summaryrefslogtreecommitdiff
path: root/iconv/gconv_db.c
blob: 66e095d8c7b6f7188df54d11f4c6c0a768284a9f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
/* Provide access to the collection of available transformation modules.
   Copyright (C) 1997-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <limits.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <libc-lock.h>
#include <locale/localeinfo.h>

#include <dlfcn.h>
#include <gconv_int.h>
#include <sysdep.h>


/* Simple data structure for alias mapping.  We have two names, `from'
   and `to'.  */
void *__gconv_alias_db;

/* Array with available modules.  */
struct gconv_module *__gconv_modules_db;

/* We modify global data.   */
__libc_lock_define_initialized (, __gconv_lock)


/* Provide access to module database.  */
struct gconv_module *
__gconv_get_modules_db (void)
{
  return __gconv_modules_db;
}

void *
__gconv_get_alias_db (void)
{
  return __gconv_alias_db;
}


/* Function for searching alias.  */
int
__gconv_alias_compare (const void *p1, const void *p2)
{
  const struct gconv_alias *s1 = (const struct gconv_alias *) p1;
  const struct gconv_alias *s2 = (const struct gconv_alias *) p2;
  return strcmp (s1->fromname, s2->fromname);
}


/* To search for a derivation we create a list of intermediate steps.
   Each element contains a pointer to the element which precedes it
   in the derivation order.  */
struct derivation_step
{
  const char *result_set;
  size_t result_set_len;
  int cost_lo;
  int cost_hi;
  struct gconv_module *code;
  struct derivation_step *last;
  struct derivation_step *next;
};

#define NEW_STEP(result, hi, lo, module, last_mod) \
  ({ struct derivation_step *newp = alloca (sizeof (struct derivation_step)); \
     newp->result_set = result;						      \
     newp->result_set_len = strlen (result);				      \
     newp->cost_hi = hi;						      \
     newp->cost_lo = lo;						      \
     newp->code = module;						      \
     newp->last = last_mod;						      \
     newp->next = NULL;							      \
     newp; })


/* If a specific transformation is used more than once we should not need
   to start looking for it again.  Instead cache each successful result.  */
struct known_derivation
{
  const char *from;
  const char *to;
  struct __gconv_step *steps;
  size_t nsteps;
};

/* Compare function for database of found derivations.  */
static int
derivation_compare (const void *p1, const void *p2)
{
  const struct known_derivation *s1 = (const struct known_derivation *) p1;
  const struct known_derivation *s2 = (const struct known_derivation *) p2;
  int result;

  result = strcmp (s1->from, s2->from);
  if (result == 0)
    result = strcmp (s1->to, s2->to);
  return result;
}

/* The search tree for known derivations.  */
static void *known_derivations;

/* Look up whether given transformation was already requested before.  */
static int
derivation_lookup (const char *fromset, const char *toset,
		   struct __gconv_step **handle, size_t *nsteps)
{
  struct known_derivation key = { fromset, toset, NULL, 0 };
  struct known_derivation **result;

  result = __tfind (&key, &known_derivations, derivation_compare);

  if (result == NULL)
    return __GCONV_NOCONV;

  *handle = (*result)->steps;
  *nsteps = (*result)->nsteps;

  /* Please note that we return GCONV_OK even if the last search for
     this transformation was unsuccessful.  */
  return __GCONV_OK;
}

/* Add new derivation to list of known ones.  */
static void
add_derivation (const char *fromset, const char *toset,
		struct __gconv_step *handle, size_t nsteps)
{
  struct known_derivation *new_deriv;
  size_t fromset_len = strlen (fromset) + 1;
  size_t toset_len = strlen (toset) + 1;

  new_deriv = (struct known_derivation *)
    malloc (sizeof (struct known_derivation) + fromset_len + toset_len);
  if (new_deriv != NULL)
    {
      new_deriv->from = (char *) (new_deriv + 1);
      new_deriv->to = memcpy (__mempcpy (new_deriv + 1, fromset, fromset_len),
			      toset, toset_len);

      new_deriv->steps = handle;
      new_deriv->nsteps = nsteps;

