fatbase

tblcmp.c (23497B)

---

 /*	$OpenBSD: tblcmp.c,v 1.6 2003/06/04 17:34:44 millert Exp $	*/
 
 /* tblcmp - table compression routines */
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
  * Vern Paxson.
  * 
  * The United States Government has rights in this work pursuant
  * to contract no. DE-AC03-76SF00098 between the United States
  * Department of Energy and the University of California.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * Neither the name of the University nor the names of its contributors
  * may be used to endorse or promote products derived from this software
  * without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE.
  */
 
 /* $Header: /cvs/src/usr.bin/lex/tblcmp.c,v 1.6 2003/06/04 17:34:44 millert Exp $ */
 
 #include "flexdef.h"
 
 
 /* declarations for functions that have forward references */
 
 void mkentry PROTO((int*, int, int, int, int));
 void mkprot PROTO((int[], int, int));
 void mktemplate PROTO((int[], int, int));
 void mv2front PROTO((int));
 int tbldiff PROTO((int[], int, int[]));
 
 
 /* bldtbl - build table entries for dfa state
  *
  * synopsis
  *   int state[numecs], statenum, totaltrans, comstate, comfreq;
  *   bldtbl( state, statenum, totaltrans, comstate, comfreq );
  *
  * State is the statenum'th dfa state.  It is indexed by equivalence class and
  * gives the number of the state to enter for a given equivalence class.
  * totaltrans is the total number of transitions out of the state.  Comstate
  * is that state which is the destination of the most transitions out of State.
  * Comfreq is how many transitions there are out of State to Comstate.
  *
  * A note on terminology:
  *    "protos" are transition tables which have a high probability of
  * either being redundant (a state processed later will have an identical
  * transition table) or nearly redundant (a state processed later will have
  * many of the same out-transitions).  A "most recently used" queue of
  * protos is kept around with the hope that most states will find a proto
  * which is similar enough to be usable, and therefore compacting the
  * output tables.
  *    "templates" are a special type of proto.  If a transition table is
  * homogeneous or nearly homogeneous (all transitions go to the same
  * destination) then the odds are good that future states will also go
  * to the same destination state on basically the same character set.
  * These homogeneous states are so common when dealing with large rule
  * sets that they merit special attention.  If the transition table were
  * simply made into a proto, then (typically) each subsequent, similar
  * state will differ from the proto for two out-transitions.  One of these
  * out-transitions will be that character on which the proto does not go
  * to the common destination, and one will be that character on which the
  * state does not go to the common destination.  Templates, on the other
  * hand, go to the common state on EVERY transition character, and therefore
  * cost only one difference.
  */
 
 void bldtbl( state, statenum, totaltrans, comstate, comfreq )
 int state[], statenum, totaltrans, comstate, comfreq;
 	{
 	int extptr, extrct[2][CSIZE + 1];
 	int mindiff, minprot, i, d;
 
 	/* If extptr is 0 then the first array of extrct holds the result
 	 * of the "best difference" to date, which is those transitions
 	 * which occur in "state" but not in the proto which, to date,
 	 * has the fewest differences between itself and "state".  If
 	 * extptr is 1 then the second array of extrct hold the best
 	 * difference.  The two arrays are toggled between so that the
 	 * best difference to date can be kept around and also a difference
 	 * just created by checking against a candidate "best" proto.
 	 */
 
 	extptr = 0;
 
