задайте и запросите значение в поле userdata (Set and query the value in the "userdata" field)
Имя (Name)
sd_bus_slot_set_userdata, sd_bus_slot_get_userdata - Set and
query the value in the "userdata" field
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
void* sd_bus_slot_set_userdata(sd_bus_slot* slot,
void* userdata);
void* sd_bus_slot_get_userdata(sd_bus_slot* slot);
Описание (Description)
The userdata pointer allows data to be passed between the point
where a callback is registered, for example when a filter is
added using sd_bus_add_filter(3) or an asynchronous function call
is made using sd_bus_call_async(3), and the point where the
callback is called, without having any global state. The pointer
has type void* and is not used by the sd-bus functions in any
way, except to pass to the callback function.
Usually, the userdata field is set when the slot object is
initially registered. sd_bus_slot_set_userdata() may be used to
change it later for the bus slot object slot. Previous value of
the field is returned. The argument and returned value may be
NULL. It will be passed as the userdata argument to the callback
function attached to the slot.
sd_bus_slot_set_userdata() gets the value of the userdata field
in the bus slot object slot.
Возвращаемое значение (Return value)
On success, these functions return the value of the userdata
field before the function call. If the slot object is NULL, NULL
will be returned to signify an error, but this is not
distinguishable from the userdata field value being NULL.
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (See also)
systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),
sd_bus_add_match(3), sd_bus_slot_get_current_userdata(3)
