iconv/gconv_db.c

   1 /* Provide access to the collection of available transformation modules.
   2    Copyright (C) 1997-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <limits.h>
  22 #include <search.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/param.h>
  26 #include <libc-lock.h>
  27 #include <locale/localeinfo.h>
  28
  29 #include <dlfcn.h>
  30 #include <gconv_int.h>
  31 #include <sysdep.h>
  32
  33
  34 /* Simple data structure for alias mapping.  We have two names, `from'
  35    and `to'.  */
  36 void *__gconv_alias_db;
  37
  38 /* Array with available modules.  */
  39 struct gconv_module *__gconv_modules_db;
  40
  41 /* We modify global data.   */
  42 __libc_lock_define_initialized (, __gconv_lock)
  43
  44
  45 /* Provide access to module database.  */
  46 struct gconv_module *
  47 __gconv_get_modules_db (void)
  48 {
  49   return __gconv_modules_db;
  50 }
  51
  52 void *
  53 __gconv_get_alias_db (void)
  54 {
  55   return __gconv_alias_db;
  56 }
  57
  58
  59 /* Function for searching alias.  */
  60 int
  61 __gconv_alias_compare (const void *p1, const void *p2)
  62 {
  63   const struct gconv_alias *s1 = (const struct gconv_alias *) p1;
  64   const struct gconv_alias *s2 = (const struct gconv_alias *) p2;
  65   return strcmp (s1->fromname, s2->fromname);
  66 }
  67
  68
  69 /* To search for a derivation we create a list of intermediate steps.
  70    Each element contains a pointer to the element which precedes it
  71    in the derivation order.  */
  72 struct derivation_step
  73 {
  74   const char *result_set;
  75   size_t result_set_len;
  76   int cost_lo;
  77   int cost_hi;
  78   struct gconv_module *code;
  79   struct derivation_step *last;
  80   struct derivation_step *next;
  81 };
  82
  83 #define NEW_STEP(result, hi, lo, module, last_mod) \
  84   ({ struct derivation_step *newp = alloca (sizeof (struct derivation_step)); \
  85      newp->result_set = result;                                               \
  86      newp->result_set_len = strlen (result);                                  \
  87      newp->cost_hi = hi;                                                      \
  88      newp->cost_lo = lo;                                                      \
  89      newp->code = module;                                                     \
  90      newp->last = last_mod;                                                   \
  91      newp->next = NULL;                                                       \
  92      newp; })
  93
  94
  95 /* If a specific transformation is used more than once we should not need
  96    to start looking for it again.  Instead cache each successful result.  */
  97 struct known_derivation
  98 {
  99   const char *from;
 100   const char *to;
 101   struct __gconv_step *steps;
 102   size_t nsteps;
 103 };
 104
 105 /* Compare function for database of found derivations.  */
 106 static int
 107 derivation_compare (const void *p1, const void *p2)
 108 {
 109   const struct known_derivation *s1 = (const struct known_derivation *) p1;
 110   const struct known_derivation *s2 = (const struct known_derivation *) p2;
 111   int result;
 112
 113   result = strcmp (s1->from, s2->from);
 114   if (result == 0)
 115     result = strcmp (s1->to, s2->to);
 116   return result;
 117 }
 118
 119 /* The search tree for known derivations.  */
 120 static void *known_derivations;
 121
 122 /* Look up whether given transformation was already requested before.  */
 123 static int
 124 derivation_lookup (const char *fromset, const char *toset,
 125                    struct __gconv_step **handle, size_t *nsteps)
 126 {
 127   struct known_derivation key = { fromset, toset, NULL, 0 };
 128   struct known_derivation **result;
 129
 130   result = __tfind (&key, &known_derivations, derivation_compare);
 131
 132   if (result == NULL)
 133     return __GCONV_NOCONV;
 134
 135   *handle = (*result)->steps;
 136   *nsteps = (*result)->nsteps;
 137
 138   /* Please note that we return GCONV_OK even if the last search for
 139      this transformation was unsuccessful.  */
 140   return __GCONV_OK;
 141 }
 142
 143 /* Add new derivation to list of known ones.  */
 144 static void
 145 add_derivation (const char *fromset, const char *toset,
 146                 struct __gconv_step *handle, size_t nsteps)
