/*-
 * 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. All advertising materials mentioning features or use of this software
 *	  must display the following acknowledgement:
 *		This product includes software developed by the University of
 *		California, Berkeley and its contributors.
 * 4. 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.
 *
 *		@(#)engine.c	8.5 (Berkeley) 3/20/94
 */

/*
 * The matching engine and friends.  This file is #included by regexec.c
 * after suitable #defines of a variety of macros used herein, so that
 * different state representations can be used without duplicating masses
 * of code.
 */

#ifdef SNAMES
#define matcher smatcher
#define fast	sfast
#define slow	sslow
#define dissect sdissect
#define backref sbackref
#define step	sstep
#define print	sprint
#define at		sat
#define match	smat
#endif
#ifdef LNAMES
#define matcher lmatcher
#define fast	lfast
#define slow	lslow
#define dissect ldissect
#define backref lbackref
#define step	lstep
#define print	lprint
#define at		lat
#define match	lmat
#endif

/* another structure passed up and down to avoid zillions of parameters */
struct match
{
	struct re_guts *g;
	int			eflags;
	regmatch_t *pmatch;			/* [nsub+1] (0 element unused) */
	pg_wchar   *offp;			/* offsets work from here */
	pg_wchar   *beginp;			/* start of string -- virtual NUL precedes */
	pg_wchar   *endp;			/* end of string -- virtual NUL here */
	pg_wchar   *coldp;			/* can be no match starting before here */
	pg_wchar   **lastpos;		/* [nplus+1] */
				STATEVARS;
	states		st;				/* current states */
	states		fresh;			/* states for a fresh start */
	states		tmp;			/* temporary */
	states		empty;			/* empty set of states */
};

/* ========= begin header generated by ./mkh ========= */
#ifdef __cplusplus
extern		"C"
{
#endif

/* === engine.c === */
	static int
				matcher(struct re_guts * g, pg_wchar *string, size_t nmatch,
									regmatch_t pmatch[], int eflags);
	static pg_wchar *
				dissect(struct match * m, pg_wchar *start, pg_wchar *stop,
									sopno startst, sopno stopst);
	static pg_wchar *
				backref(struct match * m, pg_wchar *start, pg_wchar *stop,
								 sopno startst, sopno stopst, sopno lev);
	static pg_wchar *
				fast(struct match * m, pg_wchar *start, pg_wchar *stop,
								 sopno startst, sopno stopst);
	static pg_wchar *
				slow(struct match * m, pg_wchar *start, pg_wchar *stop, sopno startst, sopno stopst);
	static		states
				step(struct re_guts * g, sopno start,
							 sopno stop, states bef, int ch, states aft);
#define BOL		(OUT+1)
#define EOL		(BOL+1)
#define BOLEOL	(BOL+2)
#define NOTHING (BOL+3)
#define BOW		(BOL+4)
#define EOW		(BOL+5)
#define CODEMAX (BOL+5)			/* highest code used */

#ifdef MB
#  if MB == MULE_INTERNAL
#    define NONCHAR(c)	((c) > 16777216)	/* 16777216 == 2^24 == 3 bytes */
#    define NNONCHAR	(CODEMAX-16777216)
#  elif MB == EUC_JP || MB == EUC_CN || MB == EUC_KR || MB == EUC_TW
#    define NONCHAR(c)	((c) > USHRT_MAX)
#    define NNONCHAR	(CODEMAX-USHRT_MAX)
#  elif MB == UNICODE
#    define NONCHAR(c)	((c) > USHRT_MAX)
#    define NNONCHAR	(CODEMAX-USHRT_MAX)
#  endif
#else
#  define NONCHAR(c)		((c) > CHAR_MAX)
#  define NNONCHAR		(CODEMAX-CHAR_MAX)
#endif

#ifdef REDEBUG
	static void
				print(struct match * m, pg_wchar *caption, states st, int ch, FILE *d);
#endif
#ifdef REDEBUG
	static void
				at(struct match * m, pg_wchar *title, pg_wchar *start, pg_wchar *stop,
							   sopno startst, sopno stopst);
#endif
#ifdef REDEBUG
	static pg_wchar *
				p_char(int ch);
#endif

