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Sourcecode: maxdb-buildtools version File versions

dfa.c

/* dfa - DFA 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: /home/daffy/u0/vern/flex/RCS/dfa.c,v 2.26 95/04/20 13:53:14 vern Exp $ */

#include "flexdef.h"


/* declare functions that have forward references */

void dump_associated_rules PROTO((FILE*, int));
void dump_transitions PROTO((FILE*, int[]));
void sympartition PROTO((int[], int, int[], int[]));
int symfollowset PROTO((int[], int, int, int[]));


/* check_for_backing_up - check a DFA state for backing up
 *
 * synopsis
 *     void check_for_backing_up( int ds, int state[numecs] );
 *
 * ds is the number of the state to check and state[] is its out-transitions,
 * indexed by equivalence class.
 */

void check_for_backing_up( ds, state )
int ds;
int state[];
      {
      if ( (reject && ! dfaacc[ds].dfaacc_set) ||
           (! reject && ! dfaacc[ds].dfaacc_state) )
            { /* state is non-accepting */
            ++num_backing_up;

            if ( backing_up_report )
                  {
                  fprintf( backing_up_file,
                        _( "State #%d is non-accepting -\n" ), ds );

                  /* identify the state */
                  dump_associated_rules( backing_up_file, ds );

                  /* Now identify it further using the out- and
                   * jam-transitions.
                   */
                  dump_transitions( backing_up_file, state );

                  putc( '\n', backing_up_file );
                  }
            }
      }


/* check_trailing_context - check to see if NFA state set constitutes
 *                          "dangerous" trailing context
 *
 * synopsis
 *    void check_trailing_context( int nfa_states[num_states+1], int num_states,
 *                      int accset[nacc+1], int nacc );
 *
 * NOTES
 *  Trailing context is "dangerous" if both the head and the trailing
 *  part are of variable size \and/ there's a DFA state which contains
 *  both an accepting state for the head part of the rule and NFA states
 *  which occur after the beginning of the trailing context.
 *
 *  When such a rule is matched, it's impossible to tell if having been
 *  in the DFA state indicates the beginning of the trailing context or
 *  further-along scanning of the pattern.  In these cases, a warning
 *  message is issued.
 *
 *    nfa_states[1 .. num_states] is the list of NFA states in the DFA.
 *    accset[1 .. nacc] is the list of accepting numbers for the DFA state.
 */

void check_trailing_context( nfa_states, num_states, accset, nacc )
int *nfa_states, num_states;
int *accset;
int nacc;
      {
      register int i, j;

      for ( i = 1; i <= num_states; ++i )
            {
            int ns = nfa_states[i];
            register int type = state_type[ns];
            register int ar = assoc_rule[ns];

            if ( type == STATE_NORMAL || rule_type[ar] != RULE_VARIABLE )
                  { /* do nothing */
                  }

            else if ( type == STATE_TRAILING_CONTEXT )
                  {
                  /* Potential trouble.  Scan set of accepting numbers
                   * for the one marking the end of the "head".  We
                   * assume that this looping will be fairly cheap
                   * since it's rare that an accepting number set
                   * is large.
                   */
                  for ( j = 1; j <= nacc; ++j )
                        if ( accset[j] & YY_TRAILING_HEAD_MASK )
                              {
                              line_warning(
                              _( "dangerous trailing context" ),
                                    rule_linenum[ar] );
                              return;
                              }
                  }
            }
      }


/* dump_associated_rules - list the rules associated with a DFA state
 *
 * Goes through the set of NFA states associated with the DFA and
 * extracts the first MAX_ASSOC_RULES unique rules, sorts them,
 * and writes a report to the given file.
 */

void dump_associated_rules( file, ds )
FILE *file;
int ds;
      {
      register int i, j;
      register int num_associated_rules = 0;
      int rule_set[MAX_ASSOC_RULES + 1];
      int *dset = dss[ds];
      int size = dfasiz[ds];

      for ( i = 1; i <= size; ++i )
            {
            register int rule_num = rule_linenum[assoc_rule[dset[i]]];

            for ( j = 1; j <= num_associated_rules; ++j )
                  if ( rule_num == rule_set[j] )
                        break;

