Varargs Value Collection

Varargs Value Collection — Converting varargs to generic values

Synopsis

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

union               GTypeCValue;
#define             G_VALUE_COLLECT_INIT                (value,
                                                         _value_type,
                                                         var_args,
                                                         flags,
                                                         __error)
#define             G_VALUE_COLLECT                     (value,
                                                         var_args,
                                                         flags,
                                                         __error)
#define             G_VALUE_LCOPY                       (value,
                                                         var_args,
                                                         flags,
                                                         __error)
#define             G_VALUE_COLLECT_FORMAT_MAX_LENGTH

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.

Details

union GTypeCValue

union _GTypeCValue
{
  gint     v_int;
  glong    v_long;
  gint64   v_int64;
  gdouble  v_double;
  gpointer v_pointer;
};

A union holding one collected value.

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_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.

`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()

#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 unitialized GValue. That variant is faster than G_VALUE_COLLECT.

`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_LCOPY()

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

Collects a value's variable argument locations from a va_list. Usage is analogous to G_VALUE_COLLECT().

`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 `lcopy_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_FORMAT_MAX_LENGTH

#define G_VALUE_COLLECT_FORMAT_MAX_LENGTH (8)

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

			GObject Reference Manual
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