 	/* If the state has too few out-transitions, don't bother trying to
 	 * compact its tables.
 	 */
 
 	if ( (totaltrans * 100) < (numecs * PROTO_SIZE_PERCENTAGE) )
 		mkentry( state, numecs, statenum, JAMSTATE, totaltrans );
 
 	else
 		{
 		/* "checkcom" is true if we should only check "state" against
 		 * protos which have the same "comstate" value.
 		 */
 		int checkcom =
 			comfreq * 100 > totaltrans * CHECK_COM_PERCENTAGE;
 
 		minprot = firstprot;
 		mindiff = totaltrans;
 
 		if ( checkcom )
 			{
 			/* Find first proto which has the same "comstate". */
 			for ( i = firstprot; i != NIL; i = protnext[i] )
 				if ( protcomst[i] == comstate )
 					{
 					minprot = i;
 					mindiff = tbldiff( state, minprot,
 							extrct[extptr] );
 					break;
 					}
 			}
 
 		else
 			{
 			/* Since we've decided that the most common destination
 			 * out of "state" does not occur with a high enough
 			 * frequency, we set the "comstate" to zero, assuring
 			 * that if this state is entered into the proto list,
 			 * it will not be considered a template.
 			 */
 			comstate = 0;
 
 			if ( firstprot != NIL )
 				{
 				minprot = firstprot;
 				mindiff = tbldiff( state, minprot,
 						extrct[extptr] );
 				}
 			}
 
 		/* We now have the first interesting proto in "minprot".  If
 		 * it matches within the tolerances set for the first proto,
 		 * we don't want to bother scanning the rest of the proto list
 		 * to see if we have any other reasonable matches.
 		 */
 
 		if ( mindiff * 100 > totaltrans * FIRST_MATCH_DIFF_PERCENTAGE )
 			{
 			/* Not a good enough match.  Scan the rest of the
 			 * protos.
 			 */
 			for ( i = minprot; i != NIL; i = protnext[i] )
 				{
 				d = tbldiff( state, i, extrct[1 - extptr] );
 				if ( d < mindiff )
 					{
 					extptr = 1 - extptr;
 					mindiff = d;
 					minprot = i;
 					}
 				}
 			}
 
 		/* Check if the proto we've decided on as our best bet is close
 		 * enough to the state we want to match to be usable.
 		 */
 
 		if ( mindiff * 100 > totaltrans * ACCEPTABLE_DIFF_PERCENTAGE )
 			{
 			/* No good.  If the state is homogeneous enough,
 			 * we make a template out of it.  Otherwise, we
 			 * make a proto.
 			 */
 
 			if ( comfreq * 100 >=
 			     totaltrans * TEMPLATE_SAME_PERCENTAGE )
 				mktemplate( state, statenum, comstate );
 
 			else
 				{
 				mkprot( state, statenum, comstate );
 				mkentry( state, numecs, statenum,
 					JAMSTATE, totaltrans );
 				}
 			}
 
 		else
 			{ /* use the proto */
 			mkentry( extrct[extptr], numecs, statenum,
 				prottbl[minprot], mindiff );
 
 			/* If this state was sufficiently different from the
 			 * proto we built it from, make it, too, a proto.
 			 */
 
 			if ( mindiff * 100 >=
 			     totaltrans * NEW_PROTO_DIFF_PERCENTAGE )
 				mkprot( state, statenum, comstate );
 
 			/* Since mkprot added a new proto to the proto queue,
 			 * it's possible that "minprot" is no longer on the
 			 * proto queue (if it happened to have been the last
 			 * entry, it would have been bumped off).  If it's
 			 * not there, then the new proto took its physical
 			 * place (though logically the new proto is at the
 			 * beginning of the queue), so in that case the
 			 * following call will do nothing.
 			 */
 
 			mv2front( minprot );
 			}
 		}
 	}
 
 
 /* cmptmps - compress template table entries
  *
  * Template tables are compressed by using the 'template equivalence
  * classes', which are collections of transition character equivalence
  * classes which always appear together in templates - really meta-equivalence
  * classes.
  */
 
 void cmptmps()
 	{
 	int tmpstorage[CSIZE + 1];
 	int *tmp = tmpstorage, i, j;
 	int totaltrans, trans;
 
 	peakpairs = numtemps * numecs + tblend;
 
 	if ( usemecs )
 		{
 		/* Create equivalence classes based on data gathered on
 		 * template transitions.
 		 */
 		nummecs = cre8ecs( tecfwd, tecbck, numecs );
 		}
 
 	else
 		nummecs = numecs;
 
 	while ( lastdfa + numtemps + 1 >= current_max_dfas )
 		increase_max_dfas();
 
