regex(3): Refactor fast/slow stepping bits in the matching engine
Adding features for matching is fairly straightforward, but this requires some duplication because of this fast/slow setup. They can be fairly trivially combined into a single walk(), so do it to make future additions less error prone. Reviewed by: cem (earlier version), emaste, pfg Approved by: emaste (mentor) Differential Revision: https://reviews.freebsd.org/D11233
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kevans
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a067da9017
@ -36,6 +36,8 @@
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <stdbool.h>
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/*
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* The matching engine and friends. This file is #included by regexec.c
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* after suitable #defines of a variety of macros used herein, so that
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@ -45,8 +47,7 @@ __FBSDID("$FreeBSD$");
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#ifdef SNAMES
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#define matcher smatcher
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#define fast sfast
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#define slow sslow
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#define walk swalk
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#define dissect sdissect
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#define backref sbackref
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#define step sstep
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@ -56,8 +57,7 @@ __FBSDID("$FreeBSD$");
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#endif
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#ifdef LNAMES
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#define matcher lmatcher
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#define fast lfast
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#define slow lslow
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#define walk lwalk
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#define dissect ldissect
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#define backref lbackref
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#define step lstep
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@ -67,8 +67,7 @@ __FBSDID("$FreeBSD$");
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#endif
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#ifdef MNAMES
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#define matcher mmatcher
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#define fast mfast
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#define slow mslow
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#define walk mwalk
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#define dissect mdissect
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#define backref mbackref
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#define step mstep
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@ -104,8 +103,7 @@ extern "C" {
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static int matcher(struct re_guts *g, const char *string, size_t nmatch, regmatch_t pmatch[], int eflags);
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static const char *dissect(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
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static const char *backref(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst, sopno lev, int);
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static const char *fast(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
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static const char *slow(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
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static const char *walk(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst, bool fast);
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static states step(struct re_guts *g, sopno start, sopno stop, states bef, wint_t ch, states aft);
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#define MAX_RECURSION 100
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#define BOL (OUT-1)
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@ -251,7 +249,7 @@ matcher(struct re_guts *g,
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/* this loop does only one repetition except for backrefs */
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for (;;) {
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endp = fast(m, start, stop, gf, gl);
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endp = walk(m, start, stop, gf, gl, true);
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if (endp == NULL) { /* a miss */
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if (m->pmatch != NULL)
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free((char *)m->pmatch);
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@ -267,7 +265,7 @@ matcher(struct re_guts *g,
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assert(m->coldp != NULL);
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for (;;) {
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NOTE("finding start");
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endp = slow(m, m->coldp, stop, gf, gl);
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endp = walk(m, m->coldp, stop, gf, gl, false);
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if (endp != NULL)
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break;
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assert(m->coldp < m->endp);
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@ -312,7 +310,7 @@ matcher(struct re_guts *g,
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if (dp != NULL || endp <= m->coldp)
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break; /* defeat */
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NOTE("backoff");
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endp = slow(m, m->coldp, endp-1, gf, gl);
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endp = walk(m, m->coldp, endp-1, gf, gl, false);
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if (endp == NULL)
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break; /* defeat */
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/* try it on a shorter possibility */
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@ -430,10 +428,10 @@ dissect(struct match *m,
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stp = stop;
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for (;;) {
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/* how long could this one be? */
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rest = slow(m, sp, stp, ss, es);
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rest = walk(m, sp, stp, ss, es, false);
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assert(rest != NULL); /* it did match */
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/* could the rest match the rest? */
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tail = slow(m, rest, stop, es, stopst);
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tail = walk(m, rest, stop, es, stopst, false);
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if (tail == stop)
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break; /* yes! */
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/* no -- try a shorter match for this one */
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@ -443,7 +441,7 @@ dissect(struct match *m,
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ssub = ss + 1;
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esub = es - 1;
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/* did innards match? */
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if (slow(m, sp, rest, ssub, esub) != NULL) {
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if (walk(m, sp, rest, ssub, esub, false) != NULL) {
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dp = dissect(m, sp, rest, ssub, esub);
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assert(dp == rest);
