/* $Xorg: mkg3states.c,v 1.3 2000/08/17 19:46:41 cpqbld Exp $ */
/*
 * Copyright (c) 1991, 1992 Sam Leffler
 * Copyright (c) 1991, 1992 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */
/* $XFree86: xc/lib/lbxutil/image/mkg3states.c,v 1.4 2001/01/17 19:43:35 dawes Exp $ */

/*
 * Program to construct Group 3 & Group 4 decoding tables.
 *
 * This code is derived from code by Michael P. Marking.  In
 * particular, the algorithms to generate the null_mode and
 * horiz_mode state tables are his.  See the comments below
 * for more information.
 *
 * BEGIN (from the original source)
 LEGAL
 *	Copyright 1989, 1990 Michael P. Marking, Post Office Box 8039,
 *	Scottsdale, Arizona 85252-8039. All rights reserved.
 *
 *	License is granted by the copyright holder to distribute and use this
 *	code without payment of royalties or the necessity of notification as
 *	long as this notice (all the text under "LEGAL") is included.
 *
 *	This program is offered without any warranty of any kind. It includes
 *	no warranty of merchantability or fitness for any purpose. Testing and
 *	suitability for any use are the sole responsibility of the user.
 *
 INFORMATION
 *	Although there is no support offered with this program, the author will
 *	endeavor to correct errors. Updates will also be made available from
 *	time to time.
 *
 *	Contact: Michael P. Marking, Post Office Box 8039, Scottsdale, Arizona
 *	85252-8039 USA. Replies are not guaranteed to be swift. Beginning
 *	July 1990, e-mail may be sent to uunet!ipel!marking.
 *
 *	Also beginning in July 1990, this code will be archived at the
 *	ipel!phoenix BBS in file g3g4.zoo. The 24-hour telephone number
 *	for 300/1200/2400 is (602)274-0462. When logging in, specify user
 *	"public", system "bbs", and password "public".
 *
 *	This code is also available from the C Users Group in volume 317.
 *
 * END (from the original source)
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#ifndef TRUE
#define	TRUE	1
#define	FALSE	0
#endif

#define WHITE	0
#define BLACK	1

/*
 * G3 2D and G4 decoding modes.  Note that
 * the vertical modes are ordered so that
 * (mode - MODE_VERT_V0) gives the vertical
 * adjustment for the b1 parameter.
 */
#define MODE_NULL	0
#define MODE_PASS	1
#define MODE_HORIZ	2
#define MODE_VERT_VL3	3
#define MODE_VERT_VL2	4
#define MODE_VERT_VL1	5
#define MODE_VERT_V0	6
#define MODE_VERT_VR1	7
#define MODE_VERT_VR2	8
#define MODE_VERT_VR3	9
#define MODE_UNCOMP	10
#define MODE_ERROR	11
#define MODE_ERROR_1	12

unsigned long append_0 ( unsigned long prefix );
unsigned long append_1 ( unsigned long prefix );

unsigned long append_0 (unsigned long prefix)
{
    return (prefix + (1L<<16));
}

unsigned long append_1 (unsigned long prefix)
{
    static unsigned short prefix_bit[16] = {
	0x8000, 0x4000, 0x2000, 0x1000,
	0x0800, 0x0400, 0x0200, 0x0100,
	0x0080, 0x0040, 0x0020, 0x0010,
	0x0008, 0x0004, 0x0002, 0x0001
    };
    unsigned char len = (prefix >> 16) & 0xf;
    return (append_0(prefix) + prefix_bit[len]);
}

#define	G3CODES
#include "lbxfax.h"
#include "lbxbwcodes.h"

short search_table ( unsigned long prefix, tableentry *tab, int n );
short white_run_length ( unsigned long prefix );
short black_run_length ( unsigned long prefix );
short horiz_mode_code_black ( short runlen );
short horiz_mode_code_white ( short runlen );
void write_define ( FILE *fd, char *name, int value, char *comment );
void write_preamble ( FILE *fd );
void extern_table ( FILE *fd, char *name );
void write_tables ( FILE *fd );
short find_null_mode_prefix ( long prefix );
short find_horiz_mode_prefix ( long prefix, int color );
short find_uncomp_mode_prefix ( long prefix );
short null_mode_type ( long prefix );
short uncomp_mode_type ( long prefix );
void build_null_mode_tables ( void );
void build_horiz_mode_tables ( void );
void build_uncomp_mode_tables ( void );

short search_table (unsigned long prefix, tableentry *tab, int n)
{
    unsigned short len = (prefix >> 16) & 0xf;
    unsigned short code = (prefix & 0xffff) >> (16 - len);

    while (n-- > 0) {
	if (tab->length == len && tab->code == code)
	    return ((short) tab->runlen);
	tab++;
    }
    return (G3CODE_INCOMP);
}