 	/* Loop through each template. */
 
 	for ( i = 1; i <= numtemps; ++i )
 		{
 		/* Number of non-jam transitions out of this template. */
 		totaltrans = 0;
 
 		for ( j = 1; j <= numecs; ++j )
 			{
 			trans = tnxt[numecs * i + j];
 
 			if ( usemecs )
 				{
 				/* The absolute value of tecbck is the
 				 * meta-equivalence class of a given
 				 * equivalence class, as set up by cre8ecs().
 				 */
 				if ( tecbck[j] > 0 )
 					{
 					tmp[tecbck[j]] = trans;
 
 					if ( trans > 0 )
 						++totaltrans;
 					}
 				}
 
 			else
 				{
 				tmp[j] = trans;
 
 				if ( trans > 0 )
 					++totaltrans;
 				}
 			}
 
 		/* It is assumed (in a rather subtle way) in the skeleton
 		 * that if we're using meta-equivalence classes, the def[]
 		 * entry for all templates is the jam template, i.e.,
 		 * templates never default to other non-jam table entries
 		 * (e.g., another template)
 		 */
 
 		/* Leave room for the jam-state after the last real state. */
 		mkentry( tmp, nummecs, lastdfa + i + 1, JAMSTATE, totaltrans );
 		}
 	}
 
 
 
 /* expand_nxt_chk - expand the next check arrays */
 
 void expand_nxt_chk()
 	{
 	int old_max = current_max_xpairs;
 
 	current_max_xpairs += MAX_XPAIRS_INCREMENT;
 
 	++num_reallocs;
 
 	nxt = reallocate_integer_array( nxt, current_max_xpairs );
 	chk = reallocate_integer_array( chk, current_max_xpairs );
 
 	zero_out( (char *) (chk + old_max),
 		(size_t) (MAX_XPAIRS_INCREMENT * sizeof( int )) );
 	}
 
 
 /* find_table_space - finds a space in the table for a state to be placed
  *
  * synopsis
  *     int *state, numtrans, block_start;
  *     int find_table_space();
  *
  *     block_start = find_table_space( state, numtrans );
  *
  * State is the state to be added to the full speed transition table.
  * Numtrans is the number of out-transitions for the state.
  *
  * find_table_space() returns the position of the start of the first block (in
  * chk) able to accommodate the state
  *
  * In determining if a state will or will not fit, find_table_space() must take
  * into account the fact that an end-of-buffer state will be added at [0],
  * and an action number will be added in [-1].
  */
 
 int find_table_space( state, numtrans )
 int *state, numtrans;
 	{
 	/* Firstfree is the position of the first possible occurrence of two
 	 * consecutive unused records in the chk and nxt arrays.
 	 */
 	int i;
 	int *state_ptr, *chk_ptr;
 	int *ptr_to_last_entry_in_state;
 
 	/* If there are too many out-transitions, put the state at the end of
 	 * nxt and chk.
 	 */
 	if ( numtrans > MAX_XTIONS_FULL_INTERIOR_FIT )
 		{
 		/* If table is empty, return the first available spot in
 		 * chk/nxt, which should be 1.
 		 */
 		if ( tblend < 2 )
 			return 1;
 
 		/* Start searching for table space near the end of
 		 * chk/nxt arrays.
 		 */
 		i = tblend - numecs;
 		}
 
 	else
 		/* Start searching for table space from the beginning
 		 * (skipping only the elements which will definitely not
 		 * hold the new state).
 		 */
 		i = firstfree;
 
 	while ( 1 )	/* loops until a space is found */
 		{
 		while ( i + numecs >= current_max_xpairs )
 			expand_nxt_chk();
 