            if ( j > num_associated_rules )
                  { /* new rule */
                  if ( num_associated_rules < MAX_ASSOC_RULES )
                        rule_set[++num_associated_rules] = rule_num;
                  }
            }

      bubble( rule_set, num_associated_rules );

      fprintf( file, _( " associated rule line numbers:" ) );

      for ( i = 1; i <= num_associated_rules; ++i )
            {
            if ( i % 8 == 1 )
                  putc( '\n', file );

            fprintf( file, "\t%d", rule_set[i] );
            }

      putc( '\n', file );
      }


/* dump_transitions - list the transitions associated with a DFA state
 *
 * synopsis
 *     dump_transitions( FILE *file, int state[numecs] );
 *
 * Goes through the set of out-transitions and lists them in human-readable
 * form (i.e., not as equivalence classes); also lists jam transitions
 * (i.e., all those which are not out-transitions, plus EOF).  The dump
 * is done to the given file.
 */

void dump_transitions( file, state )
FILE *file;
int state[];
      {
      register int i, ec;
      int out_char_set[CSIZE];

      for ( i = 0; i < csize; ++i )
            {
            ec = ABS( ecgroup[i] );
            out_char_set[i] = state[ec];
            }

      fprintf( file, _( " out-transitions: " ) );

      list_character_set( file, out_char_set );

      /* now invert the members of the set to get the jam transitions */
      for ( i = 0; i < csize; ++i )
            out_char_set[i] = ! out_char_set[i];

      fprintf( file, _( "\n jam-transitions: EOF " ) );

      list_character_set( file, out_char_set );

      putc( '\n', file );
      }


/* epsclosure - construct the epsilon closure of a set of ndfa states
 *
 * synopsis
 *    int *epsclosure( int t[num_states], int *numstates_addr,
 *                int accset[num_rules+1], int *nacc_addr,
 *                int *hashval_addr );
 *
 * NOTES
 *  The epsilon closure is the set of all states reachable by an arbitrary
 *  number of epsilon transitions, which themselves do not have epsilon
 *  transitions going out, unioned with the set of states which have non-null
 *  accepting numbers.  t is an array of size numstates of nfa state numbers.
 *  Upon return, t holds the epsilon closure and *numstates_addr is updated.
 *  accset holds a list of the accepting numbers, and the size of accset is
 *  given by *nacc_addr.  t may be subjected to reallocation if it is not
 *  large enough to hold the epsilon closure.
 *
 *  hashval is the hash value for the dfa corresponding to the state set.
 */

int *epsclosure( t, ns_addr, accset, nacc_addr, hv_addr )
int *t, *ns_addr, accset[], *nacc_addr, *hv_addr;
      {
      register int stkpos, ns, tsp;
      int numstates = *ns_addr, nacc, hashval, transsym, nfaccnum;
      int stkend, nstate;
      static int did_stk_init = false, *stk; 

#define MARK_STATE(state) \
trans1[state] = trans1[state] - MARKER_DIFFERENCE;

#define IS_MARKED(state) (trans1[state] < 0)

#define UNMARK_STATE(state) \
trans1[state] = trans1[state] + MARKER_DIFFERENCE;

#define CHECK_ACCEPT(state) \
{ \
nfaccnum = accptnum[state]; \
if ( nfaccnum != NIL ) \
accset[++nacc] = nfaccnum; \
}

#define DO_REALLOCATION \
{ \
current_max_dfa_size += MAX_DFA_SIZE_INCREMENT; \
++num_reallocs; \
t = reallocate_integer_array( t, current_max_dfa_size ); \
stk = reallocate_integer_array( stk, current_max_dfa_size ); \
} \

#define PUT_ON_STACK(state) \
{ \
if ( ++stkend >= current_max_dfa_size ) \
DO_REALLOCATION \
stk[stkend] = state; \
MARK_STATE(state) \
}

#define ADD_STATE(state) \
{ \
if ( ++numstates >= current_max_dfa_size ) \
DO_REALLOCATION \
t[numstates] = state; \
hashval += state; \
}

#define STACK_STATE(state) \
{ \
PUT_ON_STACK(state) \
CHECK_ACCEPT(state) \
if ( nfaccnum != NIL || transchar[state] != SYM_EPSILON ) \
ADD_STATE(state) \
}


      if ( ! did_stk_init )
            {
            stk = allocate_integer_array( current_max_dfa_size );
            did_stk_init = true;
            }

      nacc = stkend = hashval = 0;

      for ( nstate = 1; nstate <= numstates; ++nstate )
            {
            ns = t[nstate];

