regc_nfa.c Go to the documentation of this file. /* * NFA utilities. * This file is #included by regcomp.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. * * One or two things that technically ought to be in here are actually in * color.c, thanks to some incestuous relationships in the color chains. */ #define NISERR() VISERR(nfa->v) #define NERR(e) VERR(nfa->v, (e))  /* - newnfa - set up an NFA ^ static struct nfa *newnfa(struct vars *, struct colormap *, struct nfa *); */ static struct nfa * /* the NFA, or NULL */ newnfa( struct vars *v, struct colormap *cm, struct nfa *parent) /* NULL if primary NFA */ { struct nfa *nfa; nfa = (struct nfa *) MALLOC(sizeof(struct nfa)); if (nfa == NULL) { return NULL; } nfa->states = NULL; nfa->slast = NULL; nfa->free = NULL; nfa->nstates = 0; nfa->cm = cm; nfa->v = v; nfa->size = 0; nfa->bos[0] = nfa->bos[1] = COLORLESS; nfa->eos[0] = nfa->eos[1] = COLORLESS; nfa->parent = parent; /* Precedes newfstate so parent is valid. */ nfa->post = newfstate(nfa, '@'); /* number 0 */ nfa->pre = newfstate(nfa, '>'); /* number 1 */ nfa->init = newstate(nfa); /* May become invalid later. */ nfa->final = newstate(nfa); if (ISERR()) { freenfa(nfa); return NULL; } rainbow(nfa, nfa->cm, PLAIN, COLORLESS, nfa->pre, nfa->init); newarc(nfa, '^', 1, nfa->pre, nfa->init); newarc(nfa, '^', 0, nfa->pre, nfa->init); rainbow(nfa, nfa->cm, PLAIN, COLORLESS, nfa->final, nfa->post); newarc(nfa, '$', 1, nfa->final, nfa->post); newarc(nfa, '$', 0, nfa->final, nfa->post); if (ISERR()) { freenfa(nfa); return NULL; } return nfa; }  /* - TooManyStates - checks if the max states exceeds the compile-time value ^ static int TooManyStates(struct nfa *); */ static int TooManyStates( struct nfa *nfa) { struct nfa *parent = nfa->parent; size_t sz = nfa->size; while (parent != NULL) { sz = parent->size; parent = parent->parent; } if (sz > REG_MAX_STATES) { return 1; } return 0; }  /* - IncrementSize - increases the tracked size of the NFA and its parents. ^ static void IncrementSize(struct nfa *); */ static void IncrementSize( struct nfa *nfa) { struct nfa *parent = nfa->parent; nfa->size++; while (parent != NULL) { parent->size++; parent = parent->parent; } }  /* - DecrementSize - increases the tracked size of the NFA and its parents. ^ static void DecrementSize(struct nfa *); */ static void DecrementSize( struct nfa *nfa) { struct nfa *parent = nfa->parent; nfa->size--; while (parent != NULL) { parent->size--; parent = parent->parent; } }  /* - freenfa - free an entire NFA ^ static VOID freenfa(struct nfa *); */ static void freenfa( struct nfa *nfa) { struct state *s; while ((s = nfa->states) != NULL) { s->nins = s->nouts = 0; /* don't worry about arcs */ freestate(nfa, s); } while ((s = nfa->free) != NULL) { nfa->free = s->next; destroystate(nfa, s); } nfa->slast = NULL; nfa->nstates = -1; nfa->pre = NULL; nfa->post = NULL; FREE(nfa); }  /* - newstate - allocate an NFA state, with zero flag value ^ static struct state *newstate(struct nfa *); */ static struct state * /* NULL on error */ newstate( struct nfa *nfa) { struct state *s; if (TooManyStates(nfa)) { /* XXX: add specific error for this */ NERR(REG_ETOOBIG); return NULL; } if (nfa->free != NULL) { s = nfa->free; nfa->free = s->next; } else { s = (struct state *) MALLOC(sizeof(struct state)); if (s == NULL) { NERR(REG_ESPACE); return NULL; } s->oas.next = NULL; s->free = NULL; s->noas = 0; } assert(nfa->nstates >= 0); s->no = nfa->nstates++; s->flag = 0; if (nfa->states == NULL) { nfa->states = s; } s->nins = 0; s->ins = NULL; s->nouts = 0; s->outs = NULL; s->tmp = NULL; s->next = NULL; if (nfa->slast != NULL) { assert(nfa->slast->next == NULL); nfa->slast->next = s; } s->prev = nfa->slast; nfa->slast = s; /* * Track the current size and the parent size. */ IncrementSize(nfa); return s; }  /* - newfstate - allocate an NFA state with a specified flag value ^ static struct state *newfstate(struct nfa *, int flag); */ static struct state * /* NULL on error */ newfstate( struct nfa *nfa, int flag) { struct state *s; s = newstate(nfa); if (s != NULL) { s->flag = (char) flag; } return s; }  /* - dropstate - delete a state's inarcs and outarcs and free it ^ static VOID dropstate(struct nfa *, struct state *); */ static void dropstate( struct nfa *nfa, struct state *s) { struct arc *a; while ((a = s->ins) != NULL) { freearc(nfa, a); } while ((a = s->outs) != NULL) { freearc(nfa, a); } freestate(nfa, s); }  /* - freestate - free a state, which has no in-arcs or out-arcs ^ static VOID freestate(struct nfa *, struct state *); */ static void freestate( struct nfa *nfa, struct state *s) { assert(s != NULL); assert(s->nins == 0 && s->nouts == 0); s->no = FREESTATE; s->flag = 0; if (s->next != NULL) { s->next->prev = s->prev; } else { assert(s == nfa->slast); nfa->slast = s->prev; } if (s->prev != NULL) { s->prev->next = s->next; } else { assert(s == nfa->states); nfa->states = s->next; } s->prev = NULL; s->next = nfa->free; /* don't delete it, put it on the free list */ nfa->free = s; DecrementSize(nfa); }  /* - destroystate - really get rid of an already-freed state ^ static VOID destroystate(struct nfa *, struct state *); */ static void destroystate( struct nfa *nfa, struct state *s) { struct arcbatch *ab; struct arcbatch *abnext; assert(s->no == FREESTATE); for (ab=s->oas.next ; ab!=NULL ; ab=abnext) { abnext = ab->next; FREE(ab); } s->ins = NULL; s->outs = NULL; s->next = NULL; FREE(s); }  /* - newarc - set up a new arc within an NFA ^ static VOID newarc(struct nfa *, int, pcolor, struct state *, ^ struct state *); */ static void newarc( struct nfa *nfa, int t, pcolor co, struct state *from, struct state *to) { struct arc *a; assert(from != NULL && to != NULL); /* * Check for duplicates. */ for (a=from->outs ; a!=NULL ; a=a->outchain) { if (a->to == to && a->co == co && a->type == t) { return; } } a = allocarc(nfa, from); if (NISERR()) { return; } assert(a != NULL); a->type = t; a->co = (color) co; a->to = to; a->from = from; /* * Put the new arc on the beginning, not the end, of the chains. Not only * is this easier, it has the very useful side effect that deleting the * most-recently-added arc is the cheapest case rather than the most * expensive one. */ a->inchain = to->ins; to->ins = a; a->outchain = from->outs; from->outs = a; from->nouts++; to->nins++; if (COLORED(a) && nfa->parent == NULL) { colorchain(nfa->cm, a); } }  /* - allocarc - allocate a new out-arc within a state ^ static struct arc *allocarc(struct nfa *, struct state *); */ static struct arc * /* NULL for failure */ allocarc( struct nfa *nfa, struct state *s) { struct arc *a; /* * Shortcut */ if (s->free == NULL && s->noas < ABSIZE) { a = &s->oas.a[s->noas]; s->noas++; return a; } /* * if none at hand, get more */ if (s->free == NULL) { struct arcbatch *newAb = (struct arcbatch *) MALLOC(sizeof(struct arcbatch)); int i; if (newAb == NULL) { NERR(REG_ESPACE); return NULL; } newAb->next = s->oas.next; s->oas.next = newAb; for (i=0 ; i<ABSIZE ; i++) { newAb->a[i].type = 0; newAb->a[i].freechain = &newAb->a[i+1]; } newAb->a[ABSIZE-1].freechain = NULL; s->free = &newAb->a[0]; } assert(s->free != NULL); a = s->free; s->free = a->freechain; return a; }  /* - freearc - free an arc ^ static VOID freearc(struct nfa *, struct arc *); */ static void freearc( struct nfa *nfa, struct arc *victim) { struct state *from = victim->from; struct state *to = victim->to; struct arc *a; assert(victim->type != 0); /* * Take it off color chain if necessary. */ if (COLORED(victim) && nfa->parent == NULL) { uncolorchain(nfa->cm, victim); } /* * Take it off source's out-chain. */ assert(from != NULL); assert(from->outs != NULL); a = from->outs; if (a == victim) { /* simple case: first in chain */ from->outs = victim->outchain; } else { for (; a!=NULL && a->outchain!=victim ; a=a->outchain) { continue; } assert(a != NULL); a->outchain = victim->outchain; } from->nouts--; /* * Take it off target's in-chain. */ assert(to != NULL); assert(to->ins != NULL); a = to->ins; if (a == victim) { /* simple case: first in chain */ to->ins = victim->inchain; } else { for (; a->inchain!=victim ; a=a->inchain) { assert(a->inchain != NULL); continue; } a->inchain = victim->inchain; } to->nins--; /* * Clean up and place on free list. */ victim->type = 0; victim->from = NULL; /* precautions... */ victim->to = NULL; victim->inchain = NULL; victim->outchain = NULL; victim->freechain = from->free; from->free = victim; }  /* - findarc - find arc, if any, from given source with given type and color * If there is more than one such arc, the result is random. ^ static struct arc *findarc(struct state *, int, pcolor); */ static struct arc * findarc( struct state *s, int type, pcolor co) { struct arc *a; for (a=s->outs ; a!