src/state.c

   1 /* Type definitions for nondeterministic finite state machine for bison,
   2    Copyright (C) 2001, 2002  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 #include "system.h"
  23 #include "hash.h"
  24 #include "complain.h"
  25 #include "gram.h"
  26 #include "state.h"
  27
  28
  29                         /*-------------------.
  30                         | Shifts and Gotos.  |
  31                         `-------------------*/
  32
  33
  34 /*---------------------------------------.
  35 | Create a new array of N shifts/gotos.  |
  36 `---------------------------------------*/
  37
  38 #define TRANSITIONS_ALLOC(Nshifts)                                              \
  39   (transitions_t *) xcalloc ((unsigned) (sizeof (transitions_t)                         \
  40                                   + (Nshifts - 1) * sizeof (state_number_t)), 1)
  41
  42 static transitions_t *
  43 transitions_new (int num, state_number_t *the_states)
  44 {
  45   transitions_t *res = TRANSITIONS_ALLOC (num);
  46   res->num = num;
  47   memcpy (res->states, the_states, num * sizeof (the_states[0]));
  48   return res;
  49 }
  50
  51
  52 /*-------------------------------------------------------------------.
  53 | Return the state such these TRANSITIONS contain a shift/goto to it |
  54 | on SYMBOL.  Aborts if none found.                                  |
  55 `-------------------------------------------------------------------*/
  56
  57 state_t *
  58 transitions_to (transitions_t *shifts, symbol_number_t s)
  59 {
  60   int j;
  61   for (j = 0; j < shifts->num; j++)
  62     if (TRANSITION_SYMBOL (shifts, j) == s)
  63       return states[shifts->states[j]];
  64   abort ();
  65 }
  66
  67
  68                         /*--------------------.
  69                         | Error transitions.  |
  70                         `--------------------*/
  71
  72
  73 /*-------------------------------.
  74 | Create a new array of N errs.  |
  75 `-------------------------------*/
  76
  77 #define ERRS_ALLOC(Nerrs)                               \
  78   (errs_t *) xcalloc ((sizeof (errs_t)                  \
  79                       + (Nerrs - 1) * sizeof (symbol_number_t)), 1)
  80
  81
  82 errs_t *
  83 errs_new (int num, symbol_number_t *tokens)
  84 {
  85   errs_t *res = ERRS_ALLOC (num);
  86   res->num = num;
  87   memcpy (res->symbols, tokens, num * sizeof (tokens[0]));
  88   return res;
  89 }
  90
  91
  92
  93
  94                         /*-------------.
  95                         | Reductions.  |
  96                         `-------------*/
  97
  98
  99 /*-------------------------------------.
 100 | Create a new array of N reductions.  |
 101 `-------------------------------------*/
 102
 103 #define REDUCTIONS_ALLOC(Nreductions)                           \
 104   (reductions_t *) xcalloc ((sizeof (reductions_t)              \
 105                             + (Nreductions - 1) * sizeof (rule_number_t)), 1)
 106
 107 static reductions_t *
 108 reductions_new (int num, rule_number_t *reductions)
 109 {
 110   reductions_t *res = REDUCTIONS_ALLOC (num);
 111   res->num = num;
 112   memcpy (res->rules, reductions, num * sizeof (reductions[0]));
 113   return res;
 114 }
 115
 116
 117
 118                         /*---------.
 119                         | States.  |
 120                         `---------*/
 121
 122
 123 state_number_t nstates = 0;
 124 /* FINAL_STATE is properly set by new_state when it recognizes its
 125    accessing symbol: EOF.  */
 126 state_t *final_state = NULL;
 127
 128 #define STATE_ALLOC(Nitems)                                             \
 129   (state_t *) xcalloc ((unsigned) (sizeof (state_t)                     \
 130                                   + (Nitems - 1) * sizeof (item_number_t)), 1)
 131
 132 /*------------------------------------------------------------------.
 133 | Create a new state with ACCESSING_SYMBOL, for those items.  Store |
 134 | it in the state hash table.                                       |
 135 `------------------------------------------------------------------*/
 136
 137 state_t *
 138 state_new (symbol_number_t accessing_symbol,
 139            size_t core_size, item_number_t *core)
 140 {
 141   state_t *res;
 142
 143   if (nstates >= STATE_NUMBER_MAX)
 144     fatal (_("too many states (max %d)"), STATE_NUMBER_MAX);
 145
 146   res = STATE_ALLOC (core_size);
 147   res->accessing_symbol = accessing_symbol;
 148   res->number = nstates;
 149   ++nstates;
 150   res->solved_conflicts = NULL;
 151
 152   res->nitems = core_size;
 153   memcpy (res->items, core, core_size * sizeof (core[0]));
 154
 155   state_hash_insert (res);
 156
 157   return res;
 158 }
 159
 160
 161 /*-------------.
 162 | Free STATE.  |
 163 `-------------*/
 164
 165 static void
 166 state_free (state_t *state)
 167 {
 168   free (state->transitions);
 169   free (state->reductions);
 170   free (state->errs);
 171   free (state);
 172 }
 173
 174
 175 /*-------------------------------.