 147 {
 148   struct known_derivation *new_deriv;
 149   size_t fromset_len = strlen (fromset) + 1;
 150   size_t toset_len = strlen (toset) + 1;
 151
 152   new_deriv = (struct known_derivation *)
 153     malloc (sizeof (struct known_derivation) + fromset_len + toset_len);
 154   if (new_deriv != NULL)
 155     {
 156       new_deriv->from = (char *) (new_deriv + 1);
 157       new_deriv->to = memcpy (__mempcpy (new_deriv + 1, fromset, fromset_len),
 158                               toset, toset_len);
 159
 160       new_deriv->steps = handle;
 161       new_deriv->nsteps = nsteps;
 162
 163       if (__tsearch (new_deriv, &known_derivations, derivation_compare)
 164           == NULL)
 165         /* There is some kind of memory allocation problem.  */
 166         free (new_deriv);
 167     }
 168   /* Please note that we don't complain if the allocation failed.  This
 169      is not tragically but in case we use the memory debugging facilities
 170      not all memory will be freed.  */
 171 }
 172
 173 static void __libc_freeres_fn_section
 174 free_derivation (void *p)
 175 {
 176   struct known_derivation *deriv = (struct known_derivation *) p;
 177   size_t cnt;
 178
 179   for (cnt = 0; cnt < deriv->nsteps; ++cnt)
 180     if (deriv->steps[cnt].__counter > 0
 181         && deriv->steps[cnt].__shlib_handle != NULL)
 182       {
 183         __gconv_end_fct end_fct = deriv->steps[cnt].__end_fct;
 184 #ifdef PTR_DEMANGLE
 185         PTR_DEMANGLE (end_fct);
 186 #endif
 187         if (end_fct != NULL)
 188           DL_CALL_FCT (end_fct, (&deriv->steps[cnt]));
 189       }
 190
 191   /* Free the name strings.  */
 192   if (deriv->steps != NULL)
 193     {
 194       free ((char *) deriv->steps[0].__from_name);
 195       free ((char *) deriv->steps[deriv->nsteps - 1].__to_name);
 196       free ((struct __gconv_step *) deriv->steps);
 197     }
 198
 199   free (deriv);
 200 }
 201
 202
 203 /* Decrement the reference count for a single step in a steps array.  */
 204 void
 205 __gconv_release_step (struct __gconv_step *step)
 206 {
 207   /* Skip builtin modules; they are not reference counted.  */
 208   if (step->__shlib_handle != NULL && --step->__counter == 0)
 209     {
 210       /* Call the destructor.  */
 211         __gconv_end_fct end_fct = step->__end_fct;
 212 #ifdef PTR_DEMANGLE
 213         PTR_DEMANGLE (end_fct);
 214 #endif
 215       if (end_fct != NULL)
 216         DL_CALL_FCT (end_fct, (step));
 217
 218 #ifndef STATIC_GCONV
 219       /* Release the loaded module.  */
 220       __gconv_release_shlib (step->__shlib_handle);
 221       step->__shlib_handle = NULL;
 222 #endif
 223     }
 224   else if (step->__shlib_handle == NULL)
 225     /* Builtin modules should not have end functions.  */
 226     assert (step->__end_fct == NULL);
 227 }
 228
 229 static int
 230 gen_steps (struct derivation_step *best, const char *toset,
 231            const char *fromset, struct __gconv_step **handle, size_t *nsteps)
 232 {
 233   size_t step_cnt = 0;
 234   struct __gconv_step *result;
 235   struct derivation_step *current;
 236   int status = __GCONV_NOMEM;
 237   char *from_name = NULL;
 238   char *to_name = NULL;
 239
 240   /* First determine number of steps.  */
 241   for (current = best; current->last != NULL; current = current->last)
 242     ++step_cnt;
 243
 244   result = (struct __gconv_step *) malloc (sizeof (struct __gconv_step)
 245                                            * step_cnt);
 246   if (result != NULL)
 247     {
 248       int failed = 0;
 249
 250       status = __GCONV_OK;
 251       *nsteps = step_cnt;
 252       current = best;
 253       while (step_cnt-- > 0)
 254         {
 255           if (step_cnt == 0)
 256             {
 257               result[step_cnt].__from_name = from_name = __strdup (fromset);
 258               if (from_name == NULL)
 259                 {
 260                   failed = 1;
 261                   break;
 262                 }
 263             }
 264           else
 265             result[step_cnt].__from_name = (char *)current->last->result_set;
 266
 267           if (step_cnt + 1 == *nsteps)
 268             {
 269               result[step_cnt].__to_name = to_name
 270                 = __strdup (current->result_set);
 271               if (to_name == NULL)
 272                 {
