Provided by: libsystemd-dev_256.5-2ubuntu3.1_amd64 bug

NAME

       sd_bus_slot_set_userdata, sd_bus_slot_get_userdata - Set and query the value in the "userdata" field

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);

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.

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.

NOTES

       Functions described here are available as a shared library, which can be compiled against and linked to
       with the libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that
       the code calling the functions described here must not call setenv(3) from a parallel thread. It is
       recommended to only do calls to setenv() from an early phase of the program when no other threads have
       been started.

HISTORY

       sd_bus_slot_set_userdata() and sd_bus_slot_get_userdata() were added in version 240.

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)