      if (__tsearch (new_deriv, &known_derivations, derivation_compare)
	  == NULL)
	/* There is some kind of memory allocation problem.  */
	free (new_deriv);
    }
  /* Please note that we don't complain if the allocation failed.  This
     is not tragically but in case we use the memory debugging facilities
     not all memory will be freed.  */
}

static void __libc_freeres_fn_section
free_derivation (void *p)
{
  struct known_derivation *deriv = (struct known_derivation *) p;
  size_t cnt;

  for (cnt = 0; cnt < deriv->nsteps; ++cnt)
    if (deriv->steps[cnt].__counter > 0
	&& deriv->steps[cnt].__shlib_handle != NULL)
      {
	__gconv_end_fct end_fct = deriv->steps[cnt].__end_fct;
#ifdef PTR_DEMANGLE
	PTR_DEMANGLE (end_fct);
#endif
	if (end_fct != NULL)
	  DL_CALL_FCT (end_fct, (&deriv->steps[cnt]));
      }

  /* Free the name strings.  */
  if (deriv->steps != NULL)
    {
      free ((char *) deriv->steps[0].__from_name);
      free ((char *) deriv->steps[deriv->nsteps - 1].__to_name);
      free ((struct __gconv_step *) deriv->steps);
    }

  free (deriv);
}


/* Decrement the reference count for a single step in a steps array.  */
void
__gconv_release_step (struct __gconv_step *step)
{
  /* Skip builtin modules; they are not reference counted.  */
  if (step->__shlib_handle != NULL && --step->__counter == 0)
    {
      /* Call the destructor.  */
	__gconv_end_fct end_fct = step->__end_fct;
#ifdef PTR_DEMANGLE
	PTR_DEMANGLE (end_fct);
#endif
      if (end_fct != NULL)
	DL_CALL_FCT (end_fct, (step));

#ifndef STATIC_GCONV
      /* Release the loaded module.  */
      __gconv_release_shlib (step->__shlib_handle);
      step->__shlib_handle = NULL;
#endif
    }
  else if (step->__shlib_handle == NULL)
    /* Builtin modules should not have end functions.  */
    assert (step->__end_fct == NULL);
}

static int
gen_steps (struct derivation_step *best, const char *toset,
	   const char *fromset, struct __gconv_step **handle, size_t *nsteps)
{
  size_t step_cnt = 0;
  struct __gconv_step *result;
  struct derivation_step *current;
  int status = __GCONV_NOMEM;
  char *from_name = NULL;
  char *to_name = NULL;

  /* First determine number of steps.  */
  for (current = best; current->last != NULL; current = current->last)
    ++step_cnt;

  result = (struct __gconv_step *) malloc (sizeof (struct __gconv_step)
					   * step_cnt);
  if (result != NULL)
    {
      int failed = 0;

      status = __GCONV_OK;
      *nsteps = step_cnt;
      current = best;
      while (step_cnt-- > 0)
	{
	  if (step_cnt == 0)
	    {
	      result[step_cnt].__from_name = from_name = __strdup (fromset);
	      if (from_name == NULL)
		{
		  failed = 1;
		  break;
		}
	    }
	  else
	    result[step_cnt].__from_name = (char *)current->last->result_set;

	  if (step_cnt + 1 == *nsteps)
	    {
	      result[step_cnt].__to_name = to_name
		= __strdup (current->result_set);
	      if (to_name == NULL)
		{
		  failed = 1;
		  break;
		}
	    }
	  else
	    result[step_cnt].__to_name = result[step_cnt + 1].__from_name;

	  result[step_cnt].__counter = 1;
	  result[step_cnt].__data = NULL;

#ifndef STATIC_GCONV
	  if (current->code->module_name[0] == '/')
	    {
	      /* Load the module, return handle for it.  */
	      struct __gconv_loaded_object *shlib_handle =
		__gconv_find_shlib (current->code->module_name);

	      if (shlib_handle == NULL)
		{
		  failed = 1;
		  break;
		}

	      result[step_cnt].__shlib_handle = shlib_handle;
	      result[step_cnt].__modname = shlib_handle->name;
	      result[step_cnt].__fct = shlib_handle->fct;
	      result[step_cnt].__init_fct = shlib_handle->init_fct;
	      result[step_cnt].__end_fct = shlib_handle->end_fct;

