/*	$OpenBSD: regcomp.c,v 1.20 2010/11/21 00:02:30 tedu Exp $ */
/*-
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS OR CONTRIBUTORS 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.
 *
 *	@ (#)regcomp.c	8.5 (Berkeley) 3/20/94
 */

#include <r_th.h>
#include "r_regex.h"
#include "r_util/r_str.h"
#include "r_util/r_assert.h"

#include "utils.h"
#include "regex2.h"
#include "cclass.h"
#include "cname.h"

/*
 * parse structure, passed up and down to avoid global variables and
 * other clumsinesses
 */
struct parse {
	char *next; /* next character in RE */
	char *end; /* end of string (-> NUL normally) */
	int error; /* has an error been seen? */
	sop *strip; /* malloced strip */
	sopno ssize; /* malloced strip size (allocated) */
	sopno slen; /* malloced strip length (used) */
	int ncsalloc; /* number of csets allocated */
	struct re_guts *g;
#define NPAREN 10 /* we need to remember() 1-9 for back refs */
	sopno pbegin[NPAREN]; /* -> (([0] unused) */
	sopno pend[NPAREN]; /* -> ) ([0] unused) */
	char nuls[10]; /* place to point scanner in event of error */
};

static void p_ere(struct parse *, int);
static void p_ere_exp(struct parse *);
static void p_str(struct parse *);
static void p_bre(struct parse *, int, int);
static int p_simp_re(struct parse *, int);
static int p_count(struct parse *);
static void p_bracket(struct parse *);
static void p_b_term(struct parse *, cset *);
static void p_b_cclass(struct parse *, cset *);
static void p_b_eclass(struct parse *, cset *);
static char p_b_symbol(struct parse *);
static char p_b_coll_elem(struct parse *, int);
static char othercase(int);
static void bothcases(struct parse *, int);
static void ordinary(struct parse *, int);
static void special(struct parse *, int);
static void nonnewline(struct parse *);
static void p_fakebracket(struct parse *, char *, size_t);
static void repeat(struct parse *, sopno, int, int);
static int seterr(struct parse *, int);
static cset *allocset(struct parse *);
static void freeset(struct parse *, cset *);
static int freezeset(struct parse *, cset *);
static int firstch(struct parse *, cset *);
static int nch(struct parse *, cset *);
static void mcadd(struct parse *, cset *, const char *);
static void mcinvert(struct parse *, cset *);
static void mccase(struct parse *, cset *);
static int isinsets(struct re_guts *, int);
static int samesets(struct re_guts *, int, int);
static void categorize(struct parse *, struct re_guts *);
static sopno dupl(struct parse *, sopno, sopno);
static void doemit(struct parse *, sop, size_t);
static void doinsert(struct parse *, sop, size_t, sopno);
static void dofwd(struct parse *, sopno, sop);
static void enlarge(struct parse *, sopno);
static void stripsnug(struct parse *, struct re_guts *);
static void findmust(struct parse *, struct re_guts *);
static sopno pluscount(struct parse *, struct re_guts *);

/*
 * macros for use with parse structure
 * BEWARE:  these know that the parse structure is named `p' !!!
 */
#define PEEK() (*p->next)
#define PEEK2() (*(p->next + 1))
#define MORE() (p->next < p->end)
#define MORE2() (p->next + 1 < p->end)
#define SEE(c) (MORE () && PEEK () == (c))
#define SEETWO(a, b) (MORE () && MORE2 () && PEEK () == (a) && PEEK2 () == (b))
#define EAT(c) ((SEE (c))? (NEXT (), 1): 0)
#define EATTWO(a, b) ((SEETWO (a, b))? (NEXT2 (), 1): 0)
#define NEXT() (p->next++)
#define NEXT2() (p->next += 2)
#define NEXTn(n) (p->next += (n))
#define GETNEXT() (*p->next++)
#define SETERROR(e) seterr(p,(e))
#define REQUIRE(co, e) (void) ((co) || SETERROR (e))
#define MUSTSEE(c, e) (REQUIRE (MORE () && PEEK () == (c), e))
#define MUSTEAT(c, e) (REQUIRE (MORE () && GETNEXT () == (c), e))
#define MUSTNOTSEE(c, e) (REQUIRE (!MORE () || PEEK () != (c), e))
#define EMIT(op, sopnd) doemit(p,(sop)(op),(size_t)(sopnd))
#define INSERT(op, pos) doinsert(p,(sop)(op), HERE() -(pos) + 1, pos)
#define AHEAD(pos) dofwd(p, pos, HERE() -(pos))
#define ASTERN(sop, pos) EMIT(sop, HERE() -(pos))
#define HERE() (p->slen)
#define THERE() (p->slen - 1)
#define THERETHERE() (p->slen - 2)
#define DROP(n) (p->slen -= (n))

R_API bool r_regex_match(const char *pattern, const char *flags, const char *text) {
	RRegex rx = { 0 };
	int re_flags = r_regex_flags (flags);
	if (r_regex_init (&rx, pattern, re_flags)) {
		R_LOG_ERROR ("r_regex_match: /%s/ fails to compile", pattern);
		return false;
	}
	int rc = r_regex_exec (&rx, text, 0, 0, 0);
	r_regex_fini (&rx);
	return rc == 0;
}

R_API RList *r_regex_match_list(RRegex *rx, const char *text) {
	RList *list = r_list_newf (free);
	RRegexMatch match;
	size_t text_len = strlen (text);

	/* Initialize the boundaries for R_REGEX_STARTEND */
	match.rm_so = 0;
	match.rm_eo = text_len;
	while (!r_regex_exec (rx, text, 1, &match, rx->re_flags | R_REGEX_STARTEND)) {
		size_t entry_len = match.rm_eo - match.rm_so;
		char *entry = r_str_ndup (text + match.rm_so, entry_len);
		r_list_append (list, entry);
		/* Update the boundaries for R_REGEX_STARTEND */
		match.rm_so = match.rm_eo;
		match.rm_eo = text_len;
	}
	return list;
}