            /* The state could be marked if we've already pushed it onto
             * the stack.
             */
            if ( ! IS_MARKED(ns) )
                  {
                  PUT_ON_STACK(ns)
                  CHECK_ACCEPT(ns)
                  hashval += ns;
                  }
            }

      for ( stkpos = 1; stkpos <= stkend; ++stkpos )
            {
            ns = stk[stkpos];
            transsym = transchar[ns];

            if ( transsym == SYM_EPSILON )
                  {
                  tsp = trans1[ns] + MARKER_DIFFERENCE;

                  if ( tsp != NO_TRANSITION )
                        {
                        if ( ! IS_MARKED(tsp) )
                              STACK_STATE(tsp)

                        tsp = trans2[ns];

                        if ( tsp != NO_TRANSITION && ! IS_MARKED(tsp) )
                              STACK_STATE(tsp)
                        }
                  }
            }

      /* Clear out "visit" markers. */

      for ( stkpos = 1; stkpos <= stkend; ++stkpos )
            {
            if ( IS_MARKED(stk[stkpos]) )
                  UNMARK_STATE(stk[stkpos])
            else
                  flexfatal(
                  _( "consistency check failed in epsclosure()" ) );
            }

      *ns_addr = numstates;
      *hv_addr = hashval;
      *nacc_addr = nacc;

      return t;
      }


/* increase_max_dfas - increase the maximum number of DFAs */

void increase_max_dfas()
      {
      current_max_dfas += MAX_DFAS_INCREMENT;

      ++num_reallocs;

      base = reallocate_integer_array( base, current_max_dfas );
      def = reallocate_integer_array( def, current_max_dfas );
      dfasiz = reallocate_integer_array( dfasiz, current_max_dfas );
      accsiz = reallocate_integer_array( accsiz, current_max_dfas );
      dhash = reallocate_integer_array( dhash, current_max_dfas );
      dss = reallocate_int_ptr_array( dss, current_max_dfas );
      dfaacc = reallocate_dfaacc_union( dfaacc, current_max_dfas );

      if ( nultrans )
            nultrans =
                  reallocate_integer_array( nultrans, current_max_dfas );
      }


/* ntod - convert an ndfa to a dfa
 *
 * Creates the dfa corresponding to the ndfa we've constructed.  The
 * dfa starts out in state #1.
 */

void ntod()
      {
      int *accset, ds, nacc, newds;
      int sym, hashval, numstates, dsize;
      int num_full_table_rows;      /* used only for -f */
      int *nset, *dset;
      int targptr, totaltrans, i, comstate, comfreq, targ;
      int symlist[CSIZE + 1];
      int num_start_states;
      int todo_head, todo_next;

      /* Note that the following are indexed by *equivalence classes*
       * and not by characters.  Since equivalence classes are indexed
       * beginning with 1, even if the scanner accepts NUL's, this
       * means that (since every character is potentially in its own
       * equivalence class) these arrays must have room for indices
       * from 1 to CSIZE, so their size must be CSIZE + 1.
       */
      int duplist[CSIZE + 1], state[CSIZE + 1];
      int targfreq[CSIZE + 1], targstate[CSIZE + 1];

      accset = allocate_integer_array( num_rules + 1 );
      nset = allocate_integer_array( current_max_dfa_size );

      /* The "todo" queue is represented by the head, which is the DFA
       * state currently being processed, and the "next", which is the
       * next DFA state number available (not in use).  We depend on the
       * fact that snstods() returns DFA's \in increasing order/, and thus
       * need only know the bounds of the dfas to be processed.
       */
      todo_head = todo_next = 0;

      for ( i = 0; i <= csize; ++i )
            {
            duplist[i] = NIL;
            symlist[i] = false;
            }

      for ( i = 0; i <= num_rules; ++i )
            accset[i] = NIL;

      if ( trace )
            {
            dumpnfa( scset[1] );
            fputs( _( "\n\nDFA Dump:\n\n" ), stderr );
            }

      inittbl();

