/Users/deen/code/yugabyte-db/src/postgres/src/backend/regex/regcomp.c

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/*
 * re_*comp and friends - compile REs
 * This file #includes several others (see the bottom).
 *
 * 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.
 *
 * src/backend/regex/regcomp.c
 *
 */

#include "regex/regguts.h"

/*
 * forward declarations, up here so forward datatypes etc. are defined early
 */
/* === regcomp.c === */
static void moresubs(struct vars *, int);
static int  freev(struct vars *, int);
static void makesearch(struct vars *, struct nfa *);
static struct subre *parse(struct vars *, int, int, struct state *, struct state *);
static struct subre *parsebranch(struct vars *, int, int, struct state *, struct state *, int);
static void parseqatom(struct vars *, int, int, struct state *, struct state *, struct subre *);
static void nonword(struct vars *, int, struct state *, struct state *);
static void word(struct vars *, int, struct state *, struct state *);
static int  scannum(struct vars *);
static void repeat(struct vars *, struct state *, struct state *, int, int);
static void bracket(struct vars *, struct state *, struct state *);
static void cbracket(struct vars *, struct state *, struct state *);
static void brackpart(struct vars *, struct state *, struct state *);
static const chr *scanplain(struct vars *);
static void onechr(struct vars *, chr, struct state *, struct state *);
static void wordchrs(struct vars *);
static void processlacon(struct vars *, struct state *, struct state *, int,
       struct state *, struct state *);
static struct subre *subre(struct vars *, int, int, struct state *, struct state *);
static void freesubre(struct vars *, struct subre *);
static void freesrnode(struct vars *, struct subre *);
static void optst(struct vars *, struct subre *);
static int  numst(struct subre *, int);
static void markst(struct subre *);
static void cleanst(struct vars *);
static long nfatree(struct vars *, struct subre *, FILE *);
static long nfanode(struct vars *, struct subre *, int, FILE *);
static int  newlacon(struct vars *, struct state *, struct state *, int);
static void freelacons(struct subre *, int);
static void rfree(regex_t *);
static int  rcancelrequested(void);
static int  rstacktoodeep(void);

#ifdef REG_DEBUG
static void dump(regex_t *, FILE *);
static void dumpst(struct subre *, FILE *, int);
static void stdump(struct subre *, FILE *, int);
static const char *stid(struct subre *, char *, size_t);
#endif
/* === regc_lex.c === */
static void lexstart(struct vars *);
static void prefixes(struct vars *);
static void lexnest(struct vars *, const chr *, const chr *);
static void lexword(struct vars *);
static int  next(struct vars *);
static int  lexescape(struct vars *);
static chr  lexdigits(struct vars *, int, int, int);
static int  brenext(struct vars *, chr);
static void skip(struct vars *);
static chr  newline(void);
static chr  chrnamed(struct vars *, const chr *, const chr *, chr);

/* === regc_color.c === */
static void initcm(struct vars *, struct colormap *);
static void freecm(struct colormap *);
static color maxcolor(struct colormap *);
static color newcolor(struct colormap *);
static void freecolor(struct colormap *, color);
static color pseudocolor(struct colormap *);
static color subcolor(struct colormap *, chr);
static color subcolorhi(struct colormap *, color *);
static color newsub(struct colormap *, color);
static int  newhicolorrow(struct colormap *, int);
static void newhicolorcols(struct colormap *);
static void subcolorcvec(struct vars *, struct cvec *, struct state *, struct state *);
static void subcoloronechr(struct vars *, chr, struct state *, struct state *, color *);
static void subcoloronerange(struct vars *, chr, chr, struct state *, struct state *, color *);
static void subcoloronerow(struct vars *, int, struct state *, struct state *, color *);
static void okcolors(struct nfa *, struct colormap *);
static void colorchain(struct colormap *, struct arc *);
static void uncolorchain(struct colormap *, struct arc *);
static void rainbow(struct nfa *, struct colormap *, int, color, struct state *, struct state *);
static void colorcomplement(struct nfa *, struct colormap *, int, struct state *, struct state *, struct state *);

#ifdef REG_DEBUG
static void dumpcolors(struct colormap *, FILE *);
static void dumpchr(chr, FILE *);
#endif
/* === regc_nfa.c === */
static struct nfa *newnfa(struct vars *, struct colormap *, struct nfa *);
static void freenfa(struct nfa *);
static struct state *newstate(struct nfa *);
static struct state *newfstate(struct nfa *, int flag);
static void dropstate(struct nfa *, struct state *);
static void freestate(struct nfa *, struct state *);
static void destroystate(struct nfa *, struct state *);
static void newarc(struct nfa *, int, color, struct state *, struct state *);
static void createarc(struct nfa *, int, color, struct state *, struct state *);
static struct arc *allocarc(struct nfa *, struct state *);
static void freearc(struct nfa *, struct arc *);
static void changearctarget(struct arc *, struct state *);
static int  hasnonemptyout(struct state *);
static struct arc *findarc(struct state *, int, color);
static void cparc(struct nfa *, struct arc *, struct state *, struct state *);
static void sortins(struct nfa *, struct state *);
static int  sortins_cmp(const void *, const void *);
static void sortouts(struct nfa *, struct state *);
static int  sortouts_cmp(const void *, const void *);
static void moveins(struct nfa *, struct state *, struct state *);
static void copyins(struct nfa *, struct state *, struct state *);
static void mergeins(struct nfa *, struct state *, struct arc **, int);
static void moveouts(struct nfa *, struct state *, struct state *);
static void copyouts(struct nfa *, struct state *, struct state *);
static void cloneouts(struct nfa *, struct state *, struct state *, struct state *, int);
static void delsub(struct nfa *, struct state *, struct state *);
static void deltraverse(struct nfa *, struct state *, struct state *);
static void dupnfa(struct nfa *, struct state *, struct state *, struct state *, struct state *);
static void duptraverse(struct nfa *, struct state *, struct state *);
static void cleartraverse(struct nfa *, struct state *);
static struct state *single_color_transition(struct state *, struct state *);
static void specialcolors(struct nfa *);
static long optimize(struct nfa *, FILE *);
static void pullback(struct nfa *, FILE *);
static int  pull(struct nfa *, struct arc *, struct state **);
static void pushfwd(struct nfa *, FILE *);
static int  push(struct nfa *, struct arc *, struct state **);

#define INCOMPATIBLE  1    /* destroys arc */
#define SATISFIED 2      /* constraint satisfied */
#define COMPATIBLE  3      /* compatible but not satisfied yet */
static int  combine(struct arc *, struct arc *);
static void fixempties(struct nfa *, FILE *);
static struct state *emptyreachable(struct nfa *, struct state *,
         struct state *, struct arc **);
static int  isconstraintarc(struct arc *);
static int  hasconstraintout(struct state *);
static void fixconstraintloops(struct nfa *, FILE *);
static int  findconstraintloop(struct nfa *, struct state *);
static void breakconstraintloop(struct nfa *, struct state *);
static void clonesuccessorstates(struct nfa *, struct state *, struct state *,
           struct state *, struct arc *,
           char *, char *, int);
static void cleanup(struct nfa *);
static void markreachable(struct nfa *, struct state *, struct state *, struct state *);
static void markcanreach(struct nfa *, struct state *, struct state *, struct state *);
static long analyze(struct nfa *);
static void compact(struct nfa *, struct cnfa *);
static void carcsort(struct carc *, size_t);
static int  carc_cmp(const void *, const void *);
static void freecnfa(struct cnfa *);
static void dumpnfa(struct nfa *, FILE *);

#ifdef REG_DEBUG
static void dumpstate(struct state *, FILE *);
static void dumparcs(struct state *, FILE *);
static void dumparc(struct arc *, struct state *, FILE *);
static void dumpcnfa(struct cnfa *, FILE *);
static void dumpcstate(int, struct cnfa *, FILE *);
#endif
/* === regc_cvec.c === */
static struct cvec *newcvec(int, int);
static struct cvec *clearcvec(struct cvec *);
static void addchr(struct cvec *, chr);
static void addrange(struct cvec *, chr, chr);
static struct cvec *getcvec(struct vars *, int, int);
static void freecvec(struct cvec *);

/* === regc_pg_locale.c === */
static int  pg_wc_isdigit(pg_wchar c);
static int  pg_wc_isalpha(pg_wchar c);
static int  pg_wc_isalnum(pg_wchar c);
static int  pg_wc_isupper(pg_wchar c);
static int  pg_wc_islower(pg_wchar c);
static int  pg_wc_isgraph(pg_wchar c);
static int  pg_wc_isprint(pg_wchar c);
static int  pg_wc_ispunct(pg_wchar c);
static int  pg_wc_isspace(pg_wchar c);
static pg_wchar pg_wc_toupper(pg_wchar c);
static pg_wchar pg_wc_tolower(pg_wchar c);

