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 ((unsigned) (sizeof (errs_t)                       \
  79                                   + (Nerrs - 1) * sizeof (symbol_number_t)), 1)
  80
  81
  82 errs_t *
  83 errs_new (int n)
  84 {
  85   errs_t *res = ERRS_ALLOC (n);
  86   res->num = n;
  87   return res;
  88 }
  89
  90
  91 errs_t *
  92 errs_dup (errs_t *src)
  93 {
  94   errs_t *res = errs_new (src->num);
  95   memcpy (res->symbols, src->symbols, src->num * sizeof (src->symbols[0]));
  96   return res;
  97 }
  98
  99
 100
 101
 102                         /*-------------.
 103                         | Reductions.  |
 104                         `-------------*/
 105
 106
 107 /*-------------------------------------.
 108 | Create a new array of N reductions.  |
 109 `-------------------------------------*/
 110
 111 #define REDUCTIONS_ALLOC(Nreductions)                                   \
 112   (reductions_t *) xcalloc ((unsigned) (sizeof (reductions_t)           \
 113                                   + (Nreductions - 1) * sizeof (rule_number_t)), 1)
 114
 115 static reductions_t *
 116 reductions_new (int nreductions, short *reductions)
 117 {
 118   reductions_t *res = REDUCTIONS_ALLOC (nreductions);
 119   res->num = nreductions;
 120   memcpy (res->rules, reductions, nreductions * sizeof (reductions[0]));
 121   return res;
 122 }
 123
 124
 125
 126                         /*---------.
 127                         | States.  |
 128                         `---------*/
 129
 130
 131 state_number_t nstates = 0;
 132 /* FINAL_STATE is properly set by new_state when it recognizes its
 133    accessing symbol: EOF.  */
 134 state_t *final_state = NULL;
 135
 136 #define STATE_ALLOC(Nitems)                                             \
 137   (state_t *) xcalloc ((unsigned) (sizeof (state_t)                     \
 138                                   + (Nitems - 1) * sizeof (item_number_t)), 1)
 139
 140 /*------------------------------------------------------------.
 141 | Create a new state with ACCESSING_SYMBOL, for those items.  |
 142 `------------------------------------------------------------*/
 143
 144 state_t *
 145 state_new (symbol_number_t accessing_symbol,
 146            size_t core_size, item_number_t *core)
 147 {
 148   state_t *res;
 149
 150   if (nstates >= STATE_NUMBER_MAX)
 151     fatal (_("too many states (max %d)"), STATE_NUMBER_MAX);
 152
 153   res = STATE_ALLOC (core_size);
 154   res->accessing_symbol = accessing_symbol;
 155   res->number = nstates;
 156   ++nstates;
 157   res->solved_conflicts = NULL;
 158
 159   res->nitems = core_size;
 160   memcpy (res->items, core, core_size * sizeof (core[0]));
 161
 162   return res;
 163 }
 164
 165
 166 /*--------------------------.
 167 | Set the shifts of STATE.  |
 168 `--------------------------*/
 169
 170 void
 171 state_transitions_set (state_t *state, int nshifts, state_number_t *shifts)
 172 {
 173   state->shifts = transitions_new (nshifts, shifts);
 174 }
 175
 176
 177 /*------------------------------.
 178 | Set the reductions of STATE.  |
 179 `------------------------------*/
 180
 181 void
 182 state_reductions_set (state_t *state, int nreductions, short *reductions)
 183 {
 184   state->reductions = reductions_new (nreductions, reductions);
 185 }
 186
 187
 188
 189 /*--------------------------------------------------------------.
