1
2 /* Computation of FIRST stets */
3
4 #include "pgenheaders.h"
5 #include "grammar.h"
6 #include "token.h"
7
8 extern int Py_DebugFlag;
9
10 /* Forward */
11 static void calcfirstset(grammar *, dfa *);
12
13 void
addfirstsets(grammar * g)14 addfirstsets(grammar *g)
15 {
16 int i;
17 dfa *d;
18
19 if (Py_DebugFlag)
20 printf("Adding FIRST sets ...\n");
21 for (i = 0; i < g->g_ndfas; i++) {
22 d = &g->g_dfa[i];
23 if (d->d_first == NULL)
24 calcfirstset(g, d);
25 }
26 }
27
28 static void
calcfirstset(grammar * g,dfa * d)29 calcfirstset(grammar *g, dfa *d)
30 {
31 int i, j;
32 state *s;
33 arc *a;
34 int nsyms;
35 int *sym;
36 int nbits;
37 static bitset dummy;
38 bitset result;
39 int type;
40 dfa *d1;
41 label *l0;
42
43 if (Py_DebugFlag)
44 printf("Calculate FIRST set for '%s'\n", d->d_name);
45
46 if (dummy == NULL)
47 dummy = newbitset(1);
48 if (d->d_first == dummy) {
49 fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
50 return;
51 }
52 if (d->d_first != NULL) {
53 fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
54 d->d_name);
55 }
56 d->d_first = dummy;
57
58 l0 = g->g_ll.ll_label;
59 nbits = g->g_ll.ll_nlabels;
60 result = newbitset(nbits);
61
62 sym = (int *)PyObject_MALLOC(sizeof(int));
63 if (sym == NULL)
64 Py_FatalError("no mem for new sym in calcfirstset");
65 nsyms = 1;
66 sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
67
68 s = &d->d_state[d->d_initial];
69 for (i = 0; i < s->s_narcs; i++) {
70 a = &s->s_arc[i];
71 for (j = 0; j < nsyms; j++) {
72 if (sym[j] == a->a_lbl)
73 break;
74 }
75 if (j >= nsyms) { /* New label */
76 sym = (int *)PyObject_REALLOC(sym,
77 sizeof(int) * (nsyms + 1));
78 if (sym == NULL)
79 Py_FatalError(
80 "no mem to resize sym in calcfirstset");
81 sym[nsyms++] = a->a_lbl;
82 type = l0[a->a_lbl].lb_type;
83 if (ISNONTERMINAL(type)) {
84 d1 = PyGrammar_FindDFA(g, type);
85 if (d1->d_first == dummy) {
86 fprintf(stderr,
87 "Left-recursion below '%s'\n",
88 d->d_name);
89 }
90 else {
91 if (d1->d_first == NULL)
92 calcfirstset(g, d1);
93 mergebitset(result,
94 d1->d_first, nbits);
95 }
96 }
97 else if (ISTERMINAL(type)) {
98 addbit(result, a->a_lbl);
99 }
100 }
101 }
102 d->d_first = result;
103 if (Py_DebugFlag) {
104 printf("FIRST set for '%s': {", d->d_name);
105 for (i = 0; i < nbits; i++) {
106 if (testbit(result, i))
107 printf(" %s", PyGrammar_LabelRepr(&l0[i]));
108 }
109 printf(" }\n");
110 }
111
112 PyObject_FREE(sym);
113 }
114