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      1 /* Type definitions for the finite state machine for Bison.
      2 
      3    Copyright (C) 2001-2007, 2009-2012 Free Software Foundation, Inc.
      4 
      5    This file is part of Bison, the GNU Compiler Compiler.
      6 
      7    This program 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 3 of the License, or
     10    (at your option) any later version.
     11 
     12    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
     19 
     20 #include <config.h>
     21 #include "system.h"
     22 
     23 #include <hash.h>
     24 
     25 #include "complain.h"
     26 #include "gram.h"
     27 #include "state.h"
     28 #include "print-xml.h"
     29 
     30 
     31 			/*-------------------.
     32 			| Shifts and Gotos.  |
     33 			`-------------------*/
     34 
     35 
     36 /*-----------------------------------------.
     37 | Create a new array of NUM shifts/gotos.  |
     38 `-----------------------------------------*/
     39 
     40 static transitions *
     41 transitions_new (int num, state **the_states)
     42 {
     43   size_t states_size = num * sizeof *the_states;
     44   transitions *res = xmalloc (offsetof (transitions, states) + states_size);
     45   res->num = num;
     46   memcpy (res->states, the_states, states_size);
     47   return res;
     48 }
     49 
     50 
     51 /*-------------------------------------------------------.
     52 | Return the state such that SHIFTS contain a shift/goto |
     53 | to it on SYM.  Abort if none found.                    |
     54 `-------------------------------------------------------*/
     55 
     56 state *
     57 transitions_to (transitions *shifts, symbol_number sym)
     58 {
     59   int j;
     60   for (j = 0; ; j++)
     61     {
     62       aver (j < shifts->num);
     63       if (TRANSITION_SYMBOL (shifts, j) == sym)
     64 	return shifts->states[j];
     65     }
     66 }
     67 
     68 
     69 			/*--------------------.
     70 			| Error transitions.  |
     71 			`--------------------*/
     72 
     73 
     74 /*---------------------------------.
     75 | Create a new array of NUM errs.  |
     76 `---------------------------------*/
     77 
     78 errs *
     79 errs_new (int num, symbol **tokens)
     80 {
     81   size_t symbols_size = num * sizeof *tokens;
     82   errs *res = xmalloc (offsetof (errs, symbols) + symbols_size);
     83   res->num = num;
     84   memcpy (res->symbols, tokens, symbols_size);
     85   return res;
     86 }
     87 
     88 
     89 
     90 
     91 			/*-------------.
     92 			| Reductions.  |
     93 			`-------------*/
     94 
     95 
     96 /*---------------------------------------.
     97 | Create a new array of NUM reductions.  |
     98 `---------------------------------------*/
     99 
    100 static reductions *
    101 reductions_new (int num, rule **reds)
    102 {
    103   size_t rules_size = num * sizeof *reds;
    104   reductions *res = xmalloc (offsetof (reductions, rules) + rules_size);
    105   res->num = num;
    106   res->lookahead_tokens = NULL;
    107   memcpy (res->rules, reds, rules_size);
    108   return res;
    109 }
    110 
    111 
    112 
    113 			/*---------.
    114 			| States.  |
    115 			`---------*/
    116 
    117 
    118 state_number nstates = 0;
    119 /* FINAL_STATE is properly set by new_state when it recognizes its
    120    accessing symbol: $end.  */
    121 state *final_state = NULL;
    122 
    123 
    124 /*------------------------------------------------------------------.
    125 | Create a new state with ACCESSING_SYMBOL, for those items.  Store |
    126 | it in the state hash table.                                       |
    127 `------------------------------------------------------------------*/
    128 
    129 state *
    130 state_new (symbol_number accessing_symbol,
    131 	   size_t nitems, item_number *core)
    132 {
    133   state *res;
    134   size_t items_size = nitems * sizeof *core;
    135 
    136   aver (nstates < STATE_NUMBER_MAXIMUM);
    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->state_list = NULL;
    145   res->consistent = 0;
    146   res->solved_conflicts = NULL;
    147   res->solved_conflicts_xml = NULL;
    148 
    149   res->nitems = nitems;
    150   memcpy (res->items, core, items_size);
    151 
    152   state_hash_insert (res);
    153 
    154   return res;
    155 }
    156 
    157 state *
    158 state_new_isocore (state const *s)
    159 {
    160   state *res;
    161   size_t items_size = s->nitems * sizeof *s->items;
    162 
    163   aver (nstates < STATE_NUMBER_MAXIMUM);
    164 
    165   res = xmalloc (offsetof (state, items) + items_size);
    166   res->number = nstates++;
    167   res->accessing_symbol = s->accessing_symbol;
    168   res->transitions =
    169     transitions_new (s->transitions->num, s->transitions->states);
    170   res->reductions = reductions_new (s->reductions->num, s->reductions->rules);
    171   res->errs = NULL;
    172   res->state_list = NULL;
    173   res->consistent = s->consistent;
    174   res->solved_conflicts = NULL;
    175   res->solved_conflicts_xml = NULL;
    176 
    177   res->nitems = s->nitems;
    178   memcpy (res->items, s->items, items_size);
    179 
    180   return res;
    181 }
    182 
    183 
    184 /*---------.
