rege_dfa.c Go to the documentation of this file. /* * DFA routines * This file is #included by regexec.c. * * Copyright (c) 1998, 1999 Henry Spencer. All rights reserved. * * Development of this software was funded, in part, by Cray Research Inc., * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics * Corporation, none of whom are responsible for the results. The author * thanks all of them. * * Redistribution and use in source and binary forms -- with or without * modification -- are permitted for any purpose, provided that * redistributions in source form retain this entire copyright notice and * indicate the origin and nature of any modifications. * * I'd appreciate being given credit for this package in the documentation * of software which uses it, but that is not a requirement. * * THIS SOFTWARE IS PROVIDED ``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 * HENRY SPENCER 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. * */  /* - longest - longest-preferred matching engine ^ static chr *longest(struct vars *, struct dfa *, chr *, chr *, int *); */ static chr * /* endpoint, or NULL */ longest( struct vars *v, /* used only for debug and exec flags */ struct dfa *d, chr *start, /* where the match should start */ chr *stop, /* match must end at or before here */ int *hitstopp) /* record whether hit v->stop, if non-NULL */ { chr *cp; chr *realstop = (stop == v->stop) ? stop : stop + 1; color co; struct sset *css; struct sset *ss; chr *post; int i; struct colormap *cm = d->cm; /* * Initialize. */ css = initialize(v, d, start); cp = start; if (hitstopp != NULL) { *hitstopp = 0; } /* * Startup. */ FDEBUG(("+++ startup +++\n")); if (cp == v->start) { co = d->cnfa->bos[(v->eflags&REG_NOTBOL) ? 0 : 1]; FDEBUG(("color %ld\n", (long)co)); } else { co = GETCOLOR(cm, *(cp - 1)); FDEBUG(("char %c, color %ld\n", (char)*(cp-1), (long)co)); } css = miss(v, d, css, co, cp, start); if (css == NULL) { return NULL; } css->lastseen = cp; /* * Main loop. */ if (v->eflags&REG_FTRACE) { while (cp < realstop) { FDEBUG(("+++ at c%d +++\n", css - d->ssets)); co = GETCOLOR(cm, *cp); FDEBUG(("char %c, color %ld\n", (char)*cp, (long)co)); ss = css->outs[co]; if (ss == NULL) { ss = miss(v, d, css, co, cp+1, start); if (ss == NULL) { break; /* NOTE BREAK OUT */ } } cp++; ss->lastseen = cp; css = ss; } } else { while (cp < realstop) { co = GETCOLOR(cm, *cp); ss = css->outs[co]; if (ss == NULL) { ss = miss(v, d, css, co, cp+1, start); if (ss == NULL) { break; /* NOTE BREAK OUT */ } } cp++; ss->lastseen = cp; css = ss; } } /* * Shutdown. */ FDEBUG(("+++ shutdown at c%d +++\n", css - d->ssets)); if (cp == v->stop && stop == v->stop) { if (hitstopp != NULL) { *hitstopp = 1; } co = d->cnfa->eos[(v->eflags&REG_NOTEOL) ? 0 : 1]; FDEBUG(("color %ld\n", (long)co)); ss = miss(v, d, css, co, cp, start); /* * Special case: match ended at eol? */ if (ss != NULL && (ss->flags&POSTSTATE)) { return cp; } else if (ss != NULL) { ss->lastseen = cp; /* to be tidy */ } } /* * Find last match, if any. */ post = d->lastpost; for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--) { if ((ss->flags&POSTSTATE) && (post != ss->lastseen) && (post == NULL || post < ss->lastseen)) { post = ss->lastseen; } } if (post != NULL) { /* found one */ return post - 1; } return