R_API RRegex *r_regex_new(const char *pattern, const char *flags) {
	R_RETURN_VAL_IF_FAIL (pattern, NULL);
	RRegex *r, rx = { 0 };
	if (r_regex_init (&rx, pattern, r_regex_flags (flags))) {
		return NULL;
	}
	r = R_NEW (RRegex);
	if (!r) {
		r_regex_fini (&rx);
		return NULL;
	}
	*r = rx;
	return r;
}

R_API int r_regex_flags(const char *f) {
	int flags = 0;
	if (R_STR_ISEMPTY (f)) {
		return 0;
	}
	if (strchr (f, 'e')) {
		flags |= R_REGEX_EXTENDED;
	}
	if (strchr (f, 'i')) {
		flags |= R_REGEX_ICASE;
	}
	if (strchr (f, 's')) {
		flags |= R_REGEX_NOSUB;
	}
	if (strchr (f, 'n')) {
		flags |= R_REGEX_NEWLINE;
	}
	if (strchr (f, 'N')) {
		flags |= R_REGEX_NOSPEC;
	}
	if (strchr (f, 'p')) {
		flags |= R_REGEX_PEND;
	}
	if (strchr (f, 'd')) {
		flags |= R_REGEX_DUMP;
	}
	return flags;
}

R_API void r_regex_fini(RRegex *preg) {
	struct re_guts *g;
	if (!preg) {
		return;
	}
	if (preg->re_magic != MAGIC1) { /* oops */
		return; /* nice to complain, but hard */
	}

	g = preg->re_g;
	if (!g || g->magic != MAGIC2) { /* oops again */
		return;
	}
	preg->re_magic = 0; /* mark it invalid */
	g->magic = 0; /* mark it invalid */

	free (g->strip);
	free (g->sets);
	free (g->setbits);
	free (g->must);
	free (g);
}

R_API void r_regex_free(RRegex *preg) {
	r_regex_fini (preg);
	free (preg);
}

/*
- regcomp - interface for parser and compilation
- 0 success, otherwise R_REGEX_something
 */
R_API int r_regex_init(RRegex *preg, const char *pattern, int cflags) {
	struct parse pa;
	struct parse *p = &pa;
	int i;
	size_t len;
	cflags &= ~R_REGEX_DUMP;
	if (!preg || ((cflags & R_REGEX_EXTENDED) && (cflags & R_REGEX_NOSPEC))) {
		return R_REGEX_INVARG;
	}
	// Release any prior compilation so re-initializing the same RRegex does
	// not leak. r_regex_fini magic-checks, so it is a safe no-op on a freshly
	// zero-initialized struct. Callers must zero-initialize RRegex on first
	// use (RRegex rx = {0}) so this read sees a defined value.
	r_regex_fini (preg);
	if (cflags & R_REGEX_PEND) {
		if (preg->re_endp < pattern) {
			return R_REGEX_INVARG;
		}
		len = preg->re_endp - pattern;
	} else {
		len = strlen ((char *)pattern);
	}
	/* do the mallocs early so failure handling is easy */
	struct re_guts *g = (struct re_guts *)calloc (sizeof (struct re_guts) + (NC - 1), sizeof (cat_t));
	if (!g) {
		return R_REGEX_ESPACE;
	}
	/*
	 * Limit the pattern space to avoid a 32-bit overflow on buffer
	 * extension.  Also avoid any signed overflow in case of conversion
	 * so make the real limit based on a 31-bit overflow.
	 *
	 * Likely not applicable on 64-bit systems but handle the case
	 * generically (who are we to stop people from using ~715MB+
	 * patterns?).
	 */
	size_t maxlen = ((size_t)-1 >> 1) / sizeof (sop) * 2 / 3;
	if (len >= maxlen) {
		free (g);
		return R_REGEX_ESPACE;
	}
	preg->re_flags = cflags;
	p->ssize = len / (size_t)2 *(size_t)3 + (size_t)1; /* ugh */
	if (p->ssize < len) {
		free (g);
		return R_REGEX_ESPACE;
	}

	p->strip = (sop *)calloc (p->ssize, sizeof (sop));
	if (!p->strip) {
		free (g);
		return R_REGEX_ESPACE;
	}
	p->slen = 0;
	if (!p->strip) {
		free (g);
		return R_REGEX_ESPACE;
	}

	/* set things up */
	p->g = g;
	p->next = (char *)pattern; /* convenience; we do not modify it */
	p->end = p->next + len;
	p->error = 0;
	p->ncsalloc = 0;
	for (i = 0; i < NPAREN; i++) {
		p->pbegin[i] = 0;
		p->pend[i] = 0;
	}
	g->csetsize = NC;
	g->sets = NULL;
	g->setbits = NULL;
	g->ncsets = 0;
	g->cflags = cflags;
	g->iflags = 0;
	g->nbol = 0;
	g->neol = 0;
	g->must = NULL;
	g->mlen = 0;
	g->nsub = 0;
	g->ncategories = 1; /* category 0 is "everything else" */
	g->categories = &g->catspace[- (CHAR_MIN)]; // WTF
	(void)memset ((char *)g->catspace, 0, NC * sizeof (cat_t));
	g->backrefs = 0;

	/* do it */
	EMIT (OEND, 0);
	g->firststate = THERE ();
	if (cflags & R_REGEX_EXTENDED) {
		p_ere (p, OUT);
	} else if (cflags & R_REGEX_NOSPEC) {
		p_str (p);
	} else {
		p_bre (p, OUT, OUT);
	}
	EMIT (OEND, 0);
	g->laststate = THERE ();

	/* tidy up loose ends and fill things in */
	categorize (p, g);
	stripsnug (p, g);
	findmust (p, g);
	g->nplus = pluscount (p, g);
	g->magic = MAGIC2;
	preg->re_nsub = g->nsub;
	preg->re_g = g;
	preg->re_magic = MAGIC1;
	/* not debugging, so can't rely on the asssert() in regexec() */
	if (g->iflags & BAD) {
		SETERROR (R_REGEX_ASSERT);
	}
	if (p->error) {
		r_regex_fini (preg);
	}
	return p->error;
}