#define	NCODES(a)	(sizeof (a) / sizeof (a[0]))
short white_run_length (unsigned long prefix)
{
    return (search_table(prefix, TIFFFaxWhiteCodes, NCODES(TIFFFaxWhiteCodes)));
}

short black_run_length (unsigned long prefix)
{
    return (search_table(prefix, TIFFFaxBlackCodes, NCODES(TIFFFaxBlackCodes)));
}
#undef NCODES

#define MAX_NULLPREFIX	200	/* max # of null-mode prefixes */
typedef	unsigned char NullModeTable[MAX_NULLPREFIX][256];
#define MAX_HORIZPREFIX	250	/* max # of incomplete 1-D prefixes */
typedef	unsigned char HorizModeTable[MAX_HORIZPREFIX][256];

  /* the bit string corresponding to this row of the decoding table */
long	null_mode_prefix[MAX_NULLPREFIX];
NullModeTable null_mode;		/* MODE_*, indexed by bit and byte */
NullModeTable null_mode_next_state;	/* next row of decoding tables to use */
  /* number of prefixes or rows in the G4 decoding tables */
short	null_mode_prefix_count = 0;

void write_null_mode_table ( FILE *fd, NullModeTable table, char *name );
void write_horiz_mode_table ( FILE *fd, HorizModeTable table, char *name );

/*
 * 2D uncompressed mode codes.  Note
 * that two groups of codes are arranged
 * so that the decoder can caluclate the
 * length of the run by subtracting the
 * code from a known base value.
 */
#define	UNCOMP_INCOMP	0
/* runs of [0]*1 */
#define	UNCOMP_RUN0	1
#define	UNCOMP_RUN1	2
#define	UNCOMP_RUN2	3
#define	UNCOMP_RUN3	4
#define	UNCOMP_RUN4	5
#define	UNCOMP_RUN5	6
#define	UNCOMP_RUN6	7
/* runs of [0]* w/ terminating color */
#define	UNCOMP_TRUN0	8
#define	UNCOMP_TRUN1	9
#define	UNCOMP_TRUN2	10
#define	UNCOMP_TRUN3	11
#define	UNCOMP_TRUN4	12
/* special code for unexpected EOF */
#define	UNCOMP_EOF	13
/* invalid code encountered */
#define	UNCOMP_INVALID	14

long	uncomp_mode_prefix[MAX_NULLPREFIX];
NullModeTable uncomp_mode;
NullModeTable uncomp_mode_next_state;
short	uncomp_mode_prefix_count = 0;

/*
 * Decoding action values for horiz_mode.
 */
#define ACT_INCOMP	0		/* incompletely decoded code */
#define ACT_INVALID	1		/* invalide code */
#define	ACT_WRUNT	2		/* terminating white run code */
#define	ACT_WRUN	65		/* non-terminating white run code */
#define	ACT_BRUNT	106		/* terminating black run code */
#define	ACT_BRUN	169		/* non-terminating black run code */
#define ACT_EOL		210		/* end-of-line code */
HorizModeTable horiz_mode;

short horiz_mode_code_black (short runlen)
{
    return (runlen < 64 ? runlen + ACT_BRUNT : (runlen / 64) + ACT_BRUN);
}

short horiz_mode_code_white (short runlen)
{
    return (runlen < 64 ? runlen + ACT_WRUNT : (runlen / 64) + ACT_WRUN);
}