	      /* These settings can be overridden by the init function.  */
	      result[step_cnt].__btowc_fct = NULL;

	      /* Call the init function.  */
	      __gconv_init_fct init_fct = result[step_cnt].__init_fct;
# ifdef PTR_DEMANGLE
	      PTR_DEMANGLE (init_fct);
# endif
	      if (init_fct != NULL)
		{
		  status = DL_CALL_FCT (init_fct, (&result[step_cnt]));

		  if (__builtin_expect (status, __GCONV_OK) != __GCONV_OK)
		    {
		      failed = 1;
		      /* Do not call the end function because the init
			 function has failed.  */
		      result[step_cnt].__end_fct = NULL;
# ifdef PTR_MANGLE
		      PTR_MANGLE (result[step_cnt].__end_fct);
# endif
		      /* Make sure we unload this module.  */
		      --step_cnt;
		      break;
		    }
		}
# ifdef PTR_MANGLE
	      PTR_MANGLE (result[step_cnt].__btowc_fct);
# endif
	    }
	  else
#endif
	    /* It's a builtin transformation.  */
	    __gconv_get_builtin_trans (current->code->module_name,
				       &result[step_cnt]);

	  current = current->last;
	}

      if (__builtin_expect (failed, 0) != 0)
	{
	  /* Something went wrong while initializing the modules.  */
	  while (++step_cnt < *nsteps)
	    __gconv_release_step (&result[step_cnt]);
	  free (result);
	  free (from_name);
	  free (to_name);
	  *nsteps = 0;
	  *handle = NULL;
	  if (status == __GCONV_OK)
	    status = __GCONV_NOCONV;
	}
      else
	*handle = result;
    }
  else
    {
      *nsteps = 0;
      *handle = NULL;
    }

  return status;
}


#ifndef STATIC_GCONV
static int
increment_counter (struct __gconv_step *steps, size_t nsteps)
{
  /* Increment the user counter.  */
  size_t cnt = nsteps;
  int result = __GCONV_OK;

  while (cnt-- > 0)
    {
      struct __gconv_step *step = &steps[cnt];

      if (step->__counter++ == 0)
	{
	  /* Skip builtin modules.  */
	  if (step->__modname != NULL)
	    {
	      /* Reopen a previously used module.  */
	      step->__shlib_handle = __gconv_find_shlib (step->__modname);
	      if (step->__shlib_handle == NULL)
		{
		  /* Oops, this is the second time we use this module
		     (after unloading) and this time loading failed!?  */
		  --step->__counter;
		  while (++cnt < nsteps)
		    __gconv_release_step (&steps[cnt]);
		  result = __GCONV_NOCONV;
		  break;
		}

	      /* The function addresses defined by the module may
		 have changed.  */
	      step->__fct = step->__shlib_handle->fct;
	      step->__init_fct = step->__shlib_handle->init_fct;
	      step->__end_fct = step->__shlib_handle->end_fct;

	      /* These settings can be overridden by the init function.  */
	      step->__btowc_fct = NULL;

	      /* Call the init function.  */
	      __gconv_init_fct init_fct = step->__init_fct;
#ifdef PTR_DEMANGLE
	      PTR_DEMANGLE (init_fct);
#endif
	      if (init_fct != NULL)
		DL_CALL_FCT (init_fct, (step));

#ifdef PTR_MANGLE
	      PTR_MANGLE (step->__btowc_fct);
#endif
	    }
	}
    }
  return result;
}
#endif


/* The main function: find a possible derivation from the `fromset' (either
   the given name or the alias) to the `toset' (again with alias).  */
static int
find_derivation (const char *toset, const char *toset_expand,
		 const char *fromset, const char *fromset_expand,
		 struct __gconv_step **handle, size_t *nsteps)
{
  struct derivation_step *first, *current, **lastp, *solution = NULL;
  int best_cost_hi = INT_MAX;
  int best_cost_lo = INT_MAX;
  int result;

  /* Look whether an earlier call to `find_derivation' has already
     computed a possible derivation.  If so, return it immediately.  */
  result = derivation_lookup (fromset_expand ?: fromset, toset_expand ?: toset,
			      handle, nsteps);
  if (result == __GCONV_OK)
    {
#ifndef STATIC_GCONV
      result = increment_counter (*handle, *nsteps);
#endif
      return result;
    }

  /* The task is to find a sequence of transformations, backed by the
     existing modules - whether builtin or dynamically loadable -,
     starting at `fromset' (or `fromset_expand') and ending at `toset'
     (or `toset_expand'), and with minimal cost.