      /* Check to see whether we should build a separate table for
       * transitions on NUL characters.  We don't do this for full-speed
       * (-F) scanners, since for them we don't have a simple state
       * number lying around with which to index the table.  We also
       * don't bother doing it for scanners unless (1) NUL is in its own
       * equivalence class (indicated by a positive value of
       * ecgroup[NUL]), (2) NUL's equivalence class is the last
       * equivalence class, and (3) the number of equivalence classes is
       * the same as the number of characters.  This latter case comes
       * about when useecs is false or when it's true but every character
       * still manages to land in its own class (unlikely, but it's
       * cheap to check for).  If all these things are true then the
       * character code needed to represent NUL's equivalence class for
       * indexing the tables is going to take one more bit than the
       * number of characters, and therefore we won't be assured of
       * being able to fit it into a YY_CHAR variable.  This rules out
       * storing the transitions in a compressed table, since the code
       * for interpreting them uses a YY_CHAR variable (perhaps it
       * should just use an integer, though; this is worth pondering ...
       * ###).
       *
       * Finally, for full tables, we want the number of entries in the
       * table to be a power of two so the array references go fast (it
       * will just take a shift to compute the major index).  If
       * encoding NUL's transitions in the table will spoil this, we
       * give it its own table (note that this will be the case if we're
       * not using equivalence classes).
       */

      /* Note that the test for ecgroup[0] == numecs below accomplishes
       * both (1) and (2) above
       */
      if ( ! fullspd && ecgroup[0] == numecs )
            {
            /* NUL is alone in its equivalence class, which is the
             * last one.
             */
            int use_NUL_table = (numecs == csize);

            if ( fulltbl && ! use_NUL_table )
                  {
                  /* We still may want to use the table if numecs
                   * is a power of 2.
                   */
                  int power_of_two;

                  for ( power_of_two = 1; power_of_two <= csize;
                        power_of_two *= 2 )
                        if ( numecs == power_of_two )
                              {
                              use_NUL_table = true;
                              break;
                              }
                  }

            if ( use_NUL_table )
                  nultrans = allocate_integer_array( current_max_dfas );

            /* From now on, nultrans != nil indicates that we're
             * saving null transitions for later, separate encoding.
             */
            }


      if ( fullspd )
            {
            for ( i = 0; i <= numecs; ++i )
                  state[i] = 0;

            place_state( state, 0, 0 );
            dfaacc[0].dfaacc_state = 0;
            }

      else if ( fulltbl )
            {
            if ( nultrans )
                  /* We won't be including NUL's transitions in the
                   * table, so build it for entries from 0 .. numecs - 1.
                   */
                  num_full_table_rows = numecs;

            else
                  /* Take into account the fact that we'll be including
                   * the NUL entries in the transition table.  Build it
                   * from 0 .. numecs.
                   */
                  num_full_table_rows = numecs + 1;

            /* Unless -Ca, declare it "short" because it's a real
             * long-shot that that won't be large enough.
             */
            out_str_dec( "static yyconst %s yy_nxt[][%d] =\n    {\n",
                  /* '}' so vi doesn't get too confused */
                  long_align ? "long" : "short", num_full_table_rows );

            outn( "    {" );

            /* Generate 0 entries for state #0. */
            for ( i = 0; i < num_full_table_rows; ++i )
                  mk2data( 0 );

            dataflush();
            outn( "    },\n" );
            }

      /* Create the first states. */

      num_start_states = lastsc * 2;

      for ( i = 1; i <= num_start_states; ++i )
            {
            numstates = 1;

            /* For each start condition, make one state for the case when
             * we're at the beginning of the line (the '^' operator) and
             * one for the case when we're not.
             */
            if ( i % 2 == 1 )
                  nset[numstates] = scset[(i / 2) + 1];
            else
                  nset[numstates] =
                        mkbranch( scbol[i / 2], scset[i / 2] );

            nset = epsclosure( nset, &numstates, accset, &nacc, &hashval );

            if ( snstods( nset, numstates, accset, nacc, hashval, &ds ) )
                  {
                  numas += nacc;
                  totnst += numstates;
                  ++todo_next;

                  if ( variable_trailing_context_rules && nacc > 0 )
                        check_trailing_context( nset, numstates,
                                          accset, nacc );
                  }
            }

      if ( ! fullspd )
            {
            if ( ! snstods( nset, 0, accset, 0, 0, &end_of_buffer_state ) )
                  flexfatal(
                  _( "could not create unique end-of-buffer state" ) );