 		/* Loops until space for end-of-buffer and action number
 		 * are found.
 		 */
 		while ( 1 )
 			{
 			/* Check for action number space. */
 			if ( chk[i - 1] == 0 )
 				{
 				/* Check for end-of-buffer space. */
 				if ( chk[i] == 0 )
 					break;
 
 				else
 					/* Since i != 0, there is no use
 					 * checking to see if (++i) - 1 == 0,
 					 * because that's the same as i == 0,
 					 * so we skip a space.
 					 */
 					i += 2;
 				}
 
 			else
 				++i;
 
 			while ( i + numecs >= current_max_xpairs )
 				expand_nxt_chk();
 			}
 
 		/* If we started search from the beginning, store the new
 		 * firstfree for the next call of find_table_space().
 		 */
 		if ( numtrans <= MAX_XTIONS_FULL_INTERIOR_FIT )
 			firstfree = i + 1;
 
 		/* Check to see if all elements in chk (and therefore nxt)
 		 * that are needed for the new state have not yet been taken.
 		 */
 
 		state_ptr = &state[1];
 		ptr_to_last_entry_in_state = &chk[i + numecs + 1];
 
 		for ( chk_ptr = &chk[i + 1];
 		      chk_ptr != ptr_to_last_entry_in_state; ++chk_ptr )
 			if ( *(state_ptr++) != 0 && *chk_ptr != 0 )
 				break;
 
 		if ( chk_ptr == ptr_to_last_entry_in_state )
 			return i;
 
 		else
 		++i;
 		}
 	}
 
 
 /* inittbl - initialize transition tables
  *
  * Initializes "firstfree" to be one beyond the end of the table.  Initializes
  * all "chk" entries to be zero.
  */
 void inittbl()
 	{
 	int i;
 
 	zero_out( (char *) chk, (size_t) (current_max_xpairs * sizeof( int )) );
 
 	tblend = 0;
 	firstfree = tblend + 1;
 	numtemps = 0;
 
 	if ( usemecs )
 		{
 		/* Set up doubly-linked meta-equivalence classes; these
 		 * are sets of equivalence classes which all have identical
 		 * transitions out of TEMPLATES.
 		 */
 
 		tecbck[1] = NIL;
 
 		for ( i = 2; i <= numecs; ++i )
 			{
 			tecbck[i] = i - 1;
 			tecfwd[i - 1] = i;
 			}
 
 		tecfwd[numecs] = NIL;
 		}
 	}
 
 
 /* mkdeftbl - make the default, "jam" table entries */
 
 void mkdeftbl()
 	{
 	int i;
 
 	jamstate = lastdfa + 1;
 
 	++tblend; /* room for transition on end-of-buffer character */
 
 	while ( tblend + numecs >= current_max_xpairs )
 		expand_nxt_chk();
 
 	/* Add in default end-of-buffer transition. */
 	nxt[tblend] = end_of_buffer_state;
 	chk[tblend] = jamstate;
 
 	for ( i = 1; i <= numecs; ++i )
 		{
 		nxt[tblend + i] = 0;
 		chk[tblend + i] = jamstate;
 		}
 
 	jambase = tblend;
 
 	base[jamstate] = jambase;
 	def[jamstate] = 0;
 
 	tblend += numecs;
 	++numtemps;
 	}
 
 
 /* mkentry - create base/def and nxt/chk entries for transition array
  *
  * synopsis
  *   int state[numchars + 1], numchars, statenum, deflink, totaltrans;
  *   mkentry( state, numchars, statenum, deflink, totaltrans );
  *
  * "state" is a transition array "numchars" characters in size, "statenum"
  * is the offset to be used into the base/def tables, and "deflink" is the
  * entry to put in the "def" table entry.  If "deflink" is equal to
  * "JAMSTATE", then no attempt will be made to fit zero entries of "state"
  * (i.e., jam entries) into the table.  It is assumed that by linking to
  * "JAMSTATE" they will be taken care of.  In any case, entries in "state"
  * marking transitions to "SAME_TRANS" are treated as though they will be
  * taken care of by whereever "deflink" points.  "totaltrans" is the total
  * number of transitions out of the state.  If it is below a certain threshold,
  * the tables are searched for an interior spot that will accommodate the
  * state array.
  */
 
