src/state.c

   1 /* Type definitions for nondeterministic finite state machine for Bison.
   2
   3    Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
   4
   5    This file is part of Bison, the GNU Compiler Compiler.
   6
   7    Bison is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    Bison is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with Bison; see the file COPYING.  If not, write to
  19    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22
  23 #include "system.h"
  24
  25 #include <hash.h>
  26
  27 #include "complain.h"
  28 #include "gram.h"
  29 #include "state.h"
  30
  31
  32                         /*-------------------.
  33                         | Shifts and Gotos.  |
  34                         `-------------------*/
  35
  36
  37 /*-----------------------------------------.
  38 | Create a new array of NUM shifts/gotos.  |
  39 `-----------------------------------------*/
  40
  41 static transitions *
  42 transitions_new (int num, state **the_states)
  43 {
  44   size_t states_size = num * sizeof *the_states;
  45   transitions *res = xmalloc (offsetof (transitions, states) + states_size);
  46   res->num = num;
  47   memcpy (res->states, the_states, states_size);
  48   return res;
  49 }
  50
  51
  52 /*-------------------------------------------------------.
  53 | Return the state such that SHIFTS contain a shift/goto |
  54 | to it on SYM.  Abort if none found.                    |
  55 `-------------------------------------------------------*/
  56
  57 state *
  58 transitions_to (transitions *shifts, symbol_number sym)
  59 {
  60   int j;
  61   for (j = 0; j < shifts->num; j++)
  62     if (TRANSITION_SYMBOL (shifts, j) == sym)
  63       return shifts->states[j];
  64   abort ();
  65 }
  66
  67
  68                         /*--------------------.
  69                         | Error transitions.  |
  70                         `--------------------*/
  71
  72
  73 /*---------------------------------.
  74 | Create a new array of NUM errs.  |
  75 `---------------------------------*/
  76
  77 errs *
  78 errs_new (int num, symbol **tokens)
  79 {
  80   size_t symbols_size = num * sizeof *tokens;
  81   errs *res = xmalloc (offsetof (errs, symbols) + symbols_size);
  82   res->num = num;
  83   memcpy (res->symbols, tokens, symbols_size);
  84   return res;
  85 }
  86
  87
  88
  89
  90                         /*-------------.
  91                         | Reductions.  |
  92                         `-------------*/
  93
  94
  95 /*---------------------------------------.
  96 | Create a new array of NUM reductions.  |
  97 `---------------------------------------*/
  98
  99 static reductions *
 100 reductions_new (int num, rule **reds)
 101 {
 102   size_t rules_size = num * sizeof *reds;
 103   reductions *res = xmalloc (offsetof (reductions, rules) + rules_size);
 104   res->num = num;
 105   res->lookaheads = NULL;
 106   memcpy (res->rules, reds, rules_size);
 107   return res;
 108 }
 109
 110
 111
 112                         /*---------.
 113                         | States.  |
 114                         `---------*/
 115
 116
 117 state_number nstates = 0;
 118 /* FINAL_STATE is properly set by new_state when it recognizes its
 119    accessing symbol: $end.  */
 120 state *final_state = NULL;
 121
 122
 123 /*------------------------------------------------------------------.
 124 | Create a new state with ACCESSING_SYMBOL, for those items.  Store |
 125 | it in the state hash table.                                       |
 126 `------------------------------------------------------------------*/
 127
 128 state *
 129 state_new (symbol_number accessing_symbol,
 130            size_t nitems, item_number *core)
 131 {
 132   state *res;
 133   size_t items_size = nitems * sizeof *core;
 134
 135   if (STATE_NUMBER_MAXIMUM <= nstates)
 136     abort ();
 137
 138   res = xmalloc (offsetof (state, items) + items_size);
 139   res->number = nstates++;
 140   res->accessing_symbol = accessing_symbol;
 141   res->transitions = NULL;
 142   res->reductions = NULL;
 143   res->errs = NULL;
 144   res->consistent = 0;
 145   res->solved_conflicts = NULL;
 146
 147   res->nitems = nitems;
 148   memcpy (res->items, core, items_size);
 149
 150   state_hash_insert (res);
 151
 152   return res;
 153 }
 154
 155
 156 /*---------.
 157 | Free S.  |
 158 `---------*/
 159
 160 static void
 161 state_free (state *s)
 162 {
 163   free (s->transitions);
 164   free (s->reductions);
 165   free (s->errs);
 166   free (s);
 167 }
 168
 169
 170 /*---------------------------.
 171 | Set the transitions of S.  |
 172 `---------------------------*/
 173
 174 void
 175 state_transitions_set (state *s, int num, state **trans)
 176 {
 177   if (s->transitions)
 178     abort ();
 179   s->transitions = transitions_new (num, trans);
 180 }
 181
 182
 183 /*--------------------------.