            ++numas;
            ++num_start_states;
            ++todo_next;
            }

      while ( todo_head < todo_next )
            {
            targptr = 0;
            totaltrans = 0;

            for ( i = 1; i <= numecs; ++i )
                  state[i] = 0;

            ds = ++todo_head;

            dset = dss[ds];
            dsize = dfasiz[ds];

            if ( trace )
                  fprintf( stderr, _( "state # %d:\n" ), ds );

            sympartition( dset, dsize, symlist, duplist );

            for ( sym = 1; sym <= numecs; ++sym )
                  {
                  if ( symlist[sym] )
                        {
                        symlist[sym] = 0;

                        if ( duplist[sym] == NIL )
                              {
                              /* Symbol has unique out-transitions. */
                              numstates = symfollowset( dset, dsize,
                                                sym, nset );
                              nset = epsclosure( nset, &numstates,
                                    accset, &nacc, &hashval );

                              if ( snstods( nset, numstates, accset,
                                    nacc, hashval, &newds ) )
                                    {
                                    totnst = totnst + numstates;
                                    ++todo_next;
                                    numas += nacc;

                                    if (
                              variable_trailing_context_rules &&
                                          nacc > 0 )
                                          check_trailing_context(
                                                nset, numstates,
                                                accset, nacc );
                                    }

                              state[sym] = newds;

                              if ( trace )
                                    fprintf( stderr, "\t%d\t%d\n",
                                          sym, newds );

                              targfreq[++targptr] = 1;
                              targstate[targptr] = newds;
                              ++numuniq;
                              }

                        else
                              {
                              /* sym's equivalence class has the same
                               * transitions as duplist(sym)'s
                               * equivalence class.
                               */
                              targ = state[duplist[sym]];
                              state[sym] = targ;

                              if ( trace )
                                    fprintf( stderr, "\t%d\t%d\n",
                                          sym, targ );

                              /* Update frequency count for
                               * destination state.
                               */

                              i = 0;
                              while ( targstate[++i] != targ )
                                    ;

                              ++targfreq[i];
                              ++numdup;
                              }

                        ++totaltrans;
                        duplist[sym] = NIL;
                        }
                  }

            if ( caseins && ! useecs )
                  {
                  register int j;

                  for ( i = 'A', j = 'a'; i <= 'Z'; ++i, ++j )
                        {
                        if ( state[i] == 0 && state[j] != 0 )
                              /* We're adding a transition. */
                              ++totaltrans;

                        else if ( state[i] != 0 && state[j] == 0 )
                              /* We're taking away a transition. */
                              --totaltrans;

                        state[i] = state[j];
                        }
                  }

            numsnpairs += totaltrans;

            if ( ds > num_start_states )
                  check_for_backing_up( ds, state );

            if ( nultrans )
                  {
                  nultrans[ds] = state[NUL_ec];
                  state[NUL_ec] = 0;      /* remove transition */
                  }

            if ( fulltbl )
                  {
                  outn( "    {" );

                  /* Supply array's 0-element. */
                  if ( ds == end_of_buffer_state )
                        mk2data( -end_of_buffer_state );
                  else
                        mk2data( end_of_buffer_state );

                  for ( i = 1; i < num_full_table_rows; ++i )
                        /* Jams are marked by negative of state
                         * number.
                         */
                        mk2data( state[i] ? state[i] : -ds );

                  dataflush();
                  outn( "    },\n" );
                  }

            else if ( fullspd )
                  place_state( state, ds, totaltrans );

            else if ( ds == end_of_buffer_state )
                  /* Special case this state to make sure it does what
                   * it's supposed to, i.e., jam on end-of-buffer.
                   */
                  stack1( ds, 0, 0, JAMSTATE );

            else /* normal, compressed state */
                  {
                  /* Determine which destination state is the most
                   * common, and how many transitions to it there are.
                   */

                  comfreq = 0;
                  comstate = 0;

                  for ( i = 1; i <= targptr; ++i )
                        if ( targfreq[i] > comfreq )
                              {
                              comfreq = targfreq[i];
                              comstate = targstate[i];
                              }

                  bldtbl( state, ds, totaltrans, comstate, comfreq );
                  }
            }

      if ( fulltbl )
            dataend();

      else if ( ! fullspd )
            {
            cmptmps();  /* create compressed template entries */