/*
 * If the corresponding horiz_mode entry is ACT_INCOMP
 * this entry is a row number for decoding the next byte;
 * otherwise, it is the bit number with which to continue
 * decoding the next codeword.
 */
HorizModeTable horiz_mode_next_state;
		/* prefixes corresponding to the rows of the decoding table */
long	horiz_mode_prefix[MAX_HORIZPREFIX];
		/* color of next run, BLACK or WHITE */
char	horiz_mode_color[MAX_HORIZPREFIX];
short	horiz_mode_prefix_count = 0;

static	unsigned char bit_mask[8] =
    { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };


int	verbose = FALSE;
char	*storage_class = "";

int
main (int argc, char *argv[])
{
    while (argc > 1 && argv[1][0] == '-') {
	if (strcmp(argv[1], "-v") == 0) {
	    verbose = TRUE;
	    argc--, argv++;
	} else if (strcmp(argv[1], "-c") == 0) {
	    storage_class = "const ";
	    argc--, argv++;
	}
    }
    build_null_mode_tables();		/* null mode decoding tables */
    if (verbose) {
	fprintf(stderr, "%d null mode prefixes defined\n",
	    (int) null_mode_prefix_count);
	fprintf(stderr, "building uncompressed mode scripts...\n");
    }
    build_uncomp_mode_tables();		/* uncompressed mode decoding tables */
    if (verbose) {
	fprintf(stderr, "%d uncompressed mode prefixes defined\n",
	    (int) uncomp_mode_prefix_count);
	fprintf(stderr, "building 1D scripts...\n");
    }
    build_horiz_mode_tables();		/* 1D decoding tables */
    if (verbose)
	fprintf(stderr, "%d incomplete prefixes defined\n",
	    (int) horiz_mode_prefix_count);
    write_tables(stdout);
    exit(0);
}

void write_null_mode_table (fd, table, name)
FILE *fd;
NullModeTable table;
char *name;
{
    int i, j;
    char* outersep;
    char* sep;

    fprintf(fd, "%sunsigned char\t%s[%d][256] = {", storage_class,
	name, (int) null_mode_prefix_count);
    outersep = "";
    for (i = 0; i < null_mode_prefix_count; i++) {
	fprintf(fd, "%s\n/* prefix %d */ {\n", outersep, i);
	sep = "    ";
	for (j = 0; j < 256; j++) {
	    fprintf(fd, "%s%2d", sep, (int) table[i][j]);
	    if (((j+1) % 16) == 0) {
		fprintf(fd, ", /* %3d-%3d */\n", j-15, j);
		sep = "    ";
	    } else
		sep = ",";
	}
	fprintf(fd, "}");
	outersep = ",";
    }
    fprintf(fd, "\n};\n");
}

void 
write_horiz_mode_table (FILE *fd, HorizModeTable table, char *name)
{
    int i, j;
    char* outersep;
    char* sep;

    fprintf(fd, "%s unsigned char\t%s[%d][256] = {", storage_class,
	name, (int) horiz_mode_prefix_count);
    outersep = "";
    for (i = 0; i < horiz_mode_prefix_count; i++) {
	fprintf(fd, "%s\n/* prefix %d */ {\n", outersep, i);
	sep = "    ";
	for (j = 0; j < 256; j++) {
	    fprintf(fd, "%s%3d", sep, (int) table[i][j]);
	    if (((j+1) % 14) == 0) {
		fprintf(fd, ", /* %3d-%3d */\n", j-13, j);
		sep = "    ";
	    } else
		sep = ",";
	}
	fprintf(fd, "\n}");
	outersep = ",";
    }
    fprintf(fd, "\n};\n");
}

void
write_define(FILE *fd, char *name, int value, char *comment)
{
    fprintf(fd, "#define\t%s\t%d", name, value);
    if (comment)
	fprintf(fd, "\t/* %s */", comment);
    fprintf(fd, "\n");
}