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} else /* no */
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@ -454,10 +452,10 @@ dissect(struct match *m,
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stp = stop;
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for (;;) {
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/* how long could this one be? */
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rest = slow(m, sp, stp, ss, es);
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rest = walk(m, sp, stp, ss, es, false);
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assert(rest != NULL); /* it did match */
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/* could the rest match the rest? */
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tail = slow(m, rest, stop, es, stopst);
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tail = walk(m, rest, stop, es, stopst, false);
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if (tail == stop)
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break; /* yes! */
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/* no -- try a shorter match for this one */
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@ -469,7 +467,7 @@ dissect(struct match *m,
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ssp = sp;
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oldssp = ssp;
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for (;;) { /* find last match of innards */
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sep = slow(m, ssp, rest, ssub, esub);
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sep = walk(m, ssp, rest, ssub, esub, false);
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if (sep == NULL || sep == ssp)
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break; /* failed or matched null */
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oldssp = ssp; /* on to next try */
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@ -481,7 +479,7 @@ dissect(struct match *m,
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ssp = oldssp;
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}
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assert(sep == rest); /* must exhaust substring */
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assert(slow(m, ssp, sep, ssub, esub) == rest);
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assert(walk(m, ssp, sep, ssub, esub, false) == rest);
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dp = dissect(m, ssp, sep, ssub, esub);
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assert(dp == sep);
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sp = rest;
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@ -490,10 +488,10 @@ dissect(struct match *m,
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stp = stop;
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for (;;) {
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/* how long could this one be? */
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rest = slow(m, sp, stp, ss, es);
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rest = walk(m, sp, stp, ss, es, false);
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assert(rest != NULL); /* it did match */
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/* could the rest match the rest? */
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tail = slow(m, rest, stop, es, stopst);
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tail = walk(m, rest, stop, es, stopst, false);
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if (tail == stop)
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break; /* yes! */
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/* no -- try a shorter match for this one */
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@ -504,7 +502,7 @@ dissect(struct match *m,
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esub = ss + OPND(m->g->strip[ss]) - 1;
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assert(OP(m->g->strip[esub]) == OOR1);
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for (;;) { /* find first matching branch */
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if (slow(m, sp, rest, ssub, esub) == rest)
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if (walk(m, sp, rest, ssub, esub, false) == rest)
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break; /* it matched all of it */
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/* that one missed, try next one */
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assert(OP(m->g->strip[esub]) == OOR1);
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@ -757,124 +755,16 @@ backref(struct match *m,
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}
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/*
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- fast - step through the string at top speed
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== static const char *fast(struct match *m, const char *start, \
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== const char *stop, sopno startst, sopno stopst);
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- walk - step through the string either quickly or slowly
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== static const char *walk(struct match *m, const char *start, \
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== const char *stop, sopno startst, sopno stopst, bool fast);
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*/
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static const char * /* where tentative match ended, or NULL */
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fast( struct match *m,
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const char *start,
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const char *stop,
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sopno startst,
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sopno stopst)
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static const char * /* where it ended, or NULL */
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walk(struct match *m, const char *start, const char *stop, sopno startst,
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sopno stopst, bool fast)
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{
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states st = m->st;
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states fresh = m->fresh;
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states tmp = m->tmp;
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const char *p = start;
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wint_t c;
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wint_t lastc; /* previous c */
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wint_t flagch;
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int i;
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const char *coldp; /* last p after which no match was underway */
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size_t clen;
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CLEAR(st);
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SET1(st, startst);
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SP("fast", st, *p);
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st = step(m->g, startst, stopst, st, NOTHING, st);
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ASSIGN(fresh, st);
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SP("start", st, *p);
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coldp = NULL;
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if (start == m->offp || (start == m->beginp && !(m->eflags®_NOTBOL)))
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c = OUT;
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else {
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/*
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* XXX Wrong if the previous character was multi-byte.
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* Newline never is (in encodings supported by FreeBSD),
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* so this only breaks the ISWORD tests below.
