Parser/firstsets.c

   1 /***********************************************************
   2 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
   3 The Netherlands.
   4
   5                         All Rights Reserved
   6
   7 Permission to use, copy, modify, and distribute this software and its
   8 documentation for any purpose and without fee is hereby granted,
   9 provided that the above copyright notice appear in all copies and that
  10 both that copyright notice and this permission notice appear in
  11 supporting documentation, and that the names of Stichting Mathematisch
  12 Centrum or CWI or Corporation for National Research Initiatives or
  13 CNRI not be used in advertising or publicity pertaining to
  14 distribution of the software without specific, written prior
  15 permission.
  16
  17 While CWI is the initial source for this software, a modified version
  18 is made available by the Corporation for National Research Initiatives
  19 (CNRI) at the Internet address ftp://ftp.python.org.
  20
  21 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
  22 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
  23 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
  24 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
  25 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  26 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  27 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  28 PERFORMANCE OF THIS SOFTWARE.
  29
  30 ******************************************************************/
  31
  32 /* Computation of FIRST stets */
  33
  34 #include "pgenheaders.h"
  35 #include "grammar.h"
  36 #include "token.h"
  37
  38 extern int Py_DebugFlag;
  39
  40 /* Forward */
  41 static void calcfirstset Py_PROTO((grammar *, dfa *));
  42
  43 void
  44 addfirstsets(g)
  45         grammar *g;
  46 {
  47         int i;
  48         dfa *d;
  49
  50         printf("Adding FIRST sets ...\n");
  51         for (i = 0; i < g->g_ndfas; i++) {
  52                 d = &g->g_dfa[i];
  53                 if (d->d_first == NULL)
  54                         calcfirstset(g, d);
  55         }
  56 }
  57
  58 static void
  59 calcfirstset(g, d)
  60         grammar *g;
  61         dfa *d;
  62 {
  63         int i, j;
  64         state *s;
  65         arc *a;
  66         int nsyms;
  67         int *sym;
  68         int nbits;
  69         static bitset dummy;
  70         bitset result;
  71         int type;
  72         dfa *d1;
  73         label *l0;
  74
  75         if (Py_DebugFlag)
  76                 printf("Calculate FIRST set for '%s'\n", d->d_name);
  77
  78         if (dummy == NULL)
  79                 dummy = newbitset(1);
  80         if (d->d_first == dummy) {
  81                 fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
  82                 return;
  83         }
  84         if (d->d_first != NULL) {
  85                 fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
  86                         d->d_name);
  87         }
  88         d->d_first = dummy;
  89
  90         l0 = g->g_ll.ll_label;
  91         nbits = g->g_ll.ll_nlabels;
  92         result = newbitset(nbits);
  93
  94         sym = PyMem_NEW(int, 1);
  95         if (sym == NULL)
  96                 Py_FatalError("no mem for new sym in calcfirstset");
  97         nsyms = 1;
  98         sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
  99
 100         s = &d->d_state[d->d_initial];
 101         for (i = 0; i < s->s_narcs; i++) {
 102                 a = &s->s_arc[i];
 103                 for (j = 0; j < nsyms; j++) {
 104                         if (sym[j] == a->a_lbl)
 105                                 break;
 106                 }
 107                 if (j >= nsyms) { /* New label */
 108                         PyMem_RESIZE(sym, int, nsyms + 1);
 109                         if (sym == NULL)
 110                                 Py_FatalError(
 111                                     "no mem to resize sym in calcfirstset");
 112                         sym[nsyms++] = a->a_lbl;
 113                         type = l0[a->a_lbl].lb_type;
 114                         if (ISNONTERMINAL(type)) {
 115                                 d1 = PyGrammar_FindDFA(g, type);
 116                                 if (d1->d_first == dummy) {
 117                                         fprintf(stderr,
 118                                                 "Left-recursion below '%s'\n",
 119                                                 d->d_name);
 120                                 }
 121                                 else {
 122                                         if (d1->d_first == NULL)
 123                                                 calcfirstset(g, d1);
 124                                         mergebitset(result,
 125                                                     d1->d_first, nbits);
 126                                 }
 127                         }
 128                         else if (ISTERMINAL(type)) {
 129                                 addbit(result, a->a_lbl);
 130                         }
 131                 }
 132         }
 133         d->d_first = result;
 134         if (Py_DebugFlag) {
 135                 printf("FIRST set for '%s': {", d->d_name);
 136                 for (i = 0; i < nbits; i++) {
 137                         if (testbit(result, i))
 138                                 printf(" %s", PyGrammar_LabelRepr(&l0[i]));
 139                 }
 140                 printf(" }\n");
 141         }
 142 }