case '*':               /* match 0 or more... */
		case '+':               /* match 1 or more... */
			if (p == pat)
				return badpat("Empty closure");
			lp = sp;		/* previous opcode */
			if (*lp == CLO)		/* equivalence... */
				break;
			switch(*lp) {

			case BOL:
			case BOT:
			case EOT:
			case BOW:
			case EOW:
			case REF:
				return badpat("Illegal closure");
			default:
				break;
			}

			if (*p == '+')
				for (sp = mp; lp < sp; lp++)
					*mp++ = *lp;

			*mp++ = END;
			*mp++ = END;
			sp = mp;
			while (--mp > lp)
				*mp = mp[-1];
			*mp = CLO;
			mp = sp;
			break;

		case '\\':              /* tags, backrefs... */
			i++;
			switch(*++p) {

			case '<':
				*mp++ = BOW;
				break;
			case '>':
				if (*sp == BOW)
					return badpat("Null pattern inside \\<\\>");
				*mp++ = EOW;
				break;
			case '1':
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
			case '8':
			case '9':
				n = *p-'0';
				if (tagi > 0 && tagstk[tagi] == n)
					return badpat("Cyclical reference");
				if (tagc > n) {
					*mp++ = static_cast<char>(REF);
					*mp++ = static_cast<char>(n);
				}
				else
					return badpat("Undetermined reference");
				break;
			case 'a':
			case 'b':
			case 'n':
			case 'f':
			case 'r':
			case 't':
			case 'v':
				*mp++ = CHR;
				*mp++ = escapeValue(*p);
				break;
			default:
				if (!posix && *p == '(') {
					if (tagc < MAXTAG) {
						tagstk[++tagi] = tagc;
						*mp++ = BOT;
						*mp++ = static_cast<char>(tagc++);
					}
					else
						return badpat("Too many \\(\\) pairs");
				} else if (!posix && *p == ')') {
					if (*sp == BOT)
						return badpat("Null pattern inside \\(\\)");
					if (tagi > 0) {
						*mp++ = static_cast<char>(EOT);
						*mp++ = static_cast<char>(tagstk[tagi--]);
					}
					else
						return badpat("Unmatched \\)");
				} else {
					*mp++ = CHR;
					*mp++ = *p;
				}
			}
			break;

		default :               /* an ordinary char */
			if (posix && *p == '(') {
				if (tagc < MAXTAG) {
					tagstk[++tagi] = tagc;
					*mp++ = BOT;
					*mp++ = static_cast<char>(tagc++);
				}
				else
					return badpat("Too many () pairs");
			} else if (posix && *p == ')') {
				if (*sp == BOT)
					return badpat("Null pattern inside ()");
				if (tagi > 0) {
					*mp++ = static_cast<char>(EOT);
					*mp++ = static_cast<char>(tagstk[tagi--]);
				}
				else
					return badpat("Unmatched )");
			} else if (caseSensitive) {
				*mp++ = CHR;
				*mp++ = *p;
			} else {
				*mp++ = CCL;
				mask = 0;
				ChSetWithCase(*p, false);
				for (n = 0; n < BITBLK; bittab[n++] = (char) 0)
					*mp++ = static_cast<char>(mask ^ bittab[n]);
			}
			break;
		}
		sp = lp;
	}
	if (tagi > 0)
		return badpat((posix ? "Unmatched (" : "Unmatched \\("));
	*mp = END;
	sta = OKP;
	return 0;
}

/*
 * RESearch::Execute:
 *   execute nfa to find a match.
 *
 *  special cases: (nfa[0])
 *      BOL
 *          Match only once, starting from the
 *          beginning.
 *      CHR
 *          First locate the character without
 *          calling PMatch, and if found, call
 *          PMatch for the remaining string.
 *      END
 *          RESearch::Compile failed, poor luser did not
 *          check for it. Fail fast.
 *
 *  If a match is found, bopat[0] and eopat[0] are set
 *  to the beginning and the end of the matched fragment,
 *  respectively.
 *
 */

int RESearch::Execute(CharacterIndexer &ci, int lp, int endp) {
	char c;
	int ep = NOTFOUND;
	char *ap = nfa;

	bol = lp;
	failure = 0;

	Clear();

	switch(*ap) {

	case BOL:			/* anchored: match from BOL only */
		ep = PMatch(ci, lp, endp, ap);
		break;
	case EOL:			/* just searching for end of line normal path doesn't work */
		if (*(ap+1) == END) {
			lp = endp;
			ep = lp;
			break;
		} else {
			return 0;
		}
	case CHR:			/* ordinary char: locate it fast */
		c = *(ap+1);
		while ((lp < endp) && (ci.CharAt(lp) != c))
			lp++;
		if (lp >= endp)	/* if EOS, fail, else fall thru. */
			return 0;
	default:			/* regular matching all the way. */
		while (lp < endp) {
			ep = PMatch(ci, lp, endp, ap);
			if (ep != NOTFOUND)
				break;
			lp++;
		}
		break;
	case END:			/* munged automaton. fail always */
		return 0;
	}
	if (ep == NOTFOUND)
		return 0;