/* === regc_locale.c === */
static chr  element(struct vars *, const chr *, const chr *);
static struct cvec *range(struct vars *, chr, chr, int);
static int  before(chr, chr);
static struct cvec *eclass(struct vars *, chr, int);
static struct cvec *cclass(struct vars *, const chr *, const chr *, int);
static int  cclass_column_index(struct colormap *, chr);
static struct cvec *allcases(struct vars *, chr);
static int  cmp(const chr *, const chr *, size_t);
static int  casecmp(const chr *, const chr *, size_t);


/* internal variables, bundled for easy passing around */
struct vars
{
  regex_t    *re;
  const chr  *now;      /* scan pointer into string */
  const chr  *stop;     /* end of string */
  const chr  *savenow;    /* saved now and stop for "subroutine call" */
  const chr  *savestop;
  int     err;      /* error code (0 if none) */
  int     cflags;     /* copy of compile flags */
  int     lasttype;   /* type of previous token */
  int     nexttype;   /* type of next token */
  chr     nextvalue;    /* value (if any) of next token */
  int     lexcon;     /* lexical context type (see lex.c) */
  int     nsubexp;    /* subexpression count */
  struct subre **subs;    /* subRE pointer vector */
  size_t    nsubs;      /* length of vector */
  struct subre *sub10[10];  /* initial vector, enough for most */
  struct nfa *nfa;      /* the NFA */
  struct colormap *cm;    /* character color map */
  color   nlcolor;    /* color of newline */
  struct state *wordchrs;   /* state in nfa holding word-char outarcs */
  struct subre *tree;     /* subexpression tree */
  struct subre *treechain;  /* all tree nodes allocated */
  struct subre *treefree;   /* any free tree nodes */
  int     ntree;      /* number of tree nodes, plus one */
  struct cvec *cv;      /* interface cvec */
  struct cvec *cv2;     /* utility cvec */
  struct subre *lacons;   /* lookaround-constraint vector */
  int     nlacons;    /* size of lacons[]; note that only slots
                 * numbered 1 .. nlacons-1 are used */
  size_t    spaceused;    /* approx. space used for compilation */
};

/* parsing macros; most know that `v' is the struct vars pointer */
#define NEXT()  (next(v))    /* advance by one token */
#define SEE(t)  (v->nexttype == (t))  /* is next token this? */
#define EAT(t)  (SEE(t) && next(v)) /* if next is this, swallow it */
#define VISERR(vv)  ((vv)->err != 0)  /* have we seen an error yet? */
#define ISERR() VISERR(v)
#define VERR(vv,e)  ((vv)->nexttype = EOS, \
           (vv)->err = ((vv)->err ? (vv)->err : (e)))
#define ERR(e)  VERR(v, e)    /* record an error */
#define NOERR() {if (ISERR()) return;}  /* if error seen, return */
#define NOERRN()  {if (ISERR()) return NULL;} /* NOERR with retval */
#define NOERRZ()  {if (ISERR()) return 0;}  /* NOERR with retval */
#define INSIST(c, e) do { if (!(c)) ERR(e); } while (0) /* error if c false */
#define NOTE(b) (v->re->re_info |= (b)) /* note visible condition */
#define EMPTYARC(x, y)  newarc(v->nfa, EMPTY, 0, x, y)

/* token type codes, some also used as NFA arc types */
#define EMPTY 'n'        /* no token present */
#define EOS 'e'          /* end of string */
#define PLAIN 'p'        /* ordinary character */
#define DIGIT 'd'       /* digit (in bound) */
#define BACKREF 'b'        /* back reference */
#define COLLEL  'I'        /* start of [. */
#define ECLASS  'E'        /* start of [= */
#define CCLASS  'C'        /* start of [: */
#define END 'X'         /* end of [. [= [: */
#define RANGE 'R'        /* - within [] which might be range delim. */
#define LACON 'L'        /* lookaround constraint subRE */
#define AHEAD 'a'        /* color-lookahead arc */
#define BEHIND  'r'        /* color-lookbehind arc */
#define WBDRY 'w'        /* word boundary constraint */
#define NWBDRY  'W'        /* non-word-boundary constraint */
#define SBEGIN  'A'        /* beginning of string (even if not BOL) */
#define SEND  'Z'        /* end of string (even if not EOL) */
#define PREFER  'P'       /* length preference */

/* is an arc colored, and hence on a color chain? */
#define COLORED(a) \
  ((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND)


/* static function list */
static const struct fns functions = {
  rfree,            /* regfree insides */
  rcancelrequested,     /* check for cancel request */
  rstacktoodeep       /* check for stack getting dangerously deep */
};



/*
 * pg_regcomp - compile regular expression
 *
 * Note: on failure, no resources remain allocated, so pg_regfree()
 * need not be applied to re.
 */
int
pg_regcomp(regex_t *re,
       const chr *string,
       size_t len,
       int flags,
       Oid collation)
{
  struct vars var;
  struct vars *v = &var;
  struct guts *g;
  int     i;
  size_t    j;

#ifdef REG_DEBUG
  FILE     *debug = (flags & REG_PROGRESS) ? stdout : (FILE *) NULL;
#else
  FILE     *debug = (FILE *) NULL;
#endif

#define  CNOERR()  { if (ISERR()) return freev(v, v->err); }

  /* sanity checks */

  if (re == NULL || string == NULL)
    return REG_INVARG;
  if ((flags & REG_QUOTE) &&
    (flags & (REG_ADVANCED | REG_EXPANDED | REG_NEWLINE)))
    return REG_INVARG;
  if (!(flags & REG_EXTENDED) && (flags & REG_ADVF))
    return REG_INVARG;

  /* Initialize locale-dependent support */
  pg_set_regex_collation(collation);

  /* initial setup (after which freev() is callable) */
  v->re = re;
  v->now = string;
  v->stop = v->now + len;
  v->savenow = v->savestop = NULL;
  v->err = 0;
  v->cflags = flags;
  v->nsubexp = 0;
  v->subs = v->sub10;
  v->nsubs = 10;
  for (j = 0; j < v->nsubs; j++)
    v->subs[j] = NULL;
  v->nfa = NULL;
  v->cm = NULL;
  v->nlcolor = COLORLESS;
  v->wordchrs = NULL;
  v->tree = NULL;
  v->treechain = NULL;
  v->treefree = NULL;
  v->cv = NULL;
  v->cv2 = NULL;
  v->lacons = NULL;
  v->nlacons = 0;
  v->spaceused = 0;
  re->re_magic = REMAGIC;
  re->re_info = 0;      /* bits get set during parse */
  re->re_csize = sizeof(chr);
  re->re_collation = collation;
  re->re_guts = NULL;
  re->re_fns = VS(&functions);

  /* more complex setup, malloced things */
  re->re_guts = VS(MALLOC(sizeof(struct guts)));
  if (re->re_guts == NULL)
    return freev(v, REG_ESPACE);
  g = (struct guts *) re->re_guts;
  g->tree = NULL;
  initcm(v, &g->cmap);
  v->cm = &g->cmap;
  g->lacons = NULL;
  g->nlacons = 0;
  ZAPCNFA(g->search);
  v->nfa = newnfa(v, v->cm, (struct nfa *) NULL);
  CNOERR();
  /* set up a reasonably-sized transient cvec for getcvec usage */
  v->cv = newcvec(100, 20);
  if (v->cv == NULL)
    return freev(v, REG_ESPACE);

  /* parsing */
  lexstart(v);        /* also handles prefixes */
  if ((v->cflags & REG_NLSTOP) || (v->cflags & REG_NLANCH))
  {
    /* assign newline a unique color */
    v->nlcolor = subcolor(v->cm, newline());
    okcolors(v->nfa, v->cm);
  }
  CNOERR();
  v->tree = parse(v, EOS, PLAIN, v->nfa->init, v->nfa->final);
  assert(SEE(EOS));     /* even if error; ISERR() => SEE(EOS) */
  CNOERR();
  assert(v->tree != NULL);