void
write_preamble(FILE *fd)
{
    fprintf(fd, "%s\n",
"/* DO NOT EDIT THIS FILE, IT WAS AUTOMATICALLY CREATED BY mkg3state */");
    write_define(fd, "ACT_INCOMP", ACT_INCOMP, "incompletely decoded code");
    write_define(fd, "ACT_INVALID", ACT_INVALID, "invalide code");
    write_define(fd, "ACT_WRUNT", ACT_WRUNT, "terminating white run code");
    write_define(fd, "ACT_WRUN", ACT_WRUN, "non-terminating white run code");
    write_define(fd, "ACT_BRUNT", ACT_BRUNT, "terminating black run code");
    write_define(fd, "ACT_BRUN", ACT_BRUN, "non-terminating black run code");
    write_define(fd, "ACT_EOL", ACT_EOL, "end-of-line code");
    fprintf(fd, "\n");
    fprintf(fd, "/* modes that the decoder can be in */\n");
    write_define(fd, "MODE_NULL", MODE_NULL, NULL);
    write_define(fd, "MODE_PASS", MODE_PASS, NULL);
    write_define(fd, "MODE_HORIZ", MODE_HORIZ, NULL);
    write_define(fd, "MODE_VERT_V0", MODE_VERT_V0, NULL);
    write_define(fd, "MODE_VERT_VR1", MODE_VERT_VR1, NULL);
    write_define(fd, "MODE_VERT_VR2", MODE_VERT_VR2, NULL);
    write_define(fd, "MODE_VERT_VR3", MODE_VERT_VR3, NULL);
    write_define(fd, "MODE_VERT_VL1", MODE_VERT_VL1, NULL);
    write_define(fd, "MODE_VERT_VL2", MODE_VERT_VL2, NULL);
    write_define(fd, "MODE_VERT_VL3", MODE_VERT_VL3, NULL);
    write_define(fd, "MODE_UNCOMP", MODE_UNCOMP, NULL);
    write_define(fd, "MODE_ERROR", MODE_ERROR, NULL);
    write_define(fd, "MODE_ERROR_1", MODE_ERROR_1, NULL);
    fprintf(fd, "\n");
    fprintf(fd, "#define\tRUNLENGTH(ix)	(TIFFFaxWhiteCodes[ix].runlen)\n");
    fprintf(fd, "\n");
    write_define(fd, "UNCOMP_INCOMP", UNCOMP_INCOMP, NULL);
    fprintf(fd, "/* runs of [0]*1 */\n");
    write_define(fd, "UNCOMP_RUN0", UNCOMP_RUN0, NULL);
    write_define(fd, "UNCOMP_RUN1", UNCOMP_RUN1, NULL);
    write_define(fd, "UNCOMP_RUN2", UNCOMP_RUN2, NULL);
    write_define(fd, "UNCOMP_RUN3", UNCOMP_RUN3, NULL);
    write_define(fd, "UNCOMP_RUN4", UNCOMP_RUN4, NULL);
    write_define(fd, "UNCOMP_RUN5", UNCOMP_RUN5, NULL);
    write_define(fd, "UNCOMP_RUN6", UNCOMP_RUN6, NULL);
    fprintf(fd, "/* runs of [0]* w/ terminating color */\n");
    write_define(fd, "UNCOMP_TRUN0", UNCOMP_TRUN0, NULL);
    write_define(fd, "UNCOMP_TRUN1", UNCOMP_TRUN1, NULL);
    write_define(fd, "UNCOMP_TRUN2", UNCOMP_TRUN2, NULL);
    write_define(fd, "UNCOMP_TRUN3", UNCOMP_TRUN3, NULL);
    write_define(fd, "UNCOMP_TRUN4", UNCOMP_TRUN4, NULL);
    fprintf(fd, "/* special code for unexpected EOF */\n");
    write_define(fd, "UNCOMP_EOF", UNCOMP_EOF, NULL);
    fprintf(fd, "/* invalid code encountered */\n");
    write_define(fd, "UNCOMP_INVALID", UNCOMP_INVALID, NULL);
    fprintf(fd, "/* codes >= terminate uncompress mode */\n");
    fprintf(fd, "#define\tUNCOMP_EXIT	UNCOMP_TRUN0\n");
    fprintf(fd, "\n");
}

void
extern_table(FILE *fd, char *name)
{
    fprintf(fd, "extern\t%sunsigned char %s[][256];\n", storage_class, name);
}

void
write_tables(FILE *fd)
{
    write_preamble(fd);
    write_null_mode_table(fd, null_mode, "TIFFFax2DMode");
    write_null_mode_table(fd, null_mode_next_state, "TIFFFax2DNextState");
    write_null_mode_table(fd, uncomp_mode, "TIFFFaxUncompAction");
    write_null_mode_table(fd, uncomp_mode_next_state, "TIFFFaxUncompNextState");
    write_horiz_mode_table(fd, horiz_mode, "TIFFFax1DAction");
    write_horiz_mode_table(fd, horiz_mode_next_state, "TIFFFax1DNextState");
}

