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regexec.c

/*
 * re_*exec and friends - match REs
 *
 * Copyright (c) 1998, 1999 Henry Spencer.      All rights reserved.
 *
 * Development of this software was funded, in part, by Cray Research Inc.,
 * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
 * Corporation, none of whom are responsible for the results.  The author
 * thanks all of them.
 *
 * Redistribution and use in source and binary forms -- with or without
 * modification -- are permitted for any purpose, provided that
 * redistributions in source form retain this entire copyright notice and
 * indicate the origin and nature of any modifications.
 *
 * I'd appreciate being given credit for this package in the documentation
 * of software which uses it, but that is not a requirement.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * HENRY SPENCER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $PostgreSQL: pgsql/src/backend/regex/regexec.c,v 1.27.8.1 2010/02/01 02:45:35 tgl Exp $
 *
 */

#include "regex/regguts.h"



/* lazy-DFA representation */
struct arcp
{                                               /* "pointer" to an outarc */
      struct sset *ss;
      color       co;
};

struct sset
{                                               /* state set */
      unsigned   *states;                 /* pointer to bitvector */
      unsigned    hash;             /* hash of bitvector */
#define  HASH(bv, nw)    (((nw) == 1) ? *(bv) : hash(bv, nw))
#define  HIT(h,bv,ss,nw) ((ss)->hash == (h) && ((nw) == 1 || \
            memcmp(VS(bv), VS((ss)->states), (nw)*sizeof(unsigned)) == 0))
      int               flags;
#define  STARTER   01               /* the initial state set */
#define  POSTSTATE       02               /* includes the goal state */
#define  LOCKED          04               /* locked in cache */
#define  NOPROGRESS  010            /* zero-progress state set */
      struct arcp ins;              /* chain of inarcs pointing here */
      chr            *lastseen;           /* last entered on arrival here */
      struct sset **outs;                 /* outarc vector indexed by color */
      struct arcp *inchain;         /* chain-pointer vector for outarcs */
};

struct dfa
{
      int               nssets;                 /* size of cache */
      int               nssused;          /* how many entries occupied yet */
      int               nstates;          /* number of states */
      int               ncolors;          /* length of outarc and inchain vectors */
      int               wordsper;         /* length of state-set bitvectors */
      struct sset *ssets;                 /* state-set cache */
      unsigned   *statesarea;       /* bitvector storage */
      unsigned   *work;             /* pointer to work area within statesarea */
      struct sset **outsarea;       /* outarc-vector storage */
      struct arcp *incarea;         /* inchain storage */
      struct cnfa *cnfa;
      struct colormap *cm;
      chr            *lastpost;           /* location of last cache-flushed success */
      chr            *lastnopr;           /* location of last cache-flushed NOPROGRESS */
      struct sset *search;          /* replacement-search-pointer memory */
      int               cptsmalloced;     /* were the areas individually malloced? */
      char     *mallocarea;         /* self, or master malloced area, or NULL */
};

#define WORK      1                       /* number of work bitvectors needed */

/* setup for non-malloc allocation for small cases */
#define FEWSTATES 20                /* must be less than UBITS */
#define FEWCOLORS 15
struct smalldfa
{
      struct dfa  dfa;
      struct sset ssets[FEWSTATES * 2];
      unsigned    statesarea[FEWSTATES * 2 + WORK];
      struct sset *outsarea[FEWSTATES * 2 * FEWCOLORS];
      struct arcp incarea[FEWSTATES * 2 * FEWCOLORS];
};

#define DOMALLOC  ((struct smalldfa *)NULL)     /* force malloc */



/* internal variables, bundled for easy passing around */
struct vars
{
      regex_t    *re;
      struct guts *g;
      int               eflags;                 /* copies of arguments */
      size_t            nmatch;
      regmatch_t *pmatch;
      rm_detail_t *details;
      chr            *start;              /* start of string */
      chr            *search_start; /* search start of string */
      chr            *stop;               /* just past end of string */
      int               err;              /* error code if any (0 none) */
      regoff_t   *mem;              /* memory vector for backtracking */
      struct smalldfa dfa1;
      struct smalldfa dfa2;
};