            /* Create tables for all the states with only one
             * out-transition.
             */
            while ( onesp > 0 )
                  {
                  mk1tbl( onestate[onesp], onesym[onesp], onenext[onesp],
                  onedef[onesp] );
                  --onesp;
                  }

            mkdeftbl();
            }

      flex_free( (void *) accset );
      flex_free( (void *) nset );
      }


/* snstods - converts a set of ndfa states into a dfa state
 *
 * synopsis
 *    is_new_state = snstods( int sns[numstates], int numstates,
 *                      int accset[num_rules+1], int nacc,
 *                      int hashval, int *newds_addr );
 *
 * On return, the dfa state number is in newds.
 */

int snstods( sns, numstates, accset, nacc, hashval, newds_addr )
int sns[], numstates, accset[], nacc, hashval, *newds_addr;
      {
      int didsort = 0;
      register int i, j;
      int newds, *oldsns;

      for ( i = 1; i <= lastdfa; ++i )
            if ( hashval == dhash[i] )
                  {
                  if ( numstates == dfasiz[i] )
                        {
                        oldsns = dss[i];

                        if ( ! didsort )
                              {
                              /* We sort the states in sns so we
                               * can compare it to oldsns quickly.
                               * We use bubble because there probably
                               * aren't very many states.
                               */
                              bubble( sns, numstates );
                              didsort = 1;
                              }

                        for ( j = 1; j <= numstates; ++j )
                              if ( sns[j] != oldsns[j] )
                                    break;

                        if ( j > numstates )
                              {
                              ++dfaeql;
                              *newds_addr = i;
                              return 0;
                              }

                        ++hshcol;
                        }

                  else
                        ++hshsave;
                  }

      /* Make a new dfa. */

      if ( ++lastdfa >= current_max_dfas )
            increase_max_dfas();

      newds = lastdfa;

      dss[newds] = allocate_integer_array( numstates + 1 );

      /* If we haven't already sorted the states in sns, we do so now,
       * so that future comparisons with it can be made quickly.
       */

      if ( ! didsort )
            bubble( sns, numstates );

      for ( i = 1; i <= numstates; ++i )
            dss[newds][i] = sns[i];

      dfasiz[newds] = numstates;
      dhash[newds] = hashval;

      if ( nacc == 0 )
            {
            if ( reject )
                  dfaacc[newds].dfaacc_set = (int *) 0;
            else
                  dfaacc[newds].dfaacc_state = 0;

            accsiz[newds] = 0;
            }

      else if ( reject )
            {
            /* We sort the accepting set in increasing order so the
             * disambiguating rule that the first rule listed is considered
             * match in the event of ties will work.  We use a bubble
             * sort since the list is probably quite small.
             */

            bubble( accset, nacc );

            dfaacc[newds].dfaacc_set = allocate_integer_array( nacc + 1 );

            /* Save the accepting set for later */
            for ( i = 1; i <= nacc; ++i )
                  {
                  dfaacc[newds].dfaacc_set[i] = accset[i];

                  if ( accset[i] <= num_rules )
                        /* Who knows, perhaps a REJECT can yield
                         * this rule.
                         */
                        rule_useful[accset[i]] = true;
                  }

            accsiz[newds] = nacc;
            }

      else
            {
            /* Find lowest numbered rule so the disambiguating rule
             * will work.
             */
            j = num_rules + 1;

            for ( i = 1; i <= nacc; ++i )
                  if ( accset[i] < j )
                        j = accset[i];

            dfaacc[newds].dfaacc_state = j;

            if ( j <= num_rules )
                  rule_useful[j] = true;
            }

      *newds_addr = newds;

      return 1;
      }


/* symfollowset - follow the symbol transitions one step
 *
 * synopsis
 *    numstates = symfollowset( int ds[current_max_dfa_size], int dsize,
 *                      int transsym, int nset[current_max_dfa_size] );
 */

