/* 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. */

/*  This file is part of flex. */

/*  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. */

#include "flexdef.h"

/* declarations for functions that have forward references */

void mkentry(int *, int, int, int, int);

void mkprot(int[], int, int);

void mktemplate(int[], int, int);

void mv2front(int);

int tbldiff(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 (int state[], int statenum, int totaltrans, int comstate, int 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 (void)

{

	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 (void)

{

	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);

	memset(chk + old_max, 0, 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 (int *state, int 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 (void)

{

	int i;

	memset(chk, 0, 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 (void)

{

	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 (int *state, int numchars, int statenum, int deflink,

		 int 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 (int state, int sym, int onenxt, int 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 (int state[], int statenum, int 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 (int state[], int statenum, int comstate)

{

	int     i, numdiff, tmpbase, tmp[CSIZE + 1];

	unsigned 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 (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 (int *state, int statenum, int 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 (int statenum, int sym, int nextstate, int 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 (int state[], int pr, int 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;

}