#define VISERR(vv)      ((vv)->err != 0)  /* have we seen an error yet? */
#define ISERR() VISERR(v)
#define VERR(vv,e)      (((vv)->err) ? (vv)->err : ((vv)->err = (e)))
#define ERR(e)    VERR(v, e)        /* record an error */
#define NOERR() {if (ISERR()) return v->err;}   /* if error seen, return it */
#define OFF(p)    ((p) - v->start)
#define LOFF(p) ((long)OFF(p))



/*
 * forward declarations
 */
/* === regexec.c === */
static int  find(struct vars *, struct cnfa *, struct colormap *);
static int  cfind(struct vars *, struct cnfa *, struct colormap *);
static int  cfindloop(struct vars *, struct cnfa *, struct colormap *, struct dfa *, struct dfa *, chr **);
static void zapsubs(regmatch_t *, size_t);
static void zapmem(struct vars *, struct subre *);
static void subset(struct vars *, struct subre *, chr *, chr *);
static int  dissect(struct vars *, struct subre *, chr *, chr *);
static int  condissect(struct vars *, struct subre *, chr *, chr *);
static int  altdissect(struct vars *, struct subre *, chr *, chr *);
static int  cdissect(struct vars *, struct subre *, chr *, chr *);
static int  ccaptdissect(struct vars *, struct subre *, chr *, chr *);
static int  ccondissect(struct vars *, struct subre *, chr *, chr *);
static int  crevdissect(struct vars *, struct subre *, chr *, chr *);
static int  cbrdissect(struct vars *, struct subre *, chr *, chr *);
static int  caltdissect(struct vars *, struct subre *, chr *, chr *);

/* === rege_dfa.c === */
static chr *longest(struct vars *, struct dfa *, chr *, chr *, int *);
static chr *shortest(struct vars *, struct dfa *, chr *, chr *, chr *, chr **, int *);
static chr *lastcold(struct vars *, struct dfa *);
static struct dfa *newdfa(struct vars *, struct cnfa *, struct colormap *, struct smalldfa *);
static void freedfa(struct dfa *);
static unsigned hash(unsigned *, int);
static struct sset *initialize(struct vars *, struct dfa *, chr *);
static struct sset *miss(struct vars *, struct dfa *, struct sset *, pcolor, chr *, chr *);
static int  lacon(struct vars *, struct cnfa *, chr *, pcolor);
static struct sset *getvacant(struct vars *, struct dfa *, chr *, chr *);
static struct sset *pickss(struct vars *, struct dfa *, chr *, chr *);


/*
 * pg_regexec - match regular expression
 */
int
pg_regexec(regex_t *re,
               const chr *string,
               size_t len,
               size_t search_start,
               rm_detail_t *details,
               size_t nmatch,
               regmatch_t pmatch[],
               int flags)
{
      struct vars var;
      register struct vars *v = &var;
      int               st;
      size_t            n;
      int               backref;

#define  LOCALMAT  20
      regmatch_t  mat[LOCALMAT];

#define  LOCALMEM  40
      regoff_t    mem[LOCALMEM];

      /* sanity checks */
      if (re == NULL || string == NULL || re->re_magic != REMAGIC)
            return REG_INVARG;
      if (re->re_csize != sizeof(chr))
            return REG_MIXED;

      /* setup */
      v->re = re;
      v->g = (struct guts *) re->re_guts;
      if ((v->g->cflags & REG_EXPECT) && details == NULL)
            return REG_INVARG;
      if (v->g->info & REG_UIMPOSSIBLE)
            return REG_NOMATCH;
      backref = (v->g->info & REG_UBACKREF) ? 1 : 0;
      v->eflags = flags;
      if (v->g->cflags & REG_NOSUB)
            nmatch = 0;                   /* override client */
      v->nmatch = nmatch;
      if (backref)
      {
            /* need work area */
            if (v->g->nsub + 1 <= LOCALMAT)
                  v->pmatch = mat;
            else
                  v->pmatch = (regmatch_t *) MALLOC((v->g->nsub + 1) *
                                                                    sizeof(regmatch_t));
            if (v->pmatch == NULL)
                  return REG_ESPACE;
            v->nmatch = v->g->nsub + 1;
      }
      else
            v->pmatch = pmatch;
      v->details = details;
      v->start = (chr *) string;
      v->search_start = (chr *) string + search_start;
      v->stop = (chr *) string + len;
      v->err = 0;
      if (backref)
      {
            /* need retry memory */
            assert(v->g->ntree >= 0);
            n = (size_t) v->g->ntree;
            if (n <= LOCALMEM)
                  v->mem = mem;
            else
                  v->mem = (regoff_t *) MALLOC(n * sizeof(regoff_t));
            if (v->mem == NULL)
            {
                  if (v->pmatch != pmatch && v->pmatch != mat)
                        FREE(v->pmatch);
                  return REG_ESPACE;
            }
      }
      else
            v->mem = NULL;

