Tcl Source Code

}

/*
 - hasnonemptyout - Does state have a non-EMPTY out arc?
 ^ static int hasnonemptyout(struct state *);
 */
static int
hasnonemptyout(
    struct state *s)
{
    struct arc *a;

    for (a = s->outs; a != NULL; a = a->outchain) {
	if (a->type != EMPTY) {
	    return 1;
	}
    }
    return 0;
}

/*
 - nonemptyouts - count non-EMPTY out arcs of a state
 ^ static int nonemptyouts(struct state *);
 */
static int
nonemptyouts(
    struct state *s)
{
    int n = 0;
    struct arc *a;

    for (a = s->outs; a != NULL; a = a->outchain) {
	if (a->type != EMPTY) {
	    n++;
	}
    }
    return n;
}

/*
 - nonemptyins - count non-EMPTY in arcs of a state
 ^ static int nonemptyins(struct state *);
 */
static int
nonemptyins(
    struct state *s)
{
    int n = 0;
    struct arc *a;

    for (a = s->ins; a != NULL; a = a->inchain) {
	if (a->type != EMPTY) {
	    n++;
	}
    }
    return n;
}

/*
 - 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.

    struct state *s;
    struct state *s2;
    struct state *nexts;
    struct arc *a;
    struct arc *nexta;

    /*
     * First, get rid of any states whose sole out-arc is an EMPTY,
     * since they're basically just aliases for their successor.  The
     * parsing algorithm creates enough of these that it's worth
     * special-casing this.
     */
    for (s = nfa->states; s != NULL && !NISERR(); s = nexts) {
	nexts = s->next;
	if (s->flag || s->nouts != 1) {
	    continue;
	}
	a = s->outs;
	assert(a != NULL && a->outchain == NULL);
	if (a->type != EMPTY) {
	    continue;
	}
	if (s != a->to) {
	    moveins(nfa, s, a->to);
	}
	dropstate(nfa, s);
    }

    /*
     * Similarly, get rid of any state with a single EMPTY in-arc, by
     * folding it into its predecessor.
     */
    for (s = nfa->states; s != NULL && !NISERR(); s = nexts) {
	nexts = s->next;
	/* Ensure tmp fields are clear for next step */
	assert(s->tmp = NULL);
	if (s->flag || s->nins != 1) {
	    continue;
	}
	a = s->ins;
	assert(a != NULL && a->inchain == NULL);
	if (a->type != EMPTY) {
	    continue;



	}
	if (s != a->from) {
	    moveouts(nfa, s, a->from);
	}
	dropstate(nfa, s);
    }

    /*
     * For each remaining NFA state, find all other states that are
     * reachable from it by a chain of one or more EMPTY arcs.  Then
     * generate new arcs that eliminate the need for each such chain.
     *
     * If we just do this straightforwardly, the algorithm gets slow in
     * complex graphs, because the same arcs get copied to all
     * intermediate states of an EMPTY chain, and then uselessly pushed
     * repeatedly to the chain's final state; we waste a lot of time in
     * newarc's duplicate checking.  To improve matters, we decree that
     * any state with only EMPTY out-arcs is "doomed" and will not be
     * part of the final NFA. That can be ensured by not adding any new
     * out-arcs to such a state. Having ensured that, we need not update
     * the state's in-arcs list either; all arcs that might have gotten
     * pushed forward to it will just get pushed directly to successor
     * states.  This eliminates most of the useless duplicate arcs.
     */
    for (s = nfa->states; s != NULL && !NISERR(); s = s->next) {
	for (s2 = emptyreachable(s, s); s2 != s && !NISERR();
		s2 = nexts) {
	    /*
	     * If s2 is doomed, we decide that (1) we will always push
	     * arcs forward to it, not pull them back to s; and (2) we
	     * can optimize away the push-forward, per comment above.
	     * So do nothing.
	     */
	    if (s2->flag || hasnonemptyout(s2)) {
		replaceempty(nfa, s, s2);
	    }

	    /* Reset the tmp fields as we walk back */
	    nexts = s2->tmp;
	    s2->tmp = NULL;
	}
	s->tmp = NULL;
    }

    /*
     * Remove all the EMPTY arcs, since we don't need them anymore.
     */
    for (s = nfa->states; s != NULL; s = s->next) {
	for (a = s->outs; a != NULL; a = nexta) {
	    nexta = a->outchain;
	    if (a->type == EMPTY) {
		freearc(nfa, a);
	    }
	}
    }

    /*
     * And remove any states that have become useless.  (This cleanup is
     * not very thorough, and would be even less so if we tried to
     * combine it with the previous step; but cleanup() will take care
     * of anything we miss.)
     */
    for (s = nfa->states; s != NULL && !NISERR(); s = nexts) {
	nexts = s->next;
	if ((s->nins == 0 || s->nouts == 0) && !s->flag) {
	    dropstate(nfa, s);
	}
    }

    if (f != NULL && !NISERR()) {
	dumpnfa(nfa, f);
    }
}

/*
 - emptyreachable - recursively find all states reachable from s by EMPTY arcs
 * The return value is the last such state found.  Its tmp field links back
 * to the next-to-last such state, and so on back to s, so that all these
 * states can be located without searching the whole NFA.

    struct state *lastfound)
{
    struct arc *a;

    s->tmp = lastfound;
    lastfound = s;
    for (a = s->outs; a != NULL; a = a->outchain) {
	if (a->type == EMPTY && a->to->tmp == NULL) {
	    lastfound = emptyreachable(a->to, lastfound);
	}
    }
    return lastfound;
}

/*
 - replaceempty - replace an EMPTY arc chain with some non-empty arcs
 * The EMPTY arc(s) should be deleted later, but we can't do it here because

     * Doesn't seem to be worth the trouble to exclude empties from these
     * comparisons; that takes extra time and doesn't seem to improve the
     * resulting graph much.
     */
    if (from->nins > to->nouts) {
	copyouts(nfa, to, from, 0);
	return;
    }

    copyins(nfa, from, to, 0);


}

/*
 - cleanup - clean up NFA after optimizations
 ^ static VOID cleanup(struct nfa *);
 */
static void