nfa.c   [plain text]


/* nfa - NFA construction 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: (1) source distributions retain
 * this entire copyright notice and comment, and (2) distributions including
 * binaries display the following acknowledgement:  ``This product includes
 * software developed by the University of California, Berkeley and its
 * contributors'' in the documentation or other materials provided with the
 * distribution and in all advertising materials mentioning features or use
 * of this software.  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: /Users/Shared/flex/flex/flex/nfa.c,v 1.1 1999/04/23 00:46:30 wsanchez Exp $ */

#include "flexdef.h"


/* declare functions that have forward references */

int dupmachine PROTO((int));
void mkxtion PROTO((int, int));


/* add_accept - add an accepting state to a machine
 *
 * accepting_number becomes mach's accepting number.
 */

void add_accept( mach, accepting_number )
int mach, accepting_number;
	{
	/* Hang the accepting number off an epsilon state.  if it is associated
	 * with a state that has a non-epsilon out-transition, then the state
	 * will accept BEFORE it makes that transition, i.e., one character
	 * too soon.
	 */

	if ( transchar[finalst[mach]] == SYM_EPSILON )
		accptnum[finalst[mach]] = accepting_number;

	else
		{
		int astate = mkstate( SYM_EPSILON );
		accptnum[astate] = accepting_number;
		(void) link_machines( mach, astate );
		}
	}


/* copysingl - make a given number of copies of a singleton machine
 *
 * synopsis
 *
 *   newsng = copysingl( singl, num );
 *
 *     newsng - a new singleton composed of num copies of singl
 *     singl  - a singleton machine
 *     num    - the number of copies of singl to be present in newsng
 */

int copysingl( singl, num )
int singl, num;
	{
	int copy, i;

	copy = mkstate( SYM_EPSILON );

	for ( i = 1; i <= num; ++i )
		copy = link_machines( copy, dupmachine( singl ) );

	return copy;
	}


/* dumpnfa - debugging routine to write out an nfa */

void dumpnfa( state1 )
int state1;

	{
	int sym, tsp1, tsp2, anum, ns;

	fprintf( stderr,
	_( "\n\n********** beginning dump of nfa with start state %d\n" ),
		state1 );

	/* We probably should loop starting at firstst[state1] and going to
	 * lastst[state1], but they're not maintained properly when we "or"
	 * all of the rules together.  So we use our knowledge that the machine
	 * starts at state 1 and ends at lastnfa.
	 */

	/* for ( ns = firstst[state1]; ns <= lastst[state1]; ++ns ) */
	for ( ns = 1; ns <= lastnfa; ++ns )
		{
		fprintf( stderr, _( "state # %4d\t" ), ns );

		sym = transchar[ns];
		tsp1 = trans1[ns];
		tsp2 = trans2[ns];
		anum = accptnum[ns];

		fprintf( stderr, "%3d:  %4d, %4d", sym, tsp1, tsp2 );

		if ( anum != NIL )
			fprintf( stderr, "  [%d]", anum );

		fprintf( stderr, "\n" );
		}

	fprintf( stderr, _( "********** end of dump\n" ) );
	}


/* dupmachine - make a duplicate of a given machine
 *
 * synopsis
 *
 *   copy = dupmachine( mach );
 *
 *     copy - holds duplicate of mach
 *     mach - machine to be duplicated
 *
 * note that the copy of mach is NOT an exact duplicate; rather, all the
 * transition states values are adjusted so that the copy is self-contained,
 * as the original should have been.
 *
 * also note that the original MUST be contiguous, with its low and high
 * states accessible by the arrays firstst and lastst
 */

int dupmachine( mach )
int mach;
	{
	int i, init, state_offset;
	int state = 0;
	int last = lastst[mach];

	for ( i = firstst[mach]; i <= last; ++i )
		{
		state = mkstate( transchar[i] );

		if ( trans1[i] != NO_TRANSITION )
			{
			mkxtion( finalst[state], trans1[i] + state - i );

			if ( transchar[i] == SYM_EPSILON &&
			     trans2[i] != NO_TRANSITION )
				mkxtion( finalst[state],
					trans2[i] + state - i );
			}

		accptnum[state] = accptnum[i];
		}

	if ( state == 0 )
		flexfatal( _( "empty machine in dupmachine()" ) );

	state_offset = state - i + 1;

	init = mach + state_offset;
	firstst[init] = firstst[mach] + state_offset;
	finalst[init] = finalst[mach] + state_offset;
	lastst[init] = lastst[mach] + state_offset;