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*/
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c = (uch)*(start - 1);
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}
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for (;;) {
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/* next character */
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lastc = c;
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if (p == m->endp) {
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clen = 0;
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c = OUT;
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} else
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clen = XMBRTOWC(&c, p, m->endp - p, &m->mbs, BADCHAR);
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if (EQ(st, fresh))
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coldp = p;
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/* is there an EOL and/or BOL between lastc and c? */
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flagch = '\0';
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i = 0;
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if ( (lastc == '\n' && m->g->cflags®_NEWLINE) ||
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(lastc == OUT && !(m->eflags®_NOTBOL)) ) {
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flagch = BOL;
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i = m->g->nbol;
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}
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if ( (c == '\n' && m->g->cflags®_NEWLINE) ||
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(c == OUT && !(m->eflags®_NOTEOL)) ) {
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flagch = (flagch == BOL) ? BOLEOL : EOL;
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i += m->g->neol;
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}
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if (i != 0) {
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for (; i > 0; i--)
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st = step(m->g, startst, stopst, st, flagch, st);
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SP("boleol", st, c);
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}
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/* how about a word boundary? */
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if ( (flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
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(c != OUT && ISWORD(c)) ) {
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flagch = BOW;
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}
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if ( (lastc != OUT && ISWORD(lastc)) &&
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(flagch == EOL || (c != OUT && !ISWORD(c))) ) {
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flagch = EOW;
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}
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if (flagch == BOW || flagch == EOW) {
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st = step(m->g, startst, stopst, st, flagch, st);
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SP("boweow", st, c);
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}
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/* are we done? */
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if (ISSET(st, stopst) || p == stop || clen > stop - p)
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break; /* NOTE BREAK OUT */
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/* no, we must deal with this character */
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ASSIGN(tmp, st);
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ASSIGN(st, fresh);
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assert(c != OUT);
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st = step(m->g, startst, stopst, tmp, c, st);
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SP("aft", st, c);
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assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
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p += clen;
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}
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assert(coldp != NULL);
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m->coldp = coldp;
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if (ISSET(st, stopst))
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return(p+XMBRTOWC(NULL, p, stop - p, &m->mbs, 0));
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else
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return(NULL);
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}
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/*
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- slow - step through the string more deliberately
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== static const char *slow(struct match *m, const char *start, \
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== const char *stop, sopno startst, sopno stopst);
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*/
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static const char * /* where it ended */
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slow( struct match *m,
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const char *start,
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const char *stop,
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sopno startst,
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sopno stopst)
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{
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states st = m->st;
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states empty = m->empty;
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states tmp = m->tmp;
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const char *p = start;
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@ -890,6 +780,8 @@ slow( struct match *m,
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SET1(st, startst);
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SP("sstart", st, *p);
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st = step(m->g, startst, stopst, st, NOTHING, st);
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if (fast)
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ASSIGN(fresh, st);
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matchp = NULL;
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if (start == m->offp || (start == m->beginp && !(m->eflags®_NOTBOL)))
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c = OUT;
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@ -910,6 +802,9 @@ slow( struct match *m,
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} else
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clen = XMBRTOWC(&c, p, m->endp - p, &m->mbs, BADCHAR);
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if (fast && EQ(st, fresh))
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matchp = p;
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/* is there an EOL and/or BOL between lastc and c? */
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flagch = '\0';
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i = 0;
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@ -944,14 +839,21 @@ slow( struct match *m,
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}
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/* are we done? */
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if (ISSET(st, stopst))
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matchp = p;
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if (ISSET(st, stopst)) {
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if (fast)
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break;
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else
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matchp = p;
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}
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if (EQ(st, empty) || p == stop || clen > stop - p)
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break; /* NOTE BREAK OUT */
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/* no, we must deal with this character */
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ASSIGN(tmp, st);
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ASSIGN(st, empty);
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if (fast)
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ASSIGN(st, fresh);
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else
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ASSIGN(st, empty);
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assert(c != OUT);
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st = step(m->g, startst, stopst, tmp, c, st);
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SP("saft", st, c);
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@ -959,10 +861,17 @@ slow( struct match *m,
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p += clen;
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}
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return(matchp);
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if (fast) {
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assert(matchp != NULL);
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m->coldp = matchp;
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if (ISSET(st, stopst))
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return (p + XMBRTOWC(NULL, p, stop - p, &m->mbs, 0));
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else
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return (NULL);
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} else
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return (matchp);
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}
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/*
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- step - map set of states reachable before char to set reachable after
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== static states step(struct re_guts *g, sopno start, sopno stop, \
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@ -1173,8 +1082,7 @@ pchar(int ch)
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#endif
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#undef matcher
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#undef fast
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#undef slow
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#undef walk
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#undef dissect
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#undef backref
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#undef step
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