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 2.1 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, see <http://www.gnu.org/licenses/>.
16 */
17
18 #include "config.h"
19
20 #include "gtypeplugin.h"
21
22
23 /**
24 * SECTION:gtypeplugin
25 * @short_description: An interface for dynamically loadable types
26 * @see_also: #GTypeModule and g_type_register_dynamic().
27 * @title: GTypePlugin
28 *
29 * The GObject type system supports dynamic loading of types.
30 * The #GTypePlugin interface is used to handle the lifecycle
31 * of dynamically loaded types. It goes as follows:
32 *
33 * 1. The type is initially introduced (usually upon loading the module
34 * the first time, or by your main application that knows what modules
35 * introduces what types), like this:
36 * |[<!-- language="C" -->
37 * new_type_id = g_type_register_dynamic (parent_type_id,
38 * "TypeName",
39 * new_type_plugin,
40 * type_flags);
41 * ]|
42 * where @new_type_plugin is an implementation of the
43 * #GTypePlugin interface.
44 *
45 * 2. The type's implementation is referenced, e.g. through
46 * g_type_class_ref() or through g_type_create_instance() (this is
47 * being called by g_object_new()) or through one of the above done on
48 * a type derived from @new_type_id.
49 *
50 * 3. This causes the type system to load the type's implementation by
51 * calling g_type_plugin_use() and g_type_plugin_complete_type_info()
52 * on @new_type_plugin.
53 *
54 * 4. At some point the type's implementation isn't required anymore,
55 * e.g. after g_type_class_unref() or g_type_free_instance() (called
56 * when the reference count of an instance drops to zero).
57 *
58 * 5. This causes the type system to throw away the information retrieved
59 * from g_type_plugin_complete_type_info() and then it calls
60 * g_type_plugin_unuse() on @new_type_plugin.
61 *
62 * 6. Things may repeat from the second step.
63 *
64 * So basically, you need to implement a #GTypePlugin type that
65 * carries a use_count, once use_count goes from zero to one, you need
66 * to load the implementation to successfully handle the upcoming
67 * g_type_plugin_complete_type_info() call. Later, maybe after
68 * succeeding use/unuse calls, once use_count drops to zero, you can
69 * unload the implementation again. The type system makes sure to call
70 * g_type_plugin_use() and g_type_plugin_complete_type_info() again
71 * when the type is needed again.
72 *
73 * #GTypeModule is an implementation of #GTypePlugin that already
74 * implements most of this except for the actual module loading and
75 * unloading. It even handles multiple registered types per module.
76 */
77
78
79 /* --- functions --- */
80 GType
g_type_plugin_get_type(void)81 g_type_plugin_get_type (void)
82 {
83 static GType type_plugin_type = 0;
84
85 if (!type_plugin_type)
86 {
87 const GTypeInfo type_plugin_info = {
88 sizeof (GTypePluginClass),
89 NULL, /* base_init */
90 NULL, /* base_finalize */
91 };
92
93 type_plugin_type = g_type_register_static (G_TYPE_INTERFACE, g_intern_static_string ("GTypePlugin"), &type_plugin_info, 0);
94 }
95
96 return type_plugin_type;
97 }
98
99 /**
100 * g_type_plugin_use:
101 * @plugin: a #GTypePlugin
102 *
103 * Calls the @use_plugin function from the #GTypePluginClass of
104 * @plugin. There should be no need to use this function outside of
105 * the GObject type system itself.
106 */
107 void
g_type_plugin_use(GTypePlugin * plugin)108 g_type_plugin_use (GTypePlugin *plugin)
109 {
110 GTypePluginClass *iface;
111
112 g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
113
114 iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
115 iface->use_plugin (plugin);
116 }
117
118 /**
119 * g_type_plugin_unuse:
120 * @plugin: a #GTypePlugin
121 *
122 * Calls the @unuse_plugin function from the #GTypePluginClass of
123 * @plugin. There should be no need to use this function outside of
124 * the GObject type system itself.
125 */
126 void
g_type_plugin_unuse(GTypePlugin * plugin)127 g_type_plugin_unuse (GTypePlugin *plugin)
128 {
129 GTypePluginClass *iface;
130
131 g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
132
133 iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
134 iface->unuse_plugin (plugin);
135 }
136
137 /**
138 * g_type_plugin_complete_type_info:
139 * @plugin: a #GTypePlugin
140 * @g_type: the #GType whose info is completed
141 * @info: the #GTypeInfo struct to fill in
142 * @value_table: the #GTypeValueTable to fill in
143 *
144 * Calls the @complete_type_info function from the #GTypePluginClass of @plugin.
145 * There should be no need to use this function outside of the GObject
146 * type system itself.
147 */
148 void
g_type_plugin_complete_type_info(GTypePlugin * plugin,GType g_type,GTypeInfo * info,GTypeValueTable * value_table)149 g_type_plugin_complete_type_info (GTypePlugin *plugin,
150 GType g_type,
151 GTypeInfo *info,
152 GTypeValueTable *value_table)
153 {
154 GTypePluginClass *iface;
155
156 g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
157 g_return_if_fail (info != NULL);
158 g_return_if_fail (value_table != NULL);
159
160 iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
161 iface->complete_type_info (plugin,
162 g_type,
163 info,
164 value_table);
165 }
166
167 /**
168 * g_type_plugin_complete_interface_info:
169 * @plugin: the #GTypePlugin
170 * @instance_type: the #GType of an instantiable type to which the interface
171 * is added
172 * @interface_type: the #GType of the interface whose info is completed
173 * @info: the #GInterfaceInfo to fill in
174 *
175 * Calls the @complete_interface_info function from the
176 * #GTypePluginClass of @plugin. There should be no need to use this
177 * function outside of the GObject type system itself.
178 */
179 void
g_type_plugin_complete_interface_info(GTypePlugin * plugin,GType instance_type,GType interface_type,GInterfaceInfo * info)180 g_type_plugin_complete_interface_info (GTypePlugin *plugin,
181 GType instance_type,
182 GType interface_type,
183 GInterfaceInfo *info)
184 {
185 GTypePluginClass *iface;
186
187 g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));
188 g_return_if_fail (info != NULL);
189
190 iface = G_TYPE_PLUGIN_GET_CLASS (plugin);
191 iface->complete_interface_info (plugin,
192 instance_type,
193 interface_type,
194 info);
195 }
196