=NULL ; a=a->outchain) { if (a->type == type && a->co == co) { return a; } } return NULL; }  /* - cparc - allocate a new arc within an NFA, copying details from old one ^ static VOID cparc(struct nfa *, struct arc *, struct state *, ^ struct state *); */ static void cparc( struct nfa *nfa, struct arc *oa, struct state *from, struct state *to) { newarc(nfa, oa->type, oa->co, from, to); }  /* - moveins - move all in arcs of a state to another state * You might think this could be done better by just updating the * existing arcs, and you would be right if it weren't for the desire * for duplicate suppression, which makes it easier to just make new * ones to exploit the suppression built into newarc. ^ static VOID moveins(struct nfa *, struct state *, struct state *); */ static void moveins( struct nfa *nfa, struct state *oldState, struct state *newState) { struct arc *a; assert(oldState != newState); while ((a = oldState->ins) != NULL) { cparc(nfa, a, a->from, newState); freearc(nfa, a); } assert(oldState->nins == 0); assert(oldState->ins == NULL); }  /* - copyins - copy all in arcs of a state to another state ^ static VOID copyins(struct nfa *, struct state *, struct state *); */ static void copyins( struct nfa *nfa, struct state *oldState, struct state *newState) { struct arc *a; assert(oldState != newState); for (a=oldState->ins ; a!=NULL ; a=a->inchain) { cparc(nfa, a, a->from, newState); } }  /* - moveouts - move all out arcs of a state to another state ^ static VOID moveouts(struct nfa *, struct state *, struct state *); */ static void moveouts( struct nfa *nfa, struct state *oldState, struct state *newState) { struct arc *a; assert(oldState != newState); while ((a = oldState->outs) != NULL) { cparc(nfa, a, newState, a->to); freearc(nfa, a); } }  /* - copyouts - copy all out arcs of a state to another state ^ static VOID copyouts(struct nfa *, struct state *, struct state *); */ static void copyouts( struct nfa *nfa, struct state *oldState, struct state *newState) { struct arc *a; assert(oldState != newState); for (a=oldState->outs ; a!=NULL ; a=a->outchain) { cparc(nfa, a, newState, a->to); } }  /* - cloneouts - copy out arcs of a state to another state pair, modifying type ^ static VOID cloneouts(struct nfa *, struct state *, struct state *, ^ struct state *, int); */ static void cloneouts( struct nfa *nfa, struct state *old, struct state *from, struct state *to, int type) { struct arc *a; assert(old != from); for (a=old->outs ; a!=NULL ; a=a->outchain) { newarc(nfa, type, a->co, from, to); } }  /* - delsub - delete a sub-NFA, updating subre pointers if necessary * This uses a recursive traversal of the sub-NFA, marking already-seen * states using their tmp pointer. ^ static VOID delsub(struct nfa *, struct state *, struct state *); */ static void delsub( struct nfa *nfa, struct state *lp, /* the sub-NFA goes from here... */ struct state *rp) /* ...to here, *not* inclusive */ { assert(lp != rp); rp->tmp = rp; /* mark end */ deltraverse(nfa, lp, lp); assert(lp->nouts == 0 && rp->nins == 0); /* did the job */ assert(lp->no != FREESTATE && rp->no != FREESTATE); /* no more */ rp->tmp = NULL; /* unmark end */ lp->tmp = NULL; /* and begin, marked by deltraverse */ }  /* - deltraverse - the recursive heart of delsub * This routine's basic job is to destroy all out-arcs of the state. ^ static VOID deltraverse(struct nfa *, struct state *, struct state *); */ static void deltraverse( struct nfa *nfa, struct state *leftend, struct state *s) { struct arc *a; struct state *to; if (s->nouts == 0) { return; /* nothing to do */ } if (s->tmp != NULL) { return; /* already in progress */ } s->tmp = s; /* mark as in progress */ while ((a = s->outs) != NULL) { to = a->to; deltraverse(nfa, leftend, to); assert(to->nouts == 0 || to->tmp != NULL); freearc(nfa, a); if (to->nins == 0 && to->tmp == NULL) { assert(to->nouts == 0); freestate(nfa, to); } } assert(s->no != FREESTATE); /* we're still here */ assert(s == leftend || s->nins != 0); /* and still reachable */ assert(s->nouts == 0); /* but have no outarcs */ s->tmp = NULL; /* we're done here */ }  /* - dupnfa - duplicate sub-NFA * Another recursive traversal, this time using tmp to point to duplicates as * well as mark already-seen states. (You knew there was a reason why it's a * state pointer, didn't you? :-)) ^ static VOID dupnfa(struct nfa *, struct state *, struct state *, ^ struct state *, struct state *); */ static void dupnfa( struct nfa *nfa, struct state *start, /* duplicate of subNFA starting here */ struct state *stop, /* and stopping here */ struct state *from, /* stringing duplicate from here */ struct state *to) /* to here */ { if (start == stop) { newarc(nfa, EMPTY, 0, from, to); return; } stop->tmp = to; duptraverse(nfa, start, from); /* done, except for clearing out the tmp pointers */ stop->tmp = NULL; cleartraverse(nfa, start); }  /* - duptraverse - recursive heart of dupnfa ^ static VOID duptraverse(struct nfa *, struct state *, struct state *); */ static void duptraverse( struct nfa *nfa, struct state *s, struct state *stmp) /* s's duplicate, or NULL */ { struct arc *a; if (s->tmp != NULL) { return; /* already done */ } s->tmp = (stmp == NULL) ? newstate(nfa) : stmp; if (s->tmp == NULL) { assert(NISERR()); return; } for (a=s->outs ; a!=NULL && !NISERR() ; a=a->outchain) { duptraverse(nfa, a->to, NULL); if (NISERR()) { break; } assert(a->to->tmp != NULL); cparc(nfa, a, s->tmp, a->to->tmp); } }  /* - cleartraverse - recursive cleanup for algorithms that leave tmp ptrs set ^ static VOID cleartraverse(struct nfa *, struct state *); */ static void cleartraverse( struct nfa *nfa, struct state *s) { struct arc *a; if (s->tmp == NULL) { return; } s->tmp = NULL; for (a=s->outs ; a!=NULL ; a=a->outchain) { cleartraverse(nfa, a->to); } }  /* - specialcolors - fill in special colors for an NFA ^ static VOID specialcolors(struct nfa *); */ static void specialcolors( struct nfa *nfa) { /* * False colors for BOS, BOL, EOS, EOL */ if (nfa->parent == NULL) { nfa->bos[0] = pseudocolor(nfa->cm); nfa->bos[1] = pseudocolor(nfa->cm); nfa->eos[0] = pseudocolor(nfa->cm); nfa->eos[1] = pseudocolor(nfa->cm); } else { assert(nfa->parent->bos[0] != COLORLESS); nfa->bos[0] = nfa->parent->bos[0]; assert(nfa->parent->bos[1] != COLORLESS); nfa->bos[1] = nfa->parent->bos[1]; assert(nfa->parent->eos[0] != COLORLESS); nfa->eos[0] = nfa->parent->eos[0]; assert(nfa->parent->eos[1] != COLORLESS); nfa->eos[1] = nfa->parent->eos[1]; } }  /* - optimize - optimize an NFA ^ static long optimize(struct nfa *, FILE *); */ static long /* re_info bits */ optimize( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { int verbose = (f != NULL) ? 1 : 0; if (verbose) { fprintf(f, "\ninitial cleanup:\n"); } cleanup(nfa); /* may simplify situation */ if (verbose) { dumpnfa(nfa, f); } if (verbose) { fprintf(f, "\nempties:\n"); } fixempties(nfa, f); /* get rid of EMPTY arcs */ if (verbose) { fprintf(f, "\nconstraints:\n"); } pullback(nfa, f); /* pull back constraints backward */ pushfwd(nfa, f); /* push fwd constraints forward */ if (verbose) { fprintf(f, "\nfinal cleanup:\n"); } cleanup(nfa); /* final tidying */ return analyze(nfa); /* and analysis */ }  /* - pullback - pull back constraints backward to (with luck) eliminate them ^ static VOID pullback(struct nfa *, FILE *); */ static void pullback( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { struct state *s; struct state *nexts; struct arc *a; struct arc *nexta; int progress; /* * Find and pull until there are no more. */ do { progress = 0; for (s=nfa->states ; s!=NULL && !NISERR() ; s=nexts) { nexts = s->next; for (a=s->outs ; a!=NULL && !NISERR() ; a=nexta) { nexta = a->outchain; if (a->type == '^' || a->type == BEHIND) { if (pull(nfa, a)) { progress = 1; } } assert(nexta == NULL || s->no != FREESTATE); } } if (progress && f != NULL) { dumpnfa(nfa, f); } } while (progress && !NISERR()); if (NISERR()) { return; } for (a=nfa->pre->outs ; a!=NULL ; a=nexta) { nexta = a->outchain; if (a->type == '^') { assert(a->co == 0 || a->co == 1); newarc(nfa, PLAIN, nfa->bos[a->co], a->from, a->to); freearc(nfa, a); } } }  /* - pull - pull a back constraint backward past its source state * A significant property of this function is that it deletes at most * one state -- the constraint's from state -- and only if the constraint * was that state's last outarc. ^ static int pull(struct nfa *, struct arc *); */ static int /* 0 couldn't, 1 could */ pull( struct nfa *nfa, struct arc *con) { struct state *from = con->from; struct state *to = con->to; struct arc *a; struct arc *nexta; struct state *s; if (from == to) { /* circular constraint is pointless */ freearc(nfa, con); return 1; } if (from->flag) { /* can't pull back beyond start */ return 0; } if (from->nins == 0) { /* unreachable */ freearc(nfa, con); return 1; } /* * DGP 2007-11-15: Cloning a state with a circular constraint on