      /* do it */
      assert(v->g->tree != NULL);
      if (backref)
            st = cfind(v, &v->g->tree->cnfa, &v->g->cmap);
      else
            st = find(v, &v->g->tree->cnfa, &v->g->cmap);

      /* copy (portion of) match vector over if necessary */
      if (st == REG_OKAY && v->pmatch != pmatch && nmatch > 0)
      {
            zapsubs(pmatch, nmatch);
            n = (nmatch < v->nmatch) ? nmatch : v->nmatch;
            memcpy(VS(pmatch), VS(v->pmatch), n * sizeof(regmatch_t));
      }

      /* clean up */
      if (v->pmatch != pmatch && v->pmatch != mat)
            FREE(v->pmatch);
      if (v->mem != NULL && v->mem != mem)
            FREE(v->mem);
      return st;
}

/*
 * find - find a match for the main NFA (no-complications case)
 */
static int
find(struct vars * v,
       struct cnfa * cnfa,
       struct colormap * cm)
{
      struct dfa *s;
      struct dfa *d;
      chr            *begin;
      chr            *end = NULL;
      chr            *cold;
      chr            *open;               /* open and close of range of possible starts */
      chr            *close;
      int               hitend;
      int               shorter = (v->g->tree->flags & SHORTER) ? 1 : 0;

      /* first, a shot with the search RE */
      s = newdfa(v, &v->g->search, cm, &v->dfa1);
      assert(!(ISERR() && s != NULL));
      NOERR();
      MDEBUG(("\nsearch at %ld\n", LOFF(v->start)));
      cold = NULL;
      close = shortest(v, s, v->search_start, v->search_start, v->stop,
                               &cold, (int *) NULL);
      freedfa(s);
      NOERR();
      if (v->g->cflags & REG_EXPECT)
      {
            assert(v->details != NULL);
            if (cold != NULL)
                  v->details->rm_extend.rm_so = OFF(cold);
            else
                  v->details->rm_extend.rm_so = OFF(v->stop);
            v->details->rm_extend.rm_eo = OFF(v->stop);           /* unknown */
      }
      if (close == NULL)                  /* not found */
            return REG_NOMATCH;
      if (v->nmatch == 0)                 /* found, don't need exact location */
            return REG_OKAY;

      /* find starting point and match */
      assert(cold != NULL);
      open = cold;
      cold = NULL;
      MDEBUG(("between %ld and %ld\n", LOFF(open), LOFF(close)));
      d = newdfa(v, cnfa, cm, &v->dfa1);
      assert(!(ISERR() && d != NULL));
      NOERR();
      for (begin = open; begin <= close; begin++)
      {
            MDEBUG(("\nfind trying at %ld\n", LOFF(begin)));
            if (shorter)
                  end = shortest(v, d, begin, begin, v->stop,
                                       (chr **) NULL, &hitend);
            else
                  end = longest(v, d, begin, v->stop, &hitend);
            NOERR();
            if (hitend && cold == NULL)
                  cold = begin;
            if (end != NULL)
                  break;                        /* NOTE BREAK OUT */
      }
      assert(end != NULL);          /* search RE succeeded so loop should */
      freedfa(d);

      /* and pin down details */
      assert(v->nmatch > 0);
      v->pmatch[0].rm_so = OFF(begin);
      v->pmatch[0].rm_eo = OFF(end);
      if (v->g->cflags & REG_EXPECT)
      {
            if (cold != NULL)
                  v->details->rm_extend.rm_so = OFF(cold);
            else
                  v->details->rm_extend.rm_so = OFF(v->stop);
            v->details->rm_extend.rm_eo = OFF(v->stop);           /* unknown */
      }
      if (v->nmatch == 1)                 /* no need for submatches */
            return REG_OKAY;

