/* 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);
}