  /* finish setup of nfa and its subre tree */
  specialcolors(v->nfa);
  CNOERR();
#ifdef REG_DEBUG
  if (debug != NULL)
  {
    fprintf(debug, "\n\n\n========= RAW ==========\n");
    dumpnfa(v->nfa, debug);
    dumpst(v->tree, debug, 1);
  }
#endif
  optst(v, v->tree);
  v->ntree = numst(v->tree, 1);
  markst(v->tree);
  cleanst(v);
#ifdef REG_DEBUG
  if (debug != NULL)
  {
    fprintf(debug, "\n\n\n========= TREE FIXED ==========\n");
    dumpst(v->tree, debug, 1);
  }
#endif

  /* build compacted NFAs for tree and lacons */
  re->re_info |= nfatree(v, v->tree, debug);
  CNOERR();
  assert(v->nlacons == 0 || v->lacons != NULL);
  for (i = 1; i < v->nlacons; i++)
  {
    struct subre *lasub = &v->lacons[i];

#ifdef REG_DEBUG
    if (debug != NULL)
      fprintf(debug, "\n\n\n========= LA%d ==========\n", i);
#endif

    /* Prepend .* to pattern if it's a lookbehind LACON */
    nfanode(v, lasub, !LATYPE_IS_AHEAD(lasub->subno), debug);
  }
  CNOERR();
  if (v->tree->flags & SHORTER)
    NOTE(REG_USHORTEST);

  /* build compacted NFAs for tree, lacons, fast search */
#ifdef REG_DEBUG
  if (debug != NULL)
    fprintf(debug, "\n\n\n========= SEARCH ==========\n");
#endif
  /* can sacrifice main NFA now, so use it as work area */
  (DISCARD) optimize(v->nfa, debug);
  CNOERR();
  makesearch(v, v->nfa);
  CNOERR();
  compact(v->nfa, &g->search);
  CNOERR();

  /* looks okay, package it up */
  re->re_nsub = v->nsubexp;
  v->re = NULL;       /* freev no longer frees re */
  g->magic = GUTSMAGIC;
  g->cflags = v->cflags;
  g->info = re->re_info;
  g->nsub = re->re_nsub;
  g->tree = v->tree;
  v->tree = NULL;
  g->ntree = v->ntree;
  g->compare = (v->cflags & REG_ICASE) ? casecmp : cmp;
  g->lacons = v->lacons;
  v->lacons = NULL;
  g->nlacons = v->nlacons;

#ifdef REG_DEBUG
  if (flags & REG_DUMP)
    dump(re, stdout);
#endif

  assert(v->err == 0);
  return freev(v, 0);
}

/*
 * moresubs - enlarge subRE vector
 */
static void
moresubs(struct vars *v,
     int wanted)      /* want enough room for this one */
{
  struct subre **p;
  size_t    n;

  assert(wanted > 0 && (size_t) wanted >= v->nsubs);
  n = (size_t) wanted * 3 / 2 + 1;

  if (v->subs == v->sub10)
  {
    p = (struct subre **) MALLOC(n * sizeof(struct subre *));
    if (p != NULL)
      memcpy(VS(p), VS(v->subs),
           v->nsubs * sizeof(struct subre *));
  }
  else
    p = (struct subre **) REALLOC(v->subs, n * sizeof(struct subre *));
  if (p == NULL)
  {
    ERR(REG_ESPACE);
    return;
  }
  v->subs = p;
  for (p = &v->subs[v->nsubs]; v->nsubs < n; p++, v->nsubs++)
    *p = NULL;
  assert(v->nsubs == n);
  assert((size_t) wanted < v->nsubs);
}

/*
 * freev - free vars struct's substructures where necessary
 *
 * Optionally does error-number setting, and always returns error code
 * (if any), to make error-handling code terser.
 */
static int
freev(struct vars *v,
    int err)
{
  if (v->re != NULL)
    rfree(v->re);
  if (v->subs != v->sub10)
    FREE(v->subs);
  if (v->nfa != NULL)
    freenfa(v->nfa);
  if (v->tree != NULL)
    freesubre(v, v->tree);
  if (v->treechain != NULL)
    cleanst(v);
  if (v->cv != NULL)
    freecvec(v->cv);
  if (v->cv2 != NULL)
    freecvec(v->cv2);
  if (v->lacons != NULL)
    freelacons(v->lacons, v->nlacons);
  ERR(err);          /* nop if err==0 */

  return v->err;
}

/*
 * makesearch - turn an NFA into a search NFA (implicit prepend of .*?)
 * NFA must have been optimize()d already.
 */
static void
makesearch(struct vars *v,
       struct nfa *nfa)
{
  struct arc *a;
  struct arc *b;
  struct state *pre = nfa->pre;
  struct state *s;
  struct state *s2;
  struct state *slist;

  /* no loops are needed if it's anchored */
  for (a = pre->outs; a != NULL; a = a->outchain)
  {
    assert(a->type == PLAIN);
    if (a->co != nfa->bos[0] && a->co != nfa->bos[1])
      break;
  }
  if (a != NULL)
  {
    /* add implicit .* in front */
    rainbow(nfa, v->cm, PLAIN, COLORLESS, pre, pre);

    /* and ^* and \A* too -- not always necessary, but harmless */
    newarc(nfa, PLAIN, nfa->bos[0], pre, pre);
    newarc(nfa, PLAIN, nfa->bos[1], pre, pre);
  }

  /*
   * Now here's the subtle part.  Because many REs have no lookback
   * constraints, often knowing when you were in the pre state tells you
   * little; it's the next state(s) that are informative.  But some of them
   * may have other inarcs, i.e. it may be possible to make actual progress
   * and then return to one of them.  We must de-optimize such cases,
   * splitting each such state into progress and no-progress states.
   */

  /* first, make a list of the states reachable from pre and elsewhere */
  slist = NULL;
  for (a = pre->outs; a != NULL; a = a->outchain)
  {
    s = a->to;
    for (b = s->ins; b != NULL; b = b->inchain)
    {
      if (b->from != pre)
        break;
    }

    /*
     * We want to mark states as being in the list already by having non
     * NULL tmp fields, but we can't just store the old slist value in tmp
     * because that doesn't work for the first such state.  Instead, the
     * first list entry gets its own address in tmp.
     */
    if (b != NULL && s->tmp == NULL)
    {
      s->tmp = (slist != NULL) ? slist : s;
      slist = s;
    }
  }

  /* do the splits */
  for (s = slist; s != NULL; s = s2)
  {
    s2 = newstate(nfa);
    NOERR();
    copyouts(nfa, s, s2);
    NOERR();
    for (a = s->ins; a != NULL; a = b)
    {
      b = a->inchain;
      if (a->from != pre)
      {
        cparc(nfa, a, a->from, s2);
        freearc(nfa, a);
      }
    }
    s2 = (s->tmp != s) ? s->tmp : NULL;
    s->tmp = NULL;      /* clean up while we're at it */
  }
}

/*
 * parse - parse an RE
 *
 * This is actually just the top level, which parses a bunch of branches
 * tied together with '|'.  They appear in the tree as the left children
 * of a chain of '|' subres.
 */
static struct subre *
parse(struct vars *v,
    int stopper,        /* EOS or ')' */
    int type,         /* LACON (lookaround subRE) or PLAIN */
    struct state *init,   /* initial state */
    struct state *final)    /* final state */
{
  struct state *left;     /* scaffolding for branch */
  struct state *right;
  struct subre *branches;   /* top level */
  struct subre *branch;   /* current branch */
  struct subre *t;      /* temporary */
  int     firstbranch;  /* is this the first branch? */

  assert(stopper == ')' || stopper == EOS);

  branches = subre(v, '|', LONGER, init, final);
  NOERRN();
  branch = branches;
  firstbranch = 1;
  do
  {             /* a branch */
    if (!firstbranch)
    {
      /* need a place to hang it */
      branch->right = subre(v, '|', LONGER, init, final);
      NOERRN();
      branch = branch->right;
    }
    firstbranch = 0;
    left = newstate(v->nfa);
    right = newstate(v->nfa);
    NOERRN();
    EMPTYARC(init, left);
    EMPTYARC(right, final);
    NOERRN();
    branch->left = parsebranch(v, stopper, type, left, right, 0);
    NOERRN();
    branch->flags |= UP(branch->flags | branch->left->flags);
    if ((branch->flags & ~branches->flags) != 0)  /* new flags */
      for (t = branches; t != branch; t = t->right)
        t->flags |= branch->flags;
  } while (EAT('|'));
  assert(SEE(stopper) || SEE(EOS));

  if (!SEE(stopper))
  {
    assert(stopper == ')' && SEE(EOS));
    ERR(REG_EPAREN);
  }

