/*      $OpenBSD: dfa.c,v 1.9 2024/11/09 18:03:44 op Exp $      */

/* 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 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"
#include "tables.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 (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 (int *nfa_states, int num_states,
    int *accset, int nacc)
{
        int i, j;

        for (i = 1; i <= num_states; ++i) {
                int     ns = nfa_states[i];
                int type = state_type[ns];
                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 *file, int ds)
{
        int i, j;
        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) {
                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;
                }
        }

        qsort (&rule_set [1], num_associated_rules, sizeof (rule_set [1]), intcmp);

        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 *file, int state[])
{
        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 (int *t, int *ns_addr, int accset[], int *nacc_addr,
    int *hv_addr)
{
        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) \
do{ trans1[state] = trans1[state] - MARKER_DIFFERENCE;} while(0)

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

#define UNMARK_STATE(state) \
do{ trans1[state] = trans1[state] + MARKER_DIFFERENCE;} while(0)

#define CHECK_ACCEPT(state) \
do{ \
nfaccnum = accptnum[state]; \
if ( nfaccnum != NIL ) \
accset[++nacc] = nfaccnum; \
}while(0)

#define DO_REALLOCATION() \
do { \
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 ); \
}while(0) \

#define PUT_ON_STACK(state) \
do { \
if ( ++stkend >= current_max_dfa_size ) \
DO_REALLOCATION(); \
stk[stkend] = state; \
MARK_STATE(state); \
}while(0)

#define ADD_STATE(state) \
do { \
if ( ++numstates >= current_max_dfa_size ) \
DO_REALLOCATION(); \
t[numstates] = state; \
hashval += state; \
}while(0)

#define STACK_STATE(state) \
do { \
PUT_ON_STACK(state); \
CHECK_ACCEPT(state); \
if ( nfaccnum != NIL || transchar[state] != SYM_EPSILON ) \
ADD_STATE(state); \
}while(0)


        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 (void)
{
        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 (void)
{
        int    *accset, ds, nacc, newds;
        int     sym, hashval, numstates, dsize;
        int     num_full_table_rows=0;  /* 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;

        struct yytbl_data *yynxt_tbl = 0;
        flex_int32_t *yynxt_data = 0, yynxt_curr = 0;

        /* 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 needs to be large enough to hold all of the rules present
         * in the input, *plus* their YY_TRAILING_HEAD_MASK variants.
         */
        accset = allocate_integer_array ((num_rules + 1) * 2);
        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;

                /* Begin generating yy_nxt[][]
                 * This spans the entire LONG function.
                 * This table is tricky because we don't know how big it will be.
                 * So we'll have to realloc() on the way...
                 * we'll wait until we can calculate yynxt_tbl->td_hilen.
                 */
                yynxt_tbl =
                        (struct yytbl_data *) calloc (1,
                                                      sizeof (struct
                                                              yytbl_data));
                yytbl_data_init (yynxt_tbl, YYTD_ID_NXT);
                yynxt_tbl->td_hilen = 1;
                yynxt_tbl->td_lolen = num_full_table_rows;
                yynxt_tbl->td_data = yynxt_data =
                        (flex_int32_t *) calloc (yynxt_tbl->td_lolen *
                                            yynxt_tbl->td_hilen,
                                            sizeof (flex_int32_t));
                yynxt_curr = 0;

                buf_prints (&yydmap_buf,
                            "\t{YYTD_ID_NXT, (void**)&yy_nxt, sizeof(%s)},\n",
                            long_align ? "flex_int32_t" : "flex_int16_t");

                /* Unless -Ca, declare it "short" because it's a real
                 * long-shot that that won't be large enough.
                 */
                if (gentables)
                        out_str_dec
                                ("static yyconst %s yy_nxt[][%d] =\n    {\n",
                                 long_align ? "flex_int32_t" : "flex_int16_t",
                                 num_full_table_rows);
                else {
                        out_dec ("#undef YY_NXT_LOLEN\n#define YY_NXT_LOLEN (%d)\n", num_full_table_rows);
                        out_str ("static yyconst %s *yy_nxt =0;\n",
                                 long_align ? "flex_int32_t" : "flex_int16_t");
                }


                if (gentables)
                        outn ("    {");

                /* Generate 0 entries for state #0. */
                for (i = 0; i < num_full_table_rows; ++i) {
                        mk2data (0);
                        yynxt_data[yynxt_curr++] = 0;
                }

                dataflush ();
                if (gentables)
                        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;
                        }
                }


                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) {

                        /* Each time we hit here, it's another td_hilen, so we realloc. */
                        yynxt_tbl->td_hilen++;
                        yynxt_tbl->td_data = yynxt_data =
                                (flex_int32_t *) realloc (yynxt_data,
                                                     yynxt_tbl->td_hilen *
                                                     yynxt_tbl->td_lolen *
                                                     sizeof (flex_int32_t));


                        if (gentables)
                                outn ("    {");

                        /* Supply array's 0-element. */
                        if (ds == end_of_buffer_state) {
                                mk2data (-end_of_buffer_state);
                                yynxt_data[yynxt_curr++] =
                                        -end_of_buffer_state;
                        }
                        else {
                                mk2data (end_of_buffer_state);
                                yynxt_data[yynxt_curr++] =
                                        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);
                                yynxt_data[yynxt_curr++] =
                                        state[i] ? state[i] : -ds;
                        }

                        dataflush ();
                        if (gentables)
                                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 ();
                if (tablesext) {
                        yytbl_data_compress (yynxt_tbl);
                        if (yytbl_data_fwrite (&tableswr, yynxt_tbl) < 0)
                                flexerror (_
                                           ("Could not write yynxt_tbl[][]"));
                }
                if (yynxt_tbl) {
                        yytbl_data_destroy (yynxt_tbl);
                        yynxt_tbl = 0;
                }
        }

        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 ();
        }

        free ((void *) accset);
        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 (int sns[], int numstates, int accset[], int nacc, int hashval,
    int *newds_addr)
{
        int     didsort = 0;
        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.
                                         */
                                        qsort (&sns [1], numstates, sizeof (sns [1]), intcmp);
                                        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)
                qsort (&sns [1], numstates, sizeof (sns [1]), intcmp);

        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.
                 */

                qsort (&accset [1], nacc, sizeof (accset [1]), intcmp);

                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 (int ds[], int dsize, int transsym, int 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 == 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 (int ds[], int numstates, int symlist[], int 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;
                                        }
                        }
                }
        }
}