its list * of outs can lead to trouble [Bug 1810038], so get rid of them first. */ for (a = from->outs; a != NULL; a = nexta) { nexta = a->outchain; switch (a->type) { case '^': case '$': case BEHIND: case AHEAD: if (from == a->to) { freearc(nfa, a); } break; } } /* * First, clone from state if necessary to avoid other outarcs. */ if (from->nouts > 1) { s = newstate(nfa); if (NISERR()) { return 0; } assert(to != from); /* con is not an inarc */ copyins(nfa, from, s); /* duplicate inarcs */ cparc(nfa, con, s, to); /* move constraint arc */ freearc(nfa, con); from = s; con = from->outs; } assert(from->nouts == 1); /* * Propagate the constraint into the from state's inarcs. */ for (a=from->ins ; a!=NULL ; a=nexta) { nexta = a->inchain; switch (combine(con, a)) { case INCOMPATIBLE: /* destroy the arc */ freearc(nfa, a); break; case SATISFIED: /* no action needed */ break; case COMPATIBLE: /* swap the two arcs, more or less */ s = newstate(nfa); if (NISERR()) { return 0; } cparc(nfa, a, s, to); /* anticipate move */ cparc(nfa, con, a->from, s); if (NISERR()) { return 0; } freearc(nfa, a); break; default: assert(NOTREACHED); break; } } /* * Remaining inarcs, if any, incorporate the constraint. */ moveins(nfa, from, to); dropstate(nfa, from); /* will free the constraint */ return 1; }  /* - pushfwd - push forward constraints forward to (with luck) eliminate them ^ static VOID pushfwd(struct nfa *, FILE *); */ static void pushfwd( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { struct state *s; struct state *nexts; struct arc *a; struct arc *nexta; int progress; /* * Find and push until there are no more. */ do { progress = 0; for (s=nfa->states ; s!=NULL && !NISERR() ; s=nexts) { nexts = s->next; for (a = s->ins; a != NULL && !NISERR(); a = nexta) { nexta = a->inchain; if (a->type == '$' || a->type == AHEAD) { if (push(nfa, a)) { progress = 1; } } assert(nexta == NULL || s->no != FREESTATE); } } if (progress && f != NULL) { dumpnfa(nfa, f); } } while (progress && !NISERR()); if (NISERR()) { return; } for (a = nfa->post->ins; a != NULL; a = nexta) { nexta = a->inchain; if (a->type == '$') { assert(a->co == 0 || a->co == 1); newarc(nfa, PLAIN, nfa->eos[a->co], a->from, a->to); freearc(nfa, a); } } }  /* - push - push a forward constraint forward past its destination state * A significant property of this function is that it deletes at most * one state -- the constraint's to state -- and only if the constraint * was that state's last inarc. ^ static int push(struct nfa *, struct arc *); */ static int /* 0 couldn't, 1 could */ push( struct nfa *nfa, struct arc *con) { struct state *from = con->from; struct state *to = con->to; struct arc *a; struct arc *nexta; struct state *s; if (to == from) { /* circular constraint is pointless */ freearc(nfa, con); return 1; } if (to->flag) { /* can't push forward beyond end */ return 0; } if (to->nouts == 0) { /* dead end */ freearc(nfa, con); return 1; } /* * DGP 2007-11-15: Here we duplicate the same protections as appear * in pull() above to avoid troubles with cloning a state with a * circular constraint on its list of ins. It is not clear whether * this is necessary, or is protecting against a "can't happen". * Any test case that actually leads to a freearc() call here would * be a welcome addition to the test suite. */ for (a = to->ins; a != NULL; a = nexta) { nexta = a->inchain; switch (a->type) { case '^': case '$': case BEHIND: case AHEAD: if (a->from == to) { freearc(nfa, a); } break; } } /* * First, clone to state if necessary to avoid other inarcs. */ if (to->nins > 1) { s = newstate(nfa); if (NISERR()) { return 0; } copyouts(nfa, to, s); /* duplicate outarcs */ cparc(nfa, con, from, s); /* move constraint */ freearc(nfa, con); to = s; con = to->ins; } assert(to->nins == 1); /* * Propagate the constraint into the to state's outarcs. */ for (a = to->outs; a != NULL; a = nexta) { nexta = a->outchain; switch (combine(con, a)) { case INCOMPATIBLE: /* destroy the arc */ freearc(nfa, a); break; case SATISFIED: /* no action needed */ break; case COMPATIBLE: /* swap the two arcs, more or less */ s = newstate(nfa); if (NISERR()) { return 0; } cparc(nfa, con, s, a->to); /* anticipate move */ cparc(nfa, a, from, s); if (NISERR()) { return 0; } freearc(nfa, a); break; default: assert(NOTREACHED); break; } } /* * Remaining outarcs, if any, incorporate the constraint. */ moveouts(nfa, to, from); dropstate(nfa, to); /* will