short 
find_null_mode_prefix (long prefix)
{
    short j1;

    if (prefix == 0L)
	return (0);
    for (j1 = 8; j1 < null_mode_prefix_count; j1++)
	if (prefix == null_mode_prefix[j1])
		return (j1);
    if (null_mode_prefix_count == MAX_NULLPREFIX) {
	fprintf(stderr, "ERROR: null mode prefix table overflow\n");
	exit(1);
    }
    if (verbose)
	fprintf(stderr, "adding null mode prefix[%d] 0x%lx\n",
	    (int) null_mode_prefix_count, prefix);
    null_mode_prefix[null_mode_prefix_count++] = prefix;
    return (null_mode_prefix_count-1);
}

short 
find_horiz_mode_prefix (long prefix, int color)
{
    short j1;

    for (j1 = 0; j1 < horiz_mode_prefix_count; j1++)
	if (prefix == horiz_mode_prefix[j1] && horiz_mode_color[j1] == color)
	    return (j1);
    /*
     * It wasn't found, so add it to the tables, but first, is there room?
     */
    if (horiz_mode_prefix_count == MAX_HORIZPREFIX) {
	fprintf(stderr, "ERROR: 1D prefix table overflow\n");
	exit(1);
    }
    /* OK, there's room... */
    if (verbose)
	fprintf(stderr, "\nhoriz mode prefix %d, color %c = 0x%lx ",
	    (int) horiz_mode_prefix_count, "WB"[color], prefix);
    horiz_mode_prefix[horiz_mode_prefix_count] = prefix;
    horiz_mode_color[horiz_mode_prefix_count] = color;
    horiz_mode_prefix_count++;
    return (horiz_mode_prefix_count - 1);
}

short 
find_uncomp_mode_prefix (long prefix)
{
    short j1;

    if (prefix == 0L)
	return (0);
    for (j1 = 8; j1 < uncomp_mode_prefix_count; j1++)
	if (prefix == uncomp_mode_prefix[j1])
		return (j1);
    if (uncomp_mode_prefix_count == MAX_NULLPREFIX) {
	fprintf(stderr, "ERROR: uncomp mode prefix table overflow\n");
	exit(1);
    }
    if (verbose)
	fprintf(stderr, "adding uncomp mode prefix[%d] 0x%lx\n",
	    (int) uncomp_mode_prefix_count, prefix);
    uncomp_mode_prefix[uncomp_mode_prefix_count++] = prefix;
    return (uncomp_mode_prefix_count-1);
}

short 
null_mode_type (long prefix)
{
    switch (prefix) {
    case 0x18000L: return (MODE_VERT_V0);	/* 1 */
    case 0x36000L: return (MODE_VERT_VR1);	/* 011 */
    case 0x34000L: return (MODE_VERT_VL1);	/* 010 */
    case 0x32000L: return (MODE_HORIZ);		/* 001 */
    case 0x41000L: return (MODE_PASS);		/* 0001 */
    case 0x60C00L: return (MODE_VERT_VR2);	/* 0000 11 */
    case 0x60800L: return (MODE_VERT_VL2);	/* 0000 10 */
    case 0x70600L: return (MODE_VERT_VR3);	/* 0000 011 */
    case 0x70400L: return (MODE_VERT_VL3);	/* 0000 010 */
    case 0x80200L: return (MODE_ERROR);		/* 0000 0010 */
    case 0x90300L: return (MODE_ERROR);		/* 0000 0011 0 */
    case 0xA0380L: return (MODE_ERROR);		/* 0000 0011 10 */
    case 0xA03C0L: return (MODE_UNCOMP);	/* 0000 0011 11 */
    /*
     * Under the assumption that there are no
     * errors in the file, then this bit string
     * can only be the beginning of an EOL code.
     */
    case 0x70000L: return (MODE_ERROR_1);	/* 0000 000 */
    }
    return (-1);
}