 273                   failed = 1;
 274                   break;
 275                 }
 276             }
 277           else
 278             result[step_cnt].__to_name = result[step_cnt + 1].__from_name;
 279
 280           result[step_cnt].__counter = 1;
 281           result[step_cnt].__data = NULL;
 282
 283 #ifndef STATIC_GCONV
 284           if (current->code->module_name[0] == '/')
 285             {
 286               /* Load the module, return handle for it.  */
 287               struct __gconv_loaded_object *shlib_handle =
 288                 __gconv_find_shlib (current->code->module_name);
 289
 290               if (shlib_handle == NULL)
 291                 {
 292                   failed = 1;
 293                   break;
 294                 }
 295
 296               result[step_cnt].__shlib_handle = shlib_handle;
 297               result[step_cnt].__modname = shlib_handle->name;
 298               result[step_cnt].__fct = shlib_handle->fct;
 299               result[step_cnt].__init_fct = shlib_handle->init_fct;
 300               result[step_cnt].__end_fct = shlib_handle->end_fct;
 301
 302               /* These settings can be overridden by the init function.  */
 303               result[step_cnt].__btowc_fct = NULL;
 304
 305               /* Call the init function.  */
 306               __gconv_init_fct init_fct = result[step_cnt].__init_fct;
 307 # ifdef PTR_DEMANGLE
 308               PTR_DEMANGLE (init_fct);
 309 # endif
 310               if (init_fct != NULL)
 311                 {
 312                   status = DL_CALL_FCT (init_fct, (&result[step_cnt]));
 313
 314                   if (__builtin_expect (status, __GCONV_OK) != __GCONV_OK)
 315                     {
 316                       failed = 1;
 317                       /* Do not call the end function because the init
 318                          function has failed.  */
 319                       result[step_cnt].__end_fct = NULL;
 320 # ifdef PTR_MANGLE
 321                       PTR_MANGLE (result[step_cnt].__end_fct);
 322 # endif
 323                       /* Make sure we unload this module.  */
 324                       --step_cnt;
 325                       break;
 326                     }
 327                 }
 328 # ifdef PTR_MANGLE
 329               PTR_MANGLE (result[step_cnt].__btowc_fct);
 330 # endif
 331             }
 332           else
 333 #endif
 334             /* It's a builtin transformation.  */
 335             __gconv_get_builtin_trans (current->code->module_name,
 336                                        &result[step_cnt]);
 337
 338           current = current->last;
 339         }
 340
 341       if (__builtin_expect (failed, 0) != 0)
 342         {
 343           /* Something went wrong while initializing the modules.  */
 344           while (++step_cnt < *nsteps)
 345             __gconv_release_step (&result[step_cnt]);
 346           free (result);
 347           free (from_name);
 348           free (to_name);
 349           *nsteps = 0;
 350           *handle = NULL;
 351           if (status == __GCONV_OK)
 352             status = __GCONV_NOCONV;
 353         }
 354       else
 355         *handle = result;
 356     }
 357   else
 358     {
 359       *nsteps = 0;
 360       *handle = NULL;
 361     }
 362
 363   return status;
 364 }
 365
 366
 367 #ifndef STATIC_GCONV
 368 static int
 369 increment_counter (struct __gconv_step *steps, size_t nsteps)
 370 {
 371   /* Increment the user counter.  */
 372   size_t cnt = nsteps;
 373   int result = __GCONV_OK;
 374
 375   while (cnt-- > 0)
 376     {
 377       struct __gconv_step *step = &steps[cnt];
 378
 379       if (step->__counter++ == 0)
 380         {
 381           /* Skip builtin modules.  */
 382           if (step->__modname != NULL)
 383             {
 384               /* Reopen a previously used module.  */
 385               step->__shlib_handle = __gconv_find_shlib (step->__modname);
 386               if (step->__shlib_handle == NULL)
 387                 {
 388                   /* Oops, this is the second time we use this module
 389                      (after unloading) and this time loading failed!?  */
 390                   --step->__counter;
 391                   while (++cnt < nsteps)
 392                     __gconv_release_step (&steps[cnt]);
 393                   result = __GCONV_NOCONV;
