* NEWS (2.3a+): Mention yesterday's state-removal change.

[bison.git] / src / state.c

/* Type definitions for nondeterministic finite state machine for Bison.

   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007 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., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.  */

#include <config.h>
#include "system.h"

#include <hash.h>

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


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


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

static transitions *
transitions_new (int num, state **the_states)
{
  size_t states_size = num * sizeof *the_states;
  transitions *res = xmalloc (offsetof (transitions, states) + states_size);
  res->num = num;
  memcpy (res->states, the_states, states_size);
  return res;
}


/*-------------------------------------------------------.
| Return the state such that SHIFTS contain a shift/goto |
| to it on SYM.  Abort if none found.                    |
`-------------------------------------------------------*/

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


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


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

errs *
errs_new (int num, symbol **tokens)
{
  size_t symbols_size = num * sizeof *tokens;
  errs *res = xmalloc (offsetof (errs, symbols) + symbols_size);
  res->num = num;
  memcpy (res->symbols, tokens, symbols_size);
  return res;
}




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


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

static reductions *
reductions_new (int num, rule **reds)
{
  size_t rules_size = num * sizeof *reds;
  reductions *res = xmalloc (offsetof (reductions, rules) + rules_size);
  res->num = num;
  res->lookahead_tokens = NULL;
  memcpy (res->rules, reds, rules_size);
  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;


/*------------------------------------------------------------------.
| 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 nitems, item_number *core)
{
  state *res;
  size_t items_size = nitems * sizeof *core;

  aver (nstates < STATE_NUMBER_MAXIMUM);

  res = xmalloc (offsetof (state, items) + items_size);
  res->number = nstates++;
  res->accessing_symbol = accessing_symbol;
  res->transitions = NULL;
  res->reductions = NULL;
  res->errs = NULL;
  res->consistent = 0;
  res->solved_conflicts = NULL;
  res->reachable = false;

  res->nitems = nitems;
  memcpy (res->items, core, items_size);

  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)
{
  aver (!s->transitions);
  s->transitions = transitions_new (num, trans);
}


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

void
state_reductions_set (state *s, int num, rule **reds)
{
  aver (!s->reductions);
  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)
{
  aver (!s->errs);
  s->errs = errs_new (num, tokens);
}



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

void
state_rule_lookahead_tokens_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->lookahead_tokens && red != -1)
    {
      bitset_iterator biter;
      int k;
      char const *sep = "";
      fprintf (out, "  [");
      BITSET_FOR_EACH (biter, reds->lookahead_tokens[red], k, 0)
	{
	  fprintf (out, "%s%s", sep, symbols[k]->tag);
	  sep = ", ";
	}
      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 inline bool
state_compare (state const *s1, state const *s2)
{
  size_t 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 bool
state_comparator (void const *s1, void const *s2)
{
  return state_compare (s1, s2);
}

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

static size_t
state_hasher (void const *s, size_t tablesize)
{
  return state_hash (s, tablesize);
}


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

void
state_hash_new (void)
{
  state_table = hash_initialize (HT_INITIAL_CAPACITY,
				 NULL,
				 state_hasher,
				 state_comparator,
				 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 nitems, item_number *core)
{
  size_t items_size = nitems * sizeof *core;
  state *probe = xmalloc (offsetof (state, items) + items_size);
  state *entry;

  probe->nitems = nitems;
  memcpy (probe->items, core, items_size);
  entry = hash_lookup (state_table, probe);
  free (probe);
  return entry;
}


/*------------------------------------------------------.
| Mark S and all states reachable from S as reachable.  |
`------------------------------------------------------*/

static void
state_mark_reachable_states (state *s)
{
  if (s->reachable)
    return;
  s->reachable = true;
  for (int i = 0; i < s->transitions->num; ++i)
    if (!TRANSITION_IS_DISABLED (s->transitions, i))
      state_mark_reachable_states (s->transitions->states[i]);
}

void
state_remove_unreachable_states (state_number old_to_new[])
{
  state_number nstates_reachable = 0;
  state_mark_reachable_states (states[0]);
  for (state_number i = 0; i < nstates; ++i)
    {
      if (states[i]->reachable)
        {
          states[nstates_reachable] = states[i];
          states[nstates_reachable]->number = nstates_reachable;
          old_to_new[i] = nstates_reachable++;
        }
      else
        {
          state_free (states[i]);
          old_to_new[i] = nstates;
        }
    }
  nstates = nstates_reachable;
}

/* 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);
}