1/* GObject - GLib Type, Object, Parameter and Signal Library
2 * Copyright (C) 1997-1999, 2000-2001 Tim Janik and Red Hat, Inc.
3 *
4 * SPDX-License-Identifier: LGPL-2.1-or-later
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General
17 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 *
19 * gvalue.h: generic GValue functions
20 */
21#ifndef __G_VALUE_H__
22#define __G_VALUE_H__
23
24#if !defined (__GLIB_GOBJECT_H_INSIDE__) && !defined (GOBJECT_COMPILATION)
25#error "Only <glib-object.h> can be included directly."
26#endif
27
28#include <gobject/gtype.h>
29
30G_BEGIN_DECLS
31
32/* --- type macros --- */
33/**
34 * G_TYPE_IS_VALUE:
35 * @type: A #GType value.
36 *
37 * Checks whether the passed in type ID can be used for g_value_init().
38 *
39 * That is, this macro checks whether this type provides an implementation
40 * of the #GTypeValueTable functions required for a type to create a #GValue of.
41 *
42 * Returns: Whether @type is suitable as a #GValue type.
43 */
44#define G_TYPE_IS_VALUE(type) (g_type_check_is_value_type (type))
45/**
46 * G_IS_VALUE:
47 * @value: A #GValue structure.
48 *
49 * Checks if @value is a valid and initialized #GValue structure.
50 *
51 * Returns: %TRUE on success.
52 */
53#define G_IS_VALUE(value) (G_TYPE_CHECK_VALUE (value))
54/**
55 * G_VALUE_TYPE:
56 * @value: A #GValue structure.
57 *
58 * Get the type identifier of @value.
59 *
60 * Returns: the #GType.
61 */
62#define G_VALUE_TYPE(value) (((GValue*) (value))->g_type)
63/**
64 * G_VALUE_TYPE_NAME:
65 * @value: A #GValue structure.
66 *
67 * Gets the type name of @value.
68 *
69 * Returns: the type name.
70 */
71#define G_VALUE_TYPE_NAME(value) (g_type_name (G_VALUE_TYPE (value)))
72/**
73 * G_VALUE_HOLDS:
74 * @value: A #GValue structure.
75 * @type: A #GType value.
76 *
77 * Checks if @value holds (or contains) a value of @type.
78 * This macro will also check for @value != %NULL and issue a
79 * warning if the check fails.
80 *
81 * Returns: %TRUE if @value holds the @type.
82 */
83#define G_VALUE_HOLDS(value,type) (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
84
85
86/* --- typedefs & structures --- */
87/**
88 * GValueTransform:
89 * @src_value: Source value.
90 * @dest_value: Target value.
91 *
92 * The type of value transformation functions which can be registered with
93 * g_value_register_transform_func().
94 *
95 * @dest_value will be initialized to the correct destination type.
96 */
97typedef void (*GValueTransform) (const GValue *src_value,
98 GValue *dest_value);
99/**
100 * GValue:
101 *
102 * An opaque structure used to hold different types of values.
103 *
104 * The data within the structure has protected scope: it is accessible only
105 * to functions within a #GTypeValueTable structure, or implementations of
106 * the g_value_*() API. That is, code portions which implement new fundamental
107 * types.
108 *
109 * #GValue users cannot make any assumptions about how data is stored
110 * within the 2 element @data union, and the @g_type member should
111 * only be accessed through the G_VALUE_TYPE() macro.
112 */
113struct _GValue
114{
115 /*< private >*/
116 GType g_type;
117
118 /* public for GTypeValueTable methods */
119 union {
120 gint v_int;
121 guint v_uint;
122 glong v_long;
123 gulong v_ulong;
124 gint64 v_int64;
125 guint64 v_uint64;
126 gfloat v_float;
127 gdouble v_double;
128 gpointer v_pointer;
129 } data[2];
130};
131
132
133/* --- prototypes --- */
134GOBJECT_AVAILABLE_IN_ALL
135GValue* g_value_init (GValue *value,
136 GType g_type);
137GOBJECT_AVAILABLE_IN_ALL
138void g_value_copy (const GValue *src_value,
139 GValue *dest_value);
140GOBJECT_AVAILABLE_IN_ALL
141GValue* g_value_reset (GValue *value);
142GOBJECT_AVAILABLE_IN_ALL
143void g_value_unset (GValue *value);
144GOBJECT_AVAILABLE_IN_ALL
145void g_value_set_instance (GValue *value,
146 gpointer instance);
147GOBJECT_AVAILABLE_IN_2_42
148void g_value_init_from_instance (GValue *value,
149 gpointer instance);
150
151
152/* --- private --- */
153GOBJECT_AVAILABLE_IN_ALL
154gboolean g_value_fits_pointer (const GValue *value);
155GOBJECT_AVAILABLE_IN_ALL
156gpointer g_value_peek_pointer (const GValue *value);
157
158
159/* --- implementation details --- */
160GOBJECT_AVAILABLE_IN_ALL
161gboolean g_value_type_compatible (GType src_type,
162 GType dest_type);
163GOBJECT_AVAILABLE_IN_ALL
164gboolean g_value_type_transformable (GType src_type,
165 GType dest_type);
166GOBJECT_AVAILABLE_IN_ALL
167gboolean g_value_transform (const GValue *src_value,
168 GValue *dest_value);
169GOBJECT_AVAILABLE_IN_ALL
170void g_value_register_transform_func (GType src_type,
171 GType dest_type,
172 GValueTransform transform_func);
173
174/**
175 * G_VALUE_NOCOPY_CONTENTS:
176 *
177 * If passed to G_VALUE_COLLECT(), allocated data won't be copied
178 * but used verbatim. This does not affect ref-counted types like
179 * objects. This does not affect usage of g_value_copy(), the data will
180 * be copied if it is not ref-counted.
181 */
182#define G_VALUE_NOCOPY_CONTENTS (1 << 27)
183
184/**
185 * G_VALUE_INTERNED_STRING:
186 *
187 * For string values, indicates that the string contained is canonical and will
188 * exist for the duration of the process. See g_value_set_interned_string().
189 *
190 * Since: 2.66
191 */
192#define G_VALUE_INTERNED_STRING (1 << 28) GOBJECT_AVAILABLE_MACRO_IN_2_66
193
194/**
195 * G_VALUE_INIT:
196 *
197 * A #GValue must be initialized before it can be used. This macro can
198 * be used as initializer instead of an explicit `{ 0 }` when declaring
199 * a variable, but it cannot be assigned to a variable.
200 *
201 * |[<!-- language="C" -->
202 * GValue value = G_VALUE_INIT;
203 * ]|
204 *
205 * Since: 2.30
206 */
207#define G_VALUE_INIT { 0, { { 0 } } }
208
209
210G_END_DECLS
211
212#endif /* __G_VALUE_H__ */
213

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