short 
uncomp_mode_type (long prefix)
{
    short code;
    short len;
    switch (prefix) {
    case 0x18000L: return (UNCOMP_RUN1);	/* 1 */
    case 0x24000L: return (UNCOMP_RUN2);	/* 01 */
    case 0x32000L: return (UNCOMP_RUN3);	/* 001 */
    case 0x41000L: return (UNCOMP_RUN4);	/* 0001 */
    case 0x50800L: return (UNCOMP_RUN5);	/* 0000 1 */
    case 0x60400L: return (UNCOMP_RUN6);	/* 0000 01 */
    case 0x70200L: return (UNCOMP_TRUN0);	/* 0000 001 */
    case 0x80100L: return (UNCOMP_TRUN1);	/* 0000 0001 */
    case 0x90080L: return (UNCOMP_TRUN2);	/* 0000 0000 1 */
    case 0xA0040L: return (UNCOMP_TRUN3);	/* 0000 0000 01 */
    case 0xB0020L: return (UNCOMP_TRUN4);	/* 0000 0000 001 */
    }
    code = prefix & 0xffffL;
    len = (prefix >> 16) & 0xf;
    return ((code || len > 10) ? UNCOMP_INVALID : -1);
}

#define	BASESTATE(b)	((unsigned char) ((b) & 0x7))

void
build_null_mode_tables(void)
{
    short prefix;

    /*
     * Note: the first eight entries correspond to
     * a null prefix and starting bit numbers 0-7.
     */
    null_mode_prefix_count = 8;
    for (prefix = 0; prefix < null_mode_prefix_count; prefix++) {
	short byte;
	for (byte = 0; byte < 256; byte++) {
	    short firstbit;
	    short bit;
	    long curprefix;
	    char found_code = FALSE;

	    if (prefix < 8) {
		curprefix = 0L;
		firstbit = prefix;
	    } else {
		curprefix = null_mode_prefix[prefix];
		firstbit = 0;
	    }
	    for (bit = firstbit; bit < 8 && !found_code; bit++) {
		short mode;

		if (bit_mask[bit] & byte)
		    curprefix = append_1(curprefix);
		else
		    curprefix = append_0(curprefix);
		switch (mode = null_mode_type(curprefix)) {
		case MODE_PASS:
		case MODE_HORIZ:
		case MODE_VERT_V0:
		case MODE_VERT_VR1:
		case MODE_VERT_VR2:
		case MODE_VERT_VR3:
		case MODE_VERT_VL1:
		case MODE_VERT_VL2:
		case MODE_VERT_VL3:
		case MODE_UNCOMP:
		case MODE_ERROR:
		case MODE_ERROR_1:
		    /*
		     * NOTE: if the bit number is 8, then the table
		     * entry will be zero, which indicates a new byte
		     * is to be fetched during the decoding process
		     */
		    found_code = TRUE;
		    null_mode[prefix][byte] = (unsigned char) mode;
		    null_mode_next_state[prefix][byte] = BASESTATE(bit+1);
		    break;
		}
	    }
	    if (!found_code) {
		null_mode_next_state[prefix][byte] = (unsigned char)
		    find_null_mode_prefix(curprefix);
		/*
		 * This indicates to the decoder that
		 * no valid code has yet been identified.
		 */
		null_mode[prefix][byte] = MODE_NULL;
	    }
	}
    }
}

void
build_horiz_mode_tables(void)
{
    unsigned short byte;
    short prefix;

    /*
     * The first 8 are for white,
     * the second 8 are for black,
     * beginning with bits 0-7.
     */
    horiz_mode_prefix_count = 16;
    for (prefix = 0; prefix < horiz_mode_prefix_count; prefix++)
	for (byte = 0; byte < 256; byte++) {
	    short bits_digested = 0;
	    short bit;
	    short firstbit;
	    char color;
	    unsigned long curprefix;

	    if (prefix < 8) {
		color = WHITE;
		curprefix = 0L;
		firstbit = prefix;
	    } else if (prefix < 16) {
		color = BLACK;
		curprefix = 0L;
		firstbit = prefix - 8;
	    } else {
		color = horiz_mode_color[prefix];
		curprefix = horiz_mode_prefix[prefix];
		firstbit = 0;
	    }
	    for (bit = firstbit; bit < 8 && !bits_digested; bit++) {
		if (bit_mask[bit] & byte)
		    curprefix = append_1(curprefix);
		else
		    curprefix = append_0(curprefix);
		/*
		 * The following conversion allows for arbitrary strings of
		 * zeroes to precede the end-of-line code 0000 0000 0001.
		 * It assumes no errors in the data, and is based on
		 * the assumption that the code replaced (12 consecutive
		 * zeroes) can only be "legally" encountered before the
		 * end-of-line code.  This assumption is valid only for
		 * a Group 3 image; the combination will never occur
		 * in horizontal mode in a proper Group 4 image.
		 */
		if (curprefix == 0xC0000L)
		    curprefix = 0xB0000L;
		if (color == WHITE) {
		    short runlength = white_run_length(curprefix);