    185 | Free S.  |
    186 `---------*/
    187 
    188 static void
    189 state_free (state *s)
    190 {
    191   free (s->transitions);
    192   free (s->reductions);
    193   free (s->errs);
    194   free (s);
    195 }
    196 
    197 
    198 /*---------------------------.
    199 | Set the transitions of S.  |
    200 `---------------------------*/
    201 
    202 void
    203 state_transitions_set (state *s, int num, state **trans)
    204 {
    205   aver (!s->transitions);
    206   s->transitions = transitions_new (num, trans);
    207 }
    208 
    209 
    210 /*--------------------------.
    211 | Set the reductions of S.  |
    212 `--------------------------*/
    213 
    214 void
    215 state_reductions_set (state *s, int num, rule **reds)
    216 {
    217   aver (!s->reductions);
    218   s->reductions = reductions_new (num, reds);
    219 }
    220 
    221 
    222 int
    223 state_reduction_find (state *s, rule *r)
    224 {
    225   int i;
    226   reductions *reds = s->reductions;
    227   for (i = 0; i < reds->num; ++i)
    228     if (reds->rules[i] == r)
    229       return i;
    230   return -1;
    231 }
    232 
    233 
    234 /*--------------------.
    235 | Set the errs of S.  |
    236 `--------------------*/
    237 
    238 void
    239 state_errs_set (state *s, int num, symbol **tokens)
    240 {
    241   aver (!s->errs);
    242   s->errs = errs_new (num, tokens);
    243 }
    244 
    245 
    246 
    247 /*--------------------------------------------------.
    248 | Print on OUT all the lookahead tokens such that S |
    249 | wants to reduce R.                                |
    250 `--------------------------------------------------*/
    251 
    252 void
    253 state_rule_lookahead_tokens_print (state *s, rule *r, FILE *out)
    254 {
    255   /* Find the reduction we are handling.  */
    256   reductions *reds = s->reductions;
    257   int red = state_reduction_find (s, r);
    258 
    259   /* Print them if there are.  */
    260   if (reds->lookahead_tokens && red != -1)
    261     {
    262       bitset_iterator biter;
    263       int k;
    264       char const *sep = "";
    265       fprintf (out, "  [");
    266       BITSET_FOR_EACH (biter, reds->lookahead_tokens[red], k, 0)
    267 	{
    268 	  fprintf (out, "%s%s", sep, symbols[k]->tag);
    269 	  sep = ", ";
    270 	}
    271       fprintf (out, "]");
    272     }
    273 }
    274 
    275 void
    276 state_rule_lookahead_tokens_print_xml (state *s, rule *r,
    277 				       FILE *out, int level)
    278 {
    279   /* Find the reduction we are handling.  */
    280   reductions *reds = s->reductions;
    281   int red = state_reduction_find (s, r);
    282 
    283   /* Print them if there are.  */
    284   if (reds->lookahead_tokens && red != -1)
    285     {
    286       bitset_iterator biter;
    287       int k;
    288       xml_puts (out, level, "<lookaheads>");
    289       BITSET_FOR_EACH (biter, reds->lookahead_tokens[red], k, 0)
    290 	{
    291 	  xml_printf (out, level + 1, "<symbol>%s</symbol>",
    292 		      xml_escape (symbols[k]->tag));
    293 	}
    294       xml_puts (out, level, "</lookaheads>");
    295     }
    296 }
    297 
    298 
    299 /*---------------------.