      /* submatches */
      zapsubs(v->pmatch, v->nmatch);
      return dissect(v, v->g->tree, begin, end);
}

/*
 * cfind - find a match for the main NFA (with complications)
 */
static int
cfind(struct vars * v,
        struct cnfa * cnfa,
        struct colormap * cm)
{
      struct dfa *s;
      struct dfa *d;
      chr            *cold;
      int               ret;

      s = newdfa(v, &v->g->search, cm, &v->dfa1);
      NOERR();
      d = newdfa(v, cnfa, cm, &v->dfa2);
      if (ISERR())
      {
            assert(d == NULL);
            freedfa(s);
            return v->err;
      }

      ret = cfindloop(v, cnfa, cm, d, s, &cold);

      freedfa(d);
      freedfa(s);
      NOERR();
      if (v->g->cflags & REG_EXPECT)
      {
            assert(v->details != NULL);
            if (cold != NULL)
                  v->details->rm_extend.rm_so = OFF(cold);
            else
                  v->details->rm_extend.rm_so = OFF(v->stop);
            v->details->rm_extend.rm_eo = OFF(v->stop);           /* unknown */
      }
      return ret;
}

/*
 * cfindloop - the heart of cfind
 */
static int
cfindloop(struct vars * v,
              struct cnfa * cnfa,
              struct colormap * cm,
              struct dfa * d,
              struct dfa * s,
              chr **coldp)                /* where to put coldstart pointer */
{
      chr            *begin;
      chr            *end;
      chr            *cold;
      chr            *open;               /* open and close of range of possible starts */
      chr            *close;
      chr            *estart;
      chr            *estop;
      int               er;
      int               shorter = v->g->tree->flags & SHORTER;
      int               hitend;

      assert(d != NULL && s != NULL);
      cold = NULL;
      close = v->search_start;
      do
      {
            MDEBUG(("\ncsearch at %ld\n", LOFF(close)));
            close = shortest(v, s, close, close, v->stop, &cold, (int *) NULL);
            if (close == NULL)
                  break;                        /* NOTE BREAK */
            assert(cold != NULL);
            open = cold;
            cold = NULL;
            MDEBUG(("cbetween %ld and %ld\n", LOFF(open), LOFF(close)));
            for (begin = open; begin <= close; begin++)
            {
                  MDEBUG(("\ncfind trying at %ld\n", LOFF(begin)));
                  estart = begin;
                  estop = v->stop;
                  for (;;)
                  {
                        if (shorter)
                              end = shortest(v, d, begin, estart,
                                                   estop, (chr **) NULL, &hitend);
                        else
                              end = longest(v, d, begin, estop,
                                                  &hitend);
                        if (hitend && cold == NULL)
                              cold = begin;
                        if (end == NULL)
                              break;            /* NOTE BREAK OUT */
                        MDEBUG(("tentative end %ld\n", LOFF(end)));
                        zapsubs(v->pmatch, v->nmatch);
                        zapmem(v, v->g->tree);
                        er = cdissect(v, v->g->tree, begin, end);
                        if (er == REG_OKAY)
                        {
                              if (v->nmatch > 0)
                              {
                                    v->pmatch[0].rm_so = OFF(begin);
                                    v->pmatch[0].rm_eo = OFF(end);
                              }
                              *coldp = cold;
                              return REG_OKAY;
                        }
                        if (er != REG_NOMATCH)
                        {
                              ERR(er);
                              *coldp = cold;
                              return er;
                        }
                        if ((shorter) ? end == estop : end == begin)
                        {
                              /* no point in trying again */
                              *coldp = cold;
                              return REG_NOMATCH;
                        }
                        /* go around and try again */
                        if (shorter)
                              estart = end + 1;
                        else
                              estop = end - 1;
                  }
            }
      } while (close < v->stop);

