Update.
[glibc.git] / iconv / gconv_dl.c
blob720ae4836b9f4483ef31fdd4434deebedd9d9a66
1 /* Handle loading/unloading of shared object for transformation.
2 Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public License as
8 published by the Free Software Foundation; either version 2 of the
9 License, or (at your option) any later version.
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 Library General Public License for more details.
16 You should have received a copy of the GNU Library General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 #include <assert.h>
22 #include <dlfcn.h>
23 #include <inttypes.h>
24 #include <search.h>
25 #include <stdlib.h>
26 #include <string.h>
27 #include <bits/libc-lock.h>
28 #include <sys/param.h>
30 #include <gconv_int.h>
33 #ifdef DEBUG
34 /* For debugging purposes. */
35 static void print_all (void);
36 #endif
39 /* This is a tuning parameter. If a transformation module is not used
40 anymore it gets not immediately unloaded. Instead we wait a certain
41 number of load attempts for further modules. If none of the
42 subsequent load attempts name the same object it finally gets unloaded.
43 Otherwise it is still available which hopefully is the frequent case.
44 The following number is the number of unloading attempts we wait
45 before unloading. */
46 #define TRIES_BEFORE_UNLOAD 2
48 /* Array of loaded objects. This is shared by all threads so we have
49 to use semaphores to access it. */
50 static void *loaded;
52 /* Comparison function for searching `loaded_object' tree. */
53 static int
54 known_compare (const void *p1, const void *p2)
56 const struct __gconv_loaded_object *s1 =
57 (const struct __gconv_loaded_object *) p1;
58 const struct __gconv_loaded_object *s2 =
59 (const struct __gconv_loaded_object *) p2;
61 return strcmp (s1->name, s2->name);
64 /* Open the gconv database if necessary. A non-negative return value
65 means success. */
66 struct __gconv_loaded_object *
67 internal_function
68 __gconv_find_shlib (const char *name)
70 struct __gconv_loaded_object *found;
71 void *keyp;
73 /* Search the tree of shared objects previously requested. Data in
74 the tree are `loaded_object' structures, whose first member is a
75 `const char *', the lookup key. The search returns a pointer to
76 the tree node structure; the first member of the is a pointer to
77 our structure (i.e. what will be a `loaded_object'); since the
78 first member of that is the lookup key string, &FCT_NAME is close
79 enough to a pointer to our structure to use as a lookup key that
80 will be passed to `known_compare' (above). */
82 keyp = __tfind (&name, &loaded, known_compare);
83 if (keyp == NULL)
85 /* This name was not known before. */
86 found = malloc (sizeof (struct __gconv_loaded_object));
87 if (found != NULL)
89 /* Point the tree node at this new structure. */
90 found->name = name;
91 found->counter = -TRIES_BEFORE_UNLOAD - 1;
92 found->handle = NULL;
94 if (__builtin_expect (__tsearch (found, &loaded, known_compare)
95 == NULL, 0))
97 /* Something went wrong while inserting the entry. */
98 free (found);
99 found = NULL;
103 else
104 found = *(struct __gconv_loaded_object **) keyp;
106 /* Try to load the shared object if the usage count is 0. This
107 implies that if the shared object is not loadable, the handle is
108 NULL and the usage count > 0. */
109 if (found != NULL)
111 if (found->counter < -TRIES_BEFORE_UNLOAD)
113 assert (found->handle == NULL);
114 found->handle = __libc_dlopen (found->name);
115 if (found->handle != NULL)
117 found->fct = __libc_dlsym (found->handle, "gconv");
118 if (found->fct == NULL)
120 /* Argh, no conversion function. There is something
121 wrong here. */
122 __gconv_release_shlib (found);
123 found = NULL;
125 else
127 found->init_fct = __libc_dlsym (found->handle, "gconv_init");
128 found->end_fct = __libc_dlsym (found->handle, "gconv_end");
130 /* We have succeeded in loading the shared object. */
131 found->counter = 1;
134 else
135 /* Error while loading the shared object. */
136 found = NULL;
138 else if (found->handle != NULL)
139 found->counter = MAX (found->counter + 1, 1);
142 return found;
146 /* This is very ugly but the tsearch functions provide no way to pass
147 information to the walker function. So we use a global variable.
148 It is MT safe since we use a lock. */
149 static struct __gconv_loaded_object *release_handle;
151 static void
152 do_release_shlib (void *nodep, VISIT value, int level)
154 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
156 if (value != preorder && value != leaf)
157 return;
159 if (obj == release_handle)
161 /* This is the object we want to unload. Now decrement the
162 reference counter. */
163 assert (obj->counter > 0);
164 --obj->counter;
166 else if (obj->counter <= 0 && obj->counter >= -TRIES_BEFORE_UNLOAD
167 && --obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
169 /* Unload the shared object. */
170 __libc_dlclose (obj->handle);
171 obj->handle = NULL;
176 /* Notify system that a shared object is not longer needed. */
177 void
178 internal_function
179 __gconv_release_shlib (struct __gconv_loaded_object *handle)
181 /* Urgh, this is ugly but we have no other possibility. */
182 release_handle = handle;
184 /* Process all entries. Please note that we also visit entries
185 with release counts <= 0. This way we can finally unload them
186 if necessary. */
187 __twalk (loaded, (__action_fn_t) do_release_shlib);
191 /* We run this if we debug the memory allocation. */
192 static void
193 do_release_all (void *nodep)
195 struct __gconv_loaded_object *obj = (struct __gconv_loaded_object *) nodep;
197 /* Unload the shared object. */
198 if (obj->handle != NULL)
199 __libc_dlclose (obj->handle);
201 free (obj);
204 static void __attribute__ ((unused))
205 free_mem (void)
207 __tdestroy (loaded, do_release_all);
209 text_set_element (__libc_subfreeres, free_mem);
212 #ifdef DEBUG
213 static void
214 do_print (const void *nodep, VISIT value, int level)
216 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
218 printf ("%10s: \"%s\", %d\n",
219 value == leaf ? "leaf" :
220 value == preorder ? "preorder" :
221 value == postorder ? "postorder" : "endorder",
222 obj->name, obj->counter);
225 static void
226 print_all (void)
228 __twalk (loaded, do_print);
230 #endif