src/derives.c

   1 /* Match rules with nonterminals for bison,
   2    Copyright (C) 1984, 1989, 2000 Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to
  18    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21
  22 /* set_derives finds, for each variable (nonterminal), which rules can
  23    derive it.  It sets up the value of derives so that derives[i -
  24    ntokens] points to a vector of rule numbers, terminated with -1.
  25    */
  26
  27 #include "system.h"
  28 #include "alloc.h"
  29 #include "types.h"
  30 #include "gram.h"
  31 #include "derives.h"
  32
  33 short **derives;
  34
  35 #if DEBUG
  36
  37 static void
  38 print_derives (void)
  39 {
  40   register int i;
  41   register short *sp;
  42
  43   printf (_("\n\n\nDERIVES\n\n"));
  44
  45   for (i = ntokens; i < nsyms; i++)
  46     {
  47       printf (_("%s derives"), tags[i]);
  48       for (sp = derives[i]; *sp > 0; sp++)
  49         {
  50           printf ("  %d", *sp);
  51         }
  52       putchar ('\n');
  53     }
  54
  55   putchar ('\n');
  56 }
  57
  58 #endif
  59
  60 void
  61 set_derives (void)
  62 {
  63   register int i;
  64   register int lhs;
  65   register shorts *p;
  66   register short *q;
  67   register shorts **dset;
  68   register shorts *delts;
  69
  70   dset = NEW2 (nvars, shorts *) - ntokens;
  71   delts = NEW2 (nrules + 1, shorts);
  72
  73   p = delts;
  74   for (i = nrules; i > 0; i--)
  75     {
  76       lhs = rlhs[i];
  77       if (lhs >= 0)
  78         {
  79           p->next = dset[lhs];
  80           p->value = i;
  81           dset[lhs] = p;
  82           p++;
  83         }
  84     }
  85
  86   derives = NEW2 (nvars, short *) - ntokens;
  87   q = NEW2 (nvars + nrules, short);
  88
  89   for (i = ntokens; i < nsyms; i++)
  90     {
  91       derives[i] = q;
  92       p = dset[i];
  93       while (p)
  94         {
  95           *q++ = p->value;
  96           p = p->next;
  97         }
  98       *q++ = -1;
  99     }
 100
 101 #if DEBUG
 102   print_derives ();
 103 #endif
 104
 105   FREE (dset + ntokens);
 106   FREE (delts);
 107 }
 108
 109 void
 110 free_derives (void)
 111 {
 112   FREE (derives[ntokens]);
 113   FREE (derives + ntokens);
 114 }