = buf[11];

		while (GetDataBlock(fd, (unsigned char*) buf) != 0) {
			PPM_ASSIGN(image[ypos][xpos],
					cmap[CM_RED][v],
					cmap[CM_GREEN][v],
					cmap[CM_BLUE][v]);
			++index;
		}

		return FALSE;
#else
		break;
#endif
	case 0xff:		/* Application Extension */
/* 		str = "Application Extension"; */
		break;
	case 0xfe:		/* Comment Extension */
/* 		str = "Comment Extension"; */
		while (GetDataBlock(fd, (unsigned char*) buf) != 0) {
			if (showComment)
				pm_message("gif comment: %s", buf );
		}
		return FALSE;
	case 0xf9:		/* Graphic Control Extension */
/* 		str = "Graphic Control Extension"; */
		(void) GetDataBlock(fd, (unsigned char*) buf);
#if USE_GIF89
		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];
#endif
		while (GetDataBlock(fd, (unsigned char*) buf) != 0);

		return FALSE;
	default:
/* 		str = buf; */
		sprintf(buf, "UNKNOWN (0x%02x)", label);
		break;
	}

#if 0
	pm_message("got a '%s' extension - please report this to koblas@mips.com",
					str );
#endif

	while (GetDataBlock(fd, (unsigned char*) buf) != 0);
	return 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)
				pm_error("ran off the end of my bits" );
			return -1;
		}
		if (last_byte > 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);
		if (error) return -1;
		
		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);
			if (error) return -1;
		} while (firstcode == clear_code);
		return firstcode;
	}

	if (sp > stack)
		return *--sp;

	while ((code = GetCode(fd, code_size, FALSE)) >= 0) {
		if (error) return -1;
		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])
				return pm_error("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 unsigned char*
ReadImage(FILE *fd, int len, int height,
	  unsigned char cmap[3][MAXCOLORMAPSIZE],
	  unsigned int grayscale,
	  int interlace,
	  int ignore)
{
	unsigned char	c;	
	int		v;
	int		xpos = 0, ypos = 0, pass = 0;
	unsigned char	*image;
	unsigned char	*image_ptr;
	int nc = 3;		/* Number of components (RGB) */

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

	if (LWZReadByte(fd, TRUE, c) < 0)
	{
		pm_error("error reading image" );
		return NULL;
	}

	/*
	**  If this is an "uninteresting picture" ignore it.
	*/
	if (ignore) {
		if (verbose)
			pm_message("skipping image..." );

		while (LWZReadByte(fd, FALSE, c) >= 0);
		return NULL;
	}

	/* Allocate enough space for nc components.
	 */

	if (grayscale) nc = 1;
	if (Gif89.transparent >= 0) ++nc;

	image = (unsigned char*)malloc(nc*len*height);
	image_ptr = image;

	if (verbose)
		pm_message("reading %d by %d%s GIF image",
			len, height, interlace ? " interlaced" : "" );

	while ((v = LWZReadByte(fd,FALSE,c)) >= 0 ) {

		if (error) {
			free(image);
			return NULL;
		}

		*(image_ptr+(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:
	if (LWZReadByte(fd,FALSE,c)>=0)
		pm_message("too much input data, ignoring extra...");

	if (verbose)
		pm_message("writing output");

	return image;
}



/************************************************************************/
/*
** Copyright (C) 1988 by Jef Poskanzer.
**
** 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 <stdarg.h>

static int showmessages = 1;

static void
pm_message(const char* format, ... )
{
  va_list args;
  
  va_start( args, format );
  if ( showmessages )
    {
      fprintf( stderr, "Image reader: " );
      (void) vfprintf( stderr, format, args );
      fputc( '\n', stderr );
    }
  va_end( args );
}


static int
pm_error(const char* format, ... )
{
  va_list args;

  va_start( args, format );

  fprintf( stderr, "Image reader: ");
  (void) vfprintf( stderr, format, args );
  fputc( '\n', stderr );
  va_end( args );
  error = TRUE;
  return 0;
}