#ifdef __cplusplus
}

#endif
/* ========= end header generated by ./mkh ========= */

#ifdef REDEBUG
#define SP(t, s, c)		print(m, t, s, c, stdout)
#define AT(t, p1, p2, s1, s2)	at(m, t, p1, p2, s1, s2)
#define NOTE(str)		{ if (m->eflags&REG_TRACE) printf("=%s\n", (str)); }
#else
#define SP(t, s, c)				/* nothing */
#define AT(t, p1, p2, s1, s2)	/* nothing */
#define NOTE(s)					/* nothing */
#endif

/*
 - matcher - the actual matching engine
 == static int matcher(struct re_guts *g, pg_wchar *string, \
 ==		size_t nmatch, regmatch_t pmatch[], int eflags);
 */
static int						/* 0 success, REG_NOMATCH failure */
matcher(g, string, nmatch, pmatch, eflags)
struct re_guts *g;
pg_wchar	   *string;
size_t		nmatch;
regmatch_t	pmatch[];
int			eflags;
{
	pg_wchar	   *endp;
	int			i;
	struct match mv;
	struct match *m = &mv;
	pg_wchar	   *dp;
	const sopno gf = g->firststate + 1; /* +1 for OEND */
	const sopno gl = g->laststate;
	pg_wchar	   *start;
	pg_wchar	   *stop;

	/* simplify the situation where possible */
	if (g->cflags & REG_NOSUB)
		nmatch = 0;
	if (eflags & REG_STARTEND)
	{
		start = string + pmatch[0].rm_so;
		stop = string + pmatch[0].rm_eo;
	}
	else
	{
		start = string;
#ifdef MB
		stop = start + pg_wchar_strlen(start);
#else
		stop = start + strlen(start);
#endif
	}
	if (stop < start)
		return (REG_INVARG);

	/* prescreening; this does wonders for this rather slow code */
	if (g->must != NULL)
	{
		for (dp = start; dp < stop; dp++)
			if (*dp == g->must[0] && stop - dp >= g->mlen &&
#ifdef MB
				memcmp(dp, g->must, (size_t) (g->mlen * sizeof(pg_wchar))) == 0)
#else
				memcmp(dp, g->must, (size_t) g->mlen) == 0)
#endif
				break;
		if (dp == stop)			/* we didn't find g->must */
			return (REG_NOMATCH);
	}

	/* match struct setup */
	m->g = g;
	m->eflags = eflags;
	m->pmatch = NULL;
	m->lastpos = NULL;
	m->offp = string;
	m->beginp = start;
	m->endp = stop;
	STATESETUP(m, 4);
	SETUP(m->st);
	SETUP(m->fresh);
	SETUP(m->tmp);
	SETUP(m->empty);
	CLEAR(m->empty);

	/* this loop does only one repetition except for backrefs */
	for (;;)
	{
		endp = fast(m, start, stop, gf, gl);
		if (endp == NULL)
		{						/* a miss */
			STATETEARDOWN(m);
			return (REG_NOMATCH);
		}
		if (nmatch == 0 && !g->backrefs)
			break;				/* no further info needed */

		/* where? */
		assert(m->coldp != NULL);
		for (;;)
		{
			NOTE("finding start");
			endp = slow(m, m->coldp, stop, gf, gl);
			if (endp != NULL)
				break;
			assert(m->coldp < m->endp);
			m->coldp++;
		}
		if (nmatch == 1 && !g->backrefs)
			break;				/* no further info needed */

		/* oh my, he wants the subexpressions... */
		if (m->pmatch == NULL)
			m->pmatch = (regmatch_t *) malloc((m->g->nsub + 1) *
											  sizeof(regmatch_t));
		if (m->pmatch == NULL)
		{
			STATETEARDOWN(m);
			return (REG_ESPACE);
		}
		for (i = 1; i <= m->g->nsub; i++)
			m->pmatch[i].rm_so = m->pmatch[i].rm_eo = -1;
		if (!g->backrefs && !(m->eflags & REG_BACKR))
		{
			NOTE("dissecting");
			dp = dissect(m, m->coldp, endp, gf, gl);
		}
		else
		{
			if (g->nplus > 0 && m->lastpos == NULL)
				m->lastpos = (pg_wchar **) malloc((g->nplus + 1) *
											  sizeof(pg_wchar *));
			if (g->nplus > 0 && m->lastpos == NULL)
			{
				free(m->pmatch);
				STATETEARDOWN(m);
				return (REG_ESPACE);
			}
			NOTE("backref dissect");
			dp = backref(m, m->coldp, endp, gf, gl, (sopno) 0);
		}
		if (dp != NULL)
			break;