		    if (runlength == G3CODE_INVALID) {
			horiz_mode[prefix][byte] = (unsigned char) ACT_INVALID;
			horiz_mode_next_state[prefix][byte] = (unsigned char) bit;
			bits_digested = bit + 1;
		    } else if (runlength == G3CODE_EOL) { /* Group 3 only */
			horiz_mode[prefix][byte] = (unsigned char) ACT_EOL;
			horiz_mode_next_state[prefix][byte] = BASESTATE(bit+1);
			bits_digested = bit + 1;
		    } else if (runlength != G3CODE_INCOMP) {
			horiz_mode[prefix][byte] = (unsigned char)
			    horiz_mode_code_white(runlength);
			horiz_mode_next_state[prefix][byte] = BASESTATE(bit+1);
			bits_digested = bit + 1;
		    }
		} else {		/* color == BLACK */
		    short runlength = black_run_length(curprefix);

		    if (runlength == G3CODE_INVALID) {
			horiz_mode[prefix][byte] = (unsigned char) ACT_INVALID;
			horiz_mode_next_state[prefix][byte] = (unsigned char) (bit+8);
			bits_digested = bit + 1;
		    } else if (runlength == G3CODE_EOL) { /* Group 3 only */
			horiz_mode[prefix][byte] = (unsigned char) ACT_EOL;
			horiz_mode_next_state[prefix][byte] = BASESTATE(bit+1);
			bits_digested = bit + 1;
		    } else if (runlength != G3CODE_INCOMP) {
			horiz_mode[prefix][byte] = (unsigned char)
			    horiz_mode_code_black(runlength);
			horiz_mode_next_state[prefix][byte] = BASESTATE(bit+1);
			bits_digested = bit + 1;
		    }
		}
	    }
	    if (!bits_digested) {	/* no codewords after examining byte */
		horiz_mode[prefix][byte] = (unsigned char) ACT_INCOMP;
		horiz_mode_next_state[prefix][byte] = (unsigned char)
		    find_horiz_mode_prefix(curprefix, color);
	    }
	}
}

void
build_uncomp_mode_tables(void)
{
    short prefix;

    /*
     * Note: the first eight entries correspond to
     * a null prefix and starting bit numbers 0-7.
     */
    uncomp_mode_prefix_count = 8;
    for (prefix = 0; prefix < uncomp_mode_prefix_count; prefix++) {
	short byte;
	for (byte = 0; byte < 256; byte++) {
	    short firstbit;
	    short bit;
	    long curprefix;
	    char found_code = FALSE;

	    if (prefix < 8) {
		curprefix = 0L;
		firstbit = prefix;
	    } else {
		curprefix = uncomp_mode_prefix[prefix];
		firstbit = 0;
	    }
	    for (bit = firstbit; bit < 8 && !found_code; bit++) {
		short mode;

		if (bit_mask[bit] & byte)
		    curprefix = append_1(curprefix);
		else
		    curprefix = append_0(curprefix);
		mode = uncomp_mode_type(curprefix);
		if (mode != -1) {
		    /*
		     * NOTE: if the bit number is 8, then the table
		     * entry will be zero, which indicates a new byte
		     * is to be fetched during the decoding process
		     */
		    found_code = TRUE;
		    uncomp_mode[prefix][byte] = (unsigned char) mode;
		    uncomp_mode_next_state[prefix][byte] = BASESTATE(bit+1);
		    break;
		}
	    }
	    if (!found_code) {
		uncomp_mode_next_state[prefix][byte] = (unsigned char)
		    find_uncomp_mode_prefix(curprefix);
		/*
		 * This indicates to the decoder that
		 * no valid code has yet been identified.
		 */
		uncomp_mode[prefix][byte] = UNCOMP_INCOMP;
	    }
	}
    }
}