 190 | Print on OUT all the lookaheads such that this STATE wants to |
 191 | reduce this RULE.                                             |
 192 `--------------------------------------------------------------*/
 193
 194 void
 195 state_rule_lookaheads_print (state_t *state, rule_t *rule, FILE *out)
 196 {
 197   int j, k;
 198   bitset_iterator biter;
 199   int nlookaheads = 0;
 200   /* Count the number of lookaheads corresponding to this rule.  */
 201   for (j = 0; j < state->nlookaheads; ++j)
 202     BITSET_FOR_EACH (biter, state->lookaheads[j], k, 0)
 203       if (state->lookaheads_rule[j]->number == rule->number)
 204         nlookaheads++;
 205
 206   /* Print them if there are.  */
 207   if (nlookaheads)
 208     {
 209       fprintf (out, "  [");
 210       for (j = 0; j < state->nlookaheads; ++j)
 211         BITSET_FOR_EACH (biter, state->lookaheads[j], k, 0)
 212           if (state->lookaheads_rule[j]->number == rule->number)
 213             fprintf (out, "%s%s",
 214                      symbols[k]->tag,
 215                      --nlookaheads ? ", " : "");
 216       fprintf (out, "]");
 217     }
 218 }
 219
 220
 221 /*----------------------.
 222 | A state hash table.  |
 223 `----------------------*/
 224
 225 /* Initial capacity of states hash table.  */
 226 #define HT_INITIAL_CAPACITY 257
 227
 228 static struct hash_table *state_table = NULL;
 229
 230 /* Two states are equal if they have the same core items.  */
 231 static bool
 232 state_compare (const state_t *s1, const state_t *s2)
 233 {
 234   int i;
 235
 236   if (s1->nitems != s2->nitems)
 237     return FALSE;
 238
 239   for (i = 0; i < s1->nitems; ++i)
 240     if (s1->items[i] != s2->items[i])
 241       return FALSE;
 242
 243   return TRUE;
 244 }
 245
 246 static unsigned int
 247 state_hash (const state_t *state, unsigned int tablesize)
 248 {
 249   /* Add up the state's item numbers to get a hash key.  */
 250   int key = 0;
 251   int i;
 252   for (i = 0; i < state->nitems; ++i)
 253     key += state->items[i];
 254   return key % tablesize;
 255 }
 256
 257
 258 /*-------------------------------.
 259 | Create the states hash table.  |
 260 `-------------------------------*/
 261
 262 void
 263 state_hash_new (void)
 264 {
 265   state_table = hash_initialize (HT_INITIAL_CAPACITY,
 266                                  NULL,
 267                                  (Hash_hasher) state_hash,
 268                                  (Hash_comparator) state_compare,
 269                                  (Hash_data_freer) NULL);
 270 }
 271
 272
 273 /*---------------------------------------------.
 274 | Free the states hash table, not the states.  |
 275 `---------------------------------------------*/
 276
 277 void
 278 state_hash_free (void)
 279 {
 280   hash_free (state_table);
 281 }
 282
 283
 284 /*---------------------------------------.
 285 | Insert STATE in the state hash table.  |
 286 `---------------------------------------*/
 287
 288 void
 289 state_hash_insert (state_t *state)
 290 {
 291   hash_insert (state_table, state);
 292 }
 293
 294
 295 /*------------------------------------------------------------------.
 296 | Find the state associated to the CORE, and return it.  If it does |
 297 | not exist yet, return NULL.                                       |
 298 `------------------------------------------------------------------*/
 299
 300 state_t *
 301 state_hash_lookup (size_t core_size, item_number_t *core)
 302 {
 303   state_t *probe = STATE_ALLOC (core_size);
 304   state_t *entry;
 305
 306   probe->nitems = core_size;
 307   memcpy (probe->items, core, core_size * sizeof (core[0]));
 308   entry = hash_lookup (state_table, probe);
 309   free (probe);
 310   return entry;
 311 }
 312
 313 /* All the decorated states, indexed by the state number.  */
 314 state_t **states = NULL;
 315
 316
 317 /*----------------------.
 318 | Free all the states.  |
 319 `----------------------*/
 320
 321 void
 322 states_free (void)
 323 {
 324   state_number_t i;
 325
 326   for (i = 0; i < nstates; ++i)
 327     {
 328       free (states[i]->shifts);
 329       XFREE (states[i]->reductions);
 330       free (states[i]->errs);
 331       free (states[i]);
 332     }
 333   XFREE (states);
 334 }