 176 | Set the transitions of STATE.  |
 177 `-------------------------------*/
 178
 179 void
 180 state_transitions_set (state_t *state, int num, state_number_t *transitions)
 181 {
 182   assert (!state->transitions);
 183   state->transitions = transitions_new (num, transitions);
 184 }
 185
 186
 187 /*------------------------------.
 188 | Set the reductions of STATE.  |
 189 `------------------------------*/
 190
 191 void
 192 state_reductions_set (state_t *state, int num, rule_number_t *reductions)
 193 {
 194   assert (!state->reductions);
 195   state->reductions = reductions_new (num, reductions);
 196 }
 197
 198
 199 /*------------------------.
 200 | Set the errs of STATE.  |
 201 `------------------------*/
 202
 203 void
 204 state_errs_set (state_t *state, int num, symbol_number_t *tokens)
 205 {
 206   assert (!state->errs);
 207   state->errs = errs_new (num, tokens);
 208 }
 209
 210
 211
 212 /*--------------------------------------------------------------.
 213 | Print on OUT all the lookaheads such that this STATE wants to |
 214 | reduce this RULE.                                             |
 215 `--------------------------------------------------------------*/
 216
 217 void
 218 state_rule_lookaheads_print (state_t *state, rule_t *rule, FILE *out)
 219 {
 220   int j, k;
 221   bitset_iterator biter;
 222   int nlookaheads = 0;
 223   /* Count the number of lookaheads corresponding to this rule.  */
 224   for (j = 0; j < state->nlookaheads; ++j)
 225     BITSET_FOR_EACH (biter, state->lookaheads[j], k, 0)
 226       if (state->lookaheads_rule[j]->number == rule->number)
 227         nlookaheads++;
 228
 229   /* Print them if there are.  */
 230   if (nlookaheads)
 231     {
 232       fprintf (out, "  [");
 233       for (j = 0; j < state->nlookaheads; ++j)
 234         BITSET_FOR_EACH (biter, state->lookaheads[j], k, 0)
 235           if (state->lookaheads_rule[j]->number == rule->number)
 236             fprintf (out, "%s%s",
 237                      symbols[k]->tag,
 238                      --nlookaheads ? ", " : "");
 239       fprintf (out, "]");
 240     }
 241 }
 242
 243
 244 /*----------------------.
 245 | A state hash table.  |
 246 `----------------------*/
 247
 248 /* Initial capacity of states hash table.  */
 249 #define HT_INITIAL_CAPACITY 257
 250
 251 static struct hash_table *state_table = NULL;
 252
 253 /* Two states are equal if they have the same core items.  */
 254 static bool
 255 state_compare (const state_t *s1, const state_t *s2)
 256 {
 257   int i;
 258
 259   if (s1->nitems != s2->nitems)
 260     return FALSE;
 261
 262   for (i = 0; i < s1->nitems; ++i)
 263     if (s1->items[i] != s2->items[i])
 264       return FALSE;
 265
 266   return TRUE;
 267 }
 268
 269 static unsigned int
 270 state_hash (const state_t *state, unsigned int tablesize)
 271 {
 272   /* Add up the state's item numbers to get a hash key.  */
 273   int key = 0;
 274   int i;
 275   for (i = 0; i < state->nitems; ++i)
 276     key += state->items[i];
 277   return key % tablesize;
 278 }
 279
 280
 281 /*-------------------------------.
 282 | Create the states hash table.  |
 283 `-------------------------------*/
 284
 285 void
 286 state_hash_new (void)
 287 {
 288   state_table = hash_initialize (HT_INITIAL_CAPACITY,
 289                                  NULL,
 290                                  (Hash_hasher) state_hash,
 291                                  (Hash_comparator) state_compare,
 292                                  (Hash_data_freer) NULL);
 293 }
 294
 295
 296 /*---------------------------------------------.
 297 | Free the states hash table, not the states.  |
 298 `---------------------------------------------*/
 299
 300 void
 301 state_hash_free (void)
 302 {
 303   hash_free (state_table);
 304 }
 305
 306
 307 /*---------------------------------------.
 308 | Insert STATE in the state hash table.  |
 309 `---------------------------------------*/
 310
 311 void
 312 state_hash_insert (state_t *state)
 313 {
 314   hash_insert (state_table, state);
 315 }
 316
 317
 318 /*------------------------------------------------------------------.
 319 | Find the state associated to the CORE, and return it.  If it does |
 320 | not exist yet, return NULL.                                       |
 321 `------------------------------------------------------------------*/
 322
 323 state_t *
 324 state_hash_lookup (size_t core_size, item_number_t *core)
 325 {
 326   state_t *probe = STATE_ALLOC (core_size);
 327   state_t *entry;
 328
 329   probe->nitems = core_size;
 330   memcpy (probe->items, core, core_size * sizeof (core[0]));
 331   entry = hash_lookup (state_table, probe);
 332   free (probe);
 333   return entry;
 334 }
 335
 336 /* All the decorated states, indexed by the state number.  */
 337 state_t **states = NULL;
 338
 339
 340 /*----------------------.
 341 | Free all the states.  |
 342 `----------------------*/
 343
 344 void
 345 states_free (void)
 346 {
 347   state_number_t i;
 348   for (i = 0; i < nstates; ++i)
 349     state_free (states[i]);
 350   free (states);
 351 }