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