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      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__ */
    160