Initial revision

1 files changed, 1019 insertions, 0 deletions

diff --git a/regex/engine.c b/regex/engine.c
new file mode 100644
index 0000000..919fe3f
--- /dev/null
+++ b/regex/engine.c
@@ -0,0 +1,1019 @@
+/*
+ * 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) */
+	char *offp;		/* offsets work from here */
+	char *beginp;		/* start of string -- virtual NUL precedes */
+	char *endp;		/* end of string -- virtual NUL here */
+	char *coldp;		/* can be no match starting before here */
+	char **lastpos;		/* [nplus+1] */
+	STATEVARS;
+	states st;		/* current states */
+	states fresh;		/* states for a fresh start */
+	states tmp;		/* temporary */
+	states empty;		/* empty set of states */
+};
+
+#include "engine.ih"
+
+#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(register struct re_guts *g, char *string, \
+ ==	size_t nmatch, regmatch_t pmatch[], int eflags);
+ */
+static int			/* 0 success, REG_NOMATCH failure */
+matcher(g, string, nmatch, pmatch, eflags)
+register struct re_guts *g;
+char *string;
+size_t nmatch;
+regmatch_t pmatch[];
+int eflags;
+{
+	register char *endp;
+	register int i;
+	struct match mv;
+	register struct match *m = &mv;
+	register char *dp;
+	const register sopno gf = g->firststate+1;	/* +1 for OEND */
+	const register sopno gl = g->laststate;
+	char *start;
+	char *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;
+		stop = start + strlen(start);
+	}
+	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 &&
+				memcmp(dp, g->must, (size_t)g->mlen) == 0)
+				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 = (char **)malloc((g->nplus+1) *
+							sizeof(char *));
+			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((char *)m->pmatch);
+	if (m->lastpos != NULL)
+		free((char *)m->lastpos);
+	STATETEARDOWN(m);
+	return(0);
+}
+
+/*
+ - dissect - figure out what matched what, no back references
+ == static char *dissect(register struct match *m, char *start, \
+ ==	char *stop, sopno startst, sopno stopst);
+ */
+static char *			/* == stop (success) always */
+dissect(m, start, stop, startst, stopst)
+register struct match *m;
+char *start;
+char *stop;
+sopno startst;
+sopno stopst;
+{
+	register int i;
+	register sopno ss;	/* start sop of current subRE */
+	register sopno es;	/* end sop of current subRE */
+	register char *sp;	/* start of string matched by it */
+	register char *stp;	/* string matched by it cannot pass here */
+	register char *rest;	/* start of rest of string */
+	register char *tail;	/* string unmatched by rest of RE */
+	register sopno ssub;	/* start sop of subsubRE */
+	register sopno esub;	/* end sop of subsubRE */
+	register char *ssp;	/* start of string matched by subsubRE */
+	register char *sep;	/* end of string matched by subsubRE */
+	register char *oldssp;	/* previous ssp */
+	register char *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(register struct match *m, char *start, \
+ ==	char *stop, sopno startst, sopno stopst, sopno lev);
+ */
+static char *			/* == stop (success) or NULL (failure) */
+backref(m, start, stop, startst, stopst, lev)
+register struct match *m;
+char *start;
+char *stop;
+sopno startst;
+sopno stopst;
+sopno lev;			/* PLUS nesting level */
+{
+	register int i;
+	register sopno ss;	/* start sop of current subRE */
+	register char *sp;	/* start of string matched by it */
+	register sopno ssub;	/* start sop of subsubRE */
+	register sopno esub;	/* end sop of subsubRE */
+	register char *ssp;	/* start of string matched by subsubRE */
+	register char *dp;
+	register size_t len;
+	register int hard;
+	register sop s;
+	register regoff_t offsave;
+	register 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++ != (char)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((char *)NULL);	/* dummy */
+}
+
+/*
+ - fast - step through the string at top speed
+ == static char *fast(register struct match *m, char *start, \
+ ==	char *stop, sopno startst, sopno stopst);
+ */
+static char *			/* where tentative match ended, or NULL */
+fast(m, start, stop, startst, stopst)
+register struct match *m;
+char *start;
+char *stop;
+sopno startst;
+sopno stopst;
+{
+	register states st = m->st;
+	register states fresh = m->fresh;
+	register states tmp = m->tmp;
+	register char *p = start;
+	register int c = (start == m->beginp) ? OUT : *(start-1);
+	register int lastc;	/* previous c */
+	register int flagch;
+	register int i;
+	register char *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(register struct match *m, char *start, \
+ ==	char *stop, sopno startst, sopno stopst);
+ */
+static char *			/* where it ended */
+slow(m, start, stop, startst, stopst)
+register struct match *m;
+char *start;
+char *stop;
+sopno startst;
+sopno stopst;
+{
+	register states st = m->st;
+	register states empty = m->empty;
+	register states tmp = m->tmp;
+	register char *p = start;
+	register int c = (start == m->beginp) ? OUT : *(start-1);
+	register int lastc;	/* previous c */
+	register int flagch;
+	register int i;
+	register char *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(register struct re_guts *g, sopno start, sopno stop, \
+ ==	register states bef, int ch, register 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)
+register struct re_guts *g;
+sopno start;			/* start state within strip */
+sopno stop;			/* state after stop state within strip */
+register states bef;		/* states reachable before */
+int ch;				/* character or NONCHAR code */
+register states aft;		/* states already known reachable after */
+{
+	register cset *cs;
+	register sop s;
+	register sopno pc;
+	register onestate here;		/* note, macros know this name */
+	register sopno look;
+	register long 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 != (char)OPND(s));
+			if (ch == (char)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;
+char *caption;
+states st;
+int ch;
+FILE *d;
+{
+	register struct re_guts *g = m->g;
+	register int i;
+	register 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, char *title, char *start, char *stop, \
+ ==						sopno startst, sopno stopst);
+ == #endif
+ */
+static void
+at(m, title, start, stop, startst, stopst)
+struct match *m;
+char *title;
+char *start;
+char *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 char *			/* -> representation */
+pchar(ch)
+int ch;
+{
+	static char pbuf[10];
+
+	if (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