		/* uh-oh... we couldn't find a subexpression-level match */
		assert(g->backrefs);	/* must be back references doing it */
		assert(g->nplus == 0 || m->lastpos != NULL);
		for (;;)
		{
			if (dp != NULL || endp <= m->coldp)
				break;			/* defeat */
			NOTE("backoff");
			endp = slow(m, m->coldp, endp - 1, gf, gl);
			if (endp == NULL)
				break;			/* defeat */
			/* try it on a shorter possibility */
#ifndef NDEBUG
			for (i = 1; i <= m->g->nsub; i++)
			{
				assert(m->pmatch[i].rm_so == -1);
				assert(m->pmatch[i].rm_eo == -1);
			}
#endif
			NOTE("backoff dissect");
			dp = backref(m, m->coldp, endp, gf, gl, (sopno) 0);
		}
		assert(dp == NULL || dp == endp);
		if (dp != NULL)			/* found a shorter one */
			break;

		/* despite initial appearances, there is no match here */
		NOTE("false alarm");
		start = m->coldp + 1;	/* recycle starting later */
		assert(start <= stop);
	}

	/* fill in the details if requested */
	if (nmatch > 0)
	{
		pmatch[0].rm_so = m->coldp - m->offp;
		pmatch[0].rm_eo = endp - m->offp;
	}
	if (nmatch > 1)
	{
		assert(m->pmatch != NULL);
		for (i = 1; i < nmatch; i++)
			if (i <= m->g->nsub)
				pmatch[i] = m->pmatch[i];
			else
			{
				pmatch[i].rm_so = -1;
				pmatch[i].rm_eo = -1;
			}
	}

	if (m->pmatch != NULL)
		free((pg_wchar *) m->pmatch);
	if (m->lastpos != NULL)
		free((pg_wchar *) m->lastpos);
	STATETEARDOWN(m);
	return (0);
}

/*
 - dissect - figure out what matched what, no back references
 == static char *dissect(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst);
 */
static pg_wchar *				/* == stop (success) always */
dissect(m, start, stop, startst, stopst)
struct match *m;
pg_wchar	   *start;
pg_wchar	   *stop;
sopno		startst;
sopno		stopst;
{
	int			i;
	sopno		ss;				/* start sop of current subRE */
	sopno		es;				/* end sop of current subRE */
	pg_wchar	   *sp;			/* start of string matched by it */
	pg_wchar	   *stp;		/* string matched by it cannot pass here */
	pg_wchar	   *rest;		/* start of rest of string */
	pg_wchar	   *tail;		/* string unmatched by rest of RE */
	sopno		ssub;			/* start sop of subsubRE */
	sopno		esub;			/* end sop of subsubRE */
	pg_wchar	   *ssp;		/* start of string matched by subsubRE */
	pg_wchar	   *sep;		/* end of string matched by subsubRE */
	pg_wchar	   *oldssp;		/* previous ssp */
	pg_wchar	   *dp;

	AT("diss", start, stop, startst, stopst);
	sp = start;
	for (ss = startst; ss < stopst; ss = es)
	{
		/* identify end of subRE */
		es = ss;
		switch (OP(m->g->strip[es]))
		{
			case OPLUS_:
			case OQUEST_:
				es += OPND(m->g->strip[es]);
				break;
			case OCH_:
				while (OP(m->g->strip[es]) != O_CH)
					es += OPND(m->g->strip[es]);
				break;
		}
		es++;