int symfollowset( ds, dsize, transsym, nset )
int ds[], dsize, transsym, nset[];
      {
      int ns, tsp, sym, i, j, lenccl, ch, numstates, ccllist;

      numstates = 0;

      for ( i = 1; i <= dsize; ++i )
            { /* for each nfa state ns in the state set of ds */
            ns = ds[i];
            sym = transchar[ns];
            tsp = trans1[ns];

            if ( sym < 0 )
                  { /* it's a character class */
                  sym = -sym;
                  ccllist = cclmap[sym];
                  lenccl = ccllen[sym];

                  if ( cclng[sym] )
                        {
                        for ( j = 0; j < lenccl; ++j )
                              {
                              /* Loop through negated character
                               * class.
                               */
                              ch = ccltbl[ccllist + j];

                              if ( ch == 0 )
                                    ch = NUL_ec;

                              if ( ch > transsym )
                                    /* Transsym isn't in negated
                                     * ccl.
                                     */
                                    break;

                              else if ( ch == transsym )
                                    /* next 2 */ goto bottom;
                              }

                        /* Didn't find transsym in ccl. */
                        nset[++numstates] = tsp;
                        }

                  else
                        for ( j = 0; j < lenccl; ++j )
                              {
                              ch = ccltbl[ccllist + j];

                              if ( ch == 0 )
                                    ch = NUL_ec;

                              if ( ch > transsym )
                                    break;
                              else if ( ch == transsym )
                                    {
                                    nset[++numstates] = tsp;
                                    break;
                                    }
                              }
                  }

            else if ( sym >= 'A' && sym <= 'Z' && caseins )
                  flexfatal(
                  _( "consistency check failed in symfollowset" ) );

            else if ( sym == SYM_EPSILON )
                  { /* do nothing */
                  }

            else if ( ABS( ecgroup[sym] ) == transsym )
                  nset[++numstates] = tsp;

            bottom: ;
            }

      return numstates;
      }


/* sympartition - partition characters with same out-transitions
 *
 * synopsis
 *    sympartition( int ds[current_max_dfa_size], int numstates,
 *                int symlist[numecs], int duplist[numecs] );
 */

void sympartition( ds, numstates, symlist, duplist )
int ds[], numstates;
int symlist[], duplist[];
      {
      int tch, i, j, k, ns, dupfwd[CSIZE + 1], lenccl, cclp, ich;

      /* Partitioning is done by creating equivalence classes for those
       * characters which have out-transitions from the given state.  Thus
       * we are really creating equivalence classes of equivalence classes.
       */

      for ( i = 1; i <= numecs; ++i )
            { /* initialize equivalence class list */
            duplist[i] = i - 1;
            dupfwd[i] = i + 1;
            }

      duplist[1] = NIL;
      dupfwd[numecs] = NIL;

      for ( i = 1; i <= numstates; ++i )
            {
            ns = ds[i];
            tch = transchar[ns];

            if ( tch != SYM_EPSILON )
                  {
                  if ( tch < -lastccl || tch >= csize )
                        {
                        flexfatal(
            _( "bad transition character detected in sympartition()" ) );
                        }

                  if ( tch >= 0 )
                        { /* character transition */
                        int ec = ecgroup[tch];

                        mkechar( ec, dupfwd, duplist );
                        symlist[ec] = 1;
                        }

                  else
                        { /* character class */
                        tch = -tch;

                        lenccl = ccllen[tch];
                        cclp = cclmap[tch];
                        mkeccl( ccltbl + cclp, lenccl, dupfwd,
                              duplist, numecs, NUL_ec );

                        if ( cclng[tch] )
                              {
                              j = 0;

                              for ( k = 0; k < lenccl; ++k )
                                    {
                                    ich = ccltbl[cclp + k];

                                    if ( ich == 0 )
                                          ich = NUL_ec;

                                    for ( ++j; j < ich; ++j )
                                          symlist[j] = 1;
                                    }

                              for ( ++j; j <= numecs; ++j )
                                    symlist[j] = 1;
                              }

                        else
                              for ( k = 0; k < lenccl; ++k )
                                    {
                                    ich = ccltbl[cclp + k];

                                    if ( ich == 0 )
                                          ich = NUL_ec;

                                    symlist[ich] = 1;
                                    }
                        }
                  }
            }
      }

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