 184 | Set the reductions of S.  |
 185 `--------------------------*/
 186
 187 void
 188 state_reductions_set (state *s, int num, rule **reds)
 189 {
 190   if (s->reductions)
 191     abort ();
 192   s->reductions = reductions_new (num, reds);
 193 }
 194
 195
 196 int
 197 state_reduction_find (state *s, rule *r)
 198 {
 199   int i;
 200   reductions *reds = s->reductions;
 201   for (i = 0; i < reds->num; ++i)
 202     if (reds->rules[i] == r)
 203       return i;
 204   return -1;
 205 }
 206
 207
 208 /*--------------------.
 209 | Set the errs of S.  |
 210 `--------------------*/
 211
 212 void
 213 state_errs_set (state *s, int num, symbol **tokens)
 214 {
 215   if (s->errs)
 216     abort ();
 217   s->errs = errs_new (num, tokens);
 218 }
 219
 220
 221
 222 /*-----------------------------------------------------.
 223 | Print on OUT all the lookaheads such that S wants to |
 224 | reduce R.                                            |
 225 `-----------------------------------------------------*/
 226
 227 void
 228 state_rule_lookaheads_print (state *s, rule *r, FILE *out)
 229 {
 230   /* Find the reduction we are handling.  */
 231   reductions *reds = s->reductions;
 232   int red = state_reduction_find (s, r);
 233
 234   /* Print them if there are.  */
 235   if (reds->lookaheads && red != -1)
 236     {
 237       bitset_iterator biter;
 238       int k;
 239       int not_first = 0;
 240       fprintf (out, "  [");
 241       BITSET_FOR_EACH (biter, reds->lookaheads[red], k, 0)
 242         fprintf (out, "%s%s",
 243                  not_first++ ? ", " : "",
 244                  symbols[k]->tag);
 245       fprintf (out, "]");
 246     }
 247 }
 248
 249
 250 /*----------------------.
 251 | A state hash table.  |
 252 `----------------------*/
 253
 254 /* Initial capacity of states hash table.  */
 255 #define HT_INITIAL_CAPACITY 257
 256
 257 static struct hash_table *state_table = NULL;
 258
 259 /* Two states are equal if they have the same core items.  */
 260 static inline bool
 261 state_compare (state const *s1, state const *s2)
 262 {
 263   int i;
 264
 265   if (s1->nitems != s2->nitems)
 266     return false;
 267
 268   for (i = 0; i < s1->nitems; ++i)
 269     if (s1->items[i] != s2->items[i])
 270       return false;
 271
 272   return true;
 273 }
 274
 275 static bool
 276 state_comparator (void const *s1, void const *s2)
 277 {
 278   return state_compare (s1, s2);
 279 }
 280
 281 static inline unsigned int
 282 state_hash (state const *s, unsigned int tablesize)
 283 {
 284   /* Add up the state's item numbers to get a hash key.  */
 285   unsigned int key = 0;
 286   int i;
 287   for (i = 0; i < s->nitems; ++i)
 288     key += s->items[i];
 289   return key % tablesize;
 290 }
 291
 292 static unsigned int
 293 state_hasher (void const *s, unsigned int tablesize)
 294 {
 295   return state_hash (s, tablesize);
 296 }
 297
 298
 299 /*-------------------------------.
 300 | Create the states hash table.  |
 301 `-------------------------------*/
 302
 303 void
 304 state_hash_new (void)
 305 {
 306   state_table = hash_initialize (HT_INITIAL_CAPACITY,
 307                                  NULL,
 308                                  state_hasher,
 309                                  state_comparator,
 310                                  NULL);
 311 }
 312
 313
 314 /*---------------------------------------------.
 315 | Free the states hash table, not the states.  |
 316 `---------------------------------------------*/
 317
 318 void
 319 state_hash_free (void)
 320 {
 321   hash_free (state_table);
 322 }
 323
 324
 325 /*-----------------------------------.
 326 | Insert S in the state hash table.  |
 327 `-----------------------------------*/
 328
 329 void
 330 state_hash_insert (state *s)
 331 {
 332   hash_insert (state_table, s);
 333 }
 334
 335
 336 /*------------------------------------------------------------------.
 337 | Find the state associated to the CORE, and return it.  If it does |
 338 | not exist yet, return NULL.                                       |
 339 `------------------------------------------------------------------*/
 340
 341 state *
 342 state_hash_lookup (size_t nitems, item_number *core)
 343 {
 344   size_t items_size = nitems * sizeof *core;
 345   state *probe = xmalloc (offsetof (state, items) + items_size);
 346   state *entry;
 347
 348   probe->nitems = nitems;
 349   memcpy (probe->items, core, items_size);
 350   entry = hash_lookup (state_table, probe);
 351   free (probe);
 352   return entry;
 353 }
 354
 355 /* All the decorated states, indexed by the state number.  */
 356 state **states = NULL;
 357
 358
 359 /*----------------------.
 360 | Free all the states.  |
 361 `----------------------*/
 362
 363 void
 364 states_free (void)
 365 {
 366   state_number i;
 367   for (i = 0; i < nstates; ++i)
 368     state_free (states[i]);
 369   free (states);
 370 }