		/* figure out what it matched */
		switch (OP(m->g->strip[ss]))
		{
			case OEND:
				assert(nope);
				break;
			case OCHAR:
				sp++;
				break;
			case OBOL:
			case OEOL:
			case OBOW:
			case OEOW:
				break;
			case OANY:
			case OANYOF:
				sp++;
				break;
			case OBACK_:
			case O_BACK:
				assert(nope);
				break;
				/* cases where length of match is hard to find */
			case OQUEST_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = es - 1;
				/* did innards match? */
				if (slow(m, sp, rest, ssub, esub) != NULL)
				{
					dp = dissect(m, sp, rest, ssub, esub);
					assert(dp == rest);
				}
				else
/* no */
					assert(sp == rest);
				sp = rest;
				break;
			case OPLUS_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = es - 1;
				ssp = sp;
				oldssp = ssp;
				for (;;)
				{				/* find last match of innards */
					sep = slow(m, ssp, rest, ssub, esub);
					if (sep == NULL || sep == ssp)
						break;	/* failed or matched null */
					oldssp = ssp;		/* on to next try */
					ssp = sep;
				}
				if (sep == NULL)
				{
					/* last successful match */
					sep = ssp;
					ssp = oldssp;
				}
				assert(sep == rest);	/* must exhaust substring */
				assert(slow(m, ssp, sep, ssub, esub) == rest);
				dp = dissect(m, ssp, sep, ssub, esub);
				assert(dp == sep);
				sp = rest;
				break;
			case OCH_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = ss + OPND(m->g->strip[ss]) - 1;
				assert(OP(m->g->strip[esub]) == OOR1);
				for (;;)
				{				/* find first matching branch */
					if (slow(m, sp, rest, ssub, esub) == rest)
						break;	/* it matched all of it */
					/* that one missed, try next one */
					assert(OP(m->g->strip[esub]) == OOR1);
					esub++;
					assert(OP(m->g->strip[esub]) == OOR2);
					ssub = esub + 1;
					esub += OPND(m->g->strip[esub]);
					if (OP(m->g->strip[esub]) == OOR2)
						esub--;
					else
						assert(OP(m->g->strip[esub]) == O_CH);
				}
				dp = dissect(m, sp, rest, ssub, esub);
				assert(dp == rest);
				sp = rest;
				break;
			case O_PLUS:
			case O_QUEST:
			case OOR1:
			case OOR2:
			case O_CH:
				assert(nope);
				break;
			case OLPAREN:
				i = OPND(m->g->strip[ss]);
				assert(0 < i && i <= m->g->nsub);
				m->pmatch[i].rm_so = sp - m->offp;
				break;
			case ORPAREN:
				i = OPND(m->g->strip[ss]);
				assert(0 < i && i <= m->g->nsub);
				m->pmatch[i].rm_eo = sp - m->offp;
				break;
			default:			/* uh oh */
				assert(nope);
				break;
		}
	}

	assert(sp == stop);
	return (sp);
}

/*
 - backref - figure out what matched what, figuring in back references
 == static char *backref(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst, sopno lev);
 */
static pg_wchar *		/* == stop (success) or NULL (failure) */
backref(m, start, stop, startst, stopst, lev)
struct match *m;
pg_wchar	   *start;
pg_wchar	   *stop;
sopno		startst;
sopno		stopst;
sopno		lev;				/* PLUS nesting level */
{
	int			i;
	sopno		ss;				/* start sop of current subRE */
	pg_wchar	   *sp;			/* start of string matched by it */
	sopno		ssub;			/* start sop of subsubRE */
	sopno		esub;			/* end sop of subsubRE */
	pg_wchar	   *ssp;		/* start of string matched by subsubRE */
	pg_wchar	   *dp;
	size_t		len;
	int			hard;
	sop			s;
	regoff_t	offsave;
	cset	   *cs;

	AT("back", start, stop, startst, stopst);
	sp = start;

	/* get as far as we can with easy stuff */
	hard = 0;
	for (ss = startst; !hard && ss < stopst; ss++)
		switch (OP(s = m->g->strip[ss]))
		{
			case OCHAR:
				if (sp == stop || *sp++ != (pg_wchar) OPND(s))
					return (NULL);
				break;
			case OANY:
				if (sp == stop)
					return (NULL);
				sp++;
				break;
			case OANYOF:
				cs = &m->g->sets[OPND(s)];
				if (sp == stop || !CHIN(cs, *sp++))
					return (NULL);
				break;
			case OBOL:
				if ((sp == m->beginp && !(m->eflags & REG_NOTBOL)) ||
					(sp < m->endp && *(sp - 1) == '\n' &&
					 (m->g->cflags & REG_NEWLINE)))
				{				/* yes */
				}
				else
					return (NULL);
				break;
			case OEOL:
				if ((sp == m->endp && !(m->eflags & REG_NOTEOL)) ||
					(sp < m->endp && *sp == '\n' &&
					 (m->g->cflags & REG_NEWLINE)))
				{				/* yes */
				}
				else
					return (NULL);
				break;
			case OBOW:
				if (((sp == m->beginp && !(m->eflags & REG_NOTBOL)) ||
					 (sp < m->endp && *(sp - 1) == '\n' &&
					  (m->g->cflags & REG_NEWLINE)) ||
					 (sp > m->beginp &&
					  !ISWORD(*(sp - 1)))) &&
					(sp < m->endp && ISWORD(*sp)))
				{				/* yes */
				}
				else
					return (NULL);
				break;
			case OEOW:
				if (((sp == m->endp && !(m->eflags & REG_NOTEOL)) ||
					 (sp < m->endp && *sp == '\n' &&
					  (m->g->cflags & REG_NEWLINE)) ||
					 (sp < m->endp && !ISWORD(*sp))) &&
					(sp > m->beginp && ISWORD(*(sp - 1))))
				{				/* yes */
				}
				else
					return (NULL);
				break;
			case O_QUEST:
				break;
			case OOR1:			/* matches null but needs to skip */
				ss++;
				s = m->g->strip[ss];
				do
				{
					assert(OP(s) == OOR2);
					ss += OPND(s);
				} while (OP(s = m->g->strip[ss]) != O_CH);
				/* note that the ss++ gets us past the O_CH */
				break;
			default:			/* have to make a choice */
				hard = 1;
				break;
		}
	if (!hard)
	{							/* that was it! */
		if (sp != stop)
			return (NULL);
		return (sp);
	}
	ss--;						/* adjust for the for's final increment */