NULL; }  /* - shortest - shortest-preferred matching engine ^ static chr *shortest(struct vars *, struct dfa *, chr *, chr *, chr *, ^ chr **, int *); */ static chr * /* endpoint, or NULL */ shortest( struct vars *v, struct dfa *d, chr *start, /* where the match should start */ chr *min, /* match must end at or after here */ chr *max, /* match must end at or before here */ chr **coldp, /* store coldstart pointer here, if nonNULL */ int *hitstopp) /* record whether hit v->stop, if non-NULL */ { chr *cp; chr *realmin = (min == v->stop) ? min : min + 1; chr *realmax = (max == v->stop) ? max : max + 1; color co; struct sset *css; struct sset *ss; struct colormap *cm = d->cm; /* * Initialize. */ css = initialize(v, d, start); cp = start; if (hitstopp != NULL) { *hitstopp = 0; } /* * Startup. */ FDEBUG(("--- startup ---\n")); if (cp == v->start) { co = d->cnfa->bos[(v->eflags&REG_NOTBOL) ? 0 : 1]; FDEBUG(("color %ld\n", (long)co)); } else { co = GETCOLOR(cm, *(cp - 1)); FDEBUG(("char %c, color %ld\n", (char)*(cp-1), (long)co)); } css = miss(v, d, css, co, cp, start); if (css == NULL) { return NULL; } css->lastseen = cp; ss = css; /* * Main loop. */ if (v->eflags&REG_FTRACE) { while (cp < realmax) { FDEBUG(("--- at c%d ---\n", css - d->ssets)); co = GETCOLOR(cm, *cp); FDEBUG(("char %c, color %ld\n", (char)*cp, (long)co)); ss = css->outs[co]; if (ss == NULL) { ss = miss(v, d, css, co, cp+1, start); if (ss == NULL) { break; /* NOTE BREAK OUT */ } } cp++; ss->lastseen = cp; css = ss; if ((ss->flags&POSTSTATE) && cp >= realmin) { break; /* NOTE BREAK OUT */ } } } else { while (cp < realmax) { co = GETCOLOR(cm, *cp); ss = css->outs[co]; if (ss == NULL) { ss = miss(v, d, css, co, cp+1, start); if (ss == NULL) { break; /* NOTE BREAK OUT */ } } cp++; ss->lastseen = cp; css = ss; if ((ss->flags&POSTSTATE) && cp >= realmin) { break; /* NOTE BREAK OUT */ } } } if (ss == NULL) { return NULL; } if (coldp != NULL) { /* report last no-progress state set, if any */ *coldp = lastcold(v, d); } if ((ss->flags&POSTSTATE) && cp > min) { assert(cp >= realmin); cp--; } else if (cp == v->stop && max == v->stop) { co = d->cnfa->eos[(v->eflags&REG_NOTEOL) ? 0 : 1]; FDEBUG(("color %ld\n", (long)co)); ss = miss(v, d, css, co, cp, start); /* * Match might have ended at eol. */ if ((ss == NULL || !(ss->flags&POSTSTATE)) && hitstopp != NULL) { *hitstopp = 1; } } if (ss == NULL || !(ss->flags&POSTSTATE)) { return NULL; } return cp; }  /* - lastcold - determine last point at which no progress had been made ^ static chr *lastcold(struct vars *, struct dfa *); */ static chr * /* endpoint, or NULL */ lastcold( struct vars *v, struct dfa *d) { struct sset *ss; chr *nopr; int i; nopr = d->lastnopr; if (nopr == NULL) { nopr = v->start; } for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--) { if ((ss->flags&NOPROGRESS) && nopr < ss->lastseen) { nopr = ss->lastseen; } } return nopr; }  /* - newdfa - set up a fresh DFA ^ static struct dfa *newdfa(struct vars *, struct cnfa *, ^ struct colormap *, struct smalldfa *); */ static struct dfa * newdfa( struct vars *v, struct cnfa *cnfa, struct colormap *cm, struct smalldfa *small) /* preallocated space, may be NULL */ { struct dfa *d; size_t nss = cnfa->nstates * 2; int wordsper = (cnfa->nstates + UBITS - 1) / UBITS; struct smalldfa *smallwas = small; assert(cnfa != NULL && cnfa->nstates != 0); if (nss <= FEWSTATES && cnfa->ncolors <= FEWCOLORS) { assert(wordsper == 1); if (small == NULL) { small = (struct smalldfa *) MALLOC(sizeof(struct smalldfa)); if (small == NULL) { ERR(REG_ESPACE); return NULL; } } d = &small->dfa; d->ssets = small->ssets; d->statesarea = small->statesarea; d->work = &d->statesarea[nss]; d->outsarea = small->outsarea; d->incarea = small->incarea; d->cptsmalloced = 0; d->mallocarea = (smallwas == NULL) ? (char *)small : NULL; } else { d = (struct dfa *)MALLOC(sizeof(struct dfa)); if (d == NULL) { ERR(REG_ESPACE); return NULL; } d->ssets = (struct sset *)MALLOC(nss * sizeof(struct sset)); d->statesarea = (unsigned *) MALLOC((nss+WORK) * wordsper * sizeof(unsigned)); d->work = &d->statesarea[nss * wordsper]; d->outsarea = (struct sset **) MALLOC(nss * cnfa->ncolors * sizeof(struct sset *)); d->incarea = (struct arcp *) MALLOC(nss * cnfa->ncolors * sizeof(struct arcp)); d->cptsmalloced = 1; d->mallocarea = (char *)d; if (d->ssets == NULL || d->statesarea == NULL || d->outsarea == NULL || d->incarea == NULL) { freedfa(d); ERR(REG_ESPACE); return NULL; } } d->nssets = (v->eflags&REG_SMALL) ? 7 : nss; d->nssused = 0; d->nstates = cnfa->nstates; d->ncolors = cnfa->ncolors; d->wordsper = wordsper; d->cnfa = cnfa; d->cm = cm; d->lastpost = NULL; d->lastnopr = NULL; d->search = d->ssets; /* * Initialization of sset fields is done as needed. */ return d; }  /* - freedfa - free a DFA ^ static VOID freedfa(struct dfa *); */ static void freedfa( struct dfa *d) { if (d->cptsmalloced) { if (d->ssets != NULL) { FREE(d->ssets); } if (d->statesarea != NULL) { FREE(d->statesarea); } if (d->outsarea != NULL) { FREE(d->outsarea); } if (d->incarea != NULL) { FREE(d->incarea); } } if (d->mallocarea != NULL) { FREE(d->mallocarea); } }  /* - hash - construct a hash code for a bitvector * There are probably better ways, but they're more expensive. ^ static unsigned hash(unsigned *, int); */ static unsigned hash( unsigned *uv, int n) { int i; unsigned h; h = 0; for (i = 0; i < n; i++) { h ^= uv[i]; } return h; }  /* - initialize - hand-craft a cache entry for startup, otherwise get ready ^ static struct sset *initialize(struct vars *, struct dfa *, chr *); */ static struct sset * initialize( struct vars *v, /* used only for debug flags */ struct dfa *d, chr *start) { struct sset *ss; int i; /* * Is previous one still there? */ if (d->nssused > 0 && (d->ssets[0].flags&STARTER)) { ss = &d->ssets[0]; } else { /* no, must (re)build it */ ss = getvacant(v, d, start, start); for (i = 0; i < d->wordsper; i++) { ss->states[i] = 0; } BSET(ss->states, d->cnfa->pre); ss->hash = HASH(ss->states, d->wordsper); assert(d->cnfa->pre != d->cnfa->post); ss->flags = STARTER|LOCKED|NOPROGRESS; /* * lastseen dealt with below */ } for (i = 0; i < d->nssused; i++) { d->ssets[i].lastseen = NULL; } ss->lastseen = start; /* maybe untrue, but harmless */ d->lastpost = NULL; d->lastnopr = NULL; return ss; }  /* - miss - handle a cache miss ^ static struct sset *miss(struct vars *, struct dfa *, struct sset *, ^ pcolor, chr *, chr *); */ static struct sset * /* NULL if goes to empty set */ miss( struct vars *v, /* used only for debug flags */ struct dfa *d, struct sset *css, pcolor co, chr *cp, /* next