glib-2.0/gobject/gvalue.h

0001 /* GObject - GLib Type, Object, Parameter and Signal Library
0002  * Copyright (C) 1997-1999, 2000-2001 Tim Janik and Red Hat, Inc.
0003  *
0004  * SPDX-License-Identifier: LGPL-2.1-or-later
0005  *
0006  * This library is free software; you can redistribute it and/or
0007  * modify it under the terms of the GNU Lesser General Public
0008  * License as published by the Free Software Foundation; either
0009  * version 2.1 of the License, or (at your option) any later version.
0010  *
0011  * This library is distributed in the hope that it will be useful,
0012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
0013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
0014  * Lesser General Public License for more details.
0015  *
0016  * You should have received a copy of the GNU Lesser General
0017  * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
0018  *
0019  * gvalue.h: generic GValue functions
0020  */
0021 #ifndef __G_VALUE_H__
0022 #define __G_VALUE_H__
0023
0024 #if !defined (__GLIB_GOBJECT_H_INSIDE__) && !defined (GOBJECT_COMPILATION)
0025 #error "Only <glib-object.h> can be included directly."
0026 #endif
0027
0028 #include    <gobject/gtype.h>
0029
0030 G_BEGIN_DECLS
0031
0032 /* --- type macros --- */
0033 /**
0034  * G_TYPE_IS_VALUE:
0035  * @type: A #GType value.
0036  *
0037  * Checks whether the passed in type ID can be used for g_value_init().
0038  *
0039  * That is, this macro checks whether this type provides an implementation
0040  * of the #GTypeValueTable functions required for a type to create a #GValue of.
0041  *
0042  * Returns: Whether @type is suitable as a #GValue type.
0043  */
0044 #define G_TYPE_IS_VALUE(type)       (g_type_check_is_value_type (type))
0045 /**
0046  * G_IS_VALUE:
0047  * @value: A #GValue structure.
0048  *
0049  * Checks if @value is a valid and initialized #GValue structure.
0050  *
0051  * Returns: %TRUE on success.
0052  */
0053 #define G_IS_VALUE(value)       (G_TYPE_CHECK_VALUE (value))
0054 /**
0055  * G_VALUE_TYPE:
0056  * @value: A #GValue structure.
0057  *
0058  * Get the type identifier of @value.
0059  *
0060  * Returns: the #GType.
0061  */
0062 #define G_VALUE_TYPE(value)     (((GValue*) (value))->g_type)
0063 /**
0064  * G_VALUE_TYPE_NAME:
0065  * @value: A #GValue structure.
0066  *
0067  * Gets the type name of @value.
0068  *
0069  * Returns: the type name.
0070  */
0071 #define G_VALUE_TYPE_NAME(value)    (g_type_name (G_VALUE_TYPE (value)))
0072 /**
0073  * G_VALUE_HOLDS:
0074  * @value: A #GValue structure.
0075  * @type: A #GType value.
0076  *
0077  * Checks if @value holds (or contains) a value of @type.
0078  * This macro will also check for @value != %NULL and issue a
0079  * warning if the check fails.
0080  *
0081  * Returns: %TRUE if @value holds the @type.
0082  */
0083 #define G_VALUE_HOLDS(value,type)   (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
0084
0085
0086 /* --- typedefs & structures --- */
0087 /**
0088  * GValueTransform:
0089  * @src_value: Source value.
0090  * @dest_value: Target value.
0091  *
0092  * The type of value transformation functions which can be registered with
0093  * g_value_register_transform_func().
0094  *
0095  * @dest_value will be initialized to the correct destination type.
0096  */
0097 typedef void (*GValueTransform) (const GValue *src_value,
0098                  GValue       *dest_value);
0099 /**
0100  * GValue:
0101  *
0102  * An opaque structure used to hold different types of values.
0103  *
0104  * The data within the structure has protected scope: it is accessible only
0105  * to functions within a #GTypeValueTable structure, or implementations of
0106  * the g_value_*() API. That is, code portions which implement new fundamental
0107  * types.