	return init;
	}


/* finish_rule - finish up the processing for a rule
 *
 * An accepting number is added to the given machine.  If variable_trail_rule
 * is true then the rule has trailing context and both the head and trail
 * are variable size.  Otherwise if headcnt or trailcnt is non-zero then
 * the machine recognizes a pattern with trailing context and headcnt is
 * the number of characters in the matched part of the pattern, or zero
 * if the matched part has variable length.  trailcnt is the number of
 * trailing context characters in the pattern, or zero if the trailing
 * context has variable length.
 */

void finish_rule( mach, variable_trail_rule, headcnt, trailcnt )
int mach, variable_trail_rule, headcnt, trailcnt;
	{
	char action_text[MAXLINE];

	add_accept( mach, num_rules );

	/* We did this in new_rule(), but it often gets the wrong
	 * number because we do it before we start parsing the current rule.
	 */
	rule_linenum[num_rules] = linenum;

	/* If this is a continued action, then the line-number has already
	 * been updated, giving us the wrong number.
	 */
	if ( continued_action )
		--rule_linenum[num_rules];

	sprintf( action_text, "case %d:\n", num_rules );
	add_action( action_text );

	if ( variable_trail_rule )
		{
		rule_type[num_rules] = RULE_VARIABLE;

		if ( performance_report > 0 )
			fprintf( stderr,
			_( "Variable trailing context rule at line %d\n" ),
				rule_linenum[num_rules] );

		variable_trailing_context_rules = true;
		}

	else
		{
		rule_type[num_rules] = RULE_NORMAL;

		if ( headcnt > 0 || trailcnt > 0 )
			{
			/* Do trailing context magic to not match the trailing
			 * characters.
			 */
			char *scanner_cp = "yy_c_buf_p = yy_cp";
			char *scanner_bp = "yy_bp";

			add_action(
	"*yy_cp = yy_hold_char; /* undo effects of setting up yytext */\n" );

			if ( headcnt > 0 )
				{
				sprintf( action_text, "%s = %s + %d;\n",
				scanner_cp, scanner_bp, headcnt );
				add_action( action_text );
				}

			else
				{
				sprintf( action_text, "%s -= %d;\n",
					scanner_cp, trailcnt );
				add_action( action_text );
				}

			add_action(
			"YY_DO_BEFORE_ACTION; /* set up yytext again */\n" );
			}
		}

	/* Okay, in the action code at this point yytext and yyleng have
	 * their proper final values for this rule, so here's the point
	 * to do any user action.  But don't do it for continued actions,
	 * as that'll result in multiple YY_RULE_SETUP's.
	 */
	if ( ! continued_action )
		add_action( "YY_RULE_SETUP\n" );

	line_directive_out( (FILE *) 0, 1 );
	}


/* link_machines - connect two machines together
 *
 * synopsis
 *
 *   new = link_machines( first, last );
 *
 *     new    - a machine constructed by connecting first to last
 *     first  - the machine whose successor is to be last
 *     last   - the machine whose predecessor is to be first
 *
 * note: this routine concatenates the machine first with the machine
 *  last to produce a machine new which will pattern-match first first
 *  and then last, and will fail if either of the sub-patterns fails.
 *  FIRST is set to new by the operation.  last is unmolested.
 */

int link_machines( first, last )
int first, last;
	{
	if ( first == NIL )
		return last;

	else if ( last == NIL )
		return first;

	else
		{
		mkxtion( finalst[first], last );
		finalst[first] = finalst[last];
		lastst[first] = MAX( lastst[first], lastst[last] );
		firstst[first] = MIN( firstst[first], firstst[last] );

		return first;
		}
	}


/* mark_beginning_as_normal - mark each "beginning" state in a machine
 *                            as being a "normal" (i.e., not trailing context-
 *                            associated) states
 *
 * The "beginning" states are the epsilon closure of the first state
 */

void mark_beginning_as_normal( mach )
register int mach;
	{
	switch ( state_type[mach] )
		{
		case STATE_NORMAL:
			/* Oh, we've already visited here. */
			return;

		case STATE_TRAILING_CONTEXT:
			state_type[mach] = STATE_NORMAL;

			if ( transchar[mach] == SYM_EPSILON )
				{
				if ( trans1[mach] != NO_TRANSITION )
					mark_beginning_as_normal(
						trans1[mach] );

				if ( trans2[mach] != NO_TRANSITION )
					mark_beginning_as_normal(
						trans2[mach] );
				}
			break;

		default:
			flexerror(
			_( "bad state type in mark_beginning_as_normal()" ) );
			break;
		}
	}