chr */ chr *start) /* where the attempt got started */ { struct cnfa *cnfa = d->cnfa; int i; unsigned h; struct carc *ca; struct sset *p; int ispost; int noprogress; int gotstate; int dolacons; int sawlacons; /* * For convenience, we can be called even if it might not be a miss. */ if (css->outs[co] != NULL) { FDEBUG(("hit\n")); return css->outs[co]; } FDEBUG(("miss\n")); /* * First, what set of states would we end up in? */ for (i = 0; i < d->wordsper; i++) { d->work[i] = 0; } ispost = 0; noprogress = 1; gotstate = 0; for (i = 0; i < d->nstates; i++) { if (ISBSET(css->states, i)) { for (ca = cnfa->states[i]+1; ca->co != COLORLESS; ca++) { if (ca->co == co) { BSET(d->work, ca->to); gotstate = 1; if (ca->to == cnfa->post) { ispost = 1; } if (!cnfa->states[ca->to]->co) { noprogress = 0; } FDEBUG(("%d -> %d\n", i, ca->to)); } } } } dolacons = (gotstate) ? (cnfa->flags&HASLACONS) : 0; sawlacons = 0; while (dolacons) { /* transitive closure */ dolacons = 0; for (i = 0; i < d->nstates; i++) { if (ISBSET(d->work, i)) { for (ca = cnfa->states[i]+1; ca->co != COLORLESS; ca++) { if (ca->co <= cnfa->ncolors) { continue; /* NOTE CONTINUE */ } sawlacons = 1; if (ISBSET(d->work, ca->to)) { continue; /* NOTE CONTINUE */ } if (!lacon(v, cnfa, cp, ca->co)) { continue; /* NOTE CONTINUE */ } BSET(d->work, ca->to); dolacons = 1; if (ca->to == cnfa->post) { ispost = 1; } if (!cnfa->states[ca->to]->co) { noprogress = 0; } FDEBUG(("%d :> %d\n", i, ca->to)); } } } } if (!gotstate) { return NULL; } h = HASH(d->work, d->wordsper); /* * Next, is that in the cache? */ for (p = d->ssets, i = d->nssused; i > 0; p++, i--) { if (HIT(h, d->work, p, d->wordsper)) { FDEBUG(("cached c%d\n", p - d->ssets)); break; /* NOTE BREAK OUT */ } } if (i == 0) { /* nope, need a new cache entry */ p = getvacant(v, d, cp, start); assert(p != css); for (i = 0; i < d->wordsper; i++) { p->states[i] = d->work[i]; } p->hash = h; p->flags = (ispost) ? POSTSTATE : 0; if (noprogress) { p->flags |= NOPROGRESS; } /* * lastseen to be dealt with by caller */ } if (!sawlacons) { /* lookahead conds. always cache miss */ FDEBUG(("c%d[%d]->c%d\n", css - d->ssets, co, p - d->ssets)); css->outs[co] = p; css->inchain[co] = p->ins; p->ins.ss = css; p->ins.co = (color)co; } return p; }  /* - lacon - lookahead-constraint checker for miss() ^ static int lacon(struct vars *, struct cnfa *, chr *, pcolor); */ static int /* predicate: constraint satisfied? */ lacon( struct vars *v, struct cnfa *pcnfa, /* parent cnfa */ chr *cp, pcolor co) /* "color" of the lookahead constraint */ { int n; struct subre *sub; struct dfa *d; struct smalldfa sd; chr *end; n = co - pcnfa->ncolors; assert(n < v->g->nlacons && v->g->lacons != NULL); FDEBUG(("=== testing lacon %d\n", n)); sub = &v->g->lacons[n]; d = newdfa(v, &sub->cnfa, &v->g->cmap, &sd); if (d == NULL) { ERR(REG_ESPACE); return 0; } end = longest(v, d, cp, v->stop, (int *)NULL); freedfa(d); FDEBUG(("=== lacon %d match %d\n", n, (end != NULL))); return (sub->subno) ? (end != NULL) : (end == NULL); }  /* - getvacant - get a vacant state set * This routine clears out the inarcs and outarcs, but does not otherwise * clear the innards of the state set -- that's up to the caller. ^ static struct sset *getvacant(struct vars *, struct dfa *, chr *, chr *); */ static struct sset * getvacant( struct vars *v, /* used only for debug flags */ struct dfa *d, chr *cp, chr *start) { int i; struct sset *ss; struct sset *p; struct arcp ap; struct arcp lastap = {NULL, 0}; /* silence gcc 4 warning */ color co; ss = pickss(v, d, cp, start); assert(!