GLib.Once

Fields

Name	Type	Access	Description
retval	object	r/w	the value returned by the call to the function, if status is GLib.OnceStatus.READY
status	GLib.OnceStatus	r/w	the status of the GLib.Once

Methods

class	init_enter (location)
class	init_leave (location, result)

Details

class GLib.Once

A GLib.Once struct controls a one-time initialization function. Any one-time initialization function must have its own unique GLib.Once struct.

New in version 2.4.

classmethod init_enter(location)

Parameters:

location (object) – location of a static initializable variable containing 0

Returns:

True if the initialization section should be entered, False and blocks otherwise

Return type:

bool

Function to be called when starting a critical initialization section. The argument location must point to a static 0-initialized variable that will be set to a value other than 0 at the end of the initialization section. In combination with GLib.Once.init_leave() and the unique address value_location, it can be ensured that an initialization section will be executed only once during a program’s life time, and that concurrent threads are blocked until initialization completed. To be used in constructs like this:

static gsize initialization_value = 0;

if (g_once_init_enter (&initialization_value))
  {
    gsize setup_value = 42; // initialization code here

    g_once_init_leave (&initialization_value, setup_value);
  }

// use initialization_value here

While location has a volatile qualifier, this is a historical artifact and the pointer passed to it should not be volatile.

New in version 2.14.

classmethod init_leave(location, result)

Parameters:

• location (object) – location of a static initializable variable containing 0

• result (int) – new non-0 value for value_location

Counterpart to GLib.Once.init_enter(). Expects a location of a static 0-initialized initialization variable, and an initialization value other than 0. Sets the variable to the initialization value, and releases concurrent threads blocking in GLib.Once.init_enter() on this initialization variable.

While location has a volatile qualifier, this is a historical artifact and the pointer passed to it should not be volatile.

New in version 2.14.