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gvalue: New g_value_init_from_instance

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Used for the commonly used case (in signal emission) where we
initialize and set a GValue for an instance

Includes a fast-path for GObject

Overall makes it 6 times faster than the previous combination
of g_value_init + g_value_set_instance

Makes signal emission around 10% faster

https://bugzilla.gnome.org/show_bug.cgi?id=731950
This commit is contained in:
Edward Hervey
2014-06-19 11:28:48 +02:00
committed by Ryan Lortie
parent f727c820b8
commit c5c3c320a2
4 changed files with 71 additions and 4 deletions
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65
gobject/gvalue.c
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@@ -373,6 +373,71 @@ g_value_set_instance (GValue *value,
}
}
/**
* g_value_init_from_instance:
* @value: An uninitialized #GValue structure.
* @instance: the instance
*
* Initializes and sets @value from an instantiatable type via the
* value_table's collect_value() function.
*
* Note: The @value will be initialised with the exact type of
* @instance. If you wish to set the @value's type to a different GType
* (such as a parent class GType), you need to manually call
* g_value_init() and g_value_set_instance().
*
* Since: 2.42
*/
void
g_value_init_from_instance (GValue *value,
gpointer instance)
{
g_return_if_fail (value != NULL && G_VALUE_TYPE(value) == 0);
if (G_IS_OBJECT (instance))
{
/* Fast-path.
* If G_IS_OBJECT() succeeds we know:
* * that instance is present and valid
* * that it is a GObject, and therefore we can directly
* use the collect implementation (g_object_ref) */
value_meminit (value, G_TYPE_FROM_INSTANCE (instance));
value->data[0].v_pointer = g_object_ref (instance);
}
else
{
GType g_type;
GTypeValueTable *value_table;
GTypeCValue cvalue;
gchar *error_msg;
g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
g_type = G_TYPE_FROM_INSTANCE (instance);
value_table = g_type_value_table_peek (g_type);
g_return_if_fail (strcmp (value_table->collect_format, "p") == 0);
memset (&cvalue, 0, sizeof (cvalue));
cvalue.v_pointer = instance;
/* setup and collect */
value_meminit (value, g_type);
value_table->value_init (value);
error_msg = value_table->collect_value (value, 1, &cvalue, 0);
if (error_msg)
{
g_warning ("%s: %s", G_STRLOC, error_msg);
g_free (error_msg);
/* we purposely leak the value here, it might not be
* in a sane state if an error condition occoured
*/
value_meminit (value, g_type);
value_table->value_init (value);
}
}
}
static GValueTransform
transform_func_lookup (GType src_type,
GType dest_type)