1/*
2 * Copyright 2019 Nexenta by DDN, Inc. All rights reserved.
3 * Copyright 2012 Milan Jurik. All rights reserved.
4 * Copyright (c) 2016 by Delphix. All rights reserved.
5 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
6 * Copyright (c) 1992, 1993, 1994
7 *	The Regents of the University of California.  All rights reserved.
8 *
9 * This code is derived from software contributed to Berkeley by
10 * Henry Spencer.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#include <stdbool.h>
38
39/*
40 * The matching engine and friends.  This file is #included by regexec.c
41 * after suitable #defines of a variety of macros used herein, so that
42 * different state representations can be used without duplicating masses
43 * of code.
44 */
45
46#ifdef SNAMES
47#define	stepback sstepback
48#define	matcher	smatcher
49#define	walk	swalk
50#define	dissect	sdissect
51#define	backref	sbackref
52#define	step	sstep
53#define	print	sprint
54#define	at	sat
55#define	match	smat
56#endif
57#ifdef LNAMES
58#define	stepback lstepback
59#define	matcher	lmatcher
60#define	walk	lwalk
61#define	dissect	ldissect
62#define	backref	lbackref
63#define	step	lstep
64#define	print	lprint
65#define	at	lat
66#define	match	lmat
67#endif
68#ifdef MNAMES
69#define	stepback mstepback
70#define	matcher	mmatcher
71#define	walk	mwalk
72#define	dissect	mdissect
73#define	backref	mbackref
74#define	step	mstep
75#define	print	mprint
76#define	at	mat
77#define	match	mmat
78#endif
79
80/* another structure passed up and down to avoid zillions of parameters */
81struct match {
82	struct re_guts *g;
83	int eflags;
84	regmatch_t *pmatch;	/* [nsub+1] (0 element unused) */
85	const char *offp;	/* offsets work from here */
86	const char *beginp;	/* start of string -- virtual NUL precedes */
87	const char *endp;	/* end of string -- virtual NUL here */
88	const char *coldp;	/* can be no match starting before here */
89	const char **lastpos;	/* [nplus+1] */
90	STATEVARS;
91	states st;		/* current states */
92	states fresh;		/* states for a fresh start */
93	states tmp;		/* temporary */
94	states empty;		/* empty set of states */
95	mbstate_t mbs;		/* multibyte conversion state */
96};
97
98/* ========= begin header generated by ./mkh ========= */
99#ifdef __cplusplus
100extern "C" {
101#endif
102
103/* === engine.c === */
104static int matcher(struct re_guts *, const char *, size_t, regmatch_t[], int);
105static const char *dissect(struct match *, const char *, const char *,
106    sopno, sopno);
107static const char *backref(struct match *, const char *, const char *, sopno,
108    sopno, sopno, int);
109static const char *walk(struct match *m, const char *start, const char *stop,
110    sopno startst, sopno stopst, bool fast);
111static states step(struct re_guts *, sopno, sopno, states, wint_t, states);
112#define	MAX_RECURSION	100
113#define	BOL	(OUT-1)
114#define	EOL	(BOL-1)
115#define	BOLEOL	(BOL-2)
116#define	NOTHING	(BOL-3)
117#define	BOW	(BOL-4)
118#define	EOW	(BOL-5)
119#define	BADCHAR	(BOL-6)
120#define	NONCHAR(c)	((c) <= OUT)
121#ifdef REDEBUG
122static void print(struct match *, const char *, states, int, FILE *);
123#endif
124#ifdef REDEBUG
125static void at(struct match *, const char *, const char *, const char *,
126    sopno, sopno);
127#endif
128#ifdef REDEBUG
129static const char *pchar(int ch);
130#endif
131
132#ifdef __cplusplus
133}
134#endif
135/* ========= end header generated by ./mkh ========= */
136
137#ifdef REDEBUG
138#define	SP(t, s, c)	print(m, t, s, c, stdout)
139#define	AT(t, p1, p2, s1, s2)	at(m, t, p1, p2, s1, s2)
140#define	NOTE(str)	{ if (m->eflags&REG_TRACE) printf("=%s\n", (str)); }
141#else
142#define	SP(t, s, c)	/* nothing */
143#define	AT(t, p1, p2, s1, s2)	/* nothing */
144#define	NOTE(s)	/* nothing */
145#endif
146
147/*
148 * Given a multibyte string pointed to by start, step back nchar characters
149 * from current position pointed to by cur.