/*
- p_ere - ERE parser top level, concatenation and alternation
 */
static void p_ere(struct parse *p, int stop) { /* character this ERE should end at */
	bool isFirst = true;
	sopno prevback = 0;
	sopno prevfwd = 0;
	sopno conc = 0;
	char c;

	for (;;) {
		/* do a bunch of concatenated expressions */
		conc = HERE ();
		while (MORE () && (c = PEEK ()) != '|' && c != stop) {
			p_ere_exp (p);
		}
		REQUIRE (HERE () != conc, R_REGEX_EMPTY); /* require nonempty */

		if (!EAT ('|')) {
			break; /* NOTE BREAK OUT */
		}
		if (isFirst) {
			INSERT (OCH_, conc); /* offset is wrong */
			prevfwd = conc;
			prevback = conc;
			isFirst = false;
		}
		ASTERN (OOR1, prevback);
		prevback = THERE ();
		AHEAD (prevfwd); /* fix previous offset */
		prevfwd = HERE ();
		EMIT (OOR2, 0); /* offset is very wrong */
	}

	if (!isFirst) { /* tail-end fixups */
		AHEAD (prevfwd);
		ASTERN (O_CH, prevback);
	}
	// asert (!MORE () || SEE (stop));
}

/*
- p_ere_exp - parse one subERE, an atom possibly followed by a repetition op
 */
static void p_ere_exp(struct parse *p) {
	char c;
	sopno pos;
	int count;
	int count2;
	sopno subno;
	int wascaret = 0;

	if (!MORE ()) { /* caller should have ensured this */
		return;
	}
	c = GETNEXT ();

	pos = HERE ();
	switch (c) {
	case '(':
		REQUIRE (MORE (), R_REGEX_EPAREN);
		p->g->nsub++;
		subno = p->g->nsub;
		if (subno < NPAREN) {
			p->pbegin[subno] = HERE ();
		}
		EMIT (OLPAREN, subno);
		if (!SEE (')')) {
			p_ere (p, ')');
		}
		if (subno < NPAREN) {
			p->pend[subno] = HERE ();
			if (!p->pend[subno]) {
				break;
			}
		}
		EMIT (ORPAREN, subno);
		MUSTEAT (')', R_REGEX_EPAREN);
		break;
	case '^':
		EMIT (OBOL, 0);
		p->g->iflags |= USEBOL;
		p->g->nbol++;
		wascaret = 1;
		break;
	case '$':
		EMIT (OEOL, 0);
		p->g->iflags |= USEEOL;
		p->g->neol++;
		break;
	case '|':
		SETERROR (R_REGEX_EMPTY);
		break;
	case '*':
	case '+':
	case '?':
		SETERROR (R_REGEX_BADRPT);
		break;
	case '.':
		if (p->g->cflags & R_REGEX_NEWLINE) {
			nonnewline (p);
		} else {
			EMIT (OANY, 0);
		}
		break;
	case '[':
		p_bracket (p);
		break;
	case '\\':
		REQUIRE (MORE (), R_REGEX_EESCAPE);
		c = GETNEXT ();
		if (!isalpha (c & 0xff)) {
			ordinary (p, c);
		} else {
			special (p, c);
		}
		break;
	case '{': /* okay as ordinary except if digit follows */
		REQUIRE (!MORE () || !isdigit (PEEK () & 0xff), R_REGEX_BADRPT);
		/* FALLTHROUGH */
	default:
		ordinary (p, c);
		break;
	}

	if (!MORE ()) {
		return;
	}
	c = PEEK ();
	/* we call { a repetition if followed by a digit */
	if (! (c == '*' || c == '+' || c == '?' ||
		(c == '{' && MORE2 () && isdigit (PEEK2 () & 0xff)))) {
		return; /* no repetition, we're done */
	}
	NEXT ();

	REQUIRE (!wascaret, R_REGEX_BADRPT);
	switch (c) {
	case '*': /* implemented as +? */
		/* this case does not require the (y|) trick, noKLUDGE */
		INSERT (OPLUS_, pos);
		ASTERN (O_PLUS, pos);
		INSERT (OQUEST_, pos);
		ASTERN (O_QUEST, pos);
		break;
	case '+':
		INSERT (OPLUS_, pos);
		ASTERN (O_PLUS, pos);
		break;
	case '?':
		/* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
		INSERT (OCH_, pos); /* offset slightly wrong */
		ASTERN (OOR1, pos); /* this one's right */
		AHEAD (pos); /* fix the OCH_ */
		EMIT (OOR2, 0); /* offset very wrong... */
		AHEAD (THERE ()); /* ...so fix it */
		ASTERN (O_CH, THERETHERE ());
		break;
	case '{':
		count = p_count (p);
		if (EAT (',')) {
			if (isdigit (PEEK () & 0xff)) {
				count2 = p_count (p);
				REQUIRE (count <= count2, R_REGEX_BADBR);
			} else { /* single number with comma */
				count2 = INTFINITY;
			}
		} else { /* just a single number */
			count2 = count;
		}
		repeat (p, pos, count, count2);
		if (!EAT ('}')) { /* error heuristics */
			while (MORE () && PEEK () != '}') {
				NEXT ();
			}
			REQUIRE (MORE (), R_REGEX_EBRACE);
			SETERROR (R_REGEX_BADBR);
		}
		break;
	}

	if (!MORE ()) {
		return;
	}
	c = PEEK ();
	if (! (c == '*' || c == '+' || c == '?' ||
		(c == '{' && MORE2 () && isdigit (PEEK2 () & 0xff)))) {
		return;
	}
	SETERROR (R_REGEX_BADRPT);
}

/*
- p_str - string (no metacharacters) "parser"
 */
static void p_str(struct parse *p) {
	REQUIRE (MORE (), R_REGEX_EMPTY);
	while (MORE ()) {
		ordinary (p, GETNEXT ());
	}
}

/*
- p_bre - BRE parser top level, anchoring and concatenation
 * Giving end1 as OUT essentially eliminates the end1/end2 check.
 *
 * This implementation is a bit of a kludge, in that a trailing $ is first
 * taken as an ordinary character and then revised to be an anchor.  The
 * only undesirable side effect is that '$' gets included as a character
 * category in such cases.  This is fairly harmless; not worth fixing.
 * The amount of lookahead needed to avoid this kludge is excessive.
 */
static void p_bre(struct parse *p,
	int end1, /* first terminating character */
	int end2) /* second terminating character */
{
	sopno start = HERE ();
	int first = 1; /* first subexpression? */
	int wasdollar = 0;

	if (EAT ('^')) {
		EMIT (OBOL, 0);
		p->g->iflags |= USEBOL;
		p->g->nbol++;
	}
	while (MORE () && !SEETWO (end1, end2)) {
		wasdollar = p_simp_re (p, first);
		first = 0;
	}
	if (wasdollar) { /* oops, that was a trailing anchor */
		DROP (1);
		EMIT (OEOL, 0);
		p->g->iflags |= USEEOL;
		p->g->neol++;
	}