      *coldp = cold;
      return REG_NOMATCH;
}

/*
 * zapsubs - initialize the subexpression matches to "no match"
 */
static void
zapsubs(regmatch_t *p,
            size_t n)
{
      size_t            i;

      for (i = n - 1; i > 0; i--)
      {
            p[i].rm_so = -1;
            p[i].rm_eo = -1;
      }
}

/*
 * zapmem - initialize the retry memory of a subtree to zeros
 */
static void
zapmem(struct vars * v,
         struct subre * t)
{
      if (t == NULL)
            return;

      assert(v->mem != NULL);
      v->mem[t->retry] = 0;
      if (t->op == '(')
      {
            assert(t->subno > 0);
            v->pmatch[t->subno].rm_so = -1;
            v->pmatch[t->subno].rm_eo = -1;
      }

      if (t->left != NULL)
            zapmem(v, t->left);
      if (t->right != NULL)
            zapmem(v, t->right);
}

/*
 * subset - set any subexpression relevant to a successful subre
 */
static void
subset(struct vars * v,
         struct subre * sub,
         chr *begin,
         chr *end)
{
      int               n = sub->subno;

      assert(n > 0);
      if ((size_t) n >= v->nmatch)
            return;

      MDEBUG(("setting %d\n", n));
      v->pmatch[n].rm_so = OFF(begin);
      v->pmatch[n].rm_eo = OFF(end);
}

/*
 * dissect - determine subexpression matches (uncomplicated case)
 */
static int                                /* regexec return code */
dissect(struct vars * v,
            struct subre * t,
            chr *begin,                   /* beginning of relevant substring */
            chr *end)                     /* end of same */
{
      assert(t != NULL);
      MDEBUG(("dissect %ld-%ld\n", LOFF(begin), LOFF(end)));

      switch (t->op)
      {
            case '=':                     /* terminal node */
                  assert(t->left == NULL && t->right == NULL);
                  return REG_OKAY;  /* no action, parent did the work */
            case '|':                     /* alternation */
                  assert(t->left != NULL);
                  return altdissect(v, t, begin, end);
            case 'b':                     /* back ref -- shouldn't be calling us! */
                  return REG_ASSERT;
            case '.':                     /* concatenation */
                  assert(t->left != NULL && t->right != NULL);
                  return condissect(v, t, begin, end);
            case '(':                     /* capturing */
                  assert(t->left != NULL && t->right == NULL);
                  assert(t->subno > 0);
                  subset(v, t, begin, end);
                  return dissect(v, t->left, begin, end);
            default:
                  return REG_ASSERT;
      }
}

/*
 * condissect - determine concatenation subexpression matches (uncomplicated)
 */
static int                                /* regexec return code */
condissect(struct vars * v,
               struct subre * t,
               chr *begin,                /* beginning of relevant substring */
               chr *end)                  /* end of same */
{
      struct dfa *d;
      struct dfa *d2;
      chr            *mid;
      int               i;
      int               shorter = (t->left->flags & SHORTER) ? 1 : 0;
      chr            *stop = (shorter) ? end : begin;

      assert(t->op == '.');
      assert(t->left != NULL && t->left->cnfa.nstates > 0);
      assert(t->right != NULL && t->right->cnfa.nstates > 0);

      d = newdfa(v, &t->left->cnfa, &v->g->cmap, &v->dfa1);
      NOERR();
      d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, &v->dfa2);
      if (ISERR())
      {
            assert(d2 == NULL);
            freedfa(d);
            return v->err;
      }

      /* pick a tentative midpoint */
      if (shorter)
            mid = shortest(v, d, begin, begin, end, (chr **) NULL,
                                 (int *) NULL);
      else
            mid = longest(v, d, begin, end, (int *) NULL);
      if (mid == NULL)
      {
            freedfa(d);
            freedfa(d2);
            return REG_ASSERT;
      }
      MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));

      /* iterate until satisfaction or failure */
      while (longest(v, d2, mid, end, (int *) NULL) != end)
      {
            /* that midpoint didn't work, find a new one */
            if (mid == stop)
            {
                  /* all possibilities exhausted! */
                  MDEBUG(("no midpoint!\n"));
                  freedfa(d);
                  freedfa(d2);
                  return REG_ASSERT;
            }
            if (shorter)
                  mid = shortest(v, d, begin, mid + 1, end, (chr **) NULL,
                                       (int *) NULL);
            else
                  mid = longest(v, d, begin, mid - 1, (int *) NULL);
            if (mid == NULL)
            {
                  /* failed to find a new one! */
                  MDEBUG(("failed midpoint!\n"));
                  freedfa(d);
                  freedfa(d2);
                  return REG_ASSERT;
            }
            MDEBUG(("new midpoint %ld\n", LOFF(mid)));
      }