 394                   break;
 395                 }
 396
 397               /* The function addresses defined by the module may
 398                  have changed.  */
 399               step->__fct = step->__shlib_handle->fct;
 400               step->__init_fct = step->__shlib_handle->init_fct;
 401               step->__end_fct = step->__shlib_handle->end_fct;
 402
 403               /* These settings can be overridden by the init function.  */
 404               step->__btowc_fct = NULL;
 405
 406               /* Call the init function.  */
 407               __gconv_init_fct init_fct = step->__init_fct;
 408 #ifdef PTR_DEMANGLE
 409               PTR_DEMANGLE (init_fct);
 410 #endif
 411               if (init_fct != NULL)
 412                 DL_CALL_FCT (init_fct, (step));
 413
 414 #ifdef PTR_MANGLE
 415               PTR_MANGLE (step->__btowc_fct);
 416 #endif
 417             }
 418         }
 419     }
 420   return result;
 421 }
 422 #endif
 423
 424
 425 /* The main function: find a possible derivation from the `fromset' (either
 426    the given name or the alias) to the `toset' (again with alias).  */
 427 static int
 428 find_derivation (const char *toset, const char *toset_expand,
 429                  const char *fromset, const char *fromset_expand,
 430                  struct __gconv_step **handle, size_t *nsteps)
 431 {
 432   struct derivation_step *first, *current, **lastp, *solution = NULL;
 433   int best_cost_hi = INT_MAX;
 434   int best_cost_lo = INT_MAX;
 435   int result;
 436
 437   /* Look whether an earlier call to `find_derivation' has already
 438      computed a possible derivation.  If so, return it immediately.  */
 439   result = derivation_lookup (fromset_expand ?: fromset, toset_expand ?: toset,
 440                               handle, nsteps);
 441   if (result == __GCONV_OK)
 442     {
 443 #ifndef STATIC_GCONV
 444       result = increment_counter (*handle, *nsteps);
 445 #endif
 446       return result;
 447     }
 448
 449   /* The task is to find a sequence of transformations, backed by the
 450      existing modules - whether builtin or dynamically loadable -,
 451      starting at `fromset' (or `fromset_expand') and ending at `toset'
 452      (or `toset_expand'), and with minimal cost.
 453
 454      For computer scientists, this is a shortest path search in the
 455      graph where the nodes are all possible charsets and the edges are
 456      the transformations listed in __gconv_modules_db.
 457
 458      For now we use a simple algorithm with quadratic runtime behaviour.
 459      A breadth-first search, starting at `fromset' and `fromset_expand'.
 460      The list starting at `first' contains all nodes that have been
 461      visited up to now, in the order in which they have been visited --
 462      excluding the goal nodes `toset' and `toset_expand' which get
 463      managed in the list starting at `solution'.
 464      `current' walks through the list starting at `first' and looks
 465      which nodes are reachable from the current node, adding them to
 466      the end of the list [`first' or `solution' respectively] (if
 467      they are visited the first time) or updating them in place (if
 468      they have have already been visited).
 469      In each node of either list, cost_lo and cost_hi contain the
 470      minimum cost over any paths found up to now, starting at `fromset'
 471      or `fromset_expand', ending at that node.  best_cost_lo and
 472      best_cost_hi represent the minimum over the elements of the
 473      `solution' list.  */
 474
 475   if (fromset_expand != NULL)
 476     {
 477       first = NEW_STEP (fromset_expand, 0, 0, NULL, NULL);
 478       first->next = NEW_STEP (fromset, 0, 0, NULL, NULL);
 479       lastp = &first->next->next;
 480     }
 481   else
 482     {
 483       first = NEW_STEP (fromset, 0, 0, NULL, NULL);
 484       lastp = &first->next;
 485     }
 486
 487   for (current = first; current != NULL; current = current->next)
 488     {
 489       /* Now match all the available module specifications against the
 490          current charset name.  If any of them matches check whether
 491          we already have a derivation for this charset.  If yes, use the
 492          one with the lower costs.  Otherwise add the new charset at the
 493          end.
