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
g_type_plugin_get_type(void)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
g_type_plugin_use(GTypePlugin * plugin)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
g_type_plugin_unuse(GTypePlugin * plugin)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
g_type_plugin_complete_type_info(GTypePlugin * plugin,GType g_type,GTypeInfo * info,GTypeValueTable * value_table)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
g_type_plugin_complete_interface_info(GTypePlugin * plugin,GType instance_type,GType interface_type,GInterfaceInfo * info)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"
211