	REQUIRE (HERE () != start, R_REGEX_EMPTY); /* require nonempty */
}

/*
- p_simp_re - parse a simple RE, an atom possibly followed by a repetition
was the simple RE an unbackslashed $?
 */
static int p_simp_re(struct parse *p, int starordinary) { /* is a leading * an ordinary character? */
	int c;
	int count;
	int count2;
	sopno pos;
	int i;
	sopno subno;
#define BACKSL (1 << CHAR_BIT)

	pos = HERE (); /* repetion op, if any, covers from here */

	if (!MORE ()) { /* caller should have ensured this */
		return 0;
	}
	c = GETNEXT ();
	if (c == '\\') {
		REQUIRE (MORE (), R_REGEX_EESCAPE);
		c = BACKSL | GETNEXT ();
	}
	switch (c) {
	case '.':
		if (p->g->cflags & R_REGEX_NEWLINE) {
			nonnewline (p);
		} else {
			EMIT (OANY, 0);
		}
		break;
	case '[':
		p_bracket (p);
		break;
	case BACKSL | '{':
		SETERROR (R_REGEX_BADRPT);
		break;
	case BACKSL | '(':
		p->g->nsub++;
		subno = p->g->nsub;
		if (subno < NPAREN) {
			p->pbegin[subno] = HERE ();
		}
		EMIT (OLPAREN, subno);
		/* the MORE here is an error heuristic */
		if (MORE () && !SEETWO ('\\', ')')) {
			p_bre (p, '\\', ')');
		}
		if (subno < NPAREN) {
			p->pend[subno] = HERE ();
			if (!p->pend[subno]) {
				break;
			}
		}
		EMIT (ORPAREN, subno);
		REQUIRE (EATTWO ('\\', ')'), R_REGEX_EPAREN);
		break;
	case BACKSL | ')': /* should not get here -- must be user */
	case BACKSL | '}':
		SETERROR (R_REGEX_EPAREN);
		break;
	case BACKSL | '1':
	case BACKSL | '2':
	case BACKSL | '3':
	case BACKSL | '4':
	case BACKSL | '5':
	case BACKSL | '6':
	case BACKSL | '7':
	case BACKSL | '8':
	case BACKSL | '9':
		i = (c & ~BACKSL) - '0';
		if (p->pend[i] != 0) {
			if (i <= p->g->nsub) {
				EMIT (OBACK_, i);
				if (p->pbegin[i] != 0 && OP (p->strip[p->pbegin[i]]) == OLPAREN &&
					OP (p->strip[p->pend[i]]) == ORPAREN) {
					(void)dupl (p, p->pbegin[i] + 1, p->pend[i]);
					EMIT (O_BACK, i);
				}
			}
		} else {
			SETERROR (R_REGEX_ESUBREG);
		}
		p->g->backrefs = 1;
		break;
	case '*':
		REQUIRE (starordinary, R_REGEX_BADRPT);
		/* FALLTHROUGH */
	default:
		ordinary (p, (char)c);
		break;
	}

	if (EAT ('*')) { /* implemented as +? */
		/* this case does not require the (y|) trick, noKLUDGE */
		INSERT (OPLUS_, pos);
		ASTERN (O_PLUS, pos);
		INSERT (OQUEST_, pos);
		ASTERN (O_QUEST, pos);
	} else if (EATTWO ('\\', '{')) {
		count = p_count (p);
		if (EAT (',')) {
			if (MORE () && isdigit (PEEK () & 0xff)) {
				count2 = p_count (p);
				REQUIRE (count <= count2, R_REGEX_BADBR);
			} else { /* single number with comma */
				count2 = INTFINITY;
			}
		} else { /* just a single number */
			count2 = count;
		}
		repeat (p, pos, count, count2);
		if (!EATTWO ('\\', '}')) { /* error heuristics */
			while (MORE () && !SEETWO ('\\', '}')) {
				NEXT ();
			}
			REQUIRE (MORE (), R_REGEX_EBRACE);
			SETERROR (R_REGEX_BADBR);
		}
	} else if (c == '$') { /* $ (but not \$) ends it */
		return (1);
	}

	return 0;
}

/*
- p_count - parse a repetition count
 */
static int p_count(struct parse *p) {
	int count = 0;
	int ndigits = 0;

	while (MORE () && isdigit (PEEK () & 0xff) && count <= DUPMAX) {
		count = count * 10 + (GETNEXT () - '0');
		ndigits++;
	}

	REQUIRE (ndigits > 0 && count <= DUPMAX, R_REGEX_BADBR);
	return count;
}

/*
- p_bracket - parse a bracketed character list
 *
 * Note a significant property of this code:  if the allocset () did SETERROR,
 * no set operations are done.
 */
static void p_bracket(struct parse *p) {
	cset *cs;
	int invert = 0;