150 */
151static const char *
152stepback(const char *start, const char *cur, int nchar)
153{
154	const char *ret;
155	int wc, mbc;
156	mbstate_t mbs;
157	size_t clen;
158
159	if (MB_CUR_MAX == 1)
160		return ((cur - nchar) > start ? cur - nchar : NULL);
161
162	ret = cur;
163	for (wc = nchar; wc > 0; wc--) {
164		for (mbc = 1; mbc <= MB_CUR_MAX; mbc++) {
165			if ((ret - mbc) < start)
166				return (NULL);
167			memset(&mbs, 0, sizeof (mbs));
168			clen = mbrtowc(NULL, ret - mbc, mbc, &mbs);
169			if (clen != (size_t)-1 && clen != (size_t)-2)
170				break;
171		}
172		if (mbc > MB_CUR_MAX)
173			return (NULL);
174		ret -= mbc;
175	}
176
177	return (ret);
178}
179
180/*
181 * matcher - the actual matching engine
182 */
183static int			/* 0 success, REG_NOMATCH failure */
184matcher(struct re_guts *g, const char *string, size_t nmatch,
185    regmatch_t pmatch[], int eflags)
186{
187	const char *endp;
188	size_t i;
189	struct match mv;
190	struct match *m = &mv;
191	const char *dp = NULL;
192	const sopno gf = g->firststate+1;	/* +1 for OEND */
193	const sopno gl = g->laststate;
194	const char *start;
195	const char *stop;
196	/* Boyer-Moore algorithms variables */
197	const char *pp;
198	int cj, mj;
199	const char *mustfirst;
200	const char *mustlast;
201	int *matchjump;
202	int *charjump;
203
204	/* simplify the situation where possible */
205	if (g->cflags&REG_NOSUB)
206		nmatch = 0;
207
208	if (eflags&REG_STARTEND) {
209		start = string + pmatch[0].rm_so;
210		stop = string + pmatch[0].rm_eo;
211	} else {
212		start = string;
213		stop = start + strlen(start);
214	}
215
216	if (stop < start)
217		return (REG_EFATAL);
218
219	/* prescreening; this does wonders for this rather slow code */
220	if (g->must != NULL) {
221		if (g->charjump != NULL && g->matchjump != NULL) {
222			mustfirst = g->must;
223			mustlast = g->must + g->mlen - 1;
224			charjump = g->charjump;
225			matchjump = g->matchjump;
226			pp = mustlast;
227			for (dp = start+g->mlen-1; dp < stop; ) {
228				/* Fast skip non-matches */
229				while (dp < stop && charjump[(int)*dp])
230					dp += charjump[(int)*dp];
231
232				if (dp >= stop)
233					break;
234
235				/* Greedy matcher */
236				/*
237				 * We depend on not being used for
238				 * for strings of length 1
239				 */
240				while (*--dp == *--pp && pp != mustfirst)
241					;
242
243				if (*dp == *pp)
244					break;
245
246				/* Jump to next possible match */
247				mj = matchjump[pp - mustfirst];
248				cj = charjump[(int)*dp];
249				dp += (cj < mj ? mj : cj);
250				pp = mustlast;
251			}
252			if (pp != mustfirst)
253				return (REG_NOMATCH);
254		} else {
255			for (dp = start; dp < stop; dp++)
256				if (*dp == g->must[0] &&
257				    stop - dp >= g->mlen &&
258				    memcmp(dp, g->must, (size_t)g->mlen) == 0)
259					break;
260			if (dp == stop)		/* we didn't find g->must */
261				return (REG_NOMATCH);
262		}
263	}
264
265	/* match struct setup */
266	m->g = g;
267	m->eflags = eflags;
268	m->pmatch = NULL;
269	m->lastpos = NULL;
270	m->offp = string;
271	m->beginp = start;
272	m->endp = stop;
273	STATESETUP(m, 4);
274	SETUP(m->st);
275	SETUP(m->fresh);
276	SETUP(m->tmp);
277	SETUP(m->empty);
278	CLEAR(m->empty);
279	ZAPSTATE(&m->mbs);
280
281	/* Adjust start according to moffset, to speed things up */
282	if (dp != NULL && g->moffset > -1) {
283		const char *nstart;
284
285		nstart = stepback(start, dp, g->moffset);
286		if (nstart != NULL)
287			start = nstart;
288	}
289
290	SP("mloop", m->st, *start);
291
292	/* this loop does only one repetition except for backrefs */
293	for (;;) {
294		endp = walk(m, start, stop, gf, gl, true);
295		if (endp == NULL) {		/* a miss */
296			if (m->pmatch != NULL)
297				free((char *)m->pmatch);
298			if (m->lastpos != NULL)
299				free((char *)m->lastpos);
