bison/src/state.c

/* Type definitions for nondeterministic finite state machine for Bison.
   Copyright (C) 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 <hash.h>

#include "complain.h"
#include "gram.h"
#include "state.h"


			/*-------------------.
			| Shifts and Gotos.  |
			`-------------------*/


/*---------------------------------------.
| Create a new array of N shifts/gotos.  |
`---------------------------------------*/

#define TRANSITIONS_ALLOC(Num)						\
  (transitions *) xcalloc ((sizeof (transitions)			\
                            + (Num - 1) * sizeof (state *)),		\
			   1)

static transitions *
transitions_new (int num, state **the_states)
{
  transitions *res = TRANSITIONS_ALLOC (num);
  res->num = num;
  memcpy (res->states, the_states, num * sizeof (the_states[0]));
  return res;
}


/*-------------------------------------------------------------------.
| Return the state such these TRANSITIONS contain a shift/goto to it |
| on S.  Abort if none found.                                        |
`-------------------------------------------------------------------*/

state *
transitions_to (transitions *shifts, symbol_number s)
{
  int j;
  for (j = 0; j < shifts->num; j++)
    if (TRANSITION_SYMBOL (shifts, j) == s)
      return shifts->states[j];
  abort ();
}


			/*--------------------.
			| Error transitions.  |
			`--------------------*/


/*-------------------------------.
| Create a new array of N errs.  |
`-------------------------------*/

#define ERRS_ALLOC(Nerrs) \
  ((errs *) xcalloc ((sizeof (errs) + (Nerrs - 1) * sizeof (symbol *)), 1))


errs *
errs_new (int num, symbol **tokens)
{
  errs *res = ERRS_ALLOC (num);
  res->num = num;
  memcpy (res->symbols, tokens, num * sizeof (tokens[0]));
  return res;
}




			/*-------------.
			| Reductions.  |
			`-------------*/


/*-------------------------------------.
| Create a new array of N reductions.  |
`-------------------------------------*/

#define REDUCTIONS_ALLOC(Nreductions)                          \
  (reductions *) xcalloc ((sizeof (reductions)		       \
                          + (Nreductions - 1) * sizeof (rule *)), 1)

static reductions *
reductions_new (int num, rule **reds)
{
  reductions *res = REDUCTIONS_ALLOC (num);
  res->num = num;
  memcpy (res->rules, reds, num * sizeof (reds[0]));
  res->lookaheads = NULL;
  return res;
}



			/*---------.
			| States.  |
			`---------*/


state_number nstates = 0;
/* FINAL_STATE is properly set by new_state when it recognizes its
   accessing symbol: $end.  */
state *final_state = NULL;

#define STATE_ALLOC(Nitems)						\
  (state *) xcalloc ((sizeof (state)	 		       		\
		      + (Nitems - 1) * sizeof (item_number)),		\
		     1)

/*------------------------------------------------------------------.
| Create a new state with ACCESSING_SYMBOL, for those items.  Store |
| it in the state hash table.                                       |
`------------------------------------------------------------------*/

state *
state_new (symbol_number accessing_symbol,
	   size_t core_size, item_number *core)
{
  state *res;

  if (STATE_NUMBER_MAXIMUM <= nstates)
    abort ();

  res = STATE_ALLOC (core_size);
  res->accessing_symbol = accessing_symbol;
  res->number = nstates;
  ++nstates;
  res->solved_conflicts = NULL;

  res->nitems = core_size;
  memcpy (res->items, core, core_size * sizeof (core[0]));

  state_hash_insert (res);

  return res;
}


/*---------.
| Free S.  |
`---------*/

static void
state_free (state *s)
{
  free (s->transitions);
  free (s->reductions);
  free (s->errs);
  free (s);
}


/*---------------------------.
| Set the transitions of S.  |
`---------------------------*/

void
state_transitions_set (state *s, int num, state **trans)
{
  if (s->transitions)
    abort ();
  s->transitions = transitions_new (num, trans);
}


/*--------------------------.
| Set the reductions of S.  |
`--------------------------*/

void
state_reductions_set (state *s, int num, rule **reds)
{
  if (s->reductions)
    abort ();
  s->reductions = reductions_new (num, reds);
}


int
state_reduction_find (state *s, rule *r)
{
  int i;
  reductions *reds = s->reductions;
  for (i = 0; i < reds->num; ++i)
    if (reds->rules[i] == r)
      return i;
  return -1;
}


/*--------------------.
| Set the errs of S.  |
`--------------------*/

void
state_errs_set (state *s, int num, symbol **tokens)
{
  if (s->errs)
    abort ();
  s->errs = errs_new (num, tokens);
}



/*-----------------------------------------------------.
| Print on OUT all the lookaheads such that S wants to |
| reduce R.                                            |
`-----------------------------------------------------*/

void
state_rule_lookaheads_print (state *s, rule *r, FILE *out)
{
  /* Find the reduction we are handling.  */
  reductions *reds = s->reductions;
  int red = state_reduction_find (s, r);

  /* Print them if there are.  */
  if (reds->lookaheads && red != -1)
    {
      bitset_iterator biter;
      int k;
      int not_first = 0;
      fprintf (out, "  [");
      BITSET_FOR_EACH (biter, reds->lookaheads[red], k, 0)
	fprintf (out, "%s%s",
		 not_first++ ? ", " : "",
		 symbols[k]->tag);
      fprintf (out, "]");
    }
}


/*----------------------.
| A state hash table.  |
`----------------------*/

/* Initial capacity of states hash table.  */
#define HT_INITIAL_CAPACITY 257

static struct hash_table *state_table = NULL;

/* Two states are equal if they have the same core items.  */
static bool
state_compare (state const *s1, state const *s2)
{
  int i;

  if (s1->nitems != s2->nitems)
    return false;

  for (i = 0; i < s1->nitems; ++i)
    if (s1->items[i] != s2->items[i])
      return false;

  return true;
}

static unsigned int
state_hash (state const *s, unsigned int tablesize)
{
  /* Add up the state's item numbers to get a hash key.  */
  int key = 0;
  int i;
  for (i = 0; i < s->nitems; ++i)
    key += s->items[i];
  return key % tablesize;
}


/*-------------------------------.
| Create the states hash table.  |
`-------------------------------*/

void
state_hash_new (void)
{
  state_table = hash_initialize (HT_INITIAL_CAPACITY,
				 NULL,
				 (Hash_hasher) state_hash,
				 (Hash_comparator) state_compare,
				 (Hash_data_freer) NULL);
}


/*---------------------------------------------.
| Free the states hash table, not the states.  |
`---------------------------------------------*/

void
state_hash_free (void)
{
  hash_free (state_table);
}


/*-----------------------------------.
| Insert S in the state hash table.  |
`-----------------------------------*/

void
state_hash_insert (state *s)
{
  hash_insert (state_table, s);
}


/*------------------------------------------------------------------.
| Find the state associated to the CORE, and return it.  If it does |
| not exist yet, return NULL.                                       |
`------------------------------------------------------------------*/

state *
state_hash_lookup (size_t core_size, item_number *core)
{
  state *probe = STATE_ALLOC (core_size);
  state *entry;

  probe->nitems = core_size;
  memcpy (probe->items, core, core_size * sizeof (core[0]));
  entry = hash_lookup (state_table, probe);
  free (probe);
  return entry;
}

/* All the decorated states, indexed by the state number.  */
state **states = NULL;


/*----------------------.
| Free all the states.  |
`----------------------*/

void
states_free (void)
{
  state_number i;
  for (i = 0; i < nstates; ++i)
    state_free (states[i]);
  free (states);
}