  /* optimize out simple cases */
  if (branch == branches)
  {             /* only one branch */
    assert(branch->right == NULL);
    t = branch->left;
    branch->left = NULL;
    freesubre(v, branches);
    branches = t;
  }
  else if (!MESSY(branches->flags))
  {             /* no interesting innards */
    freesubre(v, branches->left);
    branches->left = NULL;
    freesubre(v, branches->right);
    branches->right = NULL;
    branches->op = '=';
  }

  return branches;
}

/*
 * parsebranch - parse one branch of an RE
 *
 * This mostly manages concatenation, working closely with parseqatom().
 * Concatenated things are bundled up as much as possible, with separate
 * ',' nodes introduced only when necessary due to substructure.
 */
static struct subre *
parsebranch(struct vars *v,
      int stopper,    /* EOS or ')' */
      int type,     /* LACON (lookaround subRE) or PLAIN */
      struct state *left, /* leftmost state */
      struct state *right,  /* rightmost state */
      int partial)    /* is this only part of a branch? */
{
  struct state *lp;     /* left end of current construct */
  int     seencontent;  /* is there anything in this branch yet? */
  struct subre *t;

  lp = left;
  seencontent = 0;
  t = subre(v, '=', 0, left, right);  /* op '=' is tentative */
  NOERRN();
  while (!SEE('|') && !SEE(stopper) && !SEE(EOS))
  {
    if (seencontent)
    {           /* implicit concat operator */
      lp = newstate(v->nfa);
      NOERRN();
      moveins(v->nfa, right, lp);
    }
    seencontent = 1;

    /* NB, recursion in parseqatom() may swallow rest of branch */
    parseqatom(v, stopper, type, lp, right, t);
    NOERRN();
  }

  if (!seencontent)
  {             /* empty branch */
    if (!partial)
      NOTE(REG_UUNSPEC);
    assert(lp == left);
    EMPTYARC(left, right);
  }

  return t;
}

/*
 * parseqatom - parse one quantified atom or constraint of an RE
 *
 * The bookkeeping near the end cooperates very closely with parsebranch();
 * in particular, it contains a recursion that can involve parsing the rest
 * of the branch, making this function's name somewhat inaccurate.
 */
static void
parseqatom(struct vars *v,
       int stopper,     /* EOS or ')' */
       int type,      /* LACON (lookaround subRE) or PLAIN */
       struct state *lp,  /* left state to hang it on */
       struct state *rp,  /* right state to hang it on */
       struct subre *top) /* subtree top */
{
  struct state *s;      /* temporaries for new states */
  struct state *s2;

#define  ARCV(t, val)  newarc(v->nfa, t, val, lp, rp)
  int     m,
        n;
  struct subre *atom;     /* atom's subtree */
  struct subre *t;
  int     cap;      /* capturing parens? */
  int     latype;     /* lookaround constraint type */
  int     subno;      /* capturing-parens or backref number */
  int     atomtype;
  int     qprefer;    /* quantifier short/long preference */
  int     f;
  struct subre **atomp;   /* where the pointer to atom is */

  /* initial bookkeeping */
  atom = NULL;
  assert(lp->nouts == 0);   /* must string new code */
  assert(rp->nins == 0);    /* between lp and rp */
  subno = 0;          /* just to shut lint up */

  /* an atom or constraint... */
  atomtype = v->nexttype;
  switch (atomtype)
  {
      /* first, constraints, which end by returning */
    case '^':
      ARCV('^', 1);
      if (v->cflags & REG_NLANCH)
        ARCV(BEHIND, v->nlcolor);
      NEXT();
      return;
      break;
    case '$':
      ARCV('$', 1);
      if (v->cflags & REG_NLANCH)
        ARCV(AHEAD, v->nlcolor);
      NEXT();
      return;
      break;
    case SBEGIN:
      ARCV('^', 1);   /* BOL */
      ARCV('^', 0);   /* or BOS */
      NEXT();
      return;
      break;
    case SEND:
      ARCV('$', 1);   /* EOL */
      ARCV('$', 0);   /* or EOS */
      NEXT();
      return;
      break;
    case '<':
      wordchrs(v);    /* does NEXT() */
      s = newstate(v->nfa);
      NOERR();
      nonword(v, BEHIND, lp, s);
      word(v, AHEAD, s, rp);
      return;
      break;
    case '>':
      wordchrs(v);    /* does NEXT() */
      s = newstate(v->nfa);
      NOERR();
      word(v, BEHIND, lp, s);
      nonword(v, AHEAD, s, rp);
      return;
      break;
    case WBDRY:
      wordchrs(v);    /* does NEXT() */
      s = newstate(v->nfa);
      NOERR();
      nonword(v, BEHIND, lp, s);
      word(v, AHEAD, s, rp);
      s = newstate(v->nfa);
      NOERR();
      word(v, BEHIND, lp, s);
      nonword(v, AHEAD, s, rp);
      return;
      break;
    case NWBDRY:
      wordchrs(v);    /* does NEXT() */
      s = newstate(v->nfa);
      NOERR();
      word(v, BEHIND, lp, s);
      word(v, AHEAD, s, rp);
      s = newstate(v->nfa);
      NOERR();
      nonword(v, BEHIND, lp, s);
      nonword(v, AHEAD, s, rp);
      return;
      break;
    case LACON:       /* lookaround constraint */
      latype = v->nextvalue;
      NEXT();
      s = newstate(v->nfa);
      s2 = newstate(v->nfa);
      NOERR();
      t = parse(v, ')', LACON, s, s2);
      freesubre(v, t);  /* internal structure irrelevant */
      NOERR();
      assert(SEE(')'));
      NEXT();
      processlacon(v, s, s2, latype, lp, rp);
      return;
      break;
      /* then errors, to get them out of the way */
    case '*':
    case '+':
    case '?':
    case '{':
      ERR(REG_BADRPT);
      return;
      break;
    default:
      ERR(REG_ASSERT);
      return;
      break;
      /* then plain characters, and minor variants on that theme */
    case ')':       /* unbalanced paren */
      if ((v->cflags & REG_ADVANCED) != REG_EXTENDED)
      {
        ERR(REG_EPAREN);
        return;
      }
      /* legal in EREs due to specification botch */
      NOTE(REG_UPBOTCH);
      /* fall through into case PLAIN */
      switch_fallthrough();
    case PLAIN:
      onechr(v, v->nextvalue, lp, rp);
      okcolors(v->nfa, v->cm);
      NOERR();
      NEXT();
      break;
    case '[':
      if (v->nextvalue == 1)
        bracket(v, lp, rp);
      else
        cbracket(v, lp, rp);
      assert(SEE(']') || ISERR());
      NEXT();
      break;
    case '.':
      rainbow(v->nfa, v->cm, PLAIN,
          (v->cflags & REG_NLSTOP) ? v->nlcolor : COLORLESS,
          lp, rp);
      NEXT();
      break;
      /* and finally the ugly stuff */
    case '(':       /* value flags as capturing or non */
      cap = (type == LACON) ? 0 : v->nextvalue;
      if (cap)
      {
        v->nsubexp++;
        subno = v->nsubexp;
        if ((size_t) subno >= v->nsubs)
          moresubs(v, subno);
        assert((size_t) subno < v->nsubs);
      }
      else
        atomtype = PLAIN; /* something that's not '(' */
      NEXT();
      /* need new endpoints because tree will contain pointers */
      s = newstate(v->nfa);
      s2 = newstate(v->nfa);
      NOERR();
      EMPTYARC(lp, s);
      EMPTYARC(s2, rp);
      NOERR();
      atom = parse(v, ')', type, s, s2);
      assert(SEE(')') || ISERR());
      NEXT();
      NOERR();
      if (cap)
      {
        v->subs[subno] = atom;
        t = subre(v, '(', atom->flags | CAP, lp, rp);
        NOERR();
        t->subno = subno;
        t->left = atom;
        atom = t;
      }
      /* postpone everything else pending possible {0} */
      break;
    case BACKREF:     /* the Feature From The Black Lagoon */
      INSIST(type != LACON, REG_ESUBREG);
      INSIST(v->nextvalue < v->nsubs, REG_ESUBREG);
      INSIST(v->subs[v->nextvalue] != NULL, REG_ESUBREG);
      NOERR();
      assert(v->nextvalue > 0);
      atom = subre(v, 'b', BACKR, lp, rp);
      NOERR();
      subno = v->nextvalue;
      atom->subno = subno;
      EMPTYARC(lp, rp); /* temporarily, so there's something */
      NEXT();
      break;
  }