300			STATETEARDOWN(m);
301			return (REG_NOMATCH);
302		}
303		if (nmatch == 0 && !g->backrefs)
304			break;		/* no further info needed */
305
306		/* where? */
307		assert(m->coldp != NULL);
308		for (;;) {
309			NOTE("finding start");
310			endp = walk(m, m->coldp, stop, gf, gl, false);
311			if (endp != NULL)
312				break;
313			assert(m->coldp < m->endp);
314			m->coldp += XMBRTOWC(NULL, m->coldp,
315			    m->endp - m->coldp, &m->mbs, 0);
316		}
317		if (nmatch == 1 && !g->backrefs)
318			break;		/* no further info needed */
319
320		/* oh my, it wants the subexpressions... */
321		if (m->pmatch == NULL)
322			m->pmatch = (regmatch_t *)malloc((m->g->nsub + 1) *
323			    sizeof (regmatch_t));
324		if (m->pmatch == NULL) {
325			STATETEARDOWN(m);
326			return (REG_ESPACE);
327		}
328		for (i = 1; i <= m->g->nsub; i++)
329			m->pmatch[i].rm_so = m->pmatch[i].rm_eo = -1;
330		if (!g->backrefs && !(m->eflags&REG_BACKR)) {
331			NOTE("dissecting");
332			dp = dissect(m, m->coldp, endp, gf, gl);
333		} else {
334			if (g->nplus > 0 && m->lastpos == NULL)
335				m->lastpos = malloc((g->nplus+1) *
336				    sizeof (const char *));
337			if (g->nplus > 0 && m->lastpos == NULL) {
338				free(m->pmatch);
339				STATETEARDOWN(m);
340				return (REG_ESPACE);
341			}
342			NOTE("backref dissect");
343			dp = backref(m, m->coldp, endp, gf, gl, (sopno)0, 0);
344		}
345		if (dp != NULL)
346			break;
347
348		/* uh-oh... we couldn't find a subexpression-level match */
349		assert(g->backrefs);	/* must be back references doing it */
350		assert(g->nplus == 0 || m->lastpos != NULL);
351		for (;;) {
352			if (dp != NULL || endp <= m->coldp)
353				break;		/* defeat */
354			NOTE("backoff");
355			endp = walk(m, m->coldp, endp-1, gf, gl, false);
356			if (endp == NULL)
357				break;		/* defeat */
358			/* try it on a shorter possibility */
359#ifndef NDEBUG
360			for (i = 1; i <= m->g->nsub; i++) {
361				assert(m->pmatch[i].rm_so == -1);
362				assert(m->pmatch[i].rm_eo == -1);
363			}
364#endif
365			NOTE("backoff dissect");
366			dp = backref(m, m->coldp, endp, gf, gl, (sopno)0, 0);
367		}
368		assert(dp == NULL || dp == endp);
369		if (dp != NULL)		/* found a shorter one */
370			break;
371
372		/* despite initial appearances, there is no match here */
373		NOTE("false alarm");
374		/* recycle starting later */
375		start = m->coldp + XMBRTOWC(NULL, m->coldp,
376		    stop - m->coldp, &m->mbs, 0);
377		assert(start <= stop);
378	}
379
380	/* fill in the details if requested */
381	if (nmatch > 0) {
382		pmatch[0].rm_so = m->coldp - m->offp;
383		pmatch[0].rm_eo = endp - m->offp;
384	}
385	if (nmatch > 1) {
386		assert(m->pmatch != NULL);
387		for (i = 1; i < nmatch; i++)
388			if (i <= m->g->nsub)
389				pmatch[i] = m->pmatch[i];
390			else {
391				pmatch[i].rm_so = -1;
392				pmatch[i].rm_eo = -1;
393			}
394	}
395
396	if (m->pmatch != NULL)
397		free((char *)m->pmatch);
398	if (m->lastpos != NULL)
399		free((char *)m->lastpos);
400	STATETEARDOWN(m);
401	return (0);
402}
403
404/*
405 * dissect - figure out what matched what, no back references
406 */
407static const char *
408dissect(struct match *m, const char *start, const char *stop, sopno startst,
409    sopno stopst)
410{
411	int i;
412	sopno ss;		/* start sop of current subRE */
413	sopno es;		/* end sop of current subRE */
414	const char *sp;		/* start of string matched by it */
415	const char *stp;	/* string matched by it cannot pass here */
416	const char *rest;	/* start of rest of string */
417	const char *tail;	/* string unmatched by rest of RE */
418	sopno ssub;		/* start sop of subsubRE */
419	sopno esub;		/* end sop of subsubRE */
420	const char *ssp;	/* start of string matched by subsubRE */
421	const char *sep;	/* end of string matched by subsubRE */
422	const char *oldssp;	/* previous ssp */