      /* satisfaction */
      MDEBUG(("successful\n"));
      freedfa(d);
      freedfa(d2);
      i = dissect(v, t->left, begin, mid);
      if (i != REG_OKAY)
            return i;
      return dissect(v, t->right, mid, end);
}

/*
 * altdissect - determine alternative subexpression matches (uncomplicated)
 */
static int                                /* regexec return code */
altdissect(struct vars * v,
               struct subre * t,
               chr *begin,                /* beginning of relevant substring */
               chr *end)                  /* end of same */
{
      struct dfa *d;
      int               i;

      assert(t != NULL);
      assert(t->op == '|');

      for (i = 0; t != NULL; t = t->right, i++)
      {
            MDEBUG(("trying %dth\n", i));
            assert(t->left != NULL && t->left->cnfa.nstates > 0);
            d = newdfa(v, &t->left->cnfa, &v->g->cmap, &v->dfa1);
            if (ISERR())
                  return v->err;
            if (longest(v, d, begin, end, (int *) NULL) == end)
            {
                  MDEBUG(("success\n"));
                  freedfa(d);
                  return dissect(v, t->left, begin, end);
            }
            freedfa(d);
      }
      return REG_ASSERT;                  /* none of them matched?!? */
}

/*
 * cdissect - determine subexpression matches (with complications)
 * The retry memory stores the offset of the trial midpoint from begin,
 * plus 1 so that 0 uniquely means "clean slate".
 */
static int                                /* regexec return code */
cdissect(struct vars * v,
             struct subre * t,
             chr *begin,                  /* beginning of relevant substring */
             chr *end)                    /* end of same */
{
      assert(t != NULL);
      MDEBUG(("cdissect %ld-%ld %c\n", LOFF(begin), LOFF(end), t->op));

      switch (t->op)
      {
            case '=':                     /* terminal node */
                  assert(t->left == NULL && t->right == NULL);
                  return REG_OKAY;  /* no action, parent did the work */
            case '|':                     /* alternation */
                  assert(t->left != NULL);
                  return caltdissect(v, t, begin, end);
            case 'b':                     /* back ref -- shouldn't be calling us! */
                  assert(t->left == NULL && t->right == NULL);
                  return cbrdissect(v, t, begin, end);
            case '.':                     /* concatenation */
                  assert(t->left != NULL && t->right != NULL);
                  return ccondissect(v, t, begin, end);
            case '(':                     /* capturing */
                  assert(t->left != NULL && t->right == NULL);
                  return ccaptdissect(v, t, begin, end);
            default:
                  return REG_ASSERT;
      }
}

/*
 * ccaptdissect - capture subexpression matches (with complications)
 */
static int                                /* regexec return code */
ccaptdissect(struct vars * v,
                   struct subre * t,
                   chr *begin,            /* beginning of relevant substring */
                   chr *end)              /* end of same */
{
      int               er;

      assert(t->subno > 0);

      er = cdissect(v, t->left, begin, end);
      if (er == REG_OKAY)
            subset(v, t, begin, end);
      return er;
}

/*
 * ccondissect - concatenation subexpression matches (with complications)
 * The retry memory stores the offset of the trial midpoint from begin,
 * plus 1 so that 0 uniquely means "clean slate".
 */
static int                                /* regexec return code */
ccondissect(struct vars * v,
                  struct subre * t,
                  chr *begin,             /* beginning of relevant substring */
                  chr *end)               /* end of same */
{
      struct dfa *d;
      struct dfa *d2;
      chr            *mid;
      int               er;

      assert(t->op == '.');
      assert(t->left != NULL && t->left->cnfa.nstates > 0);
      assert(t->right != NULL && t->right->cnfa.nstates > 0);

      if (t->left->flags & SHORTER)       /* reverse scan */
            return crevdissect(v, t, begin, end);

      d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
      if (ISERR())
            return v->err;
      d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, DOMALLOC);
      if (ISERR())
      {
            freedfa(d);
            return v->err;
      }
      MDEBUG(("cconcat %d\n", t->retry));

