source: trunk/essentials/sys-devel/flex/nfa.c

/* 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. */

/*  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"


/* 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,
                     pcont_act)
     int     mach, variable_trail_rule, headcnt, trailcnt, pcont_act;
{
        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];


        /* If the previous rule was continued action, then we inherit the
         * previous newline flag, possibly overriding the current one.
         */
        if (pcont_act && rule_has_nl[num_rules - 1])
                rule_has_nl[num_rules] = true;

        sprintf (action_text, "case %d:\n", num_rules);
        add_action (action_text);
        if (rule_has_nl[num_rules]) {
                sprintf (action_text, "/* rule %d can match eol */\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_G(yy_c_buf_p) = yy_cp";
                        char   *scanner_bp = "yy_bp";

                        add_action
                                ("*yy_cp = YY_G(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 INFINITE_REPEAT 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 == INFINITE_REPEAT) {
                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);
                rule_has_nl = reallocate_bool_array (rule_has_nl,
                                                     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;
        rule_has_nl[num_rules] = false;
}