423	const char *dp __unused;
424
425	AT("diss", start, stop, startst, stopst);
426	sp = start;
427	for (ss = startst; ss < stopst; ss = es) {
428		/* identify end of subRE */
429		es = ss;
430		switch (OP(m->g->strip[es])) {
431		case OPLUS_:
432		case OQUEST_:
433			es += OPND(m->g->strip[es]);
434			break;
435		case OCH_:
436			while (OP(m->g->strip[es]) != (sop)O_CH)
437				es += OPND(m->g->strip[es]);
438			break;
439		}
440		es++;
441
442		/* figure out what it matched */
443		switch (OP(m->g->strip[ss])) {
444		case OEND:
445			assert(0);
446			break;
447		case OCHAR:
448			sp += XMBRTOWC(NULL, sp, stop - start, &m->mbs, 0);
449			break;
450		case OBOL:
451		case OEOL:
452		case OBOW:
453		case OEOW:
454			break;
455		case OANY:
456		case OANYOF:
457			sp += XMBRTOWC(NULL, sp, stop - start, &m->mbs, 0);
458			break;
459		case OBACK_:
460		case O_BACK:
461			assert(0);
462			break;
463		/* cases where length of match is hard to find */
464		case OQUEST_:
465			stp = stop;
466			for (;;) {
467				/* how long could this one be? */
468				rest = walk(m, sp, stp, ss, es, false);
469				assert(rest != NULL);	/* it did match */
470				/* could the rest match the rest? */
471				tail = walk(m, rest, stop, es, stopst, false);
472				if (tail == stop)
473					break;		/* yes! */
474				/* no -- try a shorter match for this one */
475				stp = rest - 1;
476				assert(stp >= sp);	/* it did work */
477			}
478			ssub = ss + 1;
479			esub = es - 1;
480			/* did innards match? */
481			if (walk(m, sp, rest, ssub, esub, false) != NULL) {
482				dp = dissect(m, sp, rest, ssub, esub);
483				assert(dp == rest);
484			} else		/* no */
485				assert(sp == rest);
486			sp = rest;
487			break;
488		case OPLUS_:
489			stp = stop;
490			for (;;) {
491				/* how long could this one be? */
492				rest = walk(m, sp, stp, ss, es, false);
493				assert(rest != NULL);	/* it did match */
494				/* could the rest match the rest? */
495				tail = walk(m, rest, stop, es, stopst, false);
496				if (tail == stop)
497					break;		/* yes! */
498				/* no -- try a shorter match for this one */
499				stp = rest - 1;
500				assert(stp >= sp);	/* it did work */
501			}
502			ssub = ss + 1;
503			esub = es - 1;
504			ssp = sp;
505			oldssp = ssp;
506			for (;;) {	/* find last match of innards */
507				sep = walk(m, ssp, rest, ssub, esub, false);
508				if (sep == NULL || sep == ssp)
509					break;	/* failed or matched null */
510				oldssp = ssp;	/* on to next try */
511				ssp = sep;
512			}
513			if (sep == NULL) {
514				/* last successful match */
515				sep = ssp;
516				ssp = oldssp;
517			}
518			assert(sep == rest);	/* must exhaust substring */
519			assert(walk(m, ssp, sep, ssub, esub, false) == rest);
520			dp = dissect(m, ssp, sep, ssub, esub);
521			assert(dp == sep);
522			sp = rest;
523			break;
524		case OCH_:
525			stp = stop;
526			for (;;) {
527				/* how long could this one be? */
528				rest = walk(m, sp, stp, ss, es, false);
529				assert(rest != NULL);	/* it did match */
530				/* could the rest match the rest? */
531				tail = walk(m, rest, stop, es, stopst, false);
532				if (tail == stop)
533					break;		/* yes! */
534				/* no -- try a shorter match for this one */
535				stp = rest - 1;
536				assert(stp >= sp);	/* it did work */
537			}
538			ssub = ss + 1;
539			esub = ss + OPND(m->g->strip[ss]) - 1;
540			assert(OP(m->g->strip[esub]) == OOR1);
541			for (;;) {	/* find first matching branch */
542				if (walk(m, sp, rest, ssub, esub,
543				    false) == rest)
544					break;	/* it matched all of it */
545				/* that one missed, try next one */
546				assert(OP(m->g->strip[esub]) == OOR1);
547				esub++;
548				assert(OP(m->g->strip[esub]) == OOR2);
549				ssub = esub + 1;
550				esub += OPND(m->g->strip[esub]);
551				if (OP(m->g->strip[esub]) == (sop)OOR2)