	/* Dept of Truly Sickening Special-Case Kludges */
	if (p->end - p->next > 5 && r_str_startswith (p->next, "[:<:]]")) {
		EMIT (OBOW, 0);
		NEXTn (6);
		return;
	}
	if (p->end - p->next > 5 && r_str_startswith (p->next, "[:>:]]")) {
		EMIT (OEOW, 0);
		NEXTn (6);
		return;
	}

	if (! (cs = allocset (p))) {
		/* allocset did set error status in p */
		return;
	}

	if (EAT ('^')) {
		invert++; /* make note to invert set at end */
	}
	if (EAT (']')) {
		CHadd (cs, ']');
	} else if (EAT ('-')) {
		CHadd (cs, '-');
	}
	while (MORE () && PEEK () != ']' && !SEETWO ('-', ']')) {
		p_b_term (p, cs);
	}
	if (EAT ('-')) {
		CHadd (cs, '-');
	}
	MUSTEAT (']', R_REGEX_EBRACK);

	if (p->error != 0) { /* don't mess things up further */
		freeset (p, cs);
		return;
	}

	if (p->g->cflags & R_REGEX_ICASE) {
		int i;
		int ci;

		for (i = p->g->csetsize - 1; i >= 0; i--) {
			if (CHIN (cs, i) && isalpha (i & 0xff)) {
				ci = othercase (i);
				if (ci != i) {
					CHadd (cs, ci);
				}
			}
		}
		if (cs->multis) {
			mccase (p, cs);
		}
	}
	if (invert) {
		int i;

		for (i = p->g->csetsize - 1; i >= 0; i--) {
			if (CHIN (cs, i)) {
				CHsub (cs, i);
			} else {
				CHadd (cs, i);
			}
		}
		if (p->g->cflags & R_REGEX_NEWLINE) {
			CHsub (cs, '\n');
		}
		if (cs->multis) {
			mcinvert (p, cs);
		}
	}

	if (cs->multis) { /* xxx */
		return;
	}

	if (nch (p, cs) == 1) { /* optimize singleton sets */
		ordinary (p, firstch (p, cs));
		freeset (p, cs);
	} else {
		EMIT (OANYOF, freezeset (p, cs));
	}
}

/*
- p_b_term - parse one term of a bracketed character list
 */
static void p_b_term(struct parse *p, cset *cs) {
	char c;
	char start = 0, finish;
	int i;

	/* classify what we've got */
	switch ((MORE ())? PEEK (): '\0') {
	case '[':
		c = MORE2 ()? PEEK2 (): '\0';
		break;
	case '-':
		SETERROR (R_REGEX_ERANGE);
		return; /* NOTE RETURN */
		break;
	default:
		c = '\0';
		break;
	}

	switch (c) {
	case ':': /* character class */
		NEXT2 ();
		REQUIRE (MORE (), R_REGEX_EBRACK);
		c = PEEK ();
		REQUIRE (c != '-' && c != ']', R_REGEX_ECTYPE);
		p_b_cclass (p, cs);
		REQUIRE (MORE (), R_REGEX_EBRACK);
		REQUIRE (EATTWO (':', ']'), R_REGEX_ECTYPE);
		break;
	case '=': /* equivalence class */
		NEXT2 ();
		REQUIRE (MORE (), R_REGEX_EBRACK);
		c = PEEK ();
		REQUIRE (c != '-' && c != ']', R_REGEX_ECOLLATE);
		p_b_eclass (p, cs);
		REQUIRE (MORE (), R_REGEX_EBRACK);
		REQUIRE (EATTWO ('=', ']'), R_REGEX_ECOLLATE);
		break;
	default: /* symbol, ordinary character, or range */
		/* xxx revision needed for multichar stuff */
		start = p_b_symbol (p);
		if (SEE ('-') && MORE2 () && PEEK2 () != ']') {
			/* range */
			NEXT ();
			if (EAT ('-')) {
				finish = '-';
			} else {
				finish = p_b_symbol (p);
			}
		} else {
			finish = start;
		}
		/* xxx what about signed chars here... */
		REQUIRE (start <= finish, R_REGEX_ERANGE);
		for (i = start; i <= finish; i++) {
			CHadd (cs, i);
		}
		break;
	}
}

/*
- p_b_cclass - parse a character-class name and deal with it
 */
static void p_b_cclass(struct parse *p, cset *cs) {
	char *sp = p->next;
	struct cclass *cp;
	size_t len;
	const char *u;
	char c;

	while (MORE () && isalpha (0xff & PEEK ())) {
		NEXT ();
	}
	len = p->next - sp;
	for (cp = cclasses; cp->name; cp++) {
		if (strncmp (cp->name, sp, len) == 0 && cp->name[len] == '\0') {
			break;
		}
	}
	if (!cp->name) {
		/* oops, didn't find it */
		SETERROR (R_REGEX_ECTYPE);
		return;
	}

	u = cp->chars;
	while ((c = *u++) != '\0') {
		CHadd (cs, c);
	}
	for (u = cp->multis; *u != '\0'; u += strlen (u) + 1) {
		MCadd (p, cs, u);
	}
}

/*
- p_b_eclass - parse an equivalence-class name and deal with it
 *
 * This implementation is incomplete. xxx
 */
static void p_b_eclass(struct parse *p, cset *cs) {
	char c;

	c = p_b_coll_elem (p, '=');
	CHadd (cs, c);
}

/*
- p_b_symbol - parse a character or [..]ed multicharacter collating symbol
 */
static char p_b_symbol(struct parse *p) {
	char value;

	REQUIRE (MORE (), R_REGEX_EBRACK);
	if (!EATTWO ('[', '.')) {
		return (GETNEXT ());
	}

	/* collating symbol */
	value = p_b_coll_elem (p, '.');
	REQUIRE (EATTWO ('.', ']'), R_REGEX_ECOLLATE);
	return value;
}

/*
- p_b_coll_elem - parse a collating-element name and look it up
 */
static char /* value of collating element */
p_b_coll_elem(struct parse *p, int endc) { /* name ended by endc,']' */
	char *sp = p->next;
	struct cname *cp;
	int len;

	while (MORE () && !SEETWO (endc, ']')) {
		NEXT ();
	}
	if (!MORE ()) {
		SETERROR (R_REGEX_EBRACK);
		return 0;
	}
	len = p->next - sp;
	for (cp = cnames; cp->name; cp++) {
		if (strncmp (cp->name, sp, len) == 0 && cp->name[len] == '\0') {
			return (cp->code); /* known name */
		}
	}
	if (len == 1) {
		return (*sp); /* single character */
	}
	SETERROR (R_REGEX_ECOLLATE); /* neither */
	return 0;
}

/*
- othercase - return the case counterpart of an alphabetic if no counterpart, return ch
 */
static char othercase(int ch) {
	ch = (ut8) (ch & 0xff);
	if (isalpha (ch)) {
		if (isupper (ch)) {
			return ((ut8)tolower (ch));
		} else if (islower (ch)) {
			return ((ut8)toupper (ch));
		} else { /* peculiar, but could happen */
			return (ch);
		}
	}
	return ch;
}