 void mkentry( state, numchars, statenum, deflink, totaltrans )
 int *state;
 int numchars, statenum, deflink, totaltrans;
 	{
 	int minec, maxec, i, baseaddr;
 	int tblbase, tbllast;
 
 	if ( totaltrans == 0 )
 		{ /* there are no out-transitions */
 		if ( deflink == JAMSTATE )
 			base[statenum] = JAMSTATE;
 		else
 			base[statenum] = 0;
 
 		def[statenum] = deflink;
 		return;
 		}
 
 	for ( minec = 1; minec <= numchars; ++minec )
 		{
 		if ( state[minec] != SAME_TRANS )
 			if ( state[minec] != 0 || deflink != JAMSTATE )
 				break;
 		}
 
 	if ( totaltrans == 1 )
 		{
 		/* There's only one out-transition.  Save it for later to fill
 		 * in holes in the tables.
 		 */
 		stack1( statenum, minec, state[minec], deflink );
 		return;
 		}
 
 	for ( maxec = numchars; maxec > 0; --maxec )
 		{
 		if ( state[maxec] != SAME_TRANS )
 			if ( state[maxec] != 0 || deflink != JAMSTATE )
 				break;
 		}
 
 	/* Whether we try to fit the state table in the middle of the table
 	 * entries we have already generated, or if we just take the state
 	 * table at the end of the nxt/chk tables, we must make sure that we
 	 * have a valid base address (i.e., non-negative).  Note that
 	 * negative base addresses dangerous at run-time (because indexing
 	 * the nxt array with one and a low-valued character will access
 	 * memory before the start of the array.
 	 */
 
 	/* Find the first transition of state that we need to worry about. */
 	if ( totaltrans * 100 <= numchars * INTERIOR_FIT_PERCENTAGE )
 		{
 		/* Attempt to squeeze it into the middle of the tables. */
 		baseaddr = firstfree;
 
 		while ( baseaddr < minec )
 			{
 			/* Using baseaddr would result in a negative base
 			 * address below; find the next free slot.
 			 */
 			for ( ++baseaddr; chk[baseaddr] != 0; ++baseaddr )
 				;
 			}
 
 		while ( baseaddr + maxec - minec + 1 >= current_max_xpairs )
 			expand_nxt_chk();
 
 		for ( i = minec; i <= maxec; ++i )
 			if ( state[i] != SAME_TRANS &&
 			     (state[i] != 0 || deflink != JAMSTATE) &&
 			     chk[baseaddr + i - minec] != 0 )
 				{ /* baseaddr unsuitable - find another */
 				for ( ++baseaddr;
 				      baseaddr < current_max_xpairs &&
 				      chk[baseaddr] != 0; ++baseaddr )
 					;
 
 				while ( baseaddr + maxec - minec + 1 >=
 					current_max_xpairs )
 					expand_nxt_chk();
 
 				/* Reset the loop counter so we'll start all
 				 * over again next time it's incremented.
 				 */
 
 				i = minec - 1;
 				}
 		}
 
 	else
 		{
 		/* Ensure that the base address we eventually generate is
 		 * non-negative.
 		 */
 		baseaddr = MAX( tblend + 1, minec );
 		}
 
 	tblbase = baseaddr - minec;
 	tbllast = tblbase + maxec;
 
 	while ( tbllast + 1 >= current_max_xpairs )
 		expand_nxt_chk();
 
 	base[statenum] = tblbase;
 	def[statenum] = deflink;
 
