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 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, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  17  * Boston, MA 02111-1307, USA.
  18  *
  19  * gvalue.h: generic GValue functions
  20  */
  21 #if !defined (__GLIB_GOBJECT_H_INSIDE__) && !defined (GOBJECT_COMPILATION)
  22 #error "Only <glib-object.h> can be included directly."
  23 #endif
  24
  25 #ifndef __G_VALUE_H__
  26 #define __G_VALUE_H__
  27
  28 #include        <gobject/gtype.h>
  29
  30 G_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  * That is, this macro checks whether this type provides an implementation
  39  * of the #GTypeValueTable functions required for a type to create a #GValue of.
  40  *
  41  * Returns: Whether @type is suitable as a #GValue type.
  42  */
  43 #define G_TYPE_IS_VALUE(type)           (g_type_check_is_value_type (type))
  44 /**
  45  * G_IS_VALUE:
  46  * @value: A #GValue structure.
  47  *
  48  * Checks if @value is a valid and initialized #GValue structure.
  49  *
  50  * Returns: %TRUE on success.
  51  */
  52 #define G_IS_VALUE(value)               (G_TYPE_CHECK_VALUE (value))
  53 /**
  54  * G_VALUE_TYPE:
  55  * @value: A #GValue structure.
  56  *
  57  * Get the type identifier of @value.
  58  *
  59  * Returns: the #GType.
  60  */
  61 #define G_VALUE_TYPE(value)             (((GValue*) (value))->g_type)
  62 /**
  63  * G_VALUE_TYPE_NAME:
  64  * @value: A #GValue structure.
  65  *
  66  * Gets the the type name of @value.
  67  *
  68  * Returns: the type name.
  69  */
  70 #define G_VALUE_TYPE_NAME(value)        (g_type_name (G_VALUE_TYPE (value)))
  71 /**
  72  * G_VALUE_HOLDS:
  73  * @value: A #GValue structure.
  74  * @type: A #GType value.
  75  *
  76  * Checks if @value holds (or contains) a value of @type.
  77  * This macro will also check for @value != %NULL and issue a
  78  * warning if the check fails.
  79  *
  80  * Returns: %TRUE if @value holds the @type.
  81  */
  82 #define G_VALUE_HOLDS(value,type)       (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
  83
  84
  85 /* --- typedefs & structures --- */
  86 /**
  87  * GValueTransform:
  88  * @src_value: Source value.
  89  * @dest_value: Target value.
  90  *
  91  * The type of value transformation functions which can be registered with
  92  * g_value_register_transform_func().
  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 can not 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 GValue*         g_value_init            (GValue       *value,
 130                                          GType         g_type);
 131 void            g_value_copy            (const GValue *src_value,
 132                                          GValue       *dest_value);
 133 GValue*         g_value_reset           (GValue       *value);
 134 void            g_value_unset           (GValue       *value);
 135 void            g_value_set_instance    (GValue       *value,
 136                                          gpointer      instance);
 137
 138
 139 /* --- private --- */
 140 gboolean        g_value_fits_pointer    (const GValue *value);
 141 gpointer        g_value_peek_pointer    (const GValue *value);
 142
 143
 144 /* --- implementation details --- */
 145 gboolean g_value_type_compatible        (GType           src_type,
 146                                          GType           dest_type);
 147 gboolean g_value_type_transformable     (GType           src_type,
 148                                          GType           dest_type);
 149 gboolean g_value_transform              (const GValue   *src_value,
 150                                          GValue         *dest_value);
 151 void    g_value_register_transform_func (GType           src_type,
 152                                          GType           dest_type,
 153                                          GValueTransform transform_func);
 154 #define G_VALUE_NOCOPY_CONTENTS         (1 << 27)
 155
 156
 157 G_END_DECLS
 158
 159 #endif /* __G_VALUE_H__ */