0108  *
0109  * #GValue users cannot make any assumptions about how data is stored
0110  * within the 2 element @data union, and the @g_type member should
0111  * only be accessed through the G_VALUE_TYPE() macro.
0112  */
0113 struct _GValue
0114 {
0115   /*< private >*/
0116   GType     g_type;
0117
0118   /* public for GTypeValueTable methods */
0119   union {
0120     gint    v_int;
0121     guint   v_uint;
0122     glong   v_long;
0123     gulong  v_ulong;
0124     gint64      v_int64;
0125     guint64     v_uint64;
0126     gfloat  v_float;
0127     gdouble v_double;
0128     gpointer    v_pointer;
0129   } data[2];
0130 };
0131
0132
0133 /* --- prototypes --- */
0134 GOBJECT_AVAILABLE_IN_ALL
0135 GValue*         g_value_init        (GValue       *value,
0136                      GType         g_type);
0137 GOBJECT_AVAILABLE_IN_ALL
0138 void            g_value_copy        (const GValue *src_value,
0139                      GValue       *dest_value);
0140 GOBJECT_AVAILABLE_IN_ALL
0141 GValue*         g_value_reset       (GValue       *value);
0142 GOBJECT_AVAILABLE_IN_ALL
0143 void            g_value_unset       (GValue       *value);
0144 GOBJECT_AVAILABLE_IN_ALL
0145 void        g_value_set_instance    (GValue       *value,
0146                      gpointer      instance);
0147 GOBJECT_AVAILABLE_IN_2_42
0148 void            g_value_init_from_instance   (GValue       *value,
0149                                               gpointer      instance);
0150
0151
0152 /* --- private --- */
0153 GOBJECT_AVAILABLE_IN_ALL
0154 gboolean    g_value_fits_pointer    (const GValue *value);
0155 GOBJECT_AVAILABLE_IN_ALL
0156 gpointer    g_value_peek_pointer    (const GValue *value);
0157
0158
0159 /* --- implementation details --- */
0160 GOBJECT_AVAILABLE_IN_ALL
0161 gboolean g_value_type_compatible    (GType       src_type,
0162                      GType       dest_type);
0163 GOBJECT_AVAILABLE_IN_ALL
0164 gboolean g_value_type_transformable (GType           src_type,
0165                      GType           dest_type);
0166 GOBJECT_AVAILABLE_IN_ALL
0167 gboolean g_value_transform      (const GValue   *src_value,
0168                      GValue         *dest_value);
0169 GOBJECT_AVAILABLE_IN_ALL
0170 void    g_value_register_transform_func (GType       src_type,
0171                      GType       dest_type,
0172                      GValueTransform transform_func);
0173
0174 /**
0175  * G_VALUE_NOCOPY_CONTENTS:
0176  *
0177  * If passed to G_VALUE_COLLECT(), allocated data won't be copied
0178  * but used verbatim. This does not affect ref-counted types like
0179  * objects. This does not affect usage of g_value_copy(), the data will
0180  * be copied if it is not ref-counted.
0181  */
0182 #define G_VALUE_NOCOPY_CONTENTS (1 << 27)
0183
0184 /**
0185  * G_VALUE_INTERNED_STRING:
0186  *
0187  * For string values, indicates that the string contained is canonical and will
0188  * exist for the duration of the process. See g_value_set_interned_string().
0189  *
0190  * Since: 2.66
0191  */
0192 #define G_VALUE_INTERNED_STRING (1 << 28) GOBJECT_AVAILABLE_MACRO_IN_2_66
0193
0194 /**
0195  * G_VALUE_INIT:
0196  *
0197  * A #GValue must be initialized before it can be used. This macro can
0198  * be used as initializer instead of an explicit `{ 0 }` when declaring
0199  * a variable, but it cannot be assigned to a variable.
0200  *
0201  * |[<!-- language="C" -->
0202  *   GValue value = G_VALUE_INIT;
0203  * ]|
0204  *
0205  * Since: 2.30
0206  */
0207 #define G_VALUE_INIT  { 0, { { 0 } } }
0208
0209
0210 G_END_DECLS
0211
0212 #endif /* __G_VALUE_H__ */