  /* ...and an atom may be followed by a quantifier */
  switch (v->nexttype)
  {
    case '*':
      m = 0;
      n = DUPINF;
      qprefer = (v->nextvalue) ? LONGER : SHORTER;
      NEXT();
      break;
    case '+':
      m = 1;
      n = DUPINF;
      qprefer = (v->nextvalue) ? LONGER : SHORTER;
      NEXT();
      break;
    case '?':
      m = 0;
      n = 1;
      qprefer = (v->nextvalue) ? LONGER : SHORTER;
      NEXT();
      break;
    case '{':
      NEXT();
      m = scannum(v);
      if (EAT(','))
      {
        if (SEE(DIGIT))
          n = scannum(v);
        else
          n = DUPINF;
        if (m > n)
        {
          ERR(REG_BADBR);
          return;
        }
        /* {m,n} exercises preference, even if it's {m,m} */
        qprefer = (v->nextvalue) ? LONGER : SHORTER;
      }
      else
      {
        n = m;
        /* {m} passes operand's preference through */
        qprefer = 0;
      }
      if (!SEE('}'))
      {         /* catches errors too */
        ERR(REG_BADBR);
        return;
      }
      NEXT();
      break;
    default:        /* no quantifier */
      m = n = 1;
      qprefer = 0;
      break;
  }

  /* annoying special case:  {0} or {0,0} cancels everything */
  if (m == 0 && n == 0)
  {
    if (atom != NULL)
      freesubre(v, atom);
    if (atomtype == '(')
      v->subs[subno] = NULL;
    delsub(v->nfa, lp, rp);
    EMPTYARC(lp, rp);
    return;
  }

  /* if not a messy case, avoid hard part */
  assert(!MESSY(top->flags));
  f = top->flags | qprefer | ((atom != NULL) ? atom->flags : 0);
  if (atomtype != '(' && atomtype != BACKREF && !MESSY(UP(f)))
  {
    if (!(m == 1 && n == 1))
      repeat(v, lp, rp, m, n);
    if (atom != NULL)
      freesubre(v, atom);
    top->flags = f;
    return;
  }

  /*
   * hard part:  something messy
   *
   * That is, capturing parens, back reference, short/long clash, or an atom
   * with substructure containing one of those.
   */

  /* now we'll need a subre for the contents even if they're boring */
  if (atom == NULL)
  {
    atom = subre(v, '=', 0, lp, rp);
    NOERR();
  }

  /*----------
   * Prepare a general-purpose state skeleton.
   *
   * In the no-backrefs case, we want this:
   *
   * [lp] ---> [s] ---prefix---> [begin] ---atom---> [end] ---rest---> [rp]
   *
   * where prefix is some repetitions of atom.  In the general case we need
   *
   * [lp] ---> [s] ---iterator---> [s2] ---rest---> [rp]
   *
   * where the iterator wraps around [begin] ---atom---> [end]
   *
   * We make the s state here for both cases; s2 is made below if needed
   *----------
   */
  s = newstate(v->nfa);   /* first, new endpoints for the atom */
  s2 = newstate(v->nfa);
  NOERR();
  moveouts(v->nfa, lp, s);
  moveins(v->nfa, rp, s2);
  NOERR();
  atom->begin = s;
  atom->end = s2;
  s = newstate(v->nfa);   /* set up starting state */
  NOERR();
  EMPTYARC(lp, s);
  NOERR();

  /* break remaining subRE into x{...} and what follows */
  t = subre(v, '.', COMBINE(qprefer, atom->flags), lp, rp);
  NOERR();
  t->left = atom;
  atomp = &t->left;

  /* here we should recurse... but we must postpone that to the end */

  /* split top into prefix and remaining */
  assert(top->op == '=' && top->left == NULL && top->right == NULL);
  top->left = subre(v, '=', top->flags, top->begin, lp);
  NOERR();
  top->op = '.';
  top->right = t;

  /* if it's a backref, now is the time to replicate the subNFA */
  if (atomtype == BACKREF)
  {
    assert(atom->begin->nouts == 1);  /* just the EMPTY */
    delsub(v->nfa, atom->begin, atom->end);
    assert(v->subs[subno] != NULL);

    /*
     * And here's why the recursion got postponed: it must wait until the
     * skeleton is filled in, because it may hit a backref that wants to
     * copy the filled-in skeleton.
     */
    dupnfa(v->nfa, v->subs[subno]->begin, v->subs[subno]->end,
         atom->begin, atom->end);
    NOERR();
  }

  /*
   * It's quantifier time.  If the atom is just a backref, we'll let it deal
   * with quantifiers internally.
   */
  if (atomtype == BACKREF)
  {
    /* special case:  backrefs have internal quantifiers */
    EMPTYARC(s, atom->begin); /* empty prefix */
    /* just stuff everything into atom */
    repeat(v, atom->begin, atom->end, m, n);
    atom->min = (short) m;
    atom->max = (short) n;
    atom->flags |= COMBINE(qprefer, atom->flags);
    /* rest of branch can be strung starting from atom->end */
    s2 = atom->end;
  }
  else if (m == 1 && n == 1)
  {
    /* no/vacuous quantifier:  done */
    EMPTYARC(s, atom->begin); /* empty prefix */
    /* rest of branch can be strung starting from atom->end */
    s2 = atom->end;
  }
  else if (m > 0 && !(atom->flags & BACKR))
  {
    /*
     * If there's no backrefs involved, we can turn x{m,n} into
     * x{m-1,n-1}x, with capturing parens in only the second x.  This is
     * valid because we only care about capturing matches from the final
     * iteration of the quantifier.  It's a win because we can implement
     * the backref-free left side as a plain DFA node, since we don't
     * really care where its submatches are.
     */
    dupnfa(v->nfa, atom->begin, atom->end, s, atom->begin);
    assert(m >= 1 && m != DUPINF && n >= 1);
    repeat(v, s, atom->begin, m - 1, (n == DUPINF) ? n : n - 1);
    f = COMBINE(qprefer, atom->flags);
    t = subre(v, '.', f, s, atom->end); /* prefix and atom */
    NOERR();
    t->left = subre(v, '=', PREF(f), s, atom->begin);
    NOERR();
    t->right = atom;
    *atomp = t;
    /* rest of branch can be strung starting from atom->end */
    s2 = atom->end;
  }
  else
  {
    /* general case: need an iteration node */
    s2 = newstate(v->nfa);
    NOERR();
    moveouts(v->nfa, atom->end, s2);
    NOERR();
    dupnfa(v->nfa, atom->begin, atom->end, s, s2);
    repeat(v, s, s2, m, n);
    f = COMBINE(qprefer, atom->flags);
    t = subre(v, '*', f, s, s2);
    NOERR();
    t->min = (short) m;
    t->max = (short) n;
    t->left = atom;
    *atomp = t;
    /* rest of branch is to be strung from iteration's end state */
  }

  /* and finally, look after that postponed recursion */
  t = top->right;
  if (!(SEE('|') || SEE(stopper) || SEE(EOS)))
    t->right = parsebranch(v, stopper, type, s2, rp, 1);
  else
  {
    EMPTYARC(s2, rp);
    t->right = subre(v, '=', 0, s2, rp);
  }
  NOERR();
  assert(SEE('|') || SEE(stopper) || SEE(EOS));
  t->flags |= COMBINE(t->flags, t->right->flags);
  top->flags |= COMBINE(top->flags, t->flags);
}

/*
 * nonword - generate arcs for non-word-character ahead or behind
 */
static void
nonword(struct vars *v,
    int dir,        /* AHEAD or BEHIND */
    struct state *lp,
    struct state *rp)
{
  int     anchor = (dir == AHEAD) ? '$' : '^';

  assert(dir == AHEAD || dir == BEHIND);
  newarc(v->nfa, anchor, 1, lp, rp);
  newarc(v->nfa, anchor, 0, lp, rp);
  colorcomplement(v->nfa, v->cm, dir, v->wordchrs, lp, rp);
  /* (no need for special attention to \n) */
}

/*
 * word - generate arcs for word character ahead or behind
 */
static void
word(struct vars *v,
   int dir,         /* AHEAD or BEHIND */
   struct state *lp,
   struct state *rp)
{
  assert(dir == AHEAD || dir == BEHIND);
  cloneouts(v->nfa, v->wordchrs, lp, rp, dir);
  /* (no need for special attention to \n) */
}

