gobject/gtypeplugin.c

   1 /* GObject - GLib Type, Object, Parameter and Signal Library
   2  * Copyright (C) 2000 Red Hat, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General
  15  * Public License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  17  * Boston, MA 02111-1307, USA.
  18  */
  19
  20 #include "config.h"
  21
  22 #include "gtypeplugin.h"
  23 #include "gobjectalias.h"
  24
  25
  26 /**
  27  * SECTION:gtypeplugin
  28  * @short_description: An interface for dynamically loadable types
  29  * @see_also: #GTypeModule and g_type_register_dynamic().
  30  * @title: GTypePlugin
  31  *
  32  * The GObject type system supports dynamic loading of types. The
  33  * #GTypePlugin interface is used to handle the lifecycle of
  34  * dynamically loaded types.  It goes as follows:
  35  *
  36  * <orderedlist>
  37  * <listitem><para>
  38  *   The type is initially introduced (usually upon loading the module
  39  *   the first time, or by your main application that knows what modules
  40  *   introduces what types), like this:
  41  *   |[
  42  *   new_type_id = g_type_register_dynamic (parent_type_id,
  43  *                                                 "TypeName",
  44  *                                                 new_type_plugin,
  45  *                                                 type_flags);
  46  *   ]|
  47  *   where <literal>new_type_plugin</literal> is an implementation of the
  48  *   #GTypePlugin interface.
  49  * </para></listitem>
  50  * <listitem><para>
  51  *    The type's implementation is referenced, e.g. through
  52  *    g_type_class_ref() or through g_type_create_instance() (this is
  53  *    being called by g_object_new()) or through one of the above done on
  54  *    a type derived from <literal>new_type_id</literal>.
  55  * </para></listitem>
  56  * <listitem><para>
  57  *    This causes the type system to load the type's implementation by calling
  58  *    g_type_plugin_use() and g_type_plugin_complete_type_info() on
  59  *    <literal>new_type_plugin</literal>.
  60  * </para></listitem>
  61  * <listitem><para>
  62  *    At some point the type's implementation isn't required anymore, e.g. after
  63  *    g_type_class_unref() or g_type_free_instance() (called when the reference
  64  *    count of an instance drops to zero).
  65  * </para></listitem>
  66  * <listitem><para>
  67  *    This causes the type system to throw away the information retrieved from
  68  *    g_type_plugin_complete_type_info() and then it calls
  69  *    g_type_plugin_unuse() on <literal>new_type_plugin</literal>.
  70  * </para></listitem>
  71  * <listitem><para>
  72  *    Things may repeat from the second step.
  73  * </para></listitem>
  74  * </orderedlist>
  75  *
  76  * So basically, you need to implement a #GTypePlugin type that
  77  * carries a use_count, once use_count goes from zero to one, you need
  78  * to load the implementation to successfully handle the upcoming
  79  * g_type_plugin_complete_type_info() call. Later, maybe after
  80  * succeeding use/unuse calls, once use_count drops to zero, you can
  81  * unload the implementation again. The type system makes sure to call
  82  * g_type_plugin_use() and g_type_plugin_complete_type_info() again
  83  * when the type is needed again.
  84  *
  85  * #GTypeModule is an implementation of #GTypePlugin that already
  86  * implements most of this except for the actual module loading and
  87  * unloading. It even handles multiple registered types per module.
  88  */
  89
  90
  91 /* --- functions --- */
  92 GType
  93 g_type_plugin_get_type (void)
  94 {
  95   static GType type_plugin_type = 0;
  96
  97   if (!type_plugin_type)
  98     {
  99       static const GTypeInfo type_plugin_info = {
 100         sizeof (GTypePluginClass),
 101         NULL,           /* base_init */
 102         NULL,           /* base_finalize */
 103       };
 104
 105       type_plugin_type = g_type_register_static (G_TYPE_INTERFACE, g_intern_static_string ("GTypePlugin"), &type_plugin_info, 0);
 106     }
 107
 108   return type_plugin_type;
 109 }
 110
 111 /**
 112  * g_type_plugin_use:
 113  * @plugin: a #GTypePlugin
 114  *
 115  * Calls the @use_plugin function from the #GTypePluginClass of
 116  * @plugin.  There should be no need to use this function outside of
 117  * the GObject type system itself.
 118  */
 119 void
 120 g_type_plugin_use (GTypePlugin *plugin)
 121 {
 122   GTypePluginClass *iface;
 123
 124   g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
 125
 126   iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
 127   iface->use_plugin (plugin);
 128 }
 129
 130 /**
 131  * g_type_plugin_unuse:
 132  * @plugin: a #GTypePlugin
 133  *
 134  * Calls the @unuse_plugin function from the #GTypePluginClass of
 135  * @plugin.  There should be no need to use this function outside of
 136  * the GObject type system itself.
 137  */
 138 void
 139 g_type_plugin_unuse (GTypePlugin *plugin)
 140 {
 141   GTypePluginClass *iface;
 142
 143   g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
 144
 145   iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
 146   iface->unuse_plugin (plugin);
 147 }
 148
 149 /**
 150  * g_type_plugin_complete_type_info:
 151  * @plugin: a #GTypePlugin
 152  * @g_type: the #GType whose info is completed
 153  * @info: the #GTypeInfo struct to fill in
 154  * @value_table: the #GTypeValueTable to fill in
 155  *
 156  * Calls the @complete_type_info function from the #GTypePluginClass of @plugin.
 157  * There should be no need to use this function outside of the GObject
 158  * type system itself.
 159  */
 160 void
 161 g_type_plugin_complete_type_info (GTypePlugin     *plugin,
 162                                   GType            g_type,
 163                                   GTypeInfo       *info,
 164                                   GTypeValueTable *value_table)
 165 {
 166   GTypePluginClass *iface;
 167
 168   g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
 169   g_return_if_fail (info != NULL);
 170   g_return_if_fail (value_table != NULL);
 171
 172   iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
 173   iface->complete_type_info (plugin,
 174                              g_type,
 175                              info,
 176                              value_table);
 177 }
 178
 179 /**
 180  * g_type_plugin_complete_interface_info:
 181  * @plugin: the #GTypePlugin
 182  * @instance_type: the #GType of an instantiable type to which the interface
 183  *  is added
 184  * @interface_type: the #GType of the interface whose info is completed
 185  * @info: the #GInterfaceInfo to fill in
 186  *
 187  * Calls the @complete_interface_info function from the
 188  * #GTypePluginClass of @plugin. There should be no need to use this
 189  * function outside of the GObject type system itself.
 190  */
 191 void
 192 g_type_plugin_complete_interface_info (GTypePlugin    *plugin,
 193                                        GType           instance_type,
 194                                        GType           interface_type,
 195                                        GInterfaceInfo *info)
 196 {
 197   GTypePluginClass *iface;
 198
 199   g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
 200   g_return_if_fail (info != NULL);
 201
 202   iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
 203   iface->complete_interface_info (plugin,
 204                                   instance_type,
 205                                   interface_type,
 206                                   info);
 207 }
 208
 209 #define __G_TYPE_PLUGIN_C__
 210 #include "gobjectaliasdef.c"