552					esub--;
553				else
554					assert(OP(m->g->strip[esub]) == O_CH);
555			}
556			dp = dissect(m, sp, rest, ssub, esub);
557			assert(dp == rest);
558			sp = rest;
559			break;
560		case O_PLUS:
561		case O_QUEST:
562		case OOR1:
563		case OOR2:
564		case O_CH:
565			assert(0);
566			break;
567		case OLPAREN:
568			i = OPND(m->g->strip[ss]);
569			assert(0 < i && i <= m->g->nsub);
570			m->pmatch[i].rm_so = sp - m->offp;
571			break;
572		case ORPAREN:
573			i = OPND(m->g->strip[ss]);
574			assert(0 < i && i <= m->g->nsub);
575			m->pmatch[i].rm_eo = sp - m->offp;
576			break;
577		default:		/* uh oh */
578			assert(0);
579			break;
580		}
581	}
582
583	assert(sp == stop);
584	return (sp);
585}
586
587/*
588 * backref - figure out what matched what, figuring in back references
589 */
590static const char *
591backref(struct match *m, const char *start, const char *stop, sopno startst,
592    sopno stopst, sopno lev,		/* PLUS nesting level */
593    int rec)
594{
595	int i;
596	sopno ss;		/* start sop of current subRE */
597	const char *sp;		/* start of string matched by it */
598	sopno ssub;		/* start sop of subsubRE */
599	sopno esub;		/* end sop of subsubRE */
600	const char *ssp;	/* start of string matched by subsubRE */
601	const char *dp;
602	size_t len;
603	int hard;
604	sop s;
605	regoff_t offsave;
606	cset *cs;
607	wint_t wc;
608
609	AT("back", start, stop, startst, stopst);
610	sp = start;
611
612	/* get as far as we can with easy stuff */
613	hard = 0;
614	for (ss = startst; !hard && ss < stopst; ss++)
615		switch (OP(s = m->g->strip[ss])) {
616		case OCHAR:
617			if (sp == stop)
618				return (NULL);
619			sp += XMBRTOWC(&wc, sp, stop - sp, &m->mbs, BADCHAR);
620			if (wc != OPND(s))
621				return (NULL);
622			break;
623		case OANY:
624			if (sp == stop)
625				return (NULL);
626			sp += XMBRTOWC(&wc, sp, stop - sp, &m->mbs, BADCHAR);
627			if (wc == BADCHAR)
628				return (NULL);
629			break;
630		case OANYOF:
631			if (sp == stop)
632				return (NULL);
633			cs = &m->g->sets[OPND(s)];
634			sp += XMBRTOWC(&wc, sp, stop - sp, &m->mbs, BADCHAR);
635			if (wc == BADCHAR || !CHIN(cs, wc))
636				return (NULL);
637			break;
638		case OBOL:
639			if ((sp == m->beginp && !(m->eflags&REG_NOTBOL)) ||
640			    (sp > m->offp && sp < m->endp &&
641			    *(sp-1) == '\n' && (m->g->cflags&REG_NEWLINE))) {
642				break;
643			}
644			return (NULL);
645		case OEOL:
646			if ((sp == m->endp && !(m->eflags&REG_NOTEOL)) ||
647			    (sp < m->endp && *sp == '\n' &&
648			    (m->g->cflags&REG_NEWLINE))) {
649				break;
650			}
651			return (NULL);
652		case OBOW:
653			if (sp < m->endp && ISWORD(*sp) &&
654			    ((sp == m->beginp && !(m->eflags&REG_NOTBOL)) ||
655			    (sp > m->offp && !ISWORD(*(sp-1))))) {
656				break;
657			}
658			return (NULL);
659		case OEOW:
660			if (((sp == m->endp && !(m->eflags&REG_NOTEOL)) ||
661			    (sp < m->endp && *sp == '\n' &&
662			    (m->g->cflags&REG_NEWLINE)) ||
663			    (sp < m->endp && !ISWORD(*sp))) &&
664			    (sp > m->beginp && ISWORD(*(sp-1)))) {
665				break;
666			}
667			return (NULL);
668		case O_QUEST:
669			break;
670		case OOR1:	/* matches null but needs to skip */
671			ss++;
672			s = m->g->strip[ss];
673			do {
674				assert(OP(s) == OOR2);
675				ss += OPND(s);
676			} while (OP(s = m->g->strip[ss]) != (sop)O_CH);
677			/* note that the ss++ gets us past the O_CH */
678			break;
679		default:	/* have to make a choice */
680			hard = 1;
681			break;
682		}
683	if (!hard) {		/* that was it! */
684		if (sp != stop)
685			return (NULL);
686		return (sp);
687	}
688	ss--;			/* adjust for the for's final increment */
689
690	/* the hard stuff */
691	AT("hard", sp, stop, ss, stopst);
692	s = m->g->strip[ss];
693	switch (OP(s)) {
694	case OBACK_:		/* the vilest depths */