/* mkbranch - make a machine that branches to two machines
 *
 * synopsis
 *
 *   branch = mkbranch( first, second );
 *
 *     branch - a machine which matches either first's pattern or second's
 *     first, second - machines whose patterns are to be or'ed (the | operator)
 *
 * Note that first and second are NEITHER destroyed by the operation.  Also,
 * the resulting machine CANNOT be used with any other "mk" operation except
 * more mkbranch's.  Compare with mkor()
 */

int mkbranch( first, second )
int first, second;
	{
	int eps;

	if ( first == NO_TRANSITION )
		return second;

	else if ( second == NO_TRANSITION )
		return first;

	eps = mkstate( SYM_EPSILON );

	mkxtion( eps, first );
	mkxtion( eps, second );

	return eps;
	}


/* mkclos - convert a machine into a closure
 *
 * synopsis
 *   new = mkclos( state );
 *
 * new - a new state which matches the closure of "state"
 */

int mkclos( state )
int state;
	{
	return mkopt( mkposcl( state ) );
	}


/* mkopt - make a machine optional
 *
 * synopsis
 *
 *   new = mkopt( mach );
 *
 *     new  - a machine which optionally matches whatever mach matched
 *     mach - the machine to make optional
 *
 * notes:
 *     1. mach must be the last machine created
 *     2. mach is destroyed by the call
 */

int mkopt( mach )
int mach;
	{
	int eps;

	if ( ! SUPER_FREE_EPSILON(finalst[mach]) )
		{
		eps = mkstate( SYM_EPSILON );
		mach = link_machines( mach, eps );
		}

	/* Can't skimp on the following if FREE_EPSILON(mach) is true because
	 * some state interior to "mach" might point back to the beginning
	 * for a closure.
	 */
	eps = mkstate( SYM_EPSILON );
	mach = link_machines( eps, mach );

	mkxtion( mach, finalst[mach] );

	return mach;
	}


/* mkor - make a machine that matches either one of two machines
 *
 * synopsis
 *
 *   new = mkor( first, second );
 *
 *     new - a machine which matches either first's pattern or second's
 *     first, second - machines whose patterns are to be or'ed (the | operator)
 *
 * note that first and second are both destroyed by the operation
 * the code is rather convoluted because an attempt is made to minimize
 * the number of epsilon states needed
 */

int mkor( first, second )
int first, second;
	{
	int eps, orend;

	if ( first == NIL )
		return second;

	else if ( second == NIL )
		return first;

	else
		{
		/* See comment in mkopt() about why we can't use the first
		 * state of "first" or "second" if they satisfy "FREE_EPSILON".
		 */
		eps = mkstate( SYM_EPSILON );

		first = link_machines( eps, first );

		mkxtion( first, second );

		if ( SUPER_FREE_EPSILON(finalst[first]) &&
		     accptnum[finalst[first]] == NIL )
			{
			orend = finalst[first];
			mkxtion( finalst[second], orend );
			}

		else if ( SUPER_FREE_EPSILON(finalst[second]) &&
			  accptnum[finalst[second]] == NIL )
			{
			orend = finalst[second];
			mkxtion( finalst[first], orend );
			}

		else
			{
			eps = mkstate( SYM_EPSILON );

			first = link_machines( first, eps );
			orend = finalst[first];

			mkxtion( finalst[second], orend );
			}
		}

	finalst[first] = orend;
	return first;
	}


/* mkposcl - convert a machine into a positive closure
 *
 * synopsis
 *   new = mkposcl( state );
 *
 *    new - a machine matching the positive closure of "state"
 */

int mkposcl( state )
int state;
	{
	int eps;

	if ( SUPER_FREE_EPSILON(finalst[state]) )
		{
		mkxtion( finalst[state], state );
		return state;
		}

	else
		{
		eps = mkstate( SYM_EPSILON );
		mkxtion( eps, state );
		return link_machines( state, eps );
		}
	}