 494
 495          The module database is organized in a tree form which allows
 496          searching for prefixes.  So we search for the first entry with a
 497          matching prefix and any other matching entry can be found from
 498          this place.  */
 499       struct gconv_module *node;
 500
 501       /* Maybe it is not necessary anymore to look for a solution for
 502          this entry since the cost is already as high (or higher) as
 503          the cost for the best solution so far.  */
 504       if (current->cost_hi > best_cost_hi
 505           || (current->cost_hi == best_cost_hi
 506               && current->cost_lo >= best_cost_lo))
 507         continue;
 508
 509       node = __gconv_modules_db;
 510       while (node != NULL)
 511         {
 512           int cmpres = strcmp (current->result_set, node->from_string);
 513           if (cmpres == 0)
 514             {
 515               /* Walk through the list of modules with this prefix and
 516                  try to match the name.  */
 517               struct gconv_module *runp;
 518
 519               /* Check all the modules with this prefix.  */
 520               runp = node;
 521               do
 522                 {
 523                   const char *result_set = (strcmp (runp->to_string, "-") == 0
 524                                             ? (toset_expand ?: toset)
 525                                             : runp->to_string);
 526                   int cost_hi = runp->cost_hi + current->cost_hi;
 527                   int cost_lo = runp->cost_lo + current->cost_lo;
 528                   struct derivation_step *step;
 529
 530                   /* We managed to find a derivation.  First see whether
 531                      we have reached one of the goal nodes.  */
 532                   if (strcmp (result_set, toset) == 0
 533                       || (toset_expand != NULL
 534                           && strcmp (result_set, toset_expand) == 0))
 535                     {
 536                       /* Append to the `solution' list if there
 537                          is no entry with this name.  */
 538                       for (step = solution; step != NULL; step = step->next)
 539                         if (strcmp (result_set, step->result_set) == 0)
 540                           break;
 541
 542                       if (step == NULL)
 543                         {
 544                           step = NEW_STEP (result_set,
 545                                            cost_hi, cost_lo,
 546                                            runp, current);
 547                           step->next = solution;
 548                           solution = step;
 549                         }
 550                       else if (step->cost_hi > cost_hi
 551                                || (step->cost_hi == cost_hi
 552                                    && step->cost_lo > cost_lo))
 553                         {
 554                           /* A better path was found for the node,
 555                              on the `solution' list.  */
 556                           step->code = runp;
 557                           step->last = current;
 558                           step->cost_hi = cost_hi;
 559                           step->cost_lo = cost_lo;
 560                         }
 561
 562                       /* Update best_cost accordingly.  */
 563                       if (cost_hi < best_cost_hi
 564                           || (cost_hi == best_cost_hi
 565                               && cost_lo < best_cost_lo))
 566                         {
 567                           best_cost_hi = cost_hi;
 568                           best_cost_lo = cost_lo;
 569                         }
 570                     }
 571                   else if (cost_hi < best_cost_hi
 572                            || (cost_hi == best_cost_hi
 573                                && cost_lo < best_cost_lo))
 574                     {
 575                       /* Append at the end of the `first' list if there
 576                          is no entry with this name.  */
 577                       for (step = first; step != NULL; step = step->next)
 578                         if (strcmp (result_set, step->result_set) == 0)
 579                           break;
 580
 581                       if (step == NULL)
 582                         {
 583                           *lastp = NEW_STEP (result_set,
 584                                              cost_hi, cost_lo,
 585                                              runp, current);
 586                           lastp = &(*lastp)->next;
 587                         }
 588                       else if (step->cost_hi > cost_hi
 589                                || (step->cost_hi == cost_hi
 590                                    && step->cost_lo > cost_lo))
 591                         {
 592                           /* A better path was found for the node,
 593                              on the `first' list.  */
 594                           step->code = runp;
 595                           step->last = current;
 596
 597                           /* Update the cost for all steps.  */
 598                           for (step = first; step != NULL;
 599                                step = step->next)
 600                             /* But don't update the start nodes.  */
 601                             if (step->code != NULL)
 602                               {
 603                                 struct derivation_step *back;
 604                                 int hi, lo;
 605
 606                                 hi = step->code->cost_hi;
 607                                 lo = step->code->cost_lo;
 608
 609                                 for (back = step->last; back->code != NULL;
 610                                      back = back->last)
 611                                   {
 612                                     hi += back->code->cost_hi;
 613                                     lo += back->code->cost_lo;
 614                                   }
 615
 616                                 step->cost_hi = hi;
 617                                 step->cost_lo = lo;
 618                               }
 619
 620                           /* Likewise for the nodes on the solution list.