	/* the hard stuff */
	AT("hard", sp, stop, ss, stopst);
	s = m->g->strip[ss];
	switch (OP(s))
	{
		case OBACK_:			/* the vilest depths */
			i = OPND(s);
			assert(0 < i && i <= m->g->nsub);
			if (m->pmatch[i].rm_eo == -1)
				return (NULL);
			assert(m->pmatch[i].rm_so != -1);
			len = m->pmatch[i].rm_eo - m->pmatch[i].rm_so;
			assert(stop - m->beginp >= len);
			if (sp > stop - len)
				return (NULL);	/* not enough left to match */
			ssp = m->offp + m->pmatch[i].rm_so;
			if (memcmp(sp, ssp, len) != 0)
				return (NULL);
			while (m->g->strip[ss] != SOP(O_BACK, i))
				ss++;
			return (backref(m, sp + len, stop, ss + 1, stopst, lev));
			break;
		case OQUEST_:			/* to null or not */
			dp = backref(m, sp, stop, ss + 1, stopst, lev);
			if (dp != NULL)
				return (dp);	/* not */
			return (backref(m, sp, stop, ss + OPND(s) + 1, stopst, lev));
			break;
		case OPLUS_:
			assert(m->lastpos != NULL);
			assert(lev + 1 <= m->g->nplus);
			m->lastpos[lev + 1] = sp;
			return (backref(m, sp, stop, ss + 1, stopst, lev + 1));
			break;
		case O_PLUS:
			if (sp == m->lastpos[lev])	/* last pass matched null */
				return (backref(m, sp, stop, ss + 1, stopst, lev - 1));
			/* try another pass */
			m->lastpos[lev] = sp;
			dp = backref(m, sp, stop, ss - OPND(s) + 1, stopst, lev);
			if (dp == NULL)
				return (backref(m, sp, stop, ss + 1, stopst, lev - 1));
			else
				return (dp);
			break;
		case OCH_:				/* find the right one, if any */
			ssub = ss + 1;
			esub = ss + OPND(s) - 1;
			assert(OP(m->g->strip[esub]) == OOR1);
			for (;;)
			{					/* find first matching branch */
				dp = backref(m, sp, stop, ssub, esub, lev);
				if (dp != NULL)
					return (dp);
				/* that one missed, try next one */
				if (OP(m->g->strip[esub]) == O_CH)
					return (NULL);		/* there is none */
				esub++;
				assert(OP(m->g->strip[esub]) == OOR2);
				ssub = esub + 1;
				esub += OPND(m->g->strip[esub]);
				if (OP(m->g->strip[esub]) == OOR2)
					esub--;
				else
					assert(OP(m->g->strip[esub]) == O_CH);
			}
			break;
		case OLPAREN:			/* must undo assignment if rest fails */
			i = OPND(s);
			assert(0 < i && i <= m->g->nsub);
			offsave = m->pmatch[i].rm_so;
			m->pmatch[i].rm_so = sp - m->offp;
			dp = backref(m, sp, stop, ss + 1, stopst, lev);
			if (dp != NULL)
				return (dp);
			m->pmatch[i].rm_so = offsave;
			return (NULL);
			break;
		case ORPAREN:			/* must undo assignment if rest fails */
			i = OPND(s);
			assert(0 < i && i <= m->g->nsub);
			offsave = m->pmatch[i].rm_eo;
			m->pmatch[i].rm_eo = sp - m->offp;
			dp = backref(m, sp, stop, ss + 1, stopst, lev);
			if (dp != NULL)
				return (dp);
			m->pmatch[i].rm_eo = offsave;
			return (NULL);
			break;
		default:				/* uh oh */
			assert(nope);
			break;
	}

