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111 lines
2.1 KiB
111 lines
2.1 KiB
4 years ago
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/* Computation of FIRST stets */
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#include "pgenheaders.h"
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#include "grammar.h"
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#include "token.h"
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extern int Py_DebugFlag;
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/* Forward */
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static void calcfirstset(grammar *, dfa *);
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void
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addfirstsets(grammar *g)
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{
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int i;
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dfa *d;
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if (Py_DebugFlag)
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printf("Adding FIRST sets ...\n");
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for (i = 0; i < g->g_ndfas; i++) {
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d = &g->g_dfa[i];
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if (d->d_first == NULL)
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calcfirstset(g, d);
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}
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}
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static void
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calcfirstset(grammar *g, dfa *d)
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{
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int i, j;
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state *s;
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arc *a;
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int nsyms;
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int *sym;
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int nbits;
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static bitset dummy;
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bitset result;
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int type;
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dfa *d1;
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label *l0;
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if (Py_DebugFlag)
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printf("Calculate FIRST set for '%s'\n", d->d_name);
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if (dummy == NULL)
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dummy = newbitset(1);
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if (d->d_first == dummy) {
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fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
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return;
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}
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if (d->d_first != NULL) {
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fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
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d->d_name);
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}
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d->d_first = dummy;
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l0 = g->g_ll.ll_label;
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nbits = g->g_ll.ll_nlabels;
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result = newbitset(nbits);
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sym = PyMem_NEW(int, 1);
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if (sym == NULL)
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Py_FatalError("no mem for new sym in calcfirstset");
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nsyms = 1;
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sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
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s = &d->d_state[d->d_initial];
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for (i = 0; i < s->s_narcs; i++) {
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a = &s->s_arc[i];
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for (j = 0; j < nsyms; j++) {
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if (sym[j] == a->a_lbl)
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break;
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}
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if (j >= nsyms) { /* New label */
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PyMem_RESIZE(sym, int, nsyms + 1);
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if (sym == NULL)
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Py_FatalError(
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"no mem to resize sym in calcfirstset");
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sym[nsyms++] = a->a_lbl;
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type = l0[a->a_lbl].lb_type;
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if (ISNONTERMINAL(type)) {
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d1 = PyGrammar_FindDFA(g, type);
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if (d1->d_first == dummy) {
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fprintf(stderr,
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"Left-recursion below '%s'\n",
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d->d_name);
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}
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else {
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if (d1->d_first == NULL)
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calcfirstset(g, d1);
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mergebitset(result,
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d1->d_first, nbits);
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}
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}
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else if (ISTERMINAL(type)) {
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addbit(result, a->a_lbl);
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}
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}
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}
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d->d_first = result;
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if (Py_DebugFlag) {
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printf("FIRST set for '%s': {", d->d_name);
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for (i = 0; i < nbits; i++) {
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if (testbit(result, i))
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printf(" %s", PyGrammar_LabelRepr(&l0[i]));
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}
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printf(" }\n");
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}
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}
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