 621                              Also update best_cost accordingly.  */
 622                           for (step = solution; step != NULL;
 623                                step = step->next)
 624                             {
 625                               step->cost_hi = (step->code->cost_hi
 626                                                + step->last->cost_hi);
 627                               step->cost_lo = (step->code->cost_lo
 628                                                + step->last->cost_lo);
 629
 630                               if (step->cost_hi < best_cost_hi
 631                                   || (step->cost_hi == best_cost_hi
 632                                       && step->cost_lo < best_cost_lo))
 633                                 {
 634                                   best_cost_hi = step->cost_hi;
 635                                   best_cost_lo = step->cost_lo;
 636                                 }
 637                             }
 638                         }
 639                     }
 640
 641                   runp = runp->same;
 642                 }
 643               while (runp != NULL);
 644
 645               break;
 646             }
 647           else if (cmpres < 0)
 648             node = node->left;
 649           else
 650             node = node->right;
 651         }
 652     }
 653
 654   if (solution != NULL)
 655     {
 656       /* We really found a way to do the transformation.  */
 657
 658       /* Choose the best solution.  This is easy because we know that
 659          the solution list has at most length 2 (one for every possible
 660          goal node).  */
 661       if (solution->next != NULL)
 662         {
 663           struct derivation_step *solution2 = solution->next;
 664
 665           if (solution2->cost_hi < solution->cost_hi
 666               || (solution2->cost_hi == solution->cost_hi
 667                   && solution2->cost_lo < solution->cost_lo))
 668             solution = solution2;
 669         }
 670
 671       /* Now build a data structure describing the transformation steps.  */
 672       result = gen_steps (solution, toset_expand ?: toset,
 673                           fromset_expand ?: fromset, handle, nsteps);
 674     }
 675   else
 676     {
 677       /* We haven't found a transformation.  Clear the result values.  */
 678       *handle = NULL;
 679       *nsteps = 0;
 680     }
 681
 682   /* Add result in any case to list of known derivations.  */
 683   add_derivation (fromset_expand ?: fromset, toset_expand ?: toset,
 684                   *handle, *nsteps);
 685
 686   return result;
 687 }
 688
 689
 690 /* Control of initialization.  */
 691 __libc_once_define (static, once);
 692
 693
 694 static const char *
 695 do_lookup_alias (const char *name)
 696 {
 697   struct gconv_alias key;
 698   struct gconv_alias **found;
 699
 700   key.fromname = (char *) name;
 701   found = __tfind (&key, &__gconv_alias_db, __gconv_alias_compare);
 702   return found != NULL ? (*found)->toname : NULL;
 703 }
 704
 705
 706 int
 707 __gconv_compare_alias (const char *name1, const char *name2)
 708 {
 709   int result;
 710
 711   /* Ensure that the configuration data is read.  */
 712   __libc_once (once, __gconv_read_conf);
 713
 714   if (__gconv_compare_alias_cache (name1, name2, &result) != 0)
 715     result = strcmp (do_lookup_alias (name1) ?: name1,
 716                      do_lookup_alias (name2) ?: name2);
 717
 718   return result;
 719 }
 720
 721
 722 int
 723 __gconv_find_transform (const char *toset, const char *fromset,
 724                         struct __gconv_step **handle, size_t *nsteps,
 725                         int flags)
 726 {
 727   const char *fromset_expand;
 728   const char *toset_expand;
 729   int result;
 730
 731   /* Ensure that the configuration data is read.  */
 732   __libc_once (once, __gconv_read_conf);
 733
 734   /* Acquire the lock.  */
 735   __libc_lock_lock (__gconv_lock);