      /* pick a tentative midpoint */
      if (v->mem[t->retry] == 0)
      {
            mid = longest(v, d, begin, end, (int *) NULL);
            if (mid == NULL)
            {
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
            v->mem[t->retry] = (mid - begin) + 1;
      }
      else
      {
            mid = begin + (v->mem[t->retry] - 1);
            MDEBUG(("working midpoint %ld\n", LOFF(mid)));
      }

      /* iterate until satisfaction or failure */
      for (;;)
      {
            /* try this midpoint on for size */
            if (longest(v, d2, mid, end, (int *) NULL) == end)
            {
                  er = cdissect(v, t->left, begin, mid);
                  if (er == REG_OKAY)
                  {
                        er = cdissect(v, t->right, mid, end);
                        if (er == REG_OKAY)
                        {
                              /* satisfaction */
                              MDEBUG(("successful\n"));
                              freedfa(d);
                              freedfa(d2);
                              return REG_OKAY;
                        }
                  }
                  if (er != REG_OKAY && er != REG_NOMATCH)
                  {
                        freedfa(d);
                        freedfa(d2);
                        return er;
                  }
            }

            /* that midpoint didn't work, find a new one */
            if (mid == begin)
            {
                  /* all possibilities exhausted */
                  MDEBUG(("%d no midpoint\n", t->retry));
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            mid = longest(v, d, begin, mid - 1, (int *) NULL);
            if (mid == NULL)
            {
                  /* failed to find a new one */
                  MDEBUG(("%d failed midpoint\n", t->retry));
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            MDEBUG(("%d: new midpoint %ld\n", t->retry, LOFF(mid)));
            v->mem[t->retry] = (mid - begin) + 1;
            zapmem(v, t->left);
            zapmem(v, t->right);
      }

      /* can't get here */
      return REG_ASSERT;
}

/*
 * crevdissect - determine backref shortest-first subexpression matches
 * The retry memory stores the offset of the trial midpoint from begin,
 * plus 1 so that 0 uniquely means "clean slate".
 */
static int                                /* regexec return code */
crevdissect(struct vars * v,
                  struct subre * t,
                  chr *begin,             /* beginning of relevant substring */
                  chr *end)               /* end of same */
{
      struct dfa *d;
      struct dfa *d2;
      chr            *mid;
      int               er;

      assert(t->op == '.');
      assert(t->left != NULL && t->left->cnfa.nstates > 0);
      assert(t->right != NULL && t->right->cnfa.nstates > 0);
      assert(t->left->flags & SHORTER);

      /* concatenation -- need to split the substring between parts */
      d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
      if (ISERR())
            return v->err;
      d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, DOMALLOC);
      if (ISERR())
      {
            freedfa(d);
            return v->err;
      }
      MDEBUG(("crev %d\n", t->retry));

      /* pick a tentative midpoint */
      if (v->mem[t->retry] == 0)
      {
            mid = shortest(v, d, begin, begin, end, (chr **) NULL, (int *) NULL);
            if (mid == NULL)
            {
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
            v->mem[t->retry] = (mid - begin) + 1;
      }
      else
      {
            mid = begin + (v->mem[t->retry] - 1);
            MDEBUG(("working midpoint %ld\n", LOFF(mid)));
      }

      /* iterate until satisfaction or failure */
      for (;;)
      {
            /* try this midpoint on for size */
            if (longest(v, d2, mid, end, (int *) NULL) == end)
            {
                  er = cdissect(v, t->left, begin, mid);
                  if (er == REG_OKAY)
                  {
                        er = cdissect(v, t->right, mid, end);
                        if (er == REG_OKAY)
                        {
                              /* satisfaction */
                              MDEBUG(("successful\n"));
                              freedfa(d);
                              freedfa(d2);
                              return REG_OKAY;
                        }
                  }
                  if (er != REG_OKAY && er != REG_NOMATCH)
                  {
                        freedfa(d);
                        freedfa(d2);
                        return er;
                  }
            }