/* mkrep - make a replicated machine
 *
 * synopsis
 *   new = mkrep( mach, lb, ub );
 *
 *    new - a machine that matches whatever "mach" matched from "lb"
 *          number of times to "ub" number of times
 *
 * note
 *   if "ub" is INFINITY then "new" matches "lb" or more occurrences of "mach"
 */

int mkrep( mach, lb, ub )
int mach, lb, ub;
	{
	int base_mach, tail, copy, i;

	base_mach = copysingl( mach, lb - 1 );

	if ( ub == INFINITY )
		{
		copy = dupmachine( mach );
		mach = link_machines( mach,
		link_machines( base_mach, mkclos( copy ) ) );
		}

	else
		{
		tail = mkstate( SYM_EPSILON );

		for ( i = lb; i < ub; ++i )
			{
			copy = dupmachine( mach );
			tail = mkopt( link_machines( copy, tail ) );
			}

		mach = link_machines( mach, link_machines( base_mach, tail ) );
		}

	return mach;
	}


/* mkstate - create a state with a transition on a given symbol
 *
 * synopsis
 *
 *   state = mkstate( sym );
 *
 *     state - a new state matching sym
 *     sym   - the symbol the new state is to have an out-transition on
 *
 * note that this routine makes new states in ascending order through the
 * state array (and increments LASTNFA accordingly).  The routine DUPMACHINE
 * relies on machines being made in ascending order and that they are
 * CONTIGUOUS.  Change it and you will have to rewrite DUPMACHINE (kludge
 * that it admittedly is)
 */

int mkstate( sym )
int sym;
	{
	if ( ++lastnfa >= current_mns )
		{
		if ( (current_mns += MNS_INCREMENT) >= MAXIMUM_MNS )
			lerrif(
		_( "input rules are too complicated (>= %d NFA states)" ),
				current_mns );

		++num_reallocs;

		firstst = reallocate_integer_array( firstst, current_mns );
		lastst = reallocate_integer_array( lastst, current_mns );
		finalst = reallocate_integer_array( finalst, current_mns );
		transchar = reallocate_integer_array( transchar, current_mns );
		trans1 = reallocate_integer_array( trans1, current_mns );
		trans2 = reallocate_integer_array( trans2, current_mns );
		accptnum = reallocate_integer_array( accptnum, current_mns );
		assoc_rule =
			reallocate_integer_array( assoc_rule, current_mns );
		state_type =
			reallocate_integer_array( state_type, current_mns );
		}

	firstst[lastnfa] = lastnfa;
	finalst[lastnfa] = lastnfa;
	lastst[lastnfa] = lastnfa;
	transchar[lastnfa] = sym;
	trans1[lastnfa] = NO_TRANSITION;
	trans2[lastnfa] = NO_TRANSITION;
	accptnum[lastnfa] = NIL;
	assoc_rule[lastnfa] = num_rules;
	state_type[lastnfa] = current_state_type;

	/* Fix up equivalence classes base on this transition.  Note that any
	 * character which has its own transition gets its own equivalence
	 * class.  Thus only characters which are only in character classes
	 * have a chance at being in the same equivalence class.  E.g. "a|b"
	 * puts 'a' and 'b' into two different equivalence classes.  "[ab]"
	 * puts them in the same equivalence class (barring other differences
	 * elsewhere in the input).
	 */

	if ( sym < 0 )
		{
		/* We don't have to update the equivalence classes since
		 * that was already done when the ccl was created for the
		 * first time.
		 */
		}

	else if ( sym == SYM_EPSILON )
		++numeps;

	else
		{
		check_char( sym );

		if ( useecs )
			/* Map NUL's to csize. */
			mkechar( sym ? sym : csize, nextecm, ecgroup );
		}

	return lastnfa;
	}


/* mkxtion - make a transition from one state to another
 *
 * synopsis
 *
 *   mkxtion( statefrom, stateto );
 *
 *     statefrom - the state from which the transition is to be made
 *     stateto   - the state to which the transition is to be made
 */

void mkxtion( statefrom, stateto )
int statefrom, stateto;
	{
	if ( trans1[statefrom] == NO_TRANSITION )
		trans1[statefrom] = stateto;

	else if ( (transchar[statefrom] != SYM_EPSILON) ||
		  (trans2[statefrom] != NO_TRANSITION) )
		flexfatal( _( "found too many transitions in mkxtion()" ) );

	else
		{ /* second out-transition for an epsilon state */
		++eps2;
		trans2[statefrom] = stateto;
		}
	}

/* new_rule - initialize for a new rule */

void new_rule()
	{
	if ( ++num_rules >= current_max_rules )
		{
		++num_reallocs;
		current_max_rules += MAX_RULES_INCREMENT;
		rule_type = reallocate_integer_array( rule_type,
							current_max_rules );
		rule_linenum = reallocate_integer_array( rule_linenum,
							current_max_rules );
		rule_useful = reallocate_integer_array( rule_useful,
							current_max_rules );
		}

	if ( num_rules > MAX_RULE )
		lerrif( _( "too many rules (> %d)!" ), MAX_RULE );

	rule_linenum[num_rules] = linenum;
	rule_useful[num_rules] = false;
	}