     For computer scientists, this is a shortest path search in the
     graph where the nodes are all possible charsets and the edges are
     the transformations listed in __gconv_modules_db.

     For now we use a simple algorithm with quadratic runtime behaviour.
     A breadth-first search, starting at `fromset' and `fromset_expand'.
     The list starting at `first' contains all nodes that have been
     visited up to now, in the order in which they have been visited --
     excluding the goal nodes `toset' and `toset_expand' which get
     managed in the list starting at `solution'.
     `current' walks through the list starting at `first' and looks
     which nodes are reachable from the current node, adding them to
     the end of the list [`first' or `solution' respectively] (if
     they are visited the first time) or updating them in place (if
     they have have already been visited).
     In each node of either list, cost_lo and cost_hi contain the
     minimum cost over any paths found up to now, starting at `fromset'
     or `fromset_expand', ending at that node.  best_cost_lo and
     best_cost_hi represent the minimum over the elements of the
     `solution' list.  */

  if (fromset_expand != NULL)
    {
      first = NEW_STEP (fromset_expand, 0, 0, NULL, NULL);
      first->next = NEW_STEP (fromset, 0, 0, NULL, NULL);
      lastp = &first->next->next;
    }
  else
    {
      first = NEW_STEP (fromset, 0, 0, NULL, NULL);
      lastp = &first->next;
    }

  for (current = first; current != NULL; current = current->next)
    {
      /* Now match all the available module specifications against the
         current charset name.  If any of them matches check whether
         we already have a derivation for this charset.  If yes, use the
         one with the lower costs.  Otherwise add the new charset at the
         end.

	 The module database is organized in a tree form which allows
	 searching for prefixes.  So we search for the first entry with a
	 matching prefix and any other matching entry can be found from
	 this place.  */
      struct gconv_module *node;

      /* Maybe it is not necessary anymore to look for a solution for
	 this entry since the cost is already as high (or higher) as
	 the cost for the best solution so far.  */
      if (current->cost_hi > best_cost_hi
	  || (current->cost_hi == best_cost_hi
	      && current->cost_lo >= best_cost_lo))
	continue;

      node = __gconv_modules_db;
      while (node != NULL)
	{
	  int cmpres = strcmp (current->result_set, node->from_string);
	  if (cmpres == 0)
	    {
	      /* Walk through the list of modules with this prefix and
		 try to match the name.  */
	      struct gconv_module *runp;

	      /* Check all the modules with this prefix.  */
	      runp = node;
	      do
		{
		  const char *result_set = (strcmp (runp->to_string, "-") == 0
					    ? (toset_expand ?: toset)
					    : runp->to_string);
		  int cost_hi = runp->cost_hi + current->cost_hi;
		  int cost_lo = runp->cost_lo + current->cost_lo;
		  struct derivation_step *step;

		  /* We managed to find a derivation.  First see whether
		     we have reached one of the goal nodes.  */
		  if (strcmp (result_set, toset) == 0
		      || (toset_expand != NULL
			  && strcmp (result_set, toset_expand) == 0))
		    {
		      /* Append to the `solution' list if there
			 is no entry with this name.  */
		      for (step = solution; step != NULL; step = step->next)
			if (strcmp (result_set, step->result_set) == 0)
			  break;

		      if (step == NULL)
			{
			  step = NEW_STEP (result_set,
					   cost_hi, cost_lo,
					   runp, current);
			  step->next = solution;
			  solution = step;
			}
		      else if (step->cost_hi > cost_hi
			       || (step->cost_hi == cost_hi
				   && step->cost_lo > cost_lo))
			{
			  /* A better path was found for the node,
			     on the `solution' list.  */
			  step->code = runp;
			  step->last = current;
			  step->cost_hi = cost_hi;
			  step->cost_lo = cost_lo;
			}