/*
 * scannum - scan a number
 */
static int            /* value, <= DUPMAX */
scannum(struct vars *v)
{
  int     n = 0;

  while (SEE(DIGIT) && n < DUPMAX)
  {
    n = n * 10 + v->nextvalue;
    NEXT();
  }
  if (SEE(DIGIT) || n > DUPMAX)
  {
    ERR(REG_BADBR);
    return 0;
  }
  return n;
}

/*
 * repeat - replicate subNFA for quantifiers
 *
 * The sub-NFA strung from lp to rp is modified to represent m to n
 * repetitions of its initial contents.
 *
 * The duplication sequences used here are chosen carefully so that any
 * pointers starting out pointing into the subexpression end up pointing into
 * the last occurrence.  (Note that it may not be strung between the same
 * left and right end states, however!)  This used to be important for the
 * subRE tree, although the important bits are now handled by the in-line
 * code in parse(), and when this is called, it doesn't matter any more.
 */
static void
repeat(struct vars *v,
     struct state *lp,
     struct state *rp,
     int m,
     int n)
{
#define  SOME  2
#define  INF   3
#define  PAIR(x, y)  ((x)*4 + (y))
#define  REDUCE(x)   ( ((x) == DUPINF) ? INF : (((x) > 1) ? SOME : (x)) )
  const int rm = REDUCE(m);
  const int rn = REDUCE(n);
  struct state *s;
  struct state *s2;

  switch (PAIR(rm, rn))
  {
    case PAIR(0, 0):   /* empty string */
      delsub(v->nfa, lp, rp);
      EMPTYARC(lp, rp);
      break;
    case PAIR(0, 1):   /* do as x| */
      EMPTYARC(lp, rp);
      break;
    case PAIR(0, SOME):    /* do as x{1,n}| */
      repeat(v, lp, rp, 1, n);
      NOERR();
      EMPTYARC(lp, rp);
      break;
    case PAIR(0, INF):   /* loop x around */
      s = newstate(v->nfa);
      NOERR();
      moveouts(v->nfa, lp, s);
      moveins(v->nfa, rp, s);
      EMPTYARC(lp, s);
      EMPTYARC(s, rp);
      break;
    case PAIR(1, 1):   /* no action required */
      break;
    case PAIR(1, SOME):    /* do as x{0,n-1}x = (x{1,n-1}|)x */
      s = newstate(v->nfa);
      NOERR();
      moveouts(v->nfa, lp, s);
      dupnfa(v->nfa, s, rp, lp, s);
      NOERR();
      repeat(v, lp, s, 1, n - 1);
      NOERR();
      EMPTYARC(lp, s);
      break;
    case PAIR(1, INF):   /* add loopback arc */
      s = newstate(v->nfa);
      s2 = newstate(v->nfa);
      NOERR();
      moveouts(v->nfa, lp, s);
      moveins(v->nfa, rp, s2);
      EMPTYARC(lp, s);
      EMPTYARC(s2, rp);
      EMPTYARC(s2, s);
      break;
    case PAIR(SOME, SOME): /* do as x{m-1,n-1}x */
      s = newstate(v->nfa);
      NOERR();
      moveouts(v->nfa, lp, s);
      dupnfa(v->nfa, s, rp, lp, s);
      NOERR();
      repeat(v, lp, s, m - 1, n - 1);
      break;
    case PAIR(SOME, INF):  /* do as x{m-1,}x */
      s = newstate(v->nfa);
      NOERR();
      moveouts(v->nfa, lp, s);
      dupnfa(v->nfa, s, rp, lp, s);
      NOERR();
      repeat(v, lp, s, m - 1, n);
      break;
    default:
      ERR(REG_ASSERT);
      break;
  }
}

/*
 * bracket - handle non-complemented bracket expression
 * Also called from cbracket for complemented bracket expressions.
 */
static void
bracket(struct vars *v,
    struct state *lp,
    struct state *rp)
{
  assert(SEE('['));
  NEXT();
  while (!SEE(']') && !SEE(EOS))
    brackpart(v, lp, rp);
  assert(SEE(']') || ISERR());
  okcolors(v->nfa, v->cm);
}

/*
 * cbracket - handle complemented bracket expression
 * We do it by calling bracket() with dummy endpoints, and then complementing
 * the result.  The alternative would be to invoke rainbow(), and then delete
 * arcs as the b.e. is seen... but that gets messy.
 */
static void
cbracket(struct vars *v,
     struct state *lp,
     struct state *rp)
{
  struct state *left = newstate(v->nfa);
  struct state *right = newstate(v->nfa);

  NOERR();
  bracket(v, left, right);
  if (v->cflags & REG_NLSTOP)
    newarc(v->nfa, PLAIN, v->nlcolor, left, right);
  NOERR();

  assert(lp->nouts == 0);   /* all outarcs will be ours */

  /*
   * Easy part of complementing, and all there is to do since the MCCE code
   * was removed.
   */
  colorcomplement(v->nfa, v->cm, PLAIN, left, lp, rp);
  NOERR();
  dropstate(v->nfa, left);
  assert(right->nins == 0);
  freestate(v->nfa, right);
}

/*
 * brackpart - handle one item (or range) within a bracket expression
 */
static void
brackpart(struct vars *v,
      struct state *lp,
      struct state *rp)
{
  chr     startc;
  chr     endc;
  struct cvec *cv;
  const chr  *startp;
  const chr  *endp;
  chr     c[1];

  /* parse something, get rid of special cases, take shortcuts */
  switch (v->nexttype)
  {
    case RANGE:       /* a-b-c or other botch */
      ERR(REG_ERANGE);
      return;
      break;
    case PLAIN:
      c[0] = v->nextvalue;
      NEXT();
      /* shortcut for ordinary chr (not range) */
      if (!SEE(RANGE))
      {
        onechr(v, c[0], lp, rp);
        return;
      }
      startc = element(v, c, c + 1);
      NOERR();
      break;
    case COLLEL:
      startp = v->now;
      endp = scanplain(v);
      INSIST(startp < endp, REG_ECOLLATE);
      NOERR();
      startc = element(v, startp, endp);
      NOERR();
      break;
    case ECLASS:
      startp = v->now;
      endp = scanplain(v);
      INSIST(startp < endp, REG_ECOLLATE);
      NOERR();
      startc = element(v, startp, endp);
      NOERR();
      cv = eclass(v, startc, (v->cflags & REG_ICASE));
      NOERR();
      subcolorcvec(v, cv, lp, rp);
      return;
      break;
    case CCLASS:
      startp = v->now;
      endp = scanplain(v);
      INSIST(startp < endp, REG_ECTYPE);
      NOERR();
      cv = cclass(v, startp, endp, (v->cflags & REG_ICASE));
      NOERR();
      subcolorcvec(v, cv, lp, rp);
      return;
      break;
    default:
      ERR(REG_ASSERT);
      return;
      break;
  }

  if (SEE(RANGE))
  {
    NEXT();
    switch (v->nexttype)
    {
      case PLAIN:
      case RANGE:
        c[0] = v->nextvalue;
        NEXT();
        endc = element(v, c, c + 1);
        NOERR();
        break;
      case COLLEL:
        startp = v->now;
        endp = scanplain(v);
        INSIST(startp < endp, REG_ECOLLATE);
        NOERR();
        endc = element(v, startp, endp);
        NOERR();
        break;
      default:
        ERR(REG_ERANGE);
        return;
        break;
    }
  }
  else
    endc = startc;

  /*
   * Ranges are unportable.  Actually, standard C does guarantee that digits
   * are contiguous, but making that an exception is just too complicated.
   */
  if (startc != endc)
    NOTE(REG_UUNPORT);
  cv = range(v, startc, endc, (v->cflags & REG_ICASE));
  NOERR();
  subcolorcvec(v, cv, lp, rp);
}

/*
 * scanplain - scan PLAIN contents of [. etc.
 *
 * Certain bits of trickery in lex.c know that this code does not try
 * to look past the final bracket of the [. etc.
 */
static const chr *        /* just after end of sequence */
scanplain(struct vars *v)
{
  const chr  *endp;

  assert(SEE(COLLEL) || SEE(ECLASS) || SEE(CCLASS));
  NEXT();

  endp = v->now;
  while (SEE(PLAIN))
  {
    endp = v->now;
    NEXT();
  }

  assert(SEE(END) || ISERR());
  NEXT();

  return endp;
}

/*
 * onechr - fill in arcs for a plain character, and possible case complements
 * This is mostly a shortcut for efficient handling of the common case.
 */
static void
onechr(struct vars *v,
     chr c,
     struct state *lp,
     struct state *rp)
{
  if (!(v->cflags & REG_ICASE))
  {
    color   lastsubcolor = COLORLESS;

    subcoloronechr(v, c, lp, rp, &lastsubcolor);
    return;
  }

  /* rats, need general case anyway... */
  subcolorcvec(v, allcases(v, c), lp, rp);
}

