nfa.c

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/*************************************************************************\
* Copyright (c) 2002 The University of Chicago, as Operator of Argonne
*     National Laboratory.
* Copyright (c) 2002 The Regents of the University of California, as
*     Operator of Los Alamos National Laboratory.
* EPICS BASE is distributed subject to a Software License Agreement found
* in file LICENSE that is included with this distribution.
\*************************************************************************/
/* 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 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.
 */

#include "flexdef.h"


/* declare functions that have forward references */

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


/* add_accept - add an accepting state to a machine
 *
 * synopsis
 *
 *   add_accept( mach, accepting_number );
 *
 * accepting_number becomes mach's accepting number.
 */

void add_accept(int mach, int 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;
        mach = 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(int singl, int 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
 *
 * synopsis
 *    int state1;
 *    dumpnfa( state1 );
 */

void dumpnfa(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(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
 *
 * synopsis
 *
 *   finish_rule( mach, variable_trail_rule, headcnt, trailcnt );
 *
 * 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(int mach, int variable_trail_rule, int headcnt, int trailcnt)
{
    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];

    fprintf( temp_action_file, "case %d:\n", num_rules );

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

        if ( performance_report )
            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";

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

            if ( headcnt > 0 )
                fprintf( temp_action_file, "%s = %s + %d;\n",
                         scanner_cp, scanner_bp, headcnt );

            else
                fprintf( temp_action_file,
                         "%s -= %d;\n", scanner_cp, trailcnt );

            fprintf( temp_action_file,
                     "YY_DO_BEFORE_ACTION; /* set up yytext again */\n" );
            }
        }

    line_directive_out( temp_action_file );
    }


/* 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(int first, int 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
 *
 * synopsis
 *
 *   mark_beginning_as_normal( mach )
 *
 *     mach - machine to mark
 *
 * The "beginning" states are the epsilon closure of the first state
 */

void mark_beginning_as_normal(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(int first, int 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(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(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(int first, int 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(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(int mach, int lb, int 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(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
        {
        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(int statefrom, int 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
 *
 * synopsis
 *
 *   new_rule();
 *
 * the global num_rules is incremented and the any corresponding dynamic
 * arrays (such as rule_type[]) are grown as needed.
 */

void new_rule(void)
{
    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 );
        }

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

    rule_linenum[num_rules] = linenum;
    }