merged tcl 8.1 branch back into the main trunk

1 files changed, 1528 insertions, 0 deletions

diff --git a/generic/regc_nfa.c b/generic/regc_nfa.c
new file mode 100644
index 0000000..80e9ac7
--- /dev/null
+++ b/generic/regc_nfa.c
@@ -0,0 +1,1528 @@
+/*
+ * NFA utilities.
+ * This file is #included by regcomp.c.
+ *
+ * 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(v, cm, parent)
+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->bos[0] = nfa->bos[1] = COLORLESS;
+	nfa->eos[0] = nfa->eos[1] = COLORLESS;
+	nfa->post = newfstate(nfa, '@');	/* number 0 */
+	nfa->pre = newfstate(nfa, '>');		/* number 1 */
+	nfa->parent = parent;
+
+	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;
+}
+
+/*
+ - freenfa - free an entire NFA
+ ^ static VOID freenfa(struct nfa *);
+ */
+static VOID
+freenfa(nfa)
+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);
+}
+
+/*
+ - newfstate - allocate an NFA state, with specified flag value
+ ^ static struct state *newfstate(struct nfa *, int flag);
+ */
+static struct state *		/* NULL on error */
+newfstate(nfa, flag)
+struct nfa *nfa;
+int flag;
+{
+	struct state *s;
+	int i;
+
+	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 = &s->oas.a[0];
+		for (i = 0; i < ABSIZE; i++) {
+			s->oas.a[i].type = 0;
+			s->oas.a[i].freechain = &s->oas.a[i+1];
+		}
+		s->oas.a[ABSIZE-1].freechain = NULL;
+	}
+
+	assert(nfa->nstates >= 0);
+	s->no = nfa->nstates++;
+	s->flag = (char)flag;
+	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;
+	return s;
+}
+
+/*
+ - newstate - allocate an ordinary NFA state
+ ^ static struct state *newstate(struct nfa *);
+ */
+static struct state *		/* NULL on error */
+newstate(nfa)
+struct nfa *nfa;
+{
+	return newfstate(nfa, 0);
+}
+
+/*
+ - dropstate - delete a state's inarcs and outarcs and free it
+ ^ static VOID dropstate(struct nfa *, struct state *);
+ */
+static VOID
+dropstate(nfa, s)
+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(nfa, s)
+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;
+}
+
+/*
+ - destroystate - really get rid of an already-freed state
+ ^ static VOID destroystate(struct nfa *, struct state *);
+ */
+static VOID
+destroystate(nfa, s)
+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(nfa, t, co, from, to)
+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->type == t && a->co == co && a->to == to)
+			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);
+
+	return;
+}
+
+/*
+ - allocarc - allocate a new out-arc within a state
+ ^ static struct arc *allocarc(struct nfa *, struct state *);
+ */
+static struct arc *		/* NULL for failure */
+allocarc(nfa, s)
+struct nfa *nfa;
+struct state *s;
+{
+	struct arc *a;
+	struct arcbatch *new;
+	int i;
+
+	/* if none at hand, get more */
+	if (s->free == NULL) {
+		new = (struct arcbatch *)MALLOC(sizeof(struct arcbatch));
+		if (new == NULL) {
+			NERR(REG_ESPACE);
+			return NULL;
+		}
+		new->next = s->oas.next;
+		s->oas.next = new;
+
+		for (i = 0; i < ABSIZE; i++) {
+			new->a[i].type = 0;
+			new->a[i].freechain = &new->a[i+1];
+		}
+		new->a[ABSIZE-1].freechain = NULL;
+		s->free = &new->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(nfa, victim)
+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 != NULL && a->inchain != victim; a = a->inchain)
+			continue;
+		assert(a != NULL);
+		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(s, type, co)
+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(nfa, oa, from, to)
+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(nfa, old, new)
+struct nfa *nfa;
+struct state *old;
+struct state *new;
+{
+	struct arc *a;
+
+	assert(old != new);
+
+	while ((a = old->ins) != NULL) {
+		cparc(nfa, a, a->from, new);
+		freearc(nfa, a);
+	}
+	assert(old->nins == 0);
+	assert(old->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(nfa, old, new)
+struct nfa *nfa;
+struct state *old;
+struct state *new;
+{
+	struct arc *a;
+
+	assert(old != new);
+
+	for (a = old->ins; a != NULL; a = a->inchain)
+		cparc(nfa, a, a->from, new);
+}
+
+/*
+ - moveouts - move all out arcs of a state to another state
+ ^ static VOID moveouts(struct nfa *, struct state *, struct state *);
+ */
+static VOID
+moveouts(nfa, old, new)
+struct nfa *nfa;
+struct state *old;
+struct state *new;
+{
+	struct arc *a;
+
+	assert(old != new);
+
+	while ((a = old->outs) != NULL) {
+		cparc(nfa, a, new, 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(nfa, old, new)
+struct nfa *nfa;
+struct state *old;
+struct state *new;
+{
+	struct arc *a;
+
+	assert(old != new);
+
+	for (a = old->outs; a != NULL; a = a->outchain)
+		cparc(nfa, a, new, 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(nfa, old, from, to, type)
+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(nfa, lp, rp)
+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(nfa, leftend, s)
+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(nfa, start, stop, from, to)
+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(nfa, s, stmp)
+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, (struct state *)NULL);
+		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(nfa, s)
+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(nfa)
+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 int optimize(struct nfa *, FILE *);
+ */
+static int			/* re_info bits */
+optimize(nfa, f)
+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(nfa, f)
+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(nfa, con)
+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;
+	}
+
+	/* 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(nfa, f)
+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(nfa, con)
+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;
+	}
+
+	/* 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(con, a)
+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(nfa, f)
+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 = 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(nfa, a)
+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(nfa)
+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, (struct state *)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(nfa, s, okay, mark)
+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(nfa, s, okay, mark)
+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 int analyze(struct nfa *);
+ */
+static int			/* re_info bits to be ORed in */
+analyze(nfa)
+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(nfa, cnfa)
+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(first, last)
+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(cnfa)
+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(nfa, f)
+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 */
+
+/*
+ - dumpstate - dump an NFA state in human-readable form
+ ^ static VOID dumpstate(struct state *, FILE *);
+ */
+static VOID
+dumpstate(s, f)
+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(s, f)
+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(a, s, f, pos)
+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(a, s, f)
+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				/* ifdef REG_DEBUG */
+
+/*
+ - dumpcnfa - dump a compacted NFA in human-readable form
+ ^ static VOID dumpcnfa(struct cnfa *, FILE *);
+ */
+static VOID
+dumpcnfa(cnfa, f)
+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 */
+
+/*
+ - dumpcstate - dump a compacted-NFA state in human-readable form
+ ^ static VOID dumpcstate(int, struct carc *, struct cnfa *, FILE *);
+ */
+static VOID
+dumpcstate(st, ca, cnfa, f)
+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				/* ifdef REG_DEBUG */