/*
 * wordchrs - set up word-chr list for word-boundary stuff, if needed
 *
 * The list is kept as a bunch of arcs between two dummy states; it's
 * disposed of by the unreachable-states sweep in NFA optimization.
 * Does NEXT().  Must not be called from any unusual lexical context.
 * This should be reconciled with the \w etc. handling in lex.c, and
 * should be cleaned up to reduce dependencies on input scanning.
 */
static void
wordchrs(struct vars *v)
{
  struct state *left;
  struct state *right;

  if (v->wordchrs != NULL)
  {
    NEXT();         /* for consistency */
    return;
  }

  left = newstate(v->nfa);
  right = newstate(v->nfa);
  NOERR();
  /* fine point:  implemented with [::], and lexer will set REG_ULOCALE */
  lexword(v);
  NEXT();
  assert(v->savenow != NULL && SEE('['));
  bracket(v, left, right);
  assert((v->savenow != NULL && SEE(']')) || ISERR());
  NEXT();
  NOERR();
  v->wordchrs = left;
}

/*
 * processlacon - generate the NFA representation of a LACON
 *
 * In the general case this is just newlacon() + newarc(), but some cases
 * can be optimized.
 */
static void
processlacon(struct vars *v,
       struct state *begin, /* start of parsed LACON sub-re */
       struct state *end, /* end of parsed LACON sub-re */
       int latype,
       struct state *lp,  /* left state to hang it on */
       struct state *rp)  /* right state to hang it on */
{
  struct state *s1;
  int     n;

  /*
   * Check for lookaround RE consisting of a single plain color arc (or set
   * of arcs); this would typically be a simple chr or a bracket expression.
   */
  s1 = single_color_transition(begin, end);
  switch (latype)
  {
    case LATYPE_AHEAD_POS:
      /* If lookahead RE is just colorset C, convert to AHEAD(C) */
      if (s1 != NULL)
      {
        cloneouts(v->nfa, s1, lp, rp, AHEAD);
        return;
      }
      break;
    case LATYPE_AHEAD_NEG:
      /* If lookahead RE is just colorset C, convert to AHEAD(^C)|$ */
      if (s1 != NULL)
      {
        colorcomplement(v->nfa, v->cm, AHEAD, s1, lp, rp);
        newarc(v->nfa, '$', 1, lp, rp);
        newarc(v->nfa, '$', 0, lp, rp);
        return;
      }
      break;
    case LATYPE_BEHIND_POS:
      /* If lookbehind RE is just colorset C, convert to BEHIND(C) */
      if (s1 != NULL)
      {
        cloneouts(v->nfa, s1, lp, rp, BEHIND);
        return;
      }
      break;
    case LATYPE_BEHIND_NEG:
      /* If lookbehind RE is just colorset C, convert to BEHIND(^C)|^ */
      if (s1 != NULL)
      {
        colorcomplement(v->nfa, v->cm, BEHIND, s1, lp, rp);
        newarc(v->nfa, '^', 1, lp, rp);
        newarc(v->nfa, '^', 0, lp, rp);
        return;
      }
      break;
    default:
      assert(NOTREACHED);
  }

  /* General case: we need a LACON subre and arc */
  n = newlacon(v, begin, end, latype);
  newarc(v->nfa, LACON, n, lp, rp);
}

/*
 * subre - allocate a subre
 */
static struct subre *
subre(struct vars *v,
    int op,
    int flags,
    struct state *begin,
    struct state *end)
{
  struct subre *ret = v->treefree;

  /*
   * Checking for stack overflow here is sufficient to protect parse() and
   * its recursive subroutines.
   */
  if (STACK_TOO_DEEP(v->re))
  {
    ERR(REG_ETOOBIG);
    return NULL;
  }

  if (ret != NULL)
    v->treefree = ret->left;
  else
  {
    ret = (struct subre *) MALLOC(sizeof(struct subre));
    if (ret == NULL)
    {
      ERR(REG_ESPACE);
      return NULL;
    }
    ret->chain = v->treechain;
    v->treechain = ret;
  }

  assert(strchr("=b|.*(", op) != NULL);

  ret->op = op;
  ret->flags = flags;
  ret->id = 0;        /* will be assigned later */
  ret->subno = 0;
  ret->min = ret->max = 1;
  ret->left = NULL;
  ret->right = NULL;
  ret->begin = begin;
  ret->end = end;
  ZAPCNFA(ret->cnfa);

  return ret;
}

/*
 * freesubre - free a subRE subtree
 */
static void
freesubre(struct vars *v,   /* might be NULL */
      struct subre *sr)
{
  if (sr == NULL)
    return;

  if (sr->left != NULL)
    freesubre(v, sr->left);
  if (sr->right != NULL)
    freesubre(v, sr->right);

  freesrnode(v, sr);
}

/*
 * freesrnode - free one node in a subRE subtree
 */
static void
freesrnode(struct vars *v,    /* might be NULL */
       struct subre *sr)
{
  if (sr == NULL)
    return;

  if (!NULLCNFA(sr->cnfa))
    freecnfa(&sr->cnfa);
  sr->flags = 0;

  if (v != NULL && v->treechain != NULL)
  {
    /* we're still parsing, maybe we can reuse the subre */
    sr->left = v->treefree;
    v->treefree = sr;
  }
  else
    FREE(sr);
}

/*
 * optst - optimize a subRE subtree
 */
static void
optst(struct vars *v,
    struct subre *t)
{
  /*
   * DGP (2007-11-13): I assume it was the programmer's intent to eventually
   * come back and add code to optimize subRE trees, but the routine coded
   * just spends effort traversing the tree and doing nothing. We can do
   * nothing with less effort.
   */
  return;
}

/*
 * numst - number tree nodes (assigning "id" indexes)
 */
static int            /* next number */
numst(struct subre *t,
    int start)        /* starting point for subtree numbers */
{
  int     i;

  assert(t != NULL);

  i = start;
  t->id = (short) i++;
  if (t->left != NULL)
    i = numst(t->left, i);
  if (t->right != NULL)
    i = numst(t->right, i);
  return i;
}

/*
 * markst - mark tree nodes as INUSE
 *
 * Note: this is a great deal more subtle than it looks.  During initial
 * parsing of a regex, all subres are linked into the treechain list;
 * discarded ones are also linked into the treefree list for possible reuse.
 * After we are done creating all subres required for a regex, we run markst()
 * then cleanst(), which results in discarding all subres not reachable from
 * v->tree.  We then clear v->treechain, indicating that subres must be found
 * by descending from v->tree.  This changes the behavior of freesubre(): it
 * will henceforth FREE() unwanted subres rather than sticking them into the
 * treefree list.  (Doing that any earlier would result in dangling links in
 * the treechain list.)  This all means that freev() will clean up correctly
 * if invoked before or after markst()+cleanst(); but it would not work if
 * called partway through this state conversion, so we mustn't error out
 * in or between these two functions.
 */
static void
markst(struct subre *t)
{
  assert(t != NULL);

  t->flags |= INUSE;
  if (t->left != NULL)
    markst(t->left);
  if (t->right != NULL)
    markst(t->right);
}

/*
 * cleanst - free any tree nodes not marked INUSE
 */
static void
cleanst(struct vars *v)
{
  struct subre *t;
  struct subre *next;

  for (t = v->treechain; t != NULL; t = next)
  {
    next = t->chain;
    if (!(t->flags & INUSE))
      FREE(t);
  }
  v->treechain = NULL;
  v->treefree = NULL;     /* just on general principles */
}

/*
 * nfatree - turn a subRE subtree into a tree of compacted NFAs
 */
static long           /* optimize results from top node */
nfatree(struct vars *v,
    struct subre *t,
    FILE *f)        /* for debug output */
{
  assert(t != NULL && t->begin != NULL);

  if (t->left != NULL)
    (DISCARD) nfatree(v, t->left, f);
  if (t->right != NULL)
    (DISCARD) nfatree(v, t->right, f);

  return nfanode(v, t, 0, f);
}

/*
 * nfanode - do one NFA for nfatree or lacons
 *
 * If converttosearch is true, apply makesearch() to the NFA.
 */
static long           /* optimize results */
nfanode(struct vars *v,
    struct subre *t,
    int converttosearch,
    FILE *f)        /* for debug output */
{
  struct nfa *nfa;
  long    ret = 0;

  assert(t->begin != NULL);