		      /* Update best_cost accordingly.  */
		      if (cost_hi < best_cost_hi
			  || (cost_hi == best_cost_hi
			      && cost_lo < best_cost_lo))
			{
			  best_cost_hi = cost_hi;
			  best_cost_lo = cost_lo;
			}
		    }
		  else if (cost_hi < best_cost_hi
			   || (cost_hi == best_cost_hi
			       && cost_lo < best_cost_lo))
		    {
		      /* Append at the end of the `first' list if there
			 is no entry with this name.  */
		      for (step = first; step != NULL; step = step->next)
			if (strcmp (result_set, step->result_set) == 0)
			  break;

		      if (step == NULL)
			{
			  *lastp = NEW_STEP (result_set,
					     cost_hi, cost_lo,
					     runp, current);
			  lastp = &(*lastp)->next;
			}
		      else if (step->cost_hi > cost_hi
			       || (step->cost_hi == cost_hi
				   && step->cost_lo > cost_lo))
			{
			  /* A better path was found for the node,
			     on the `first' list.  */
			  step->code = runp;
			  step->last = current;

			  /* Update the cost for all steps.  */
			  for (step = first; step != NULL;
			       step = step->next)
			    /* But don't update the start nodes.  */
			    if (step->code != NULL)
			      {
				struct derivation_step *back;
				int hi, lo;

				hi = step->code->cost_hi;
				lo = step->code->cost_lo;

				for (back = step->last; back->code != NULL;
				     back = back->last)
				  {
				    hi += back->code->cost_hi;
				    lo += back->code->cost_lo;
				  }

				step->cost_hi = hi;
				step->cost_lo = lo;
			      }

			  /* Likewise for the nodes on the solution list.
			     Also update best_cost accordingly.  */
			  for (step = solution; step != NULL;
			       step = step->next)
			    {
			      step->cost_hi = (step->code->cost_hi
					       + step->last->cost_hi);
			      step->cost_lo = (step->code->cost_lo
					       + step->last->cost_lo);

			      if (step->cost_hi < best_cost_hi
				  || (step->cost_hi == best_cost_hi
				      && step->cost_lo < best_cost_lo))
				{
				  best_cost_hi = step->cost_hi;
				  best_cost_lo = step->cost_lo;
				}
			    }
			}
		    }

		  runp = runp->same;
		}
	      while (runp != NULL);

	      break;
	    }
	  else if (cmpres < 0)
	    node = node->left;
	  else
	    node = node->right;
	}
    }

  if (solution != NULL)
    {
      /* We really found a way to do the transformation.  */

      /* Choose the best solution.  This is easy because we know that
	 the solution list has at most length 2 (one for every possible
	 goal node).  */
      if (solution->next != NULL)
	{
	  struct derivation_step *solution2 = solution->next;

	  if (solution2->cost_hi < solution->cost_hi
	      || (solution2->cost_hi == solution->cost_hi
		  && solution2->cost_lo < solution->cost_lo))
	    solution = solution2;
	}

      /* Now build a data structure describing the transformation steps.  */
      result = gen_steps (solution, toset_expand ?: toset,
			  fromset_expand ?: fromset, handle, nsteps);
    }
  else
    {
      /* We haven't found a transformation.  Clear the result values.  */
      *handle = NULL;
      *nsteps = 0;
    }

  /* Add result in any case to list of known derivations.  */
  add_derivation (fromset_expand ?: fromset, toset_expand ?: toset,
		  *handle, *nsteps);

  return result;
}


/* Control of initialization.  */
__libc_once_define (static, once);


static const char *
do_lookup_alias (const char *name)
{
  struct gconv_alias key;
  struct gconv_alias **found;

  key.fromname = (char *) name;
  found = __tfind (&key, &__gconv_alias_db, __gconv_alias_compare);
  return found != NULL ? (*found)->toname : NULL;
}


int
__gconv_compare_alias (const char *name1, const char *name2)
{
  int result;

