1 /* Handle loading/unloading of shared object for transformation.
2 Copyright (C) 1997,1998,1999,2000,2001,2002 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 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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
27 #include <bits/libc-lock.h>
28 #include <sys/param.h>
30 #include <gconv_int.h>
34 /* For debugging purposes. */
35 static void print_all (void);
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
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. */
52 /* Comparison function for searching `loaded_object' tree. */
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
66 struct __gconv_loaded_object *
68 __gconv_find_shlib (const char *name)
70 struct __gconv_loaded_object *found;
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);
85 /* This name was not known before. */
86 size_t namelen = strlen (name) + 1;
88 found = malloc (sizeof (struct __gconv_loaded_object) + namelen);
91 /* Point the tree node at this new structure. */
92 found->name = (char *) memcpy (found + 1, name, namelen);
93 found->counter = -TRIES_BEFORE_UNLOAD - 1;
96 if (__builtin_expect (__tsearch (found, &loaded, known_compare)
99 /* Something went wrong while inserting the entry. */
106 found = *(struct __gconv_loaded_object **) keyp;
108 /* Try to load the shared object if the usage count is 0. This
109 implies that if the shared object is not loadable, the handle is
110 NULL and the usage count > 0. */
113 if (found->counter < -TRIES_BEFORE_UNLOAD)
115 assert (found->handle == NULL);
116 found->handle = __libc_dlopen (found->name);
117 if (found->handle != NULL)
119 found->fct = __libc_dlsym (found->handle, "gconv");
120 if (found->fct == NULL)
122 /* Argh, no conversion function. There is something
124 __gconv_release_shlib (found);
129 found->init_fct = __libc_dlsym (found->handle, "gconv_init");
130 found->end_fct = __libc_dlsym (found->handle, "gconv_end");
132 /* We have succeeded in loading the shared object. */
137 /* Error while loading the shared object. */
140 else if (found->handle != NULL)
141 found->counter = MAX (found->counter + 1, 1);
148 /* This is very ugly but the tsearch functions provide no way to pass
149 information to the walker function. So we use a global variable.
150 It is MT safe since we use a lock. */
151 static struct __gconv_loaded_object *release_handle;
154 do_release_shlib (void *nodep, VISIT value, int level)
156 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
158 if (value != preorder && value != leaf)
161 if (obj == release_handle)
163 /* This is the object we want to unload. Now decrement the
164 reference counter. */
165 assert (obj->counter > 0);
168 else if (obj->counter <= 0 && obj->counter >= -TRIES_BEFORE_UNLOAD
169 && --obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
171 /* Unload the shared object. */
172 __libc_dlclose (obj->handle);
178 /* Notify system that a shared object is not longer needed. */
181 __gconv_release_shlib (struct __gconv_loaded_object *handle)
183 /* Urgh, this is ugly but we have no other possibility. */
184 release_handle = handle;
186 /* Process all entries. Please note that we also visit entries
187 with release counts <= 0. This way we can finally unload them
189 __twalk (loaded, (__action_fn_t) do_release_shlib);
193 /* We run this if we debug the memory allocation. */
195 do_release_all (void *nodep)
197 struct __gconv_loaded_object *obj = (struct __gconv_loaded_object *) nodep;
199 /* Unload the shared object. */
200 if (obj->handle != NULL)
201 __libc_dlclose (obj->handle);
206 libc_freeres_fn (free_mem)
208 __tdestroy (loaded, do_release_all);
215 do_print (const void *nodep, VISIT value, int level)
217 struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep;
219 printf ("%10s: \"%s\", %d\n",
220 value == leaf ? "leaf" :
221 value == preorder ? "preorder" :
222 value == postorder ? "postorder" : "endorder",
223 obj->name, obj->counter);
229 __twalk (loaded, do_print);