1 files changed, 254 insertions, 0 deletions
diff --git a/iconv/gconv_dl.c b/iconv/gconv_dl.c
new file mode 100644
index 0000000000..a0003a82db
--- /dev/null
+++ b/iconv/gconv_dl.c
@@ -0,0 +1,254 @@
+/* Handle loading/unloading of shared object for transformation.
+   Copyright (C) 1997 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <dlfcn.h>
+#include <gconv.h>
+#include <inttypes.h>
+#include <link.h>
+#include <search.h>
+#include <stdlib.h>
+#include <string.h>
+#include <bits/libc-lock.h>
+#include <sys/param.h>
+
+
+/* This is a tuning parameter.  If a transformation module is not used
+   anymore it gets not immediately unloaded.  Instead we wait a certain
+   number of load attempts for further modules.  If none of the
+   subsequent load attempts name the same object it finally gets unloaded.
+   Otherwise it is still available which hopefully is the frequent case.
+   The following number is the number of unloading attempts we wait
+   before unloading.  */
+#define TRIES_BEFORE_UNLOAD	2
+
+
+/* Structure describing one loaded shared object.  This normally are
+   objects to perform conversation but as a special case the db shared
+   object is also handled.  */
+struct loaded_object
+{
+  /* Name of the object.  */
+  const char *name;
+
+  /* Reference counter for the db functionality.  If no conversion is
+     needed we unload the db library.  */
+  int counter;
+
+  /* The handle for the shared object.  */
+  void *handle;
+};
+
+
+/* Array of loaded objects.  This is shared by all threads so we have
+   to use semaphores to access it.  */
+static void *loaded;
+__libc_lock_define_initialized (static, lock)
+
+
+
+/* Comparison function for searching `loaded_object' tree.  */
+static int
+known_compare (const void *p1, const void *p2)
+{
+  const struct loaded_object *s1 = (const struct loaded_object *) p1;
+  const struct loaded_object *s2 = (const struct loaded_object *) p2;
+
+  return (intptr_t) s1->handle - (intptr_t) s2->handle;
+}
+
+
+static void
+do_open (void *a)
+{
+  struct loaded_object *args = (struct loaded_object *) a;
+  /* Open and relocate the shared object.  */
+  args->handle = _dl_open (args->name, RTLD_LAZY);
+}
+
+
+static int
+dlerror_run (void (*operate) (void *), void *args)
+{
+  char *last_errstring = NULL;
+  const char *last_object_name = NULL;
+  int result;
+
+  (void) _dl_catch_error (&last_errstring, &last_object_name, operate, args);
+
+  result = last_errstring != NULL;
+  if (result)
+    free (last_errstring);
+
+  return result;
+}
+
+
+struct get_sym_args
+{
+  /* Arguments to get_sym.  */
+  struct link_map *map;
+  const char *name;
+
+  /* Return values of get_sym.  */
+  ElfW(Addr) loadbase;
+  const ElfW(Sym) *ref;
+};
+
+static void
+get_sym (void *a)
+{
+  struct get_sym_args *args = (struct get_sym_args *) a;
+  struct link_map *scope[2] = { args->map, NULL };
+  args->ref = NULL;
+  args->loadbase = _dl_lookup_symbol (args->name, &args->ref,
+				      scope, args->map->l_name, 0);
+}
+
+
+void *
+__gconv_find_func (void *handle, const char *name)
+{
+  struct get_sym_args args;
+
+  args.map = handle;
+  args.name = name;
+
+  return (dlerror_run (get_sym, &args) ? NULL
+	  : (void *) (args.loadbase + args.ref->st_value));
+}
+
+
+
+/* Open the gconv database if necessary.  A non-negative return value
+   means success.  */
+void *
+__gconv_find_shlib (const char *name)
+{
+  void *result = NULL;
+  struct loaded_object *found;
+
+  /* Acquire the lock.  */
+  __libc_lock_lock (lock);
+
+  /* Search the tree of shared objects previously requested.  Data in
+     the tree are `loaded_object' structures, whose first member is a
+     `const char *', the lookup key.  The search returns a pointer to
+     the tree node structure; the first member of the is a pointer to
+     our structure (i.e. what will be a `loaded_object'); since the
+     first member of that is the lookup key string, &FCT_NAME is close
+     enough to a pointer to our structure to use as a lookup key that
+     will be passed to `known_compare' (above).  */
+
+  found = __tfind (&name, loaded, known_compare);
+  if (found == NULL)
+    {
+      /* This name was not known before.  */
+      found = malloc (sizeof (struct loaded_object));
+      if (found != NULL)
+	{
+	  /* Point the tree node at this new structure.  */
+	  found->name = name;
+	  found->counter = -TRIES_BEFORE_UNLOAD - 1;
+	  found->handle = NULL;
+
+	  if (__tsearch (found, &loaded, known_compare) == NULL)
+	    {
+	      /* Something went wrong while inserting the entry.  */
+	      free (found);
+	      found = NULL;
+	    }
+	}
+    }
+
+  /* Try to load the shared object if the usage count is 0.  This
+     implies that if the shared object is not loadable, the handle is
+     NULL and the usage count > 0.  */
+  if (found != NULL)
+    {
+      if (found->counter < -TRIES_BEFORE_UNLOAD)
+	{
+	  if (dlerror_run (do_open, found) == 0)
+	    found->counter = 1;
+	}
+      else if (found->handle != NULL)
+	found->counter = MAX (found->counter + 1, 1);
+
+      result = found->handle;
+    }
+
+  /* Release the lock.  */
+  __libc_lock_unlock (lock);
+
+  return result;
+}
+
+
+/* This is very ugly but the tsearch functions provide no way to pass
+   information to the walker function.  So we use a global variable.
+   It is MT safe since we use a lock.  */
+static void *release_handle;
+
+static void
+do_release_shlib (const void *nodep, VISIT value, int level)
+{
+  struct loaded_object *obj = (struct loaded_object *) nodep;
+
+  if (value != preorder && value != leaf)
+    return;
+
+  if (obj->handle == release_handle)
+    /* This is the object we want to unload.  Now set the release
+       counter to zero.  */
+    obj->counter = 0;
+  else if (obj->counter <= 0)
+    {
+      if (--obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
+	{
+	  /* Unload the shared object.  We don't use the trick to
+	     catch errors since in the case an error is signalled
+	     something is really wrong.  */
+	  _dl_close ((struct link_map *) obj->handle);
+
+	  obj->handle = NULL;
+	}
+    }
+}
+
+
+/* Notify system that a shared object is not longer needed.  */
+int
+__gconv_release_shlib (void *handle)
+{
+  /* Acquire the lock.  */
+  __libc_lock_lock (lock);
+
+  /* Urgh, this is ugly but we have no other possibility.  */
+  release_handle = handle;
+
+  /* Process all entries.  Please note that we also visit entries
+     with release counts <= 0.  This way we can finally unload them
+     if necessary.  */
+  __twalk (loaded, do_release_shlib);
+
+  /* Release the lock.  */
+  __libc_lock_unlock (lock);
+
+  return GCONV_OK;
+}