695		i = OPND(s);
696		assert(0 < i && i <= m->g->nsub);
697		if (m->pmatch[i].rm_eo == -1)
698			return (NULL);
699		assert(m->pmatch[i].rm_so != -1);
700		len = m->pmatch[i].rm_eo - m->pmatch[i].rm_so;
701		if (len == 0 && rec++ > MAX_RECURSION)
702			return (NULL);
703		assert(stop - m->beginp >= len);
704		if (sp > stop - len)
705			return (NULL);	/* not enough left to match */
706		ssp = m->offp + m->pmatch[i].rm_so;
707		if (memcmp(sp, ssp, len) != 0)
708			return (NULL);
709		while (m->g->strip[ss] != (sop)SOP(O_BACK, i))
710			ss++;
711		return (backref(m, sp+len, stop, ss+1, stopst, lev, rec));
712	case OQUEST_:		/* to null or not */
713		dp = backref(m, sp, stop, ss+1, stopst, lev, rec);
714		if (dp != NULL)
715			return (dp);	/* not */
716		return (backref(m, sp, stop, ss+OPND(s)+1, stopst, lev, rec));
717	case OPLUS_:
718		assert(m->lastpos != NULL);
719		assert(lev+1 <= m->g->nplus);
720		m->lastpos[lev+1] = sp;
721		return (backref(m, sp, stop, ss+1, stopst, lev+1, rec));
722	case O_PLUS:
723		if (sp == m->lastpos[lev])	/* last pass matched null */
724			return (backref(m, sp, stop, ss+1, stopst, lev-1, rec));
725		/* try another pass */
726		m->lastpos[lev] = sp;
727		dp = backref(m, sp, stop, ss-OPND(s)+1, stopst, lev, rec);
728		if (dp == NULL)
729			return (backref(m, sp, stop, ss+1, stopst, lev-1, rec));
730		return (dp);
731	case OCH_:		/* find the right one, if any */
732		ssub = ss + 1;
733		esub = ss + OPND(s) - 1;
734		assert(OP(m->g->strip[esub]) == OOR1);
735		for (;;) {	/* find first matching branch */
736			dp = backref(m, sp, stop, ssub, esub, lev, rec);
737			if (dp != NULL)
738				return (dp);
739			/* that one missed, try next one */
740			if (OP(m->g->strip[esub]) == (sop)O_CH)
741				return (NULL);	/* there is none */
742			esub++;
743			assert(OP(m->g->strip[esub]) == (sop)OOR2);
744			ssub = esub + 1;
745			esub += OPND(m->g->strip[esub]);
746			if (OP(m->g->strip[esub]) == (sop)OOR2)
747				esub--;
748			else
749				assert(OP(m->g->strip[esub]) == O_CH);
750		}
751		/* NOTREACHED */
752		break;
753	case OLPAREN:		/* must undo assignment if rest fails */
754		i = OPND(s);
755		assert(0 < i && i <= m->g->nsub);
756		offsave = m->pmatch[i].rm_so;
757		m->pmatch[i].rm_so = sp - m->offp;
758		dp = backref(m, sp, stop, ss+1, stopst, lev, rec);
759		if (dp != NULL)
760			return (dp);
761		m->pmatch[i].rm_so = offsave;
762		return (NULL);
763	case ORPAREN:		/* must undo assignment if rest fails */
764		i = OPND(s);
765		assert(0 < i && i <= m->g->nsub);
766		offsave = m->pmatch[i].rm_eo;
767		m->pmatch[i].rm_eo = sp - m->offp;
768		dp = backref(m, sp, stop, ss+1, stopst, lev, rec);
769		if (dp != NULL)
770			return (dp);
771		m->pmatch[i].rm_eo = offsave;
772		return (NULL);
773	default:		/* uh oh */
774		assert(0);
775		break;
776	}
777
778	/* "can't happen" */
779	assert(0);
780	return (NULL);
781}
782
783/*
784 * Step through the string either quickly or slowly.  Returns where it ended
785 * or NULL.
786 */
787static const char *
788walk(struct match *m, const char *start, const char *stop, sopno startst,
789    sopno stopst, bool fast)
790{
791	states st = m->st;
792	states fresh = m->fresh;
793	states empty = m->empty;
794	states tmp = m->tmp;
795	const char *p = start;
796	wint_t c;
797	wint_t lastc;		/* previous c */
798	wint_t flagch;
799	int i;
800	const char *matchp;	/* last p at which a match ended */
801	size_t clen;
802
803	AT("slow", start, stop, startst, stopst);
804	CLEAR(st);
805	SET1(st, startst);
806	SP("sstart", st, *p);
807	st = step(m->g, startst, stopst, st, NOTHING, st);
808	if (fast)
809		ASSIGN(fresh, st);
810	matchp = NULL;
811	if (start == m->offp || (start == m->beginp && !(m->eflags&REG_NOTBOL)))
812		c = OUT;
813	else {
814		/*
815		 * XXX Wrong if the previous character was multi-byte.