#ifdef REG_DEBUG
  if (f != NULL)
  {
    char    idbuf[50];

    fprintf(f, "\n\n\n========= TREE NODE %s ==========\n",
        stid(t, idbuf, sizeof(idbuf)));
  }
#endif
  nfa = newnfa(v, v->cm, v->nfa);
  NOERRZ();
  dupnfa(nfa, t->begin, t->end, nfa->init, nfa->final);
  if (!ISERR())
    specialcolors(nfa);
  if (!ISERR())
    ret = optimize(nfa, f);
  if (converttosearch && !ISERR())
    makesearch(v, nfa);
  if (!ISERR())
    compact(nfa, &t->cnfa);

  freenfa(nfa);
  return ret;
}

/*
 * newlacon - allocate a lookaround-constraint subRE
 */
static int            /* lacon number */
newlacon(struct vars *v,
     struct state *begin,
     struct state *end,
     int latype)
{
  int     n;
  struct subre *newlacons;
  struct subre *sub;

  if (v->nlacons == 0)
  {
    n = 1;          /* skip 0th */
    newlacons = (struct subre *) MALLOC(2 * sizeof(struct subre));
  }
  else
  {
    n = v->nlacons;
    newlacons = (struct subre *) REALLOC(v->lacons,
                       (n + 1) * sizeof(struct subre));
  }
  if (newlacons == NULL)
  {
    ERR(REG_ESPACE);
    return 0;
  }
  v->lacons = newlacons;
  v->nlacons = n + 1;
  sub = &v->lacons[n];
  sub->begin = begin;
  sub->end = end;
  sub->subno = latype;
  ZAPCNFA(sub->cnfa);
  return n;
}

/*
 * freelacons - free lookaround-constraint subRE vector
 */
static void
freelacons(struct subre *subs,
       int n)
{
  struct subre *sub;
  int     i;

  assert(n > 0);
  for (sub = subs + 1, i = n - 1; i > 0; sub++, i--) /* no 0th */
    if (!NULLCNFA(sub->cnfa))
      freecnfa(&sub->cnfa);
  FREE(subs);
}

/*
 * rfree - free a whole RE (insides of regfree)
 */
static void
rfree(regex_t *re)
{
  struct guts *g;

  if (re == NULL || re->re_magic != REMAGIC)
    return;

  re->re_magic = 0;     /* invalidate RE */
  g = (struct guts *) re->re_guts;
  re->re_guts = NULL;
  re->re_fns = NULL;
  if (g != NULL)
  {
    g->magic = 0;
    freecm(&g->cmap);
    if (g->tree != NULL)
      freesubre((struct vars *) NULL, g->tree);
    if (g->lacons != NULL)
      freelacons(g->lacons, g->nlacons);
    if (!NULLCNFA(g->search))
      freecnfa(&g->search);
    FREE(g);
  }
}

/*
 * rcancelrequested - check for external request to cancel regex operation
 *
 * Return nonzero to fail the operation with error code REG_CANCEL,
 * zero to keep going
 *
 * The current implementation is Postgres-specific.  If we ever get around
 * to splitting the regex code out as a standalone library, there will need
 * to be some API to let applications define a callback function for this.
 */
static int
rcancelrequested(void)
{
  return InterruptPending && (QueryCancelPending || ProcDiePending);
}

/*
 * rstacktoodeep - check for stack getting dangerously deep
 *
 * Return nonzero to fail the operation with error code REG_ETOOBIG,
 * zero to keep going
 *
 * The current implementation is Postgres-specific.  If we ever get around
 * to splitting the regex code out as a standalone library, there will need
 * to be some API to let applications define a callback function for this.
 */
static int
rstacktoodeep(void)
{
  return stack_is_too_deep();
}

#ifdef REG_DEBUG

/*
 * dump - dump an RE in human-readable form
 */
static void
dump(regex_t *re,
   FILE *f)
{
  struct guts *g;
  int     i;

  if (re->re_magic != REMAGIC)
    fprintf(f, "bad magic number (0x%x not 0x%x)\n", re->re_magic,
        REMAGIC);
  if (re->re_guts == NULL)
  {
    fprintf(f, "NULL guts!!!\n");
    return;
  }
  g = (struct guts *) re->re_guts;
  if (g->magic != GUTSMAGIC)
    fprintf(f, "bad guts magic number (0x%x not 0x%x)\n", g->magic,
        GUTSMAGIC);

  fprintf(f, "\n\n\n========= DUMP ==========\n");
  fprintf(f, "nsub %d, info 0%lo, csize %d, ntree %d\n",
      (int) re->re_nsub, re->re_info, re->re_csize, g->ntree);

  dumpcolors(&g->cmap, f);
  if (!NULLCNFA(g->search))
  {
    fprintf(f, "\nsearch:\n");
    dumpcnfa(&g->search, f);
  }
  for (i = 1; i < g->nlacons; i++)
  {
    struct subre *lasub = &g->lacons[i];
    const char *latype;

    switch (lasub->subno)
    {
      case LATYPE_AHEAD_POS:
        latype = "positive lookahead";
        break;
      case LATYPE_AHEAD_NEG:
        latype = "negative lookahead";
        break;
      case LATYPE_BEHIND_POS:
        latype = "positive lookbehind";
        break;
      case LATYPE_BEHIND_NEG:
        latype = "negative lookbehind";
        break;
      default:
        latype = "???";
        break;
    }
    fprintf(f, "\nla%d (%s):\n", i, latype);
    dumpcnfa(&lasub->cnfa, f);
  }
  fprintf(f, "\n");
  dumpst(g->tree, f, 0);
}

/*
 * dumpst - dump a subRE tree
 */
static void
dumpst(struct subre *t,
     FILE *f,
     int nfapresent)      /* is the original NFA still around? */
{
  if (t == NULL)
    fprintf(f, "null tree\n");
  else
    stdump(t, f, nfapresent);
  fflush(f);
}

/*
 * stdump - recursive guts of dumpst
 */
static void
stdump(struct subre *t,
     FILE *f,
     int nfapresent)      /* is the original NFA still around? */
{
  char    idbuf[50];

  fprintf(f, "%s. `%c'", stid(t, idbuf, sizeof(idbuf)), t->op);
  if (t->flags & LONGER)
    fprintf(f, " longest");
  if (t->flags & SHORTER)
    fprintf(f, " shortest");
  if (t->flags & MIXED)
    fprintf(f, " hasmixed");
  if (t->flags & CAP)
    fprintf(f, " hascapture");
  if (t->flags & BACKR)
    fprintf(f, " hasbackref");
  if (!(t->flags & INUSE))
    fprintf(f, " UNUSED");
  if (t->subno != 0)
    fprintf(f, " (#%d)", t->subno);
  if (t->min != 1 || t->max != 1)
  {
    fprintf(f, " {%d,", t->min);
    if (t->max != DUPINF)
      fprintf(f, "%d", t->max);
    fprintf(f, "}");
  }
  if (nfapresent)
    fprintf(f, " %ld-%ld", (long) t->begin->no, (long) t->end->no);
  if (t->left != NULL)
    fprintf(f, " L:%s", stid(t->left, idbuf, sizeof(idbuf)));
  if (t->right != NULL)
    fprintf(f, " R:%s", stid(t->right, idbuf, sizeof(idbuf)));
  if (!NULLCNFA(t->cnfa))
  {
    fprintf(f, "\n");
    dumpcnfa(&t->cnfa, f);
  }
  fprintf(f, "\n");
  if (t->left != NULL)
    stdump(t->left, f, nfapresent);
  if (t->right != NULL)
    stdump(t->right, f, nfapresent);
}

/*
 * stid - identify a subtree node for dumping
 */
static const char *       /* points to buf or constant string */
stid(struct subre *t,
   char *buf,
   size_t bufsize)
{
  /* big enough for hex int or decimal t->id? */
  if (bufsize < sizeof(void *) * 2 + 3 || bufsize < sizeof(t->id) * 3 + 1)
    return "unable";
  if (t->id != 0)
    sprintf(buf, "%d", t->id);
  else
    sprintf(buf, "%p", t);
  return buf;
}
#endif              /* REG_DEBUG */


#include "regc_lex.c"
#include "regc_color.c"
#include "regc_nfa.c"
#include "regc_cvec.c"
#include "regc_pg_locale.c"
#include "regc_locale.c"

YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

Coverage Report

Created: 2022-03-09 17:30