            /* that midpoint didn't work, find a new one */
            if (mid == end)
            {
                  /* all possibilities exhausted */
                  MDEBUG(("%d no midpoint\n", t->retry));
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            mid = shortest(v, d, begin, mid + 1, end, (chr **) NULL, (int *) NULL);
            if (mid == NULL)
            {
                  /* failed to find a new one */
                  MDEBUG(("%d failed midpoint\n", t->retry));
                  freedfa(d);
                  freedfa(d2);
                  return REG_NOMATCH;
            }
            MDEBUG(("%d: new midpoint %ld\n", t->retry, LOFF(mid)));
            v->mem[t->retry] = (mid - begin) + 1;
            zapmem(v, t->left);
            zapmem(v, t->right);
      }

      /* can't get here */
      return REG_ASSERT;
}

/*
 * cbrdissect - determine backref subexpression matches
 */
static int                                /* regexec return code */
cbrdissect(struct vars * v,
               struct subre * t,
               chr *begin,                /* beginning of relevant substring */
               chr *end)                  /* end of same */
{
      int               i;
      int               n = t->subno;
      size_t            len;
      chr            *paren;
      chr            *p;
      chr            *stop;
      int               min = t->min;
      int               max = t->max;

      assert(t != NULL);
      assert(t->op == 'b');
      assert(n >= 0);
      assert((size_t) n < v->nmatch);

      MDEBUG(("cbackref n%d %d{%d-%d}\n", t->retry, n, min, max));

      if (v->pmatch[n].rm_so == -1)
            return REG_NOMATCH;
      paren = v->start + v->pmatch[n].rm_so;
      len = v->pmatch[n].rm_eo - v->pmatch[n].rm_so;

      /* no room to maneuver -- retries are pointless */
      if (v->mem[t->retry])
            return REG_NOMATCH;
      v->mem[t->retry] = 1;

      /* special-case zero-length string */
      if (len == 0)
      {
            if (begin == end)
                  return REG_OKAY;
            return REG_NOMATCH;
      }

      /* and too-short string */
      assert(end >= begin);
      if ((size_t) (end - begin) < len)
            return REG_NOMATCH;
      stop = end - len;

      /* count occurrences */
      i = 0;
      for (p = begin; p <= stop && (i < max || max == INFINITY); p += len)
      {
            if ((*v->g->compare) (paren, p, len) != 0)
                  break;
            i++;
      }
      MDEBUG(("cbackref found %d\n", i));

      /* and sort it out */
      if (p != end)                       /* didn't consume all of it */
            return REG_NOMATCH;
      if (min <= i && (i <= max || max == INFINITY))
            return REG_OKAY;
      return REG_NOMATCH;                 /* out of range */
}

/*
 * caltdissect - determine alternative subexpression matches (w. complications)
 */
static int                                /* regexec return code */
caltdissect(struct vars * v,
                  struct subre * t,
                  chr *begin,             /* beginning of relevant substring */
                  chr *end)               /* end of same */
{
      struct dfa *d;
      int               er;

#define  UNTRIED 0                        /* not yet tried at all */
#define  TRYING  1                        /* top matched, trying submatches */
#define  TRIED     2                      /* top didn't match or submatches exhausted */

      if (t == NULL)
            return REG_NOMATCH;
      assert(t->op == '|');
      if (v->mem[t->retry] == TRIED)
            return caltdissect(v, t->right, begin, end);

      MDEBUG(("calt n%d\n", t->retry));
      assert(t->left != NULL);

      if (v->mem[t->retry] == UNTRIED)
      {
            d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
            if (ISERR())
                  return v->err;
            if (longest(v, d, begin, end, (int *) NULL) != end)
            {
                  freedfa(d);
                  v->mem[t->retry] = TRIED;
                  return caltdissect(v, t->right, begin, end);
            }
            freedfa(d);
            MDEBUG(("calt matched\n"));
            v->mem[t->retry] = TRYING;
      }

      er = cdissect(v, t->left, begin, end);
      if (er != REG_NOMATCH)
            return er;

      v->mem[t->retry] = TRIED;
      return caltdissect(v, t->right, begin, end);
}



#include "rege_dfa.c"

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