816		 * Newline never is (in encodings supported by FreeBSD),
817		 * so this only breaks the ISWORD tests below.
818		 */
819		c = (uch)*(start - 1);
820	}
821	for (;;) {
822		/* next character */
823		lastc = c;
824		if (p == m->endp) {
825			c = OUT;
826			clen = 0;
827		} else
828			clen = XMBRTOWC(&c, p, m->endp - p, &m->mbs, BADCHAR);
829
830		if (fast && EQ(st, fresh))
831			matchp = p;
832
833		/* is there an EOL and/or BOL between lastc and c? */
834		flagch = '\0';
835		i = 0;
836		if ((lastc == '\n' && m->g->cflags&REG_NEWLINE) ||
837		    (lastc == OUT && !(m->eflags&REG_NOTBOL))) {
838			flagch = BOL;
839			i = m->g->nbol;
840		}
841		if ((c == '\n' && m->g->cflags&REG_NEWLINE) ||
842		    (c == OUT && !(m->eflags&REG_NOTEOL))) {
843			flagch = (flagch == BOL) ? BOLEOL : EOL;
844			i += m->g->neol;
845		}
846		if (i != 0) {
847			for (; i > 0; i--)
848				st = step(m->g, startst, stopst, st,
849				    flagch, st);
850			SP("sboleol", st, c);
851		}
852
853		/* how about a word boundary? */
854		if ((flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
855		    (c != OUT && ISWORD(c))) {
856			flagch = BOW;
857		}
858		if ((lastc != OUT && ISWORD(lastc)) &&
859		    (flagch == EOL || (c != OUT && !ISWORD(c)))) {
860			flagch = EOW;
861		}
862		if (flagch == BOW || flagch == EOW) {
863			st = step(m->g, startst, stopst, st, flagch, st);
864			SP("sboweow", st, c);
865		}
866
867		/* are we done? */
868		if (ISSET(st, stopst)) {
869			if (fast)
870				break;
871			else
872				matchp = p;
873		}
874		if (EQ(st, empty) || p == stop || clen > (size_t)(stop - p))
875			break;		/* NOTE BREAK OUT */
876
877		/* no, we must deal with this character */
878		ASSIGN(tmp, st);
879		if (fast)
880			ASSIGN(st, fresh);
881		else
882			ASSIGN(st, empty);
883		assert(c != OUT);
884		st = step(m->g, startst, stopst, tmp, c, st);
885		SP("saft", st, c);
886		assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
887		p += clen;
888	}
889
890	if (fast) {
891		assert(matchp != NULL);
892		m->coldp = matchp;
893		if (ISSET(st, stopst))
894			return (p + XMBRTOWC(NULL, p, stop - p, &m->mbs, 0));
895		else
896			return (NULL);
897	} else
898		return (matchp);
899}
900
901/*
902 * step - map set of states reachable before char to set reachable after
903 */
904static states
905step(struct re_guts *g,
906    sopno start,	/* start state within strip */
907    sopno stop,		/* state after stop state within strip */
908    states bef,		/* states reachable before */
909    wint_t ch,		/* character or NONCHAR code */
910    states aft)		/* states already known reachable after */
911{
912	cset *cs;
913	sop s;
914	sopno pc;
915	onestate here;		/* note, macros know this name */
916	sopno look;
917	int i;
918
919	for (pc = start, INIT(here, pc); pc != stop; pc++, INC(here)) {
920		s = g->strip[pc];
921		switch (OP(s)) {
922		case OEND:
923			assert(pc == stop-1);
924			break;
925		case OCHAR:
926			/* only characters can match */
927			assert(!NONCHAR(ch) || ch != OPND(s));
928			if (ch == OPND(s))
929				FWD(aft, bef, 1);
930			break;
931		case OBOL:
932			if (ch == BOL || ch == BOLEOL)
933				FWD(aft, bef, 1);
934			break;
935		case OEOL:
936			if (ch == EOL || ch == BOLEOL)
937				FWD(aft, bef, 1);
938			break;
939		case OBOW:
940			if (ch == BOW)
941				FWD(aft, bef, 1);
942			break;
943		case OEOW:
944			if (ch == EOW)
945				FWD(aft, bef, 1);
946			break;
947		case OANY:
948			if (!NONCHAR(ch))
949				FWD(aft, bef, 1);
950			break;
951		case OANYOF:
952			cs = &g->sets[OPND(s)];