/*
- bothcases - emit a dualcase version of a two-case character
 *
 * Boy, is this implementation ever a kludge...
 */
static void p_fakebracket(struct parse *p, char *bracket, size_t len) {
	char *oldnext = p->next;
	char *oldend = p->end;

	p->next = bracket;
	p->end = bracket + len;
	p_bracket (p);
	if (p->next == bracket + len) {
		p->next = oldnext;
		p->end = oldend;
	}
}

static void bothcases(struct parse *p, int ch) {
	char bracket[] = { 0, ']', 0 };
	ch = (ut8)ch;
	if (othercase (ch) == ch) {
		return;
	}
	bracket[0] = ch;
	p_fakebracket (p, bracket, sizeof (bracket) - 1);
}

/*
- ordinary - emit an ordinary character
 */
static void
ordinary(struct parse *p, int ch) {
	cat_t *cap = p->g->categories;

	if ((p->g->cflags & R_REGEX_ICASE) && isalpha ((ut8)ch) && othercase (ch) != ch) {
		bothcases (p, ch);
	} else {
		EMIT (OCHAR, (ut8)ch);
		if (cap[ch] == 0) {
			cap[ch] = p->g->ncategories++;
		}
	}
}

static void
special(struct parse *p, int ch) {
	char digits[3] = { 0 };
	char c;
	switch (ch) {
	case 'x':
		digits[0] = GETNEXT ();
		digits[1] = GETNEXT ();
		c = (char)strtol (digits, NULL, 16);
		ordinary (p, c);
		return;
	case 'n':
		ordinary (p, '\n');
		return;
	case 't':
		ordinary (p, '\t');
		return;
	case 'r':
		ordinary (p, '\r');
		return;
	case 's': {
		char bracket[] = "\t\r\n ]";
		p_fakebracket (p, bracket, sizeof (bracket) - 1);
		return;
	}
	case 'd': {
		char bracket[] = "0-9]";
		p_fakebracket (p, bracket, sizeof (bracket) - 1);
		return;
	}
	case 'w': {
		char bracket[] = "a-z]";
		p_fakebracket (p, bracket, sizeof (bracket) - 1);
		return;
	}
	default:
		SETERROR (R_REGEX_INVARG);
		return;
	}
}

/*
- nonnewline - emit R_REGEX_NEWLINE version of OANY
 *
 * Boy, is this implementation ever a kludge...
 */
static void
nonnewline(struct parse *p) {
	char bracket[] = "^\n]";
	p_fakebracket (p, bracket, sizeof (bracket) - 1);
}

/*
- repeat - generate code for a bounded repetition, recursively if needed
 */
static void repeat(struct parse *p,
	sopno start, /* operand from here to end of strip */
	int from, /* repeated from this number */
	int to) /* to this number of times (maybe INTFINITY) */
{
	sopno finish = HERE ();
#define N 2
#define INF 3
#define REP(f, t) ((f) * 8 + (t))
#define MAP(n) (((n) <= 1)? (n): ((n) == INTFINITY)? INF \
							: N)
	sopno copy;

	if (p->error != 0) { /* head off possible runaway recursion */
		return;
	}

	if (from > to) {
		return;
	}

	switch (REP (MAP (from), MAP (to))) {
	case REP (0, 0): /* must be user doing this */
		DROP (finish - start); /* drop the operand */
		break;
	case REP (0, 1): /* as x{1,1}? */
	case REP (0, N): /* as x{1,n}? */
	case REP (0, INF): /* as x{1,}? */
		/* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
		INSERT (OCH_, start); /* offset is wrong... */
		repeat (p, start + 1, 1, to);
		ASTERN (OOR1, start);
		AHEAD (start); /* ... fix it */
		EMIT (OOR2, 0);
		AHEAD (THERE ());
		ASTERN (O_CH, THERETHERE ());
		break;
	case REP (1, 1): /* trivial case */
		/* done */
		break;
	case REP (1, N): /* as x? x{1,n-1} */
		/* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
		INSERT (OCH_, start);
		ASTERN (OOR1, start);
		AHEAD (start);
		EMIT (OOR2, 0); /* offset very wrong... */
		AHEAD (THERE ()); /* ...so fix it */
		ASTERN (O_CH, THERETHERE ());
		copy = dupl (p, start + 1, finish + 1);
		if (copy == finish + 4) {
			repeat (p, copy, 1, to - 1);
		}
		break;
	case REP (1, INF): /* as x+ */
		INSERT (OPLUS_, start);
		ASTERN (O_PLUS, start);
		break;
	case REP (N, N): /* as xx{m-1,n-1} */
		copy = dupl (p, start, finish);
		repeat (p, copy, from - 1, to - 1);
		break;
	case REP (N, INF): /* as xx{n-1,INF} */
		copy = dupl (p, start, finish);
		repeat (p, copy, from - 1, to);
		break;
	default: /* "can't happen" */
		SETERROR (R_REGEX_ASSERT); /* just in case */
		break;
	}
}

/*
- seterr - set an error condition
 */
static int seterr(struct parse *p, int e) {
	if (p->error == 0) { /* keep earliest error condition */
		p->error = e;
	}
	p->next = p->nuls; /* try to bring things to a halt */
	p->end = p->nuls;
	return 0; /* make the return value well-defined */
}

/*
- allocset - allocate a set of characters for []
 */
static cset *allocset(struct parse *p) {
	int no = p->g->ncsets++;
	size_t nc;
	size_t nbytes;
	cset *cs;
	size_t css = (size_t)p->g->csetsize;
	int i;

	if (no >= p->ncsalloc) { /* need another column of space */
		void *ptr;

		p->ncsalloc += CHAR_BIT;
		nc = p->ncsalloc;
		if (nc % CHAR_BIT) {
			goto nomem;
		}
		nbytes = nc / CHAR_BIT * css;

		ptr = (cset *)realloc ((char *)p->g->sets, nc * sizeof (cset));
		if (!ptr) {
			goto nomem;
		}
		p->g->sets = ptr;

		ptr = (ut8 *)realloc ((char *)p->g->setbits, nbytes);
		if (!ptr) {
			goto nomem;
		}
		p->g->setbits = ptr;

		for (i = 0; i < no; i++) {
			p->g->sets[i].ptr = p->g->setbits + css *(i / CHAR_BIT);
		}