free the constraint */ return 1; }  /* - combine - constraint lands on an arc, what happens? ^ #def INCOMPATIBLE 1 // destroys arc ^ #def SATISFIED 2 // constraint satisfied ^ #def COMPATIBLE 3 // compatible but not satisfied yet ^ static int combine(struct arc *, struct arc *); */ static int combine( struct arc *con, struct arc *a) { #define CA(ct,at) (((ct)<<CHAR_BIT) | (at)) switch (CA(con->type, a->type)) { case CA('^', PLAIN): /* newlines are handled separately */ case CA('$', PLAIN): return INCOMPATIBLE; break; case CA(AHEAD, PLAIN): /* color constraints meet colors */ case CA(BEHIND, PLAIN): if (con->co == a->co) { return SATISFIED; } return INCOMPATIBLE; break; case CA('^', '^'): /* collision, similar constraints */ case CA('$', '$'): case CA(AHEAD, AHEAD): case CA(BEHIND, BEHIND): if (con->co == a->co) { /* true duplication */ return SATISFIED; } return INCOMPATIBLE; break; case CA('^', BEHIND): /* collision, dissimilar constraints */ case CA(BEHIND, '^'): case CA('$', AHEAD): case CA(AHEAD, '$'): return INCOMPATIBLE; break; case CA('^', '$'): /* constraints passing each other */ case CA('^', AHEAD): case CA(BEHIND, '$'): case CA(BEHIND, AHEAD): case CA('$', '^'): case CA('$', BEHIND): case CA(AHEAD, '^'): case CA(AHEAD, BEHIND): case CA('^', LACON): case CA(BEHIND, LACON): case CA('$', LACON): case CA(AHEAD, LACON): return COMPATIBLE; break; } assert(NOTREACHED); return INCOMPATIBLE; /* for benefit of blind compilers */ }  /* - fixempties - get rid of EMPTY arcs ^ static VOID fixempties(struct nfa *, FILE *); */ static void fixempties( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { struct state *s; struct state *nexts; struct arc *a; struct arc *nexta; int progress; /* * Find and eliminate empties until there are no more. */ do { progress = 0; for (s = nfa->states; s != NULL && !NISERR() && s->no != FREESTATE; s = nexts) { nexts = s->next; for (a = s->outs; a != NULL && !NISERR(); a = nexta) { nexta = a->outchain; if (a->type == EMPTY && unempty(nfa, a)) { progress = 1; } assert(nexta == NULL || s->no != FREESTATE); } } if (progress && f != NULL) { dumpnfa(nfa, f); } } while (progress && !NISERR()); }  /* - unempty - optimize out an EMPTY arc, if possible * Actually, as it stands this function always succeeds, but the return value * is kept with an eye on possible future changes. ^ static int unempty(struct nfa *, struct arc *); */ static int /* 0 couldn't, 1 could */ unempty( struct nfa *nfa, struct arc *a) { struct state *from = a->from; struct state *to = a->to; int usefrom; /* work on from, as opposed to to? */ assert(a->type == EMPTY); assert(from != nfa->pre && to != nfa->post); if (from == to) { /* vacuous loop */ freearc(nfa, a); return 1; } /* * Decide which end to work on. */ usefrom = 1; /* default: attack from */ if (from->nouts > to->nins) { usefrom = 0; } else if (from->nouts == to->nins) { /* * Decide on secondary issue: move/copy fewest arcs. */ if (from->nins > to->nouts) { usefrom = 0; } } freearc(nfa, a); if (usefrom) { if (from->nouts == 0) { /* * Was the state's only outarc. */ moveins(nfa, from, to); freestate(nfa, from); } else { copyins(nfa, from, to); } } else { if (to->nins == 0) { /* * Was the state's only inarc. */ moveouts(nfa, to, from); freestate(nfa, to); } else { copyouts(nfa, to, from); } } return 1; }  /* - cleanup - clean up NFA after optimizations ^ static VOID cleanup(struct nfa *); */ static void cleanup( struct nfa *nfa) { struct state *s; struct state *nexts; int n; /* * Clear out unreachable or dead-end states. Use pre to mark reachable, * then post to mark can-reach-post. */ markreachable(nfa, nfa->pre, NULL, nfa->pre); markcanreach(nfa, nfa->post, nfa->pre, nfa->post); for (s = nfa->states; s != NULL; s = nexts) { nexts = s->next; if (s->tmp != nfa->post && !s->flag) { dropstate(nfa, s); } } assert(nfa->post->nins == 0 || nfa->post->tmp == nfa->post); cleartraverse(nfa, nfa->pre); assert(nfa->post->nins == 0 || nfa->post->tmp == NULL); /* the nins==0 (final unreachable) case will be caught later */ /* * Renumber surviving states. */ n = 0; for (s = nfa->states; s != NULL; s = s->next) { s->no = n++; } nfa->nstates = n; }  /* - markreachable - recursive marking of reachable states ^ static VOID markreachable(struct nfa *, struct state *, struct state *, ^ struct state *); */ static void markreachable( struct nfa *nfa, struct state *s, struct state *okay, /* consider only states with this mark */ struct state *mark) /* the value to mark with */ { struct arc *a; if (s->tmp != okay) { return; } s->tmp = mark; for (a = s->outs; a != NULL; a = a->outchain) { markreachable(nfa, a->to, okay, mark); } }  /* - markcanreach - recursive marking of states which can reach here ^ static VOID markcanreach(struct nfa *, struct state *, struct state *, ^ struct state *); */ static void markcanreach( struct nfa *nfa, struct state *s, struct state *okay, /* consider only states with this mark */ struct state *mark) /* the value to mark with */ { struct arc *a; if (s->tmp != okay) { return; } s->tmp = mark; for (a = s->ins; a != NULL; a = a->inchain) { markcanreach(nfa, a->from, okay, mark); } }  /* - analyze - ascertain potentially-useful facts about an optimized NFA ^ static long analyze(struct nfa *); */ static long /* re_info bits to be ORed in */ analyze( struct nfa *nfa) { struct arc *a; struct arc *aa; if (nfa->pre->outs == NULL) { return REG_UIMPOSSIBLE; } for (a = nfa->pre->outs; a != NULL; a = a->outchain) { for (aa = a->to->outs; aa != NULL; aa = aa->outchain) { if (aa->to == nfa->post) { return REG_UEMPTYMATCH; } } } return 0; }  /* - compact - compact an NFA ^ static VOID compact(struct nfa *, struct cnfa *); */ static void compact( struct nfa *nfa, struct cnfa *cnfa) { struct state *s; struct arc *a; size_t nstates; size_t narcs; struct carc *ca; struct carc *first; assert(!NISERR()); nstates = 0; narcs = 0; for (s = nfa->states; s != NULL; s = s->next) { nstates++; narcs += 1 + s->nouts + 1; /* 1 as a fake for flags, nouts for arcs, 1 as endmarker */ } cnfa->states = (struct carc **) MALLOC(nstates * sizeof(struct carc *)); cnfa->arcs = (struct carc *) MALLOC(narcs * sizeof(struct carc)); if (cnfa->states == NULL || cnfa->arcs == NULL) { if (cnfa->states != NULL) { FREE(cnfa->states); } if (cnfa->arcs != NULL) { FREE(cnfa->arcs); } NERR(REG_ESPACE); return; } cnfa->nstates = nstates; cnfa->pre = nfa->pre->no; cnfa->post = nfa->post->no; cnfa->bos[0] = nfa->bos[0]; cnfa->bos[1] = nfa->bos[1]; cnfa->eos[0] = nfa->eos[0]; cnfa->eos[1] = nfa->eos[1]; cnfa->ncolors = maxcolor(nfa->cm) + 1; cnfa->flags = 0; ca = cnfa->arcs; for (s = nfa->states; s != NULL; s = s->next) { assert((size_t) s->no < nstates); cnfa->states[s->no] = ca; ca->co = 0; /* clear and skip flags "arc" */ ca++; first = ca; for (a = s->outs; a != NULL; a = a->outchain) { switch (a->type) { case PLAIN: ca->co = a->co; ca->to = a->to->no; ca++; break; case LACON: assert(s->no != cnfa->pre); ca->co = (color) (cnfa->ncolors + a->co); ca->to = a->to->no; ca++; cnfa->flags |= HASLACONS; break; default: assert(NOTREACHED); break; } } carcsort(first, ca-1); ca->co = COLORLESS; ca->to = 0; ca++; } assert(ca == &cnfa->arcs[narcs]); assert(cnfa->nstates != 0); /* * Mark no-progress states. */ for (a = nfa->pre->outs; a != NULL; a = a->outchain) { cnfa->states[a->to->no]->co = 1; } cnfa->states[nfa->pre->no]->co = 1; }  /* - carcsort - sort compacted-NFA arcs by color * Really dumb algorithm, but if the list is long enough for that to matter, * you're in real trouble anyway. ^ static VOID carcsort(struct carc *, struct carc *); */ static void carcsort( struct carc *first, struct carc *last) { struct carc *p; struct carc *q; struct carc tmp; if (last - first <= 1) { return; } for (p = first; p <= last; p++) { for (q = p; q <= last; q++) { if (p->co > q->co || (p->co == q->co && p->to > q->to)) { assert(p != q); tmp = *p; *p = *q; *q = tmp; } } } }  /* - freecnfa - free a compacted NFA ^ static VOID freecnfa(struct cnfa *); */ static void freecnfa( struct cnfa *cnfa) { assert(cnfa->nstates != 0); /* not empty already */ cnfa->nstates = 0; FREE(cnfa->states); FREE(cnfa->arcs); }  /* - dumpnfa - dump an NFA in human-readable form ^ static VOID dumpnfa(struct nfa *, FILE *); */ static void dumpnfa( struct nfa *nfa, FILE *f) { #ifdef REG_DEBUG struct state *s; fprintf(f, "pre %d, post %d", nfa->pre->no, nfa->post->no); if (nfa->bos[0] != COLORLESS) { fprintf(f, ", bos [%ld]", (long) nfa->bos[0]); } if (nfa->bos[1] != COLORLESS) { fprintf(f, ", bol [%ld]", (long) nfa->bos[1]); } if (nfa->eos[0] != COLORLESS) { fprintf(f, ", eos [%ld]", (long) nfa->eos[0]); } if (nfa->eos[1] != COLORLESS) { fprintf(f, ", eol [%ld]", (long) nfa->eos[1]); } fprintf(f, "\n"); for (s = nfa->states; s != NULL; s = s->next) { dumpstate(s, f); } if (nfa->parent == NULL) { dumpcolors(nfa->cm, f); } fflush(f); #endif }  #ifdef REG_DEBUG /* subordinates of dumpnfa */ /* ^ #ifdef REG_DEBUG */ /* - dumpstate - dump an NFA state in human-readable form ^ static VOID dumpstate(struct state *, FILE *); */ static void dumpstate( struct state *s, FILE *f) { struct arc *a; fprintf(f, "%d%s%c", s->no, (s->tmp != NULL) ? "T" : "", (s->flag) ? s->flag : '.'); if (s->prev != NULL && s->prev->next != s) { fprintf(f, "\tstate chain bad\n"); } if (s->nouts == 0) { fprintf(f, "\tno out arcs\n"); } else { dumparcs(s, f); } fflush(f); for (a = s->ins; a != NULL; a = a->inchain) { if (a->to != s) { fprintf(f, "\tlink from %d to %d on %d's in-chain\n", a->from->no, a->to->no, s->no); } } }  /* - dumparcs - dump out-arcs in human-readable form ^ static VOID dumparcs(struct state *, FILE *); */ static void dumparcs( struct state *s, FILE *f) { int pos; assert(s->nouts > 0); /* printing arcs in reverse order is usually clearer */ pos = dumprarcs(s->outs, s, f, 1); if (pos != 1) { fprintf(f, "\n"); } }  /* - dumprarcs - dump remaining outarcs, recursively, in reverse order ^ static int dumprarcs(struct arc *, struct state *, FILE *, int); */ static int /* resulting print position */ dumprarcs( struct arc *a, struct state *s, FILE *f, int pos) /* initial print position */ { if (a->outchain != NULL) { pos = dumprarcs(a->outchain, s, f, pos); } dumparc(a, s, f); if (pos == 5) { fprintf(f, "\n"); pos = 1; } else { pos++; } return pos; }  /* - dumparc - dump one outarc in readable form, including prefixing tab ^ static VOID dumparc(struct arc *, struct state *, FILE *); */ static void dumparc( struct arc *a, struct state *s, FILE *f) { struct arc *aa; struct arcbatch *ab; fprintf(f, "\t"); switch (a->type) { case PLAIN: fprintf(f, "[%ld]", (long) a->co); break; case AHEAD: fprintf(f, ">%ld>", (long) a->co); break; case BEHIND: fprintf(f, "<%ld<", (long) a->co); break; case LACON: fprintf(f, ":%ld:", (long) a->co); break; case '^': case '$': fprintf(f, "%c%d", a->type, (int) a->co); break; case EMPTY: break; default: fprintf(f, "0x%x/0%lo", a->type, (long) a->co); break; } if (a->from != s) { fprintf(f, "?%d?", a->from->no); } for (ab = &a->from->oas; ab != NULL; ab = ab->next) { for (aa = &ab->a[0]; aa < &ab->a[ABSIZE]; aa++) { if (aa == a) { break; /* NOTE BREAK OUT */ } } if (aa < &ab->a[ABSIZE]) { /* propagate break */ break; /* NOTE BREAK OUT */ } } if (ab == NULL) { fprintf(f, "?!?"); /* not in allocated space */ } fprintf(f, "->"); if (a->to == NULL) { fprintf(f, "NULL"); return; } fprintf(f, "%d", a->to->no); for (aa = a->to->ins; aa != NULL; aa = aa->inchain) { if (aa == a) { break; /* NOTE BREAK OUT */ } } if (aa == NULL) { fprintf(f, "?!?"); /* missing from in-chain */ } } /* ^ #endif */ #endif /* ifdef REG_DEBUG */  /* - dumpcnfa - dump a compacted NFA in human-readable form ^ static VOID dumpcnfa(struct cnfa *, FILE *); */ static void dumpcnfa( struct cnfa *cnfa, FILE *f) { #ifdef REG_DEBUG int st; fprintf(f, "pre %d, post %d", cnfa->pre, cnfa->post); if (cnfa->bos[0] != COLORLESS) { fprintf(f, ", bos [%ld]", (long) cnfa->bos[0]); } if (cnfa->bos[1] != COLORLESS) { fprintf(f, ", bol [%ld]", (long) cnfa->bos[1]); } if (cnfa->eos[0] != COLORLESS) { fprintf(f, ", eos [%ld]", (long) cnfa->eos[0]); } if (cnfa->eos[1] != COLORLESS) { fprintf(f, ", eol [%ld]", (long) cnfa->eos[1]); } if (cnfa->flags&HASLACONS) { fprintf(f, ", haslacons"); } fprintf(f, "\n"); for (st = 0; st < cnfa->nstates; st++) { dumpcstate(st, cnfa->states[st], cnfa, f); } fflush(f); #endif }  #ifdef REG_DEBUG /* subordinates of dumpcnfa */ /* ^ #ifdef REG_DEBUG */ /* - dumpcstate - dump a compacted-NFA state in human-readable form ^ static VOID dumpcstate(int, struct carc *, struct cnfa *, FILE *); */ static void dumpcstate( int st, struct carc *ca, struct cnfa *cnfa, FILE *f) { int i; int pos; fprintf(f, "%d%s", st, (ca[0].co) ? ":" : "."); pos = 1; for (i = 1; ca[i].co != COLORLESS; i++) { if (ca[i].co < cnfa->ncolors) { fprintf(f, "\t[%ld]->%d", (long) ca[i].co, ca[i].to); } else { fprintf(f, "\t:%ld:->%d", (long) ca[i].co-cnfa->ncolors,ca[i].to); } if (pos == 5) { fprintf(f, "\n"); pos = 1; } else { pos++; } } if (i == 1 || pos != 1) { fprintf(f, "\n"); } fflush(f); } /* ^ #endif */ #endif /* ifdef REG_DEBUG */  /* * Local Variables: * mode: c * c-basic-offset: 4 * fill-column: 78 * End: */

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