 	for ( i = minec; i <= maxec; ++i )
 		if ( state[i] != SAME_TRANS )
 			if ( state[i] != 0 || deflink != JAMSTATE )
 				{
 				nxt[tblbase + i] = state[i];
 				chk[tblbase + i] = statenum;
 				}
 
 	if ( baseaddr == firstfree )
 		/* Find next free slot in tables. */
 		for ( ++firstfree; chk[firstfree] != 0; ++firstfree )
 			;
 
 	tblend = MAX( tblend, tbllast );
 	}
 
 
 /* mk1tbl - create table entries for a state (or state fragment) which
  *            has only one out-transition
  */
 
 void mk1tbl( state, sym, onenxt, onedef )
 int state, sym, onenxt, onedef;
 	{
 	if ( firstfree < sym )
 		firstfree = sym;
 
 	while ( chk[firstfree] != 0 )
 		if ( ++firstfree >= current_max_xpairs )
 			expand_nxt_chk();
 
 	base[state] = firstfree - sym;
 	def[state] = onedef;
 	chk[firstfree] = state;
 	nxt[firstfree] = onenxt;
 
 	if ( firstfree > tblend )
 		{
 		tblend = firstfree++;
 
 		if ( firstfree >= current_max_xpairs )
 			expand_nxt_chk();
 		}
 	}
 
 
 /* mkprot - create new proto entry */
 
 void mkprot( state, statenum, comstate )
 int state[], statenum, comstate;
 	{
 	int i, slot, tblbase;
 
 	if ( ++numprots >= MSP || numecs * numprots >= PROT_SAVE_SIZE )
 		{
 		/* Gotta make room for the new proto by dropping last entry in
 		 * the queue.
 		 */
 		slot = lastprot;
 		lastprot = protprev[lastprot];
 		protnext[lastprot] = NIL;
 		}
 
 	else
 		slot = numprots;
 
 	protnext[slot] = firstprot;
 
 	if ( firstprot != NIL )
 		protprev[firstprot] = slot;
 
 	firstprot = slot;
 	prottbl[slot] = statenum;
 	protcomst[slot] = comstate;
 
 	/* Copy state into save area so it can be compared with rapidly. */
 	tblbase = numecs * (slot - 1);
 
 	for ( i = 1; i <= numecs; ++i )
 		protsave[tblbase + i] = state[i];
 	}
 
 
 /* mktemplate - create a template entry based on a state, and connect the state
  *              to it
  */
 
 void mktemplate( state, statenum, comstate )
 int state[], statenum, comstate;
 	{
 	int i, numdiff, tmpbase, tmp[CSIZE + 1];
 	Char transset[CSIZE + 1];
 	int tsptr;
 
 	++numtemps;
 
 	tsptr = 0;
 
 	/* Calculate where we will temporarily store the transition table
 	 * of the template in the tnxt[] array.  The final transition table
 	 * gets created by cmptmps().
 	 */
 
 	tmpbase = numtemps * numecs;
 
 	if ( tmpbase + numecs >= current_max_template_xpairs )
 		{
 		current_max_template_xpairs += MAX_TEMPLATE_XPAIRS_INCREMENT;
 
 		++num_reallocs;
 
 		tnxt = reallocate_integer_array( tnxt,
 			current_max_template_xpairs );
 		}
 
 	for ( i = 1; i <= numecs; ++i )
 		if ( state[i] == 0 )
 			tnxt[tmpbase + i] = 0;
 		else
 			{
 			transset[tsptr++] = i;
 			tnxt[tmpbase + i] = comstate;
 			}
 
 	if ( usemecs )
 		mkeccl( transset, tsptr, tecfwd, tecbck, numecs, 0 );
 
 	mkprot( tnxt + tmpbase, -numtemps, comstate );
 
 	/* We rely on the fact that mkprot adds things to the beginning
 	 * of the proto queue.
 	 */
 
 	numdiff = tbldiff( state, firstprot, tmp );
 	mkentry( tmp, numecs, statenum, -numtemps, numdiff );
 	}
 