  /* Ensure that the configuration data is read.  */
  __libc_once (once, __gconv_read_conf);

  if (__gconv_compare_alias_cache (name1, name2, &result) != 0)
    result = strcmp (do_lookup_alias (name1) ?: name1,
		     do_lookup_alias (name2) ?: name2);

  return result;
}


int
__gconv_find_transform (const char *toset, const char *fromset,
			struct __gconv_step **handle, size_t *nsteps,
			int flags)
{
  const char *fromset_expand;
  const char *toset_expand;
  int result;

  /* Ensure that the configuration data is read.  */
  __libc_once (once, __gconv_read_conf);

  /* Acquire the lock.  */
  __libc_lock_lock (__gconv_lock);

  result = __gconv_lookup_cache (toset, fromset, handle, nsteps, flags);
  if (result != __GCONV_NODB)
    {
      /* We have a cache and could resolve the request, successful or not.  */
      __libc_lock_unlock (__gconv_lock);
      return result;
    }

  /* If we don't have a module database return with an error.  */
  if (__gconv_modules_db == NULL)
    {
      __libc_lock_unlock (__gconv_lock);
      return __GCONV_NOCONV;
    }

  /* See whether the names are aliases.  */
  fromset_expand = do_lookup_alias (fromset);
  toset_expand = do_lookup_alias (toset);

  if (__builtin_expect (flags & GCONV_AVOID_NOCONV, 0)
      /* We are not supposed to create a pseudo transformation (means
	 copying) when the input and output character set are the same.  */
      && (strcmp (toset, fromset) == 0
	  || (toset_expand != NULL && strcmp (toset_expand, fromset) == 0)
	  || (fromset_expand != NULL
	      && (strcmp (toset, fromset_expand) == 0
		  || (toset_expand != NULL
		      && strcmp (toset_expand, fromset_expand) == 0)))))
    {
      /* Both character sets are the same.  */
      __libc_lock_unlock (__gconv_lock);
      return __GCONV_NULCONV;
    }

  result = find_derivation (toset, toset_expand, fromset, fromset_expand,
			    handle, nsteps);

  /* Release the lock.  */
  __libc_lock_unlock (__gconv_lock);

  /* The following code is necessary since `find_derivation' will return
     GCONV_OK even when no derivation was found but the same request
     was processed before.  I.e., negative results will also be cached.  */
  return (result == __GCONV_OK
	  ? (*handle == NULL ? __GCONV_NOCONV : __GCONV_OK)
	  : result);
}


/* Release the entries of the modules list.  */
int
__gconv_close_transform (struct __gconv_step *steps, size_t nsteps)
{
  int result = __GCONV_OK;
  size_t cnt;

  /* Acquire the lock.  */
  __libc_lock_lock (__gconv_lock);

#ifndef STATIC_GCONV
  cnt = nsteps;
  while (cnt-- > 0)
    __gconv_release_step (&steps[cnt]);
#endif

  /* If we use the cache we free a bit more since we don't keep any
     transformation records around, they are cheap enough to
     recreate.  */
  __gconv_release_cache (steps, nsteps);

  /* Release the lock.  */
  __libc_lock_unlock (__gconv_lock);

  return result;
}


/* Free the modules mentioned.  */
static void
__libc_freeres_fn_section
free_modules_db (struct gconv_module *node)
{
  if (node->left != NULL)
    free_modules_db (node->left);
  if (node->right != NULL)
    free_modules_db (node->right);
  do
    {
      struct gconv_module *act = node;
      node = node->same;
      if (act->module_name[0] == '/')
	free (act);
    }
  while (node != NULL);
}


/* Free all resources if necessary.  */
libc_freeres_fn (free_mem)
{
  /* First free locale memory.  This needs to be done before freeing
     derivations, as ctype cleanup functions dereference steps arrays which we
     free below.  */
  _nl_locale_subfreeres ();

  /* finddomain.c has similar problem.  */
  extern void _nl_finddomain_subfreeres (void) attribute_hidden;
  _nl_finddomain_subfreeres ();

  if (__gconv_alias_db != NULL)
    __tdestroy (__gconv_alias_db, free);

  if (__gconv_modules_db != NULL)
    free_modules_db (__gconv_modules_db);

  if (known_derivations != NULL)
    __tdestroy (known_derivations, free_derivation);
}