	/* "can't happen" */
	assert(nope);
	/* NOTREACHED */
	return 0;
}

/*
 - fast - step through the string at top speed
 == static char *fast(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst);
 */
static pg_wchar *		/* where tentative match ended, or NULL */
fast(m, start, stop, startst, stopst)
struct match *m;
pg_wchar	   *start;
pg_wchar	   *stop;
sopno		startst;
sopno		stopst;
{
	states		st = m->st;
	states		fresh = m->fresh;
	states		tmp = m->tmp;
	pg_wchar	   *p = start;
	int			c = (start == m->beginp) ? OUT : *(start - 1);
	int			lastc;			/* previous c */
	int			flagch;
	int			i;
	pg_wchar	   *coldp;		/* last p after which no match was
								 * underway */

	CLEAR(st);
	SET1(st, startst);
	st = step(m->g, startst, stopst, st, NOTHING, st);
	ASSIGN(fresh, st);
	SP("start", st, *p);
	coldp = NULL;
	for (;;)
	{
		/* next character */
		lastc = c;
		c = (p == m->endp) ? OUT : *p;
		if (EQ(st, fresh))
			coldp = p;

		/* is there an EOL and/or BOL between lastc and c? */
		flagch = '\0';
		i = 0;
		if ((lastc == '\n' && m->g->cflags & REG_NEWLINE) ||
			(lastc == OUT && !(m->eflags & REG_NOTBOL)))
		{
			flagch = BOL;
			i = m->g->nbol;
		}
		if ((c == '\n' && m->g->cflags & REG_NEWLINE) ||
			(c == OUT && !(m->eflags & REG_NOTEOL)))
		{
			flagch = (flagch == BOL) ? BOLEOL : EOL;
			i += m->g->neol;
		}
		if (i != 0)
		{
			for (; i > 0; i--)
				st = step(m->g, startst, stopst, st, flagch, st);
			SP("boleol", st, c);
		}

		/* how about a word boundary? */
		if ((flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
			(c != OUT && ISWORD(c)))
		{
			flagch = BOW;
		}
		if ((lastc != OUT && ISWORD(lastc)) &&
			(flagch == EOL || (c != OUT && !ISWORD(c))))
		{
			flagch = EOW;
		}
		if (flagch == BOW || flagch == EOW)
		{
			st = step(m->g, startst, stopst, st, flagch, st);
			SP("boweow", st, c);
		}

		/* are we done? */
		if (ISSET(st, stopst) || p == stop)
			break;				/* NOTE BREAK OUT */

		/* no, we must deal with this character */
		ASSIGN(tmp, st);
		ASSIGN(st, fresh);
		assert(c != OUT);
		st = step(m->g, startst, stopst, tmp, c, st);
		SP("aft", st, c);
		assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
		p++;
	}

	assert(coldp != NULL);
	m->coldp = coldp;
	if (ISSET(st, stopst))
		return (p + 1);
	else
		return (NULL);
}

/*
 - slow - step through the string more deliberately
 == static char *slow(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst);
 */
static pg_wchar *					/* where it ended */
slow(m, start, stop, startst, stopst)
struct match *m;
pg_wchar	   *start;
pg_wchar	   *stop;
sopno		startst;
sopno		stopst;
{
	states		st = m->st;
	states		empty = m->empty;
	states		tmp = m->tmp;
	pg_wchar	   *p = start;
	int			c = (start == m->beginp) ? OUT : *(start - 1);
	int			lastc;			/* previous c */
	int			flagch;
	int			i;
	pg_wchar	   *matchp;	/* last p at which a match ended */

	AT("slow", start, stop, startst, stopst);
	CLEAR(st);
	SET1(st, startst);
	SP("sstart", st, *p);
	st = step(m->g, startst, stopst, st, NOTHING, st);
	matchp = NULL;
	for (;;)
	{
		/* next character */
		lastc = c;
		c = (p == m->endp) ? OUT : *p;