 
 /* mv2front - move proto queue element to front of queue */
 
 void mv2front( qelm )
 int qelm;
 	{
 	if ( firstprot != qelm )
 		{
 		if ( qelm == lastprot )
 			lastprot = protprev[lastprot];
 
 		protnext[protprev[qelm]] = protnext[qelm];
 
 		if ( protnext[qelm] != NIL )
 			protprev[protnext[qelm]] = protprev[qelm];
 
 		protprev[qelm] = NIL;
 		protnext[qelm] = firstprot;
 		protprev[firstprot] = qelm;
 		firstprot = qelm;
 		}
 	}
 
 
 /* place_state - place a state into full speed transition table
  *
  * State is the statenum'th state.  It is indexed by equivalence class and
  * gives the number of the state to enter for a given equivalence class.
  * Transnum is the number of out-transitions for the state.
  */
 
 void place_state( state, statenum, transnum )
 int *state, statenum, transnum;
 	{
 	int i;
 	int *state_ptr;
 	int position = find_table_space( state, transnum );
 
 	/* "base" is the table of start positions. */
 	base[statenum] = position;
 
 	/* Put in action number marker; this non-zero number makes sure that
 	 * find_table_space() knows that this position in chk/nxt is taken
 	 * and should not be used for another accepting number in another
 	 * state.
 	 */
 	chk[position - 1] = 1;
 
 	/* Put in end-of-buffer marker; this is for the same purposes as
 	 * above.
 	 */
 	chk[position] = 1;
 
 	/* Place the state into chk and nxt. */
 	state_ptr = &state[1];
 
 	for ( i = 1; i <= numecs; ++i, ++state_ptr )
 		if ( *state_ptr != 0 )
 			{
 			chk[position + i] = i;
 			nxt[position + i] = *state_ptr;
 			}
 
 	if ( position + numecs > tblend )
 		tblend = position + numecs;
 	}
 
 
 /* stack1 - save states with only one out-transition to be processed later
  *
  * If there's room for another state on the "one-transition" stack, the
  * state is pushed onto it, to be processed later by mk1tbl.  If there's
  * no room, we process the sucker right now.
  */
 
 void stack1( statenum, sym, nextstate, deflink )
 int statenum, sym, nextstate, deflink;
 	{
 	if ( onesp >= ONE_STACK_SIZE - 1 )
 		mk1tbl( statenum, sym, nextstate, deflink );
 
 	else
 		{
 		++onesp;
 		onestate[onesp] = statenum;
 		onesym[onesp] = sym;
 		onenext[onesp] = nextstate;
 		onedef[onesp] = deflink;
 		}
 	}
 
 
 /* tbldiff - compute differences between two state tables
  *
  * "state" is the state array which is to be extracted from the pr'th
  * proto.  "pr" is both the number of the proto we are extracting from
  * and an index into the save area where we can find the proto's complete
  * state table.  Each entry in "state" which differs from the corresponding
  * entry of "pr" will appear in "ext".
  *
  * Entries which are the same in both "state" and "pr" will be marked
  * as transitions to "SAME_TRANS" in "ext".  The total number of differences
  * between "state" and "pr" is returned as function value.  Note that this
  * number is "numecs" minus the number of "SAME_TRANS" entries in "ext".
  */
 
 int tbldiff( state, pr, ext )
 int state[], pr, ext[];
 	{
 	int i, *sp = state, *ep = ext, *protp;
 	int numdiff = 0;
 
 	protp = &protsave[numecs * (pr - 1)];
 
 	for ( i = numecs; i > 0; --i )
 		{
 		if ( *++protp == *++sp )
 			*++ep = SAME_TRANS;
 		else
 			{
 			*++ep = *sp;
 			++numdiff;
 			}
 		}
 
 	return numdiff;
 	}