/* Computation of FIRST stets */

#include "pgenheaders.h"

#include "grammar.h"

#include "token.h"

extern int Py_DebugFlag;

/* Forward */

static void calcfirstset(grammar *, dfa *);

void

addfirstsets(grammar *g)

{

	int i;

	dfa *d;

	if (Py_DebugFlag)

		printf("Adding FIRST sets ...\n");

	for (i = 0; i < g->g_ndfas; i++) {

		d = &g->g_dfa[i];

		if (d->d_first == NULL)

			calcfirstset(g, d);

	}

}

static void

calcfirstset(grammar *g, dfa *d)

{

	int i, j;

	state *s;

	arc *a;

	int nsyms;

	int *sym;

	int nbits;

	static bitset dummy;

	bitset result;

	int type;

	dfa *d1;

	label *l0;

	if (Py_DebugFlag)

		printf("Calculate FIRST set for '%s'\n", d->d_name);

	if (dummy == NULL)

		dummy = newbitset(1);

	if (d->d_first == dummy) {

		fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);

		return;

	}

	if (d->d_first != NULL) {

		fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",

			d->d_name);

	}

	d->d_first = dummy;

	l0 = g->g_ll.ll_label;

	nbits = g->g_ll.ll_nlabels;

	result = newbitset(nbits);

	sym = (int *)PyObject_MALLOC(sizeof(int));

	if (sym == NULL)

		Py_FatalError("no mem for new sym in calcfirstset");

	nsyms = 1;

	sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);

	s = &d->d_state[d->d_initial];

	for (i = 0; i < s->s_narcs; i++) {

		a = &s->s_arc[i];

		for (j = 0; j < nsyms; j++) {

			if (sym[j] == a->a_lbl)

				break;

		}

		if (j >= nsyms) { /* New label */

			sym = (int *)PyObject_REALLOC(sym, 

                                                sizeof(int) * (nsyms + 1));

			if (sym == NULL)

				Py_FatalError(

				    "no mem to resize sym in calcfirstset");

			sym[nsyms++] = a->a_lbl;

			type = l0[a->a_lbl].lb_type;

			if (ISNONTERMINAL(type)) {

				d1 = PyGrammar_FindDFA(g, type);

				if (d1->d_first == dummy) {

					fprintf(stderr,

						"Left-recursion below '%s'\n",

						d->d_name);

				}

				else {

					if (d1->d_first == NULL)

						calcfirstset(g, d1);

					mergebitset(result,

						    d1->d_first, nbits);

				}

			}

			else if (ISTERMINAL(type)) {

				addbit(result, a->a_lbl);

			}

		}

	}

	d->d_first = result;

	if (Py_DebugFlag) {

		printf("FIRST set for '%s': {", d->d_name);

		for (i = 0; i < nbits; i++) {

			if (testbit(result, i))

				printf(" %s", PyGrammar_LabelRepr(&l0[i]));

		}

		printf(" }\n");

	}

	PyObject_FREE(sym);

}