		(void)memset ((char *)p->g->setbits + (nbytes - css), 0, css);
	}
	/* XXX should not happen */
	if (!p->g->sets || !p->g->setbits) {
		goto nomem;
	}

	cs = &p->g->sets[no];
	cs->ptr = p->g->setbits + css *((no) / CHAR_BIT);
	cs->mask = 1 << ((no) % CHAR_BIT);
	cs->hash = 0;
	cs->smultis = 0;
	cs->multis = NULL;

	return cs;
nomem:
	R_FREE (p->g->sets);
	R_FREE (p->g->setbits);

	SETERROR (R_REGEX_ESPACE);
	/* caller's responsibility not to do set ops */
	return NULL;
}

/*
- freeset - free a now-unused set
 */
static void freeset(struct parse *p, cset *cs) {
	int i;
	cset *top = &p->g->sets[p->g->ncsets];
	size_t css = (size_t)p->g->csetsize;

	for (i = 0; i < css; i++) {
		CHsub (cs, i);
	}
	if (cs == top - 1) { /* recover only the easy case */
		p->g->ncsets--;
	}
}

/*
- freezeset - final processing on a set of characters
 *
 * The main task here is merging identical sets.  This is usually a waste
 * of time (although the hash code minimizes the overhead), but can win
 * big if R_REGEX_ICASE is being used.  R_REGEX_ICASE, by the way, is why the hash
 * is done using addition rather than xor -- all ASCII [aA] sets xor to
 * the same value!
 */
static int /* set number */
freezeset(struct parse *p, cset *cs) {
	ut8 h = cs->hash;
	int i;
	cset *top = &p->g->sets[p->g->ncsets];
	cset *cs2;
	size_t css = (size_t)p->g->csetsize;

	/* look for an earlier one which is the same */
	for (cs2 = &p->g->sets[0]; cs2 < top; cs2++) {
		if (cs2->hash == h && cs2 != cs) {
			/* maybe */
			for (i = 0; i < css; i++) {
				if (!!CHIN (cs2, i) != !!CHIN (cs, i)) {
					break; /* no */
				}
			}
			if (i == css) {
				break; /* yes */
			}
		}
	}

	if (cs2 < top) { /* found one */
		freeset (p, cs);
		cs = cs2;
	}

	return (int) (cs - p->g->sets);
}

/*
- firstch - return first character in a set (which must have at least one)
 */
static int /* character; there is no "none" value */
firstch(struct parse *p, cset *cs) {
	int i;
	size_t css = (size_t)p->g->csetsize;

	for (i = 0; i < css; i++) {
		if (CHIN (cs, i)) {
			return ((char)i);
		}
	}
	return 0; /* arbitrary */
}

/*
- nch - number of characters in a set
 */
static int nch(struct parse *p, cset *cs) {
	int i;
	size_t css = (size_t)p->g->csetsize;
	int n = 0;

	for (i = 0; i < css; i++) {
		if (CHIN (cs, i)) {
			n++;
		}
	}
	return n;
}

/*
- mcadd - add a collating element to a cset
 */
static void mcadd(struct parse *p, cset *cs, const char *cp) {
	size_t oldend = cs->smultis;
	void *np;

	cs->smultis += strlen (cp) + 1;
	np = realloc (cs->multis, cs->smultis);
	if (!np) {
		free (cs->multis);
		cs->multis = NULL;
		SETERROR (R_REGEX_ESPACE);
		return;
	}
	cs->multis = np;

	r_str_ncpy (cs->multis + oldend, cp, cs->smultis - oldend);
}

/*
- mcinvert - invert the list of collating elements in a cset
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
/* ARGSUSED */
static void mcinvert(struct parse *p, cset *cs) {
	// asert (!cs->multis);	/* xxx */
	return;
}

/*
- mccase - add case counterparts of the list of collating elements in a cset
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
/* ARGSUSED */
static void mccase(struct parse *p, cset *cs) {
	// asert (!cs->multis);	/* xxx */
	return;
}

/*
- isinsets - is this character in any sets?
 */
static int isinsets(struct re_guts *g, int c) {
	ut8 *col;
	int i;
	int ncols = (g->ncsets + (CHAR_BIT - 1)) / CHAR_BIT;
	unsigned uc = (ut8)c;

	for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize) {
		if (col[uc] != 0) {
			return (1);
		}
	}
	return 0;
}

/*
- samesets - are these two characters in exactly the same sets?
 */
static int samesets(struct re_guts *g, int c1, int c2) {
	ut8 *col;
	int i;
	int ncols = (g->ncsets + (CHAR_BIT - 1)) / CHAR_BIT;
	unsigned uc1 = (ut8)c1;
	unsigned uc2 = (ut8)c2;

	for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize) {
		if (col[uc1] != col[uc2]) {
			return (0);
		}
	}
	return 1;
}

/*
- categorize - sort out character categories
 */
static void categorize(struct parse *p, struct re_guts *g) {
	cat_t *cats = g? g->categories: NULL;
	unsigned int c;
	unsigned int c2;
	cat_t cat;

	/* avoid making error situations worse */
	if (!p || p->error != 0 || !cats) {
		return;
	}

	for (c = CHAR_MIN; c <= CHAR_MAX; c++) {
		if (*(cats + c) && isinsets (g, c)) {
			cat = g->ncategories++;
			cats[c] = cat;
			for (c2 = c + 1; c2 <= CHAR_MAX; c2++) {
				if (cats[c2] == 0 && samesets (g, c, c2)) {
					cats[c2] = cat;
				}
			}
		}
	}
}

/*
- dupl - emit a duplicate of a bunch of sops
 */
static sopno /* start of duplicate */
dupl(struct parse *p,
	sopno start, /* from here */
	sopno finish) /* to this less one */
{
	sopno ret = HERE ();
	sopno len = finish - start;
	sopno i;

	if (finish >= start) {
		if (len == 0) {
			return (ret);
		}
		enlarge (p, p->ssize + len); /* this many unexpected additions */
		if (p->ssize >= p->slen + len) {
			for (i = 0; i < len; i++) {
				p->strip[p->slen + i] = p->strip[start + i];
			}
			p->slen += len;
			return ret;
		}
	}
	return ret;
}