	bopat[0] = lp;
	eopat[0] = ep;
	return 1;
}

/*
 * PMatch: internal routine for the hard part
 *
 *  This code is partly snarfed from an early grep written by
 *  David Conroy. The backref and tag stuff, and various other
 *  innovations are by oz.
 *
 *  special case optimizations: (nfa[n], nfa[n+1])
 *      CLO ANY
 *          We KNOW .* will match everything upto the
 *          end of line. Thus, directly go to the end of
 *          line, without recursive PMatch calls. As in
 *          the other closure cases, the remaining pattern
 *          must be matched by moving backwards on the
 *          string recursively, to find a match for xy
 *          (x is ".*" and y is the remaining pattern)
 *          where the match satisfies the LONGEST match for
 *          x followed by a match for y.
 *      CLO CHR
 *          We can again scan the string forward for the
 *          single char and at the point of failure, we
 *          execute the remaining nfa recursively, same as
 *          above.
 *
 *  At the end of a successful match, bopat[n] and eopat[n]
 *  are set to the beginning and end of subpatterns matched
 *  by tagged expressions (n = 1 to 9).
 */

extern void re_fail(char *,char);

#define isinset(x,y)	((x)[((y)&BLKIND)>>3] & bitarr[(y)&BITIND])

/*
 * skip values for CLO XXX to skip past the closure
 */

#define ANYSKIP 2 	/* [CLO] ANY END          */
#define CHRSKIP 3	/* [CLO] CHR chr END      */
#define CCLSKIP 34	/* [CLO] CCL 32 bytes END */

int RESearch::PMatch(CharacterIndexer &ci, int lp, int endp, char *ap) {
	int op, c, n;
	int e;		/* extra pointer for CLO  */
	int bp;		/* beginning of subpat... */
	int ep;		/* ending of subpat...    */
	int are;	/* to save the line ptr.  */

	while ((op = *ap++) != END)
		switch(op) {

		case CHR:
			if (ci.CharAt(lp++) != *ap++)
				return NOTFOUND;
			break;
		case ANY:
			if (lp++ >= endp)
				return NOTFOUND;
			break;
		case CCL:
			c = ci.CharAt(lp++);
			if (!isinset(ap,c))
				return NOTFOUND;
			ap += BITBLK;
			break;
		case BOL:
			if (lp != bol)
				return NOTFOUND;
			break;
		case EOL:
			if (lp < endp)
				return NOTFOUND;
			break;
		case BOT:
			bopat[*ap++] = lp;
			break;
		case EOT:
			eopat[*ap++] = lp;
			break;
 		case BOW:
			if (lp!=bol && iswordc(ci.CharAt(lp-1)) || !iswordc(ci.CharAt(lp)))
				return NOTFOUND;
			break;
		case EOW:
			if (lp==bol || !iswordc(ci.CharAt(lp-1)) || iswordc(ci.CharAt(lp)))
				return NOTFOUND;
			break;
		case REF:
			n = *ap++;
			bp = bopat[n];
			ep = eopat[n];
			while (bp < ep)
				if (ci.CharAt(bp++) != ci.CharAt(lp++))
					return NOTFOUND;
			break;
		case CLO:
			are = lp;
			switch(*ap) {

			case ANY:
				while (lp < endp)
					lp++;
				n = ANYSKIP;
				break;
			case CHR:
				c = *(ap+1);
				while ((lp < endp) && (c == ci.CharAt(lp)))
					lp++;
				n = CHRSKIP;
				break;
			case CCL:
				while ((lp < endp) && isinset(ap+1,ci.CharAt(lp)))
					lp++;
				n = CCLSKIP;
				break;
			default:
				failure = true;
				//re_fail("closure: bad nfa.", *ap);
				return NOTFOUND;
			}

			ap += n;

			while (lp >= are) {
				if ((e = PMatch(ci, lp, endp, ap)) != NOTFOUND)
					return e;
				--lp;
			}
			return NOTFOUND;
		default:
			//re_fail("RESearch::Execute: bad nfa.", static_cast<char>(op));
			return NOTFOUND;
		}
	return lp;
}

/*
 * RESearch::Substitute:
 *  substitute the matched portions of the src in dst.
 *
 *  &    substitute the entire matched pattern.
 *
 *  \digit  substitute a subpattern, with the given tag number.
 *      Tags are numbered from 1 to 9. If the particular
 *      tagged subpattern does not exist, null is substituted.
 */
int RESearch::Substitute(CharacterIndexer &ci, char *src, char *dst) {
	char c;
	int  pin;
	int bp;
	int ep;

	if (!*src || !bopat[0])
		return 0;

	while ((c = *src++) != 0) {
		switch(c) {

		case '&':
			pin = 0;
			break;

		case '\\':
			c = *src++;
			if (c >= '0' && c <= '9') {
				pin = c - '0';
				break;
			}

		default:
			*dst++ = c;
			continue;
		}

		if ((bp = bopat[pin]) != 0 && (ep = eopat[pin]) != 0) {
			while (ci.CharAt(bp) && bp < ep)
				*dst++ = ci.CharAt(bp++);
			if (bp < ep)
				return 0;
		}
	}
	*dst = (char) 0;
	return 1;
}