1/* GObject - GLib Type, Object, Parameter and Signal Library
2 * Copyright (C) 1997-1999, 2000-2001 Tim Janik and 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 * gvalue.h: generic GValue functions
18 */
19#ifndef __G_VALUE_H__
20#define __G_VALUE_H__
21
22#if !defined (__GLIB_GOBJECT_H_INSIDE__) && !defined (GOBJECT_COMPILATION)
23#error "Only <glib-object.h> can be included directly."
24#endif
25
26#include <gobject/gtype.h>
27
28G_BEGIN_DECLS
29
30/* --- type macros --- */
31/**
32 * G_TYPE_IS_VALUE:
33 * @type: A #GType value.
34 *
35 * Checks whether the passed in type ID can be used for g_value_init().
36 *
37 * That is, this macro checks whether this type provides an implementation
38 * of the #GTypeValueTable functions required for a type to create a #GValue of.
39 *
40 * Returns: Whether @type is suitable as a #GValue type.
41 */
42#define G_TYPE_IS_VALUE(type) (g_type_check_is_value_type (type))
43/**
44 * G_IS_VALUE:
45 * @value: A #GValue structure.
46 *
47 * Checks if @value is a valid and initialized #GValue structure.
48 *
49 * Returns: %TRUE on success.
50 */
51#define G_IS_VALUE(value) (G_TYPE_CHECK_VALUE (value))
52/**
53 * G_VALUE_TYPE:
54 * @value: A #GValue structure.
55 *
56 * Get the type identifier of @value.
57 *
58 * Returns: the #GType.
59 */
60#define G_VALUE_TYPE(value) (((GValue*) (value))->g_type)
61/**
62 * G_VALUE_TYPE_NAME:
63 * @value: A #GValue structure.
64 *
65 * Gets the type name of @value.
66 *
67 * Returns: the type name.
68 */
69#define G_VALUE_TYPE_NAME(value) (g_type_name (G_VALUE_TYPE (value)))
70/**
71 * G_VALUE_HOLDS:
72 * @value: A #GValue structure.
73 * @type: A #GType value.
74 *
75 * Checks if @value holds (or contains) a value of @type.
76 * This macro will also check for @value != %NULL and issue a
77 * warning if the check fails.
78 *
79 * Returns: %TRUE if @value holds the @type.
80 */
81#define G_VALUE_HOLDS(value,type) (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
82
83
84/* --- typedefs & structures --- */
85/**
86 * GValueTransform:
87 * @src_value: Source value.
88 * @dest_value: Target value.
89 *
90 * The type of value transformation functions which can be registered with
91 * g_value_register_transform_func().
92 *
93 * @dest_value will be initialized to the correct destination type.
94 */
95typedef void (*GValueTransform) (const GValue *src_value,
96 GValue *dest_value);
97/**
98 * GValue:
99 *
100 * An opaque structure used to hold different types of values.
101 *
102 * The data within the structure has protected scope: it is accessible only
103 * to functions within a #GTypeValueTable structure, or implementations of
104 * the g_value_*() API. That is, code portions which implement new fundamental
105 * types.
106 *
107 * #GValue users cannot make any assumptions about how data is stored
108 * within the 2 element @data union, and the @g_type member should
109 * only be accessed through the G_VALUE_TYPE() macro.
110 */
111struct _GValue
112{
113 /*< private >*/
114 GType g_type;
115
116 /* public for GTypeValueTable methods */
117 union {
118 gint v_int;
119 guint v_uint;
120 glong v_long;
121 gulong v_ulong;
122 gint64 v_int64;
123 guint64 v_uint64;
124 gfloat v_float;
125 gdouble v_double;
126 gpointer v_pointer;
127 } data[2];
128};
129
130
131/* --- prototypes --- */
132GLIB_AVAILABLE_IN_ALL
133GValue* g_value_init (GValue *value,
134 GType g_type);
135GLIB_AVAILABLE_IN_ALL
136void g_value_copy (const GValue *src_value,
137 GValue *dest_value);
138GLIB_AVAILABLE_IN_ALL
139GValue* g_value_reset (GValue *value);
140GLIB_AVAILABLE_IN_ALL
141void g_value_unset (GValue *value);
142GLIB_AVAILABLE_IN_ALL
143void g_value_set_instance (GValue *value,
144 gpointer instance);
145GLIB_AVAILABLE_IN_2_42
146void g_value_init_from_instance (GValue *value,
147 gpointer instance);
148
149
150/* --- private --- */
151GLIB_AVAILABLE_IN_ALL
152gboolean g_value_fits_pointer (const GValue *value);
153GLIB_AVAILABLE_IN_ALL
154gpointer g_value_peek_pointer (const GValue *value);
155
156
157/* --- implementation details --- */
158GLIB_AVAILABLE_IN_ALL
159gboolean g_value_type_compatible (GType src_type,
160 GType dest_type);
161GLIB_AVAILABLE_IN_ALL
162gboolean g_value_type_transformable (GType src_type,
163 GType dest_type);
164GLIB_AVAILABLE_IN_ALL
165gboolean g_value_transform (const GValue *src_value,
166 GValue *dest_value);
167GLIB_AVAILABLE_IN_ALL
168void g_value_register_transform_func (GType src_type,
169 GType dest_type,
170 GValueTransform transform_func);
171
172/**
173 * G_VALUE_NOCOPY_CONTENTS:
174 *
175 * If passed to G_VALUE_COLLECT(), allocated data won't be copied
176 * but used verbatim. This does not affect ref-counted types like
177 * objects. This does not affect usage of g_value_copy(), the data will
178 * be copied if it is not ref-counted.
179 */
180#define G_VALUE_NOCOPY_CONTENTS (1 << 27)
181
182/**
183 * G_VALUE_INTERNED_STRING:
184 *
185 * For string values, indicates that the string contained is canonical and will
186 * exist for the duration of the process. See g_value_set_interned_string().
187 *
188 * Since: 2.66
189 */
190#define G_VALUE_INTERNED_STRING (1 << 28) GLIB_AVAILABLE_MACRO_IN_2_66
191
192/**
193 * G_VALUE_INIT:
194 *
195 * A #GValue must be initialized before it can be used. This macro can
196 * be used as initializer instead of an explicit `{ 0 }` when declaring
197 * a variable, but it cannot be assigned to a variable.
198 *
199 * |[<!-- language="C" -->
200 * GValue value = G_VALUE_INIT;
201 * ]|
202 *
203 * Since: 2.30
204 */
205#define G_VALUE_INIT { 0, { { 0 } } }
206
207
208G_END_DECLS
209
210#endif /* __G_VALUE_H__ */
211

source code of include/glib-2.0/gobject/gvalue.h