953			if (!NONCHAR(ch) && CHIN(cs, ch))
954				FWD(aft, bef, 1);
955			break;
956		case OBACK_:		/* ignored here */
957		case O_BACK:
958			FWD(aft, aft, 1);
959			break;
960		case OPLUS_:		/* forward, this is just an empty */
961			FWD(aft, aft, 1);
962			break;
963		case O_PLUS:		/* both forward and back */
964			FWD(aft, aft, 1);
965			i = ISSETBACK(aft, OPND(s));
966			BACK(aft, aft, OPND(s));
967			if (!i && ISSETBACK(aft, OPND(s))) {
968				/* oho, must reconsider loop body */
969				pc -= OPND(s) + 1;
970				INIT(here, pc);
971			}
972			break;
973		case OQUEST_:		/* two branches, both forward */
974			FWD(aft, aft, 1);
975			FWD(aft, aft, OPND(s));
976			break;
977		case O_QUEST:		/* just an empty */
978			FWD(aft, aft, 1);
979			break;
980		case OLPAREN:		/* not significant here */
981		case ORPAREN:
982			FWD(aft, aft, 1);
983			break;
984		case OCH_:		/* mark the first two branches */
985			FWD(aft, aft, 1);
986			assert(OP(g->strip[pc+OPND(s)]) == (sop)OOR2);
987			FWD(aft, aft, OPND(s));
988			break;
989		case OOR1:		/* done a branch, find the O_CH */
990			if (ISSTATEIN(aft, here)) {
991				for (look = 1;
992				    OP(s = g->strip[pc+look]) != (sop)O_CH;
993				    look += OPND(s))
994					assert(OP(s) == (sop)OOR2);
995				FWD(aft, aft, look + 1);
996			}
997			break;
998		case OOR2:		/* propagate OCH_'s marking */
999			FWD(aft, aft, 1);
1000			if (OP(g->strip[pc+OPND(s)]) != (sop)O_CH) {
1001				assert(OP(g->strip[pc+OPND(s)]) == (sop)OOR2);
1002				FWD(aft, aft, OPND(s));
1003			}
1004			break;
1005		case O_CH:		/* just empty */
1006			FWD(aft, aft, 1);
1007			break;
1008		default:		/* ooooops... */
1009			assert(0);
1010			break;
1011		}
1012	}
1013
1014	return (aft);
1015}
1016
1017#ifdef REDEBUG
1018/*
1019 * print - print a set of states
1020 */
1021static void
1022print(struct match *m, const char *caption, states st, int ch, FILE *d)
1023{
1024	struct re_guts *g = m->g;
1025	sopno i;
1026	int first = 1;
1027
1028	if (!(m->eflags&REG_TRACE))
1029		return;
1030
1031	(void) fprintf(d, "%s", caption);
1032	if (ch != '\0')
1033		(void) fprintf(d, " %s", pchar(ch));
1034	for (i = 0; i < g->nstates; i++)
1035		if (ISSET(st, i)) {
1036			(void) fprintf(d, "%s%d", (first) ? "\t" : ", ", i);
1037			first = 0;
1038		}
1039	(void) fprintf(d, "\n");
1040}
1041
1042/*
1043 * at - print current situation
1044 */
1045static void
1046at(struct match *m, const char *title, const char *start, const char *stop,
1047    sopno startst, sopno stopst)
1048{
1049	if (!(m->eflags&REG_TRACE))
1050		return;
1051
1052	(void) printf("%s %s-", title, pchar(*start));
1053	(void) printf("%s ", pchar(*stop));
1054	(void) printf("%ld-%ld\n", (long)startst, (long)stopst);
1055}
1056
1057#ifndef PCHARDONE
1058#define	PCHARDONE	/* never again */
1059/*
1060 * pchar - make a character printable
1061 *
1062 * Is this identical to regchar() over in debug.c?  Well, yes.  But a
1063 * duplicate here avoids having a debugging-capable regexec.o tied to
1064 * a matching debug.o, and this is convenient.  It all disappears in
1065 * the non-debug compilation anyway, so it doesn't matter much.
1066 */
1067static const char *
1068pchar(int ch)
1069{
1070	static char pbuf[10];
1071
1072	if (isprint((uch)ch) || ch == ' ')
1073		(void) sprintf(pbuf, "%c", ch);
1074	else
1075		(void) sprintf(pbuf, "\\%o", ch);
1076	return (pbuf);
1077}
1078#endif
1079#endif
1080
1081#undef	stepback
1082#undef	matcher
1083#undef	walk
1084#undef	dissect
1085#undef	backref
1086#undef	step
1087#undef	print
1088#undef	at
1089#undef	match
1090