 736
 737   result = __gconv_lookup_cache (toset, fromset, handle, nsteps, flags);
 738   if (result != __GCONV_NODB)
 739     {
 740       /* We have a cache and could resolve the request, successful or not.  */
 741       __libc_lock_unlock (__gconv_lock);
 742       return result;
 743     }
 744
 745   /* If we don't have a module database return with an error.  */
 746   if (__gconv_modules_db == NULL)
 747     {
 748       __libc_lock_unlock (__gconv_lock);
 749       return __GCONV_NOCONV;
 750     }
 751
 752   /* See whether the names are aliases.  */
 753   fromset_expand = do_lookup_alias (fromset);
 754   toset_expand = do_lookup_alias (toset);
 755
 756   if (__builtin_expect (flags & GCONV_AVOID_NOCONV, 0)
 757       /* We are not supposed to create a pseudo transformation (means
 758          copying) when the input and output character set are the same.  */
 759       && (strcmp (toset, fromset) == 0
 760           || (toset_expand != NULL && strcmp (toset_expand, fromset) == 0)
 761           || (fromset_expand != NULL
 762               && (strcmp (toset, fromset_expand) == 0
 763                   || (toset_expand != NULL
 764                       && strcmp (toset_expand, fromset_expand) == 0)))))
 765     {
 766       /* Both character sets are the same.  */
 767       __libc_lock_unlock (__gconv_lock);
 768       return __GCONV_NULCONV;
 769     }
 770
 771   result = find_derivation (toset, toset_expand, fromset, fromset_expand,
 772                             handle, nsteps);
 773
 774   /* Release the lock.  */
 775   __libc_lock_unlock (__gconv_lock);
 776
 777   /* The following code is necessary since `find_derivation' will return
 778      GCONV_OK even when no derivation was found but the same request
 779      was processed before.  I.e., negative results will also be cached.  */
 780   return (result == __GCONV_OK
 781           ? (*handle == NULL ? __GCONV_NOCONV : __GCONV_OK)
 782           : result);
 783 }
 784
 785
 786 /* Release the entries of the modules list.  */
 787 int
 788 __gconv_close_transform (struct __gconv_step *steps, size_t nsteps)
 789 {
 790   int result = __GCONV_OK;
 791   size_t cnt;
 792
 793   /* Acquire the lock.  */
 794   __libc_lock_lock (__gconv_lock);
 795
 796 #ifndef STATIC_GCONV
 797   cnt = nsteps;
 798   while (cnt-- > 0)
 799     __gconv_release_step (&steps[cnt]);
 800 #endif
 801
 802   /* If we use the cache we free a bit more since we don't keep any
 803      transformation records around, they are cheap enough to
 804      recreate.  */
 805   __gconv_release_cache (steps, nsteps);
 806
 807   /* Release the lock.  */
 808   __libc_lock_unlock (__gconv_lock);
 809
 810   return result;
 811 }
 812
 813
 814 /* Free the modules mentioned.  */
 815 static void
 816 __libc_freeres_fn_section
 817 free_modules_db (struct gconv_module *node)
 818 {
 819   if (node->left != NULL)
 820     free_modules_db (node->left);
 821   if (node->right != NULL)
 822     free_modules_db (node->right);
 823   do
 824     {
 825       struct gconv_module *act = node;
 826       node = node->same;
 827       if (act->module_name[0] == '/')
 828         free (act);
 829     }
 830   while (node != NULL);
 831 }
 832
 833
 834 /* Free all resources if necessary.  */
 835 libc_freeres_fn (free_mem)
 836 {
 837   /* First free locale memory.  This needs to be done before freeing
 838      derivations, as ctype cleanup functions dereference steps arrays which we
 839      free below.  */
 840   _nl_locale_subfreeres ();
 841
 842   /* finddomain.c has similar problem.  */
 843   extern void _nl_finddomain_subfreeres (void) attribute_hidden;
 844   _nl_finddomain_subfreeres ();
 845
 846   if (__gconv_alias_db != NULL)
 847     __tdestroy (__gconv_alias_db, free);
 848
 849   if (__gconv_modules_db != NULL)
 850     free_modules_db (__gconv_modules_db);
 851
 852   if (known_derivations != NULL)
 853     __tdestroy (known_derivations, free_derivation);
 854 }