gobject/gvalue.h

   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
  28 G_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  *
  92  * @dest_value will be initialized to the correct destination type.
  93  */
  94 typedef void (*GValueTransform) (const GValue *src_value,
  95                                  GValue       *dest_value);
  96 /**
  97  * GValue:
  98  *
  99  * An opaque structure used to hold different types of values.
 100  * The data within the structure has protected scope: it is accessible only
 101  * to functions within a #GTypeValueTable structure, or implementations of
 102  * the g_value_*() API. That is, code portions which implement new fundamental
 103  * types.
 104  * #GValue users cannot make any assumptions about how data is stored
 105  * within the 2 element @data union, and the @g_type member should
 106  * only be accessed through the G_VALUE_TYPE() macro.
 107  */
 108 struct _GValue
 109 {
 110   /*< private >*/
 111   GType         g_type;
 112
 113   /* public for GTypeValueTable methods */
 114   union {
 115     gint        v_int;
 116     guint       v_uint;
 117     glong       v_long;
 118     gulong      v_ulong;
 119     gint64      v_int64;
 120     guint64     v_uint64;
 121     gfloat      v_float;
 122     gdouble     v_double;
 123     gpointer    v_pointer;
 124   } data[2];
 125 };
 126
 127
 128 /* --- prototypes --- */
 129 GLIB_AVAILABLE_IN_ALL
 130 GValue*         g_value_init            (GValue       *value,
 131                                          GType         g_type);
 132 GLIB_AVAILABLE_IN_ALL
 133 void            g_value_copy            (const GValue *src_value,
 134                                          GValue       *dest_value);
 135 GLIB_AVAILABLE_IN_ALL
 136 GValue*         g_value_reset           (GValue       *value);
 137 GLIB_AVAILABLE_IN_ALL
 138 void            g_value_unset           (GValue       *value);
 139 GLIB_AVAILABLE_IN_ALL
 140 void            g_value_set_instance    (GValue       *value,
 141                                          gpointer      instance);
 142 GLIB_AVAILABLE_IN_2_42
 143 void            g_value_init_from_instance   (GValue       *value,
 144                                               gpointer      instance);
 145
 146
 147 /* --- private --- */
 148 GLIB_AVAILABLE_IN_ALL
 149 gboolean        g_value_fits_pointer    (const GValue *value);
 150 GLIB_AVAILABLE_IN_ALL
 151 gpointer        g_value_peek_pointer    (const GValue *value);
 152
 153
 154 /* --- implementation details --- */
 155 GLIB_AVAILABLE_IN_ALL
 156 gboolean g_value_type_compatible        (GType           src_type,
 157                                          GType           dest_type);
 158 GLIB_AVAILABLE_IN_ALL
 159 gboolean g_value_type_transformable     (GType           src_type,
 160                                          GType           dest_type);
 161 GLIB_AVAILABLE_IN_ALL
 162 gboolean g_value_transform              (const GValue   *src_value,
 163                                          GValue         *dest_value);
 164 GLIB_AVAILABLE_IN_ALL
 165 void    g_value_register_transform_func (GType           src_type,
 166                                          GType           dest_type,
 167                                          GValueTransform transform_func);
 168
 169 /**
 170  * G_VALUE_NOCOPY_CONTENTS:
 171  *
 172  * If passed to G_VALUE_COLLECT(), allocated data won't be copied
 173  * but used verbatim. This does not affect ref-counted types like
 174  * objects.
 175  */
 176 #define G_VALUE_NOCOPY_CONTENTS (1 << 27)
 177
 178 /**
 179  * G_VALUE_INIT:
 180  *
 181  * A #GValue must be initialized before it can be used. This macro can
 182  * be used as initializer instead of an explicit `{ 0 }` when declaring
 183  * a variable, but it cannot be assigned to a variable.
 184  *
 185  * |[
 186  *   GValue value = G_VALUE_INIT;
 187  * ]|
 188  *
 189  * Since: 2.30
 190  */
 191 #define G_VALUE_INIT  { 0, { { 0 } } }
 192
 193
 194 G_END_DECLS
 195
 196 #endif /* __G_VALUE_H__ */