Add HACKING.

[bison.git] / src / derives.c

/* Match rules with nonterminals for bison,
   Copyright 1984, 1989, 2000, 2001, 2002  Free Software Foundation, Inc.

   This file is part of Bison, the GNU Compiler Compiler.

   Bison is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   Bison is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Bison; see the file COPYING.  If not, write to
   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */


#include "system.h"
#include "getargs.h"
#include "symtab.h"
#include "reader.h"
#include "gram.h"
#include "derives.h"

/* Linked list of rule numbers.  */
typedef struct rule_list_s
{
  struct rule_list_s *next;
  rule_number_t value;
} rule_list_t;

rule_number_t **derives = NULL;

static void
print_derives (void)
{
  int i;

  fputs ("DERIVES\n", stderr);

  for (i = ntokens; i < nsyms; i++)
    {
      rule_number_t *rp;
      fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
      for (rp = derives[i]; *rp >= 0; rp++)
	{
	  fprintf (stderr, "\t\t%3d ", *rp);
	  rule_rhs_print (&rules[*rp], stderr);
	}
    }

  fputs ("\n\n", stderr);
}


void
set_derives (void)
{
  symbol_number_t i;
  int r;
  rule_number_t *q;

  /* DSET[NTERM] -- A linked list of the numbers of the rules whose
     LHS is NTERM.  */
  rule_list_t **dset = XCALLOC (rule_list_t *, nvars) - ntokens;

  /* DELTS[RULE] -- There are NRULES rule number to attach to nterms.
     Instead of performing NRULES allocations for each, have an array
     indexed by rule numbers.  */
  rule_list_t *delts = XCALLOC (rule_list_t, nrules);

  for (r = nrules - 1; r >= 0; --r)
    {
      symbol_number_t lhs = rules[r].lhs->number;
      rule_list_t *p = &delts[r];
      /* A new LHS is found.  */
      p->next = dset[lhs];
      p->value = r;
      dset[lhs] = p;
    }

  /* DSET contains what we need under the form of a linked list.  Make
     it a single array.  */

  derives = XCALLOC (rule_number_t *, nvars) - ntokens;
  q = XCALLOC (rule_number_t, nvars + int_of_rule_number (nrules));

  for (i = ntokens; i < nsyms; i++)
    {
      rule_list_t *p = dset[i];
      derives[i] = q;
      while (p)
	{
	  *q++ = p->value;
	  p = p->next;
	}
      *q++ = -1;
    }

  if (trace_flag)
    print_derives ();

  free (dset + ntokens);
  free (delts);
}


void
free_derives (void)
{
  XFREE (derives[ntokens]);
  XFREE (derives + ntokens);
}