		/* is there an EOL and/or BOL between lastc and c? */
		flagch = '\0';
		i = 0;
		if ((lastc == '\n' && m->g->cflags & REG_NEWLINE) ||
			(lastc == OUT && !(m->eflags & REG_NOTBOL)))
		{
			flagch = BOL;
			i = m->g->nbol;
		}
		if ((c == '\n' && m->g->cflags & REG_NEWLINE) ||
			(c == OUT && !(m->eflags & REG_NOTEOL)))
		{
			flagch = (flagch == BOL) ? BOLEOL : EOL;
			i += m->g->neol;
		}
		if (i != 0)
		{
			for (; i > 0; i--)
				st = step(m->g, startst, stopst, st, flagch, st);
			SP("sboleol", st, c);
		}

		/* how about a word boundary? */
		if ((flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
			(c != OUT && ISWORD(c)))
		{
			flagch = BOW;
		}
		if ((lastc != OUT && ISWORD(lastc)) &&
			(flagch == EOL || (c != OUT && !ISWORD(c))))
		{
			flagch = EOW;
		}
		if (flagch == BOW || flagch == EOW)
		{
			st = step(m->g, startst, stopst, st, flagch, st);
			SP("sboweow", st, c);
		}

		/* are we done? */
		if (ISSET(st, stopst))
			matchp = p;
		if (EQ(st, empty) || p == stop)
			break;				/* NOTE BREAK OUT */

		/* no, we must deal with this character */
		ASSIGN(tmp, st);
		ASSIGN(st, empty);
		assert(c != OUT);
		st = step(m->g, startst, stopst, tmp, c, st);
		SP("saft", st, c);
		assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
		p++;
	}

	return (matchp);
}


/*
 - step - map set of states reachable before char to set reachable after
 == static states step(struct re_guts *g, sopno start, sopno stop, \
 ==		states bef, int ch, states aft);
 == #define		BOL		(OUT+1)
 == #define		EOL		(BOL+1)
 == #define		BOLEOL	(BOL+2)
 == #define		NOTHING (BOL+3)
 == #define		BOW		(BOL+4)
 == #define		EOW		(BOL+5)
 == #define		CODEMAX (BOL+5)			// highest code used
 == #define		NONCHAR(c)		((c) > CHAR_MAX)
 == #define		NNONCHAR		(CODEMAX-CHAR_MAX)
 */
static states
step(g, start, stop, bef, ch, aft)
struct re_guts *g;
sopno		start;				/* start state within strip */
sopno		stop;				/* state after stop state within strip */
states		bef;				/* states reachable before */
int			ch;					/* character or NONCHAR code */
states		aft;				/* states already known reachable after */
{
	cset	   *cs;
	sop			s;
	sopno		pc;
	onestate	here;			/* note, macros know this name */
	sopno		look;
	int			i;

