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[glibc/history.git] / iconv / gconv_dl.c
blob8217b7e55322b8a8820f06289df24b6ac041cd60
1 /* Handle loading/unloading of shared object for transformation.
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2004, 2005
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library 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 GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, write to the Free
19 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
20 02111-1307 USA. */
22 #include <assert.h>
23 #include <dlfcn.h>
24 #include <inttypes.h>
25 #include <search.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <bits/libc-lock.h>
29 #include <sys/param.h>
31 #include <gconv_int.h>
32 #include <sysdep.h>
35 #ifdef DEBUG
36 /* For debugging purposes. */
37 static void print_all (void);
38 #endif
41 /* This is a tuning parameter. If a transformation module is not used
42 anymore it gets not immediately unloaded. Instead we wait a certain
43 number of load attempts for further modules. If none of the
44 subsequent load attempts name the same object it finally gets unloaded.
45 Otherwise it is still available which hopefully is the frequent case.
46 The following number is the number of unloading attempts we wait
47 before unloading. */
48 #define TRIES_BEFORE_UNLOAD 2
50 /* Array of loaded objects. This is shared by all threads so we have
51 to use semaphores to access it. */
52 static void *loaded;
54 /* Comparison function for searching `loaded_object' tree. */
55 static int
56 known_compare (const void *p1, const void *p2)
58 const struct __gconv_loaded_object *s1 =
59 (const struct __gconv_loaded_object *) p1;
60 const struct __gconv_loaded_object *s2 =
61 (const struct __gconv_loaded_object *) p2;
63 return strcmp (s1->name, s2->name);
66 /* Open the gconv database if necessary. A non-negative return value
67 means success. */
68 struct __gconv_loaded_object *
69 internal_function
70 __gconv_find_shlib (const char *name)
72 struct __gconv_loaded_object *found;
73 void *keyp;
75 /* Search the tree of shared objects previously requested. Data in
76 the tree are `loaded_object' structures, whose first member is a
77 `const char *', the lookup key. The search returns a pointer to
78 the tree node structure; the first member of the is a pointer to
79 our structure (i.e. what will be a `loaded_object'); since the
80 first member of that is the lookup key string, &FCT_NAME is close
81 enough to a pointer to our structure to use as a lookup key that
82 will be passed to `known_compare' (above). */
84 keyp = __tfind (&name, &loaded, known_compare);
85 if (keyp == NULL)
87 /* This name was not known before. */
88 size_t namelen = strlen (name) + 1;
90 found = malloc (sizeof (struct __gconv_loaded_object) + namelen);
91 if (found != NULL)
93 /* Point the tree node at this new structure. */
94 found->name = (char *) memcpy (found + 1, name, namelen);
95 found->counter = -TRIES_BEFORE_UNLOAD - 1;
96 found->handle = NULL;
98 if (__builtin_expect (__tsearch (found, &loaded, known_compare)
99 == NULL, 0))
101 /* Something went wrong while inserting the entry. */
102 free (found);
103 found = NULL;
107 else
108 found = *(struct __gconv_loaded_object **) keyp;
110 /* Try to load the shared object if the usage count is 0. This
111 implies that if the shared object is not loadable, the handle is
112 NULL and the usage count > 0. */
113 if (found != NULL)
115 if (found->counter < -TRIES_BEFORE_UNLOAD)
117 assert (found->handle == NULL);
118 found->handle = __libc_dlopen (found->name);
119 if (found->handle != NULL)
121 found->fct = __libc_dlsym (found->handle, "gconv");
122 if (found->fct == NULL)
124 /* Argh, no conversion function. There is something
125 wrong here. */
126 __gconv_release_shlib (found);
127 found = NULL;
129 else
131 found->init_fct = __libc_dlsym (found->handle, "gconv_init");
132 found->end_fct = __libc_dlsym (found->handle, "gconv_end");
134 #ifdef PTR_MANGLE
135 PTR_MANGLE (found->fct);
136 if (found->init_fct != NULL)
137 PTR_MANGLE (found->init_fct);
138 if (found->end_fct != NULL)
139 PTR_MANGLE (found->end_fct);
140 #endif
142 /* We have succeeded in loading the shared object. */
143 found->counter = 1;
146 else
147 /* Error while loading the shared object. */
148 found = NULL;
150 else if (found->handle != NULL)
151 found->counter = MAX (found->counter + 1, 1);
154 return found;
158 /* This is very ugly but the tsearch functions provide no way to pass
159 information to the walker function. So we use a global variable.
160 It is MT safe since we use a lock. */
161 static struct __gconv_loaded_object *release_handle;
163 static void
164 do_release_shlib (void *nodep, VISIT value, int level)
166 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
168 if (value != preorder && value != leaf)
169 return;
171 if (obj == release_handle)
173 /* This is the object we want to unload. Now decrement the
174 reference counter. */
175 assert (obj->counter > 0);
176 --obj->counter;
178 else if (obj->counter <= 0 && obj->counter >= -TRIES_BEFORE_UNLOAD
179 && --obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
181 /* Unload the shared object. */
182 __libc_dlclose (obj->handle);
183 obj->handle = NULL;
188 /* Notify system that a shared object is not longer needed. */
189 void
190 internal_function
191 __gconv_release_shlib (struct __gconv_loaded_object *handle)
193 /* Urgh, this is ugly but we have no other possibility. */
194 release_handle = handle;
196 /* Process all entries. Please note that we also visit entries
197 with release counts <= 0. This way we can finally unload them
198 if necessary. */
199 __twalk (loaded, (__action_fn_t) do_release_shlib);
203 /* We run this if we debug the memory allocation. */
204 static void __libc_freeres_fn_section
205 do_release_all (void *nodep)
207 struct __gconv_loaded_object *obj = (struct __gconv_loaded_object *) nodep;
209 /* Unload the shared object. */
210 if (obj->handle != NULL)
211 __libc_dlclose (obj->handle);
213 free (obj);
216 libc_freeres_fn (free_mem)
218 __tdestroy (loaded, do_release_all);
219 loaded = NULL;
223 #ifdef DEBUG
224 static void
225 do_print (const void *nodep, VISIT value, int level)
227 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
229 printf ("%10s: \"%s\", %d\n",
230 value == leaf ? "leaf" :
231 value == preorder ? "preorder" :
232 value == postorder ? "postorder" : "endorder",
233 obj->name, obj->counter);
236 static void
237 print_all (void)
239 __twalk (loaded, do_print);
241 #endif