Varargs Value Collection: GObject Reference Manual

Varargs Value Collection

Varargs Value Collection — Converting varargs to generic values

Functions

#define	G_VALUE_COLLECT_INIT()
#define	G_VALUE_COLLECT_INIT2()
#define	G_VALUE_COLLECT()
#define	G_VALUE_COLLECT_SKIP()
#define	G_VALUE_LCOPY()

Types and Values

	GTypeCValue
#define	G_VALUE_COLLECT_FORMAT_MAX_LENGTH

Includes

#include <glib-object.h>
#include <gobject/gvaluecollector.h>

Description

The macros in this section provide the varargs parsing support needed in variadic GObject functions such as g_object_new() or g_object_set().

They currently support the collection of integral types, floating point types and pointers.

Functions

G_VALUE_COLLECT_INIT()

#define             G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)

Collects a variable argument value from a va_list.

We have to implement the varargs collection as a macro, because on some systems va_list variables cannot be passed by reference.

Parameters

value	a GValue return location. `value` must contain only 0 bytes.
_value_type	the GType to use for `value` .
var_args	the va_list variable; it may be evaluated multiple times
flags	flags which are passed on to the `collect_value()` function of the GTypeValueTable of `value` .
__error	a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails

Since: 2.24

G_VALUE_COLLECT_INIT2()

#define             G_VALUE_COLLECT_INIT2(value, g_vci_vtab, _value_type, var_args, flags, __error)

A variant of G_VALUE_COLLECT_INIT() that provides the GTypeValueTable to the caller.

Parameters

value	a GValue return location. `value` must contain only 0 bytes.
g_vci_vtab	a GTypeValueTable pointer that will be set to the value table for `_value_type`
_value_type	the GType to use for `value` .
var_args	the va_list variable; it may be evaluated multiple times
flags	flags which are passed on to the `collect_value()` function of the GTypeValueTable of `value` .
__error	a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails

Since: 2.74

G_VALUE_COLLECT()

#define             G_VALUE_COLLECT(value, var_args, flags, __error)

Collects a variable argument value from a va_list.

We have to implement the varargs collection as a macro, because on some systems va_list variables cannot be passed by reference.

Note: If you are creating the value argument just before calling this macro, you should use the G_VALUE_COLLECT_INIT() variant and pass the uninitialized GValue. That variant is faster than G_VALUE_COLLECT().

Parameters

value	a GValue return location. `value` is supposed to be initialized according to the value type to be collected
var_args	the va_list variable; it may be evaluated multiple times
flags	flags which are passed on to the `collect_value()` function of the GTypeValueTable of `value` .
__error	a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails

G_VALUE_COLLECT_SKIP()

#define             G_VALUE_COLLECT_SKIP(_value_type, var_args)

Skip an argument of type _value_type from var_args .

Parameters

_value_type	the GType of the value to skip
var_args	the va_list variable; it may be evaluated multiple times

G_VALUE_LCOPY()

#define             G_VALUE_LCOPY(value, var_args, flags, __error)

Stores a value’s value into one or more argument locations from a va_list.

This is the inverse of G_VALUE_COLLECT().

Parameters

value	a GValue to store into the `var_args` ; this must be initialized and set
var_args	the va_list variable; it may be evaluated multiple times
flags	flags which are passed on to the `lcopy_value()` function of the GTypeValueTable of `value` .
__error	a gchar** variable that will be modified to hold a `g_new()` allocated error message if something fails

Types and Values

GTypeCValue

A union holding one collected value.

Members

gint `v_int`;	the field for holding integer values
glong `v_long`;	the field for holding long integer values
gint64 `v_int64`;	the field for holding 64 bit integer values
gdouble `v_double`;	the field for holding floating point values
gpointer `v_pointer`;	the field for holding pointers

G_VALUE_COLLECT_FORMAT_MAX_LENGTH

#define G_VALUE_COLLECT_FORMAT_MAX_LENGTH (8)

The maximal number of GTypeCValues which can be collected for a single GValue.