(ss->flags&LOCKED)); /* * Clear out its inarcs, including self-referential ones. */ ap = ss->ins; while ((p = ap.ss) != NULL) { co = ap.co; FDEBUG(("zapping c%d's %ld outarc\n", p - d->ssets, (long)co)); p->outs[co] = NULL; ap = p->inchain[co]; p->inchain[co].ss = NULL; /* paranoia */ } ss->ins.ss = NULL; /* * Take it off the inarc chains of the ssets reached by its outarcs. */ for (i = 0; i < d->ncolors; i++) { p = ss->outs[i]; assert(p != ss); /* not self-referential */ if (p == NULL) { continue; /* NOTE CONTINUE */ } FDEBUG(("del outarc %d from c%d's in chn\n", i, p - d->ssets)); if (p->ins.ss == ss && p->ins.co == i) { p->ins = ss->inchain[i]; } else { assert(p->ins.ss != NULL); for (ap = p->ins; ap.ss != NULL && !(ap.ss == ss && ap.co == i); ap = ap.ss->inchain[ap.co]) { lastap = ap; } assert(ap.ss != NULL); lastap.ss->inchain[lastap.co] = ss->inchain[i]; } ss->outs[i] = NULL; ss->inchain[i].ss = NULL; } /* * If ss was a success state, may need to remember location. */ if ((ss->flags&POSTSTATE) && ss->lastseen != d->lastpost && (d->lastpost == NULL || d->lastpost < ss->lastseen)) { d->lastpost = ss->lastseen; } /* * Likewise for a no-progress state. */ if ((ss->flags&NOPROGRESS) && ss->lastseen != d->lastnopr && (d->lastnopr == NULL || d->lastnopr < ss->lastseen)) { d->lastnopr = ss->lastseen; } return ss; }  /* - pickss - pick the next stateset to be used ^ static struct sset *pickss(struct vars *, struct dfa *, chr *, chr *); */ static struct sset * pickss( struct vars *v, /* used only for debug flags */ struct dfa *d, chr *cp, chr *start) { int i; struct sset *ss; struct sset *end; chr *ancient; /* * Shortcut for cases where cache isn't full. */ if (d->nssused < d->nssets) { i = d->nssused; d->nssused++; ss = &d->ssets[i]; FDEBUG(("new c%d\n", i)); /* * Set up innards. */ ss->states = &d->statesarea[i * d->wordsper]; ss->flags = 0; ss->ins.ss = NULL; ss->ins.co = WHITE; /* give it some value */ ss->outs = &d->outsarea[i * d->ncolors]; ss->inchain = &d->incarea[i * d->ncolors]; for (i = 0; i < d->ncolors; i++) { ss->outs[i] = NULL; ss->inchain[i].ss = NULL; } return ss; } /* * Look for oldest, or old enough anyway. */ if (cp - start > d->nssets*2/3) { /* oldest 33% are expendable */ ancient = cp - d->nssets*2/3; } else { ancient = start; } for (ss = d->search, end = &d->ssets[d->nssets]; ss < end; ss++) { if ((ss->lastseen == NULL || ss->lastseen < ancient) && !(ss->flags&LOCKED)) { d->search = ss + 1; FDEBUG(("replacing c%d\n", ss - d->ssets)); return ss; } } for (ss = d->ssets, end = d->search; ss < end; ss++) { if ((ss->lastseen == NULL || ss->lastseen < ancient) && !(ss->flags&LOCKED)) { d->search = ss + 1; FDEBUG(("replacing c%d\n", ss - d->ssets)); return ss; } } /* * Nobody's old enough?!? -- something's really wrong. */ FDEBUG(("can't find victim to replace!\n")); assert(NOTREACHED); ERR(REG_ASSERT); return d->ssets; }  /* * Local Variables: * mode: c * c-basic-offset: 4 * fill-column: 78 * End: */

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