	for (pc = start, INIT(here, pc); pc != stop; pc++, INC(here))
	{
		s = g->strip[pc];
		switch (OP(s))
		{
			case OEND:
				assert(pc == stop - 1);
				break;
			case OCHAR:
				/* only characters can match */
				assert(!NONCHAR(ch) || ch != (pg_wchar) OPND(s));
				if (ch == (pg_wchar) OPND(s))
					FWD(aft, bef, 1);
				break;
			case OBOL:
				if (ch == BOL || ch == BOLEOL)
					FWD(aft, bef, 1);
				break;
			case OEOL:
				if (ch == EOL || ch == BOLEOL)
					FWD(aft, bef, 1);
				break;
			case OBOW:
				if (ch == BOW)
					FWD(aft, bef, 1);
				break;
			case OEOW:
				if (ch == EOW)
					FWD(aft, bef, 1);
				break;
			case OANY:
				if (!NONCHAR(ch))
					FWD(aft, bef, 1);
				break;
			case OANYOF:
				cs = &g->sets[OPND(s)];
				if (!NONCHAR(ch) && CHIN(cs, ch))
					FWD(aft, bef, 1);
				break;
			case OBACK_:		/* ignored here */
			case O_BACK:
				FWD(aft, aft, 1);
				break;
			case OPLUS_:		/* forward, this is just an empty */
				FWD(aft, aft, 1);
				break;
			case O_PLUS:		/* both forward and back */
				FWD(aft, aft, 1);
				i = ISSETBACK(aft, OPND(s));
				BACK(aft, aft, OPND(s));
				if (!i && ISSETBACK(aft, OPND(s)))
				{
					/* oho, must reconsider loop body */
					pc -= OPND(s) + 1;
					INIT(here, pc);
				}
				break;
			case OQUEST_:		/* two branches, both forward */
				FWD(aft, aft, 1);
				FWD(aft, aft, OPND(s));
				break;
			case O_QUEST:		/* just an empty */
				FWD(aft, aft, 1);
				break;
			case OLPAREN:		/* not significant here */
			case ORPAREN:
				FWD(aft, aft, 1);
				break;
			case OCH_:			/* mark the first two branches */
				FWD(aft, aft, 1);
				assert(OP(g->strip[pc + OPND(s)]) == OOR2);
				FWD(aft, aft, OPND(s));
				break;
			case OOR1:			/* done a branch, find the O_CH */
				if (ISSTATEIN(aft, here))
				{
					for (look = 1;
						 OP(s = g->strip[pc + look]) != O_CH;
						 look += OPND(s))
						assert(OP(s) == OOR2);
					FWD(aft, aft, look);
				}
				break;
			case OOR2:			/* propagate OCH_'s marking */
				FWD(aft, aft, 1);
				if (OP(g->strip[pc + OPND(s)]) != O_CH)
				{
					assert(OP(g->strip[pc + OPND(s)]) == OOR2);
					FWD(aft, aft, OPND(s));
				}
				break;
			case O_CH:			/* just empty */
				FWD(aft, aft, 1);
				break;
			default:			/* ooooops... */
				assert(nope);
				break;
		}
	}

	return (aft);
}

#ifdef REDEBUG
/*
 - print - print a set of states
 == #ifdef REDEBUG
 == static void print(struct match *m, char *caption, states st, \
 ==		int ch, FILE *d);
 == #endif
 */
static void
print(m, caption, st, ch, d)
struct match *m;
pg_wchar	   *caption;
states		st;
int			ch;
FILE	   *d;
{
	struct re_guts *g = m->g;
	int			i;
	int			first = 1;

	if (!(m->eflags & REG_TRACE))
		return;

	fprintf(d, "%s", caption);
	if (ch != '\0')
		fprintf(d, " %s", pchar(ch));
	for (i = 0; i < g->nstates; i++)
		if (ISSET(st, i))
		{
			fprintf(d, "%s%d", (first) ? "\t" : ", ", i);
			first = 0;
		}
	fprintf(d, "\n");
}

/*
 - at - print current situation
 == #ifdef REDEBUG
 == static void at(struct match *m, pg_wchar *title, pg_wchar *start, pg_wchar *stop, \
 ==												sopno startst, sopno stopst);
 == #endif
 */
static void
at(m, title, start, stop, startst, stopst)
struct match *m;
pg_wchar	   *title;
pg_wchar	   *start;
pg_wchar	   *stop;
sopno		startst;
sopno		stopst;
{
	if (!(m->eflags & REG_TRACE))
		return;

	printf("%s %s-", title, pchar(*start));
	printf("%s ", pchar(*stop));
	printf("%ld-%ld\n", (long) startst, (long) stopst);
}

#ifndef PCHARDONE
#define PCHARDONE				/* never again */
/*
 - pchar - make a character printable
 == #ifdef REDEBUG
 == static char *pchar(int ch);
 == #endif
 *
 * Is this identical to regchar() over in debug.c?	Well, yes.	But a
 * duplicate here avoids having a debugging-capable regexec.o tied to
 * a matching debug.o, and this is convenient.	It all disappears in
 * the non-debug compilation anyway, so it doesn't matter much.
 */


static int pg_isprint(int c)
{
#ifdef MB
  return(c >= 0 && c <= UCHAR_MAX && isprint(c));
#else
  return(isprint(c));
#endif
}

static pg_wchar *					/* -> representation */
pchar(ch)
int			ch;
{
	static pg_wchar pbuf[10];

	if (pg_isprint(ch) || ch == ' ')
		sprintf(pbuf, "%c", ch);
	else
		sprintf(pbuf, "\\%o", ch);
	return (pbuf);
}

#endif
#endif

#undef	matcher
#undef	fast
#undef	slow
#undef	dissect
#undef	backref
#undef	step
#undef	print
#undef	at
#undef	match
