sd_bus_slot_set_userdata(3) — Linux manual page



NAME         top

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

SYNOPSIS         top

       #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         top

       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         top

       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         top

       These APIs are implemented as a shared library, which can be
       compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),
       sd_bus_add_match(3), sd_bus_slot_get_current_userdata(3)

COLOPHON         top

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       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
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systemd 249                                  SD_BUS_SLOT_SET_USERDATA(3)

Pages that refer to this page: sd-bus(3)sd_bus_slot_set_description(3)sd_bus_slot_set_destroy_callback(3)