/*
- doemit - emit a strip operator
 *
 * It might seem better to implement this as a macro with a function as
 * hard-case backup, but it's just too big and messy unless there are
 * some changes to the data structures.  Maybe later.
 */
static void doemit(struct parse *p, sop op, size_t opnd) {
	/* avoid making error situations worse */
	if (p->error != 0) {
		return;
	}

	/* deal with oversize operands ("can't happen", more or less) */
	if (opnd < 1 << OPSHIFT) {

		/* deal with undersized strip */
		if (p->slen >= p->ssize) {
			enlarge (p, (p->ssize + 1) / 2 * 3); /* +50% */
		}
		if (p->slen < p->ssize) {
			/* finally, it's all reduced to the easy case */
			p->strip[p->slen++] = SOP (op, opnd);
		}
	}
}

/*
- doinsert - insert a sop into the strip
 */
static void doinsert(struct parse *p, sop op, size_t opnd, sopno pos) {
	sopno sn;
	sopno i;
	sop s;

	/* avoid making error situations worse */
	if (p->error != 0) {
		return;
	}

	sn = HERE ();
	EMIT (op, opnd); /* do checks, ensure space */
	if (HERE () != sn + 1) {
		return;
	}
	s = p->strip[sn];

	/* adjust paren pointers */
	if (pos > 0) {
		int j;
		for (j = 1; j < NPAREN; j++) {
			if (p->pbegin[j] >= pos) {
				p->pbegin[j]++;
			}
			if (p->pend[j] >= pos) {
				p->pend[j]++;
			}
		}
	}
	for (i = sn; i > pos; i--) {
		p->strip[i] = p->strip[i - 1];
	}
	p->strip[pos] = s;
}

/*
- dofwd - complete a forward reference
 */
static void dofwd(struct parse *p, sopno pos, sop value) {
	/* avoid making error situations worse */
	if (p->error != 0) {
		return;
	}

	if (value < 1 << OPSHIFT) {
		p->strip[pos] = OP (p->strip[pos]) | value;
	}
}

/*
- enlarge - enlarge the strip
 */
static void enlarge(struct parse *p, sopno size) {
	sop *sp;

	if (p->ssize >= size) {
		return;
	}
	if (size > MAXSTRIP) { /* e.g. (((a{255}){255}){255}){255} */
		SETERROR (R_REGEX_ESPACE);
		return;
	}

	sp = (sop *)realloc (p->strip, size * sizeof (sop));
	if (!sp) {
		SETERROR (R_REGEX_ESPACE);
		return;
	}
	p->strip = sp;
	p->ssize = size;
}

/*
- stripsnug - compact the strip
 */
static void stripsnug(struct parse *p, struct re_guts *g) {
	g->nstates = p->slen;
	g->strip = (sop *)realloc ((char *)p->strip, p->slen * sizeof (sop));
	if (!g->strip) {
		SETERROR (R_REGEX_ESPACE);
		g->strip = p->strip;
	}
}

/*
- findmust - fill in must and mlen with longest mandatory literal string
 *
 * This algorithm could do fancy things like analyzing the operands of |
 * for common subsequences.  Someday.  This code is simple and finds most
 * of the interesting cases.
 *
 * Note that must and mlen got initialized during setup.
 */
static void findmust(struct parse *p, struct re_guts *g) {
	sop *scan;
	sop *start = NULL; /* start initialized in the default case, after that */
	sop *newstart = NULL; /* newstart was initialized in the OCHAR case */
	sopno newlen;
	sop s;
	char *cp;
	sopno i;

	/* avoid making error situations worse */
	if (p->error != 0) {
		return;
	}

	/* find the longest OCHAR sequence in strip */
	newlen = 0;
	start = scan = g->strip + 1;
	do {
		s = *scan++;
		switch (OP (s)) {
		case OCHAR: /* sequence member */
			if (newlen == 0) { /* new sequence */
				newstart = scan - 1;
			}
			newlen++;
			break;
		case OPLUS_: /* things that don't break one */
		case OLPAREN:
		case ORPAREN:
			break;
		case OQUEST_: /* things that must be skipped */
		case OCH_:
			scan--;
			do {
				scan += OPND (s);
				s = *scan;
				/* asert () interferes w debug printouts */
				if (OP (s) != O_QUEST && OP (s) != O_CH &&
					OP (s) != OOR2) {
					g->iflags |= BAD;
					return;
				}
			} while (OP (s) != O_QUEST && OP (s) != O_CH);
			/* fallthrough */
		default: /* things that break a sequence */
			if (newlen > g->mlen) { /* ends one */
				start = newstart;
				g->mlen = newlen;
			}
			newlen = 0;
			break;
		}
	} while (OP (s) != OEND);

	if (g->mlen == 0) { /* there isn't one */
		return;
	}

	/* turn it into a character string */
	g->must = malloc ((size_t)g->mlen + 1);
	if (!g->must) { /* argh; just forget it */
		g->mlen = 0;
		return;
	}
	cp = g->must;
	scan = start;
	for (i = g->mlen; i > 0; i--) {
		while (OP (s = *scan++) != OCHAR) {
			continue;
		}
		if (cp < g->must + g->mlen) {
			*cp++ = (char)OPND (s);
		}
	}
	if (cp == g->must + g->mlen) {
		 *cp++ = '\0'; /* just on general principles */
	}
}

/*
- pluscount - count + nesting
 */
static sopno pluscount(struct parse *p, struct re_guts *g) {
	sop *scan;
	sop s;
	sopno plusnest = 0;
	sopno maxnest = 0;

	if (p->error != 0) {
		return (0); /* there may not be an OEND */
	}

	scan = g->strip + 1;
	do {
		s = *scan++;
		switch (OP (s)) {
		case OPLUS_:
			plusnest++;
			break;
		case O_PLUS:
			if (plusnest > maxnest) {
				maxnest = plusnest;
			}
			plusnest--;
			break;
		}
	} while (OP (s) != OEND);
	if (plusnest != 0) {
		g->iflags |= BAD;
	}
	return maxnest;
}