    300 | A state hash table.  |
    301 `---------------------*/
    302 
    303 /* Initial capacity of states hash table.  */
    304 #define HT_INITIAL_CAPACITY 257
    305 
    306 static struct hash_table *state_table = NULL;
    307 
    308 /* Two states are equal if they have the same core items.  */
    309 static inline bool
    310 state_compare (state const *s1, state const *s2)
    311 {
    312   size_t i;
    313 
    314   if (s1->nitems != s2->nitems)
    315     return false;
    316 
    317   for (i = 0; i < s1->nitems; ++i)
    318     if (s1->items[i] != s2->items[i])
    319       return false;
    320 
    321   return true;
    322 }
    323 
    324 static bool
    325 state_comparator (void const *s1, void const *s2)
    326 {
    327   return state_compare (s1, s2);
    328 }
    329 
    330 static inline size_t
    331 state_hash (state const *s, size_t tablesize)
    332 {
    333   /* Add up the state's item numbers to get a hash key.  */
    334   size_t key = 0;
    335   size_t i;
    336   for (i = 0; i < s->nitems; ++i)
    337     key += s->items[i];
    338   return key % tablesize;
    339 }
    340 
    341 static size_t
    342 state_hasher (void const *s, size_t tablesize)
    343 {
    344   return state_hash (s, tablesize);
    345 }
    346 
    347 
    348 /*-------------------------------.
    349 | Create the states hash table.  |
    350 `-------------------------------*/
    351 
    352 void
    353 state_hash_new (void)
    354 {
    355   state_table = hash_initialize (HT_INITIAL_CAPACITY,
    356 				 NULL,
    357 				 state_hasher,
    358 				 state_comparator,
    359 				 NULL);
    360 }
    361 
    362 
    363 /*---------------------------------------------.
    364 | Free the states hash table, not the states.  |
    365 `---------------------------------------------*/
    366 
    367 void
    368 state_hash_free (void)
    369 {
    370   hash_free (state_table);
    371 }
    372 
    373 
    374 /*-----------------------------------.
    375 | Insert S in the state hash table.  |
    376 `-----------------------------------*/
    377 
    378 void
    379 state_hash_insert (state *s)
    380 {
    381   if (!hash_insert (state_table, s))
    382     xalloc_die ();
    383 }
    384 
    385 
    386 /*------------------------------------------------------------------.
    387 | Find the state associated to the CORE, and return it.  If it does |
    388 | not exist yet, return NULL.                                       |
    389 `------------------------------------------------------------------*/
    390 
    391 state *
    392 state_hash_lookup (size_t nitems, item_number *core)
    393 {
    394   size_t items_size = nitems * sizeof *core;
    395   state *probe = xmalloc (offsetof (state, items) + items_size);
    396   state *entry;
    397 
    398   probe->nitems = nitems;
    399   memcpy (probe->items, core, items_size);
    400   entry = hash_lookup (state_table, probe);
    401   free (probe);
    402   return entry;
    403 }
    404 
    405 
    406 /*--------------------------------------------------------.
    407 | Record S and all states reachable from S in REACHABLE.  |
    408 `--------------------------------------------------------*/
    409 
    410 static void
    411 state_record_reachable_states (state *s, bitset reachable)
    412 {
    413   if (bitset_test (reachable, s->number))
    414     return;
    415   bitset_set (reachable, s->number);
    416   {
    417     int i;
    418     for (i = 0; i < s->transitions->num; ++i)
    419       if (!TRANSITION_IS_DISABLED (s->transitions, i))
    420         state_record_reachable_states (s->transitions->states[i], reachable);
    421   }
    422 }
    423 
    424 void
    425 state_remove_unreachable_states (state_number old_to_new[])
    426 {
    427   state_number nstates_reachable = 0;
    428   bitset reachable = bitset_create (nstates, BITSET_FIXED);
    429   state_record_reachable_states (states[0], reachable);
    430   {
    431     state_number i;
    432     for (i = 0; i < nstates; ++i)
    433       {
    434         if (bitset_test (reachable, states[i]->number))
    435           {
    436             states[nstates_reachable] = states[i];
    437             states[nstates_reachable]->number = nstates_reachable;
    438             old_to_new[i] = nstates_reachable++;
    439           }
    440         else
    441           {
    442             state_free (states[i]);
    443             old_to_new[i] = nstates;
    444           }
    445       }
    446   }
    447   nstates = nstates_reachable;
    448   bitset_free (reachable);
    449 }
    450 
    451 /* All the decorated states, indexed by the state number.  */
    452 state **states = NULL;
    453 
    454 
    455 /*----------------------.
    456 | Free all the states.  |
    457 `----------------------*/
    458 
    459 void
    460 states_free (void)
    461 {
    462   state_number i;
    463   for (i = 0; i < nstates; ++i)
    464     state_free (states[i]);
    465   free (states);
    466 }
    467