Ubuntu Manpage: sd_bus_slot_set_floating, sd_bus_slot_get_floating

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

NAME

       sd_bus_slot_set_floating, sd_bus_slot_get_floating - Control whether a bus slot object is
       "floating"

SYNOPSIS

       #include <systemd/sd-bus.h>

       int sd_bus_slot_set_floating(sd_bus_slot *slot, int b);

       int sd_bus_slot_get_floating(sd_bus_slot *slot);

DESCRIPTION

sd_bus_slot_set_floating() controls whether the specified bus slot object slot shall be
"floating" or not. A floating bus slot object's lifetime is bound to the lifetime of the
bus object it is associated with, meaning that it remains allocated as long as the bus
object itself and is freed automatically when the bus object is freed. Regular (i.e.
non-floating) bus slot objects keep the bus referenced, hence the bus object remains
allocated at least as long as there remains at least one referenced bus slot object
around. The floating state hence controls the direction of referencing between the bus
object and the bus slot objects: if floating the bus pins the bus slot, and otherwise the
bus slot pins the bus objects. Use sd_bus_slot_set_floating() to switch between both
modes: if the b parameter is zero, the slot object is considered floating, otherwise it is
made a regular (non-floating) slot object.

Bus slot objects may be allocated with calls such as sd_bus_add_match(3). If the slot of
these functions is non-NULL the slot object will be of the regular kind (i.e.
non-floating), otherwise it will be created floating. With sd_bus_slot_set_floating() a
bus slot object allocated as regular can be converted into a floating object and back.
This is particularly useful for creating a bus slot object, then changing parameters of
it, and then turning it into a floating object, whose lifecycle is managed by the bus
object.

sd_bus_slot_get_floating() returns the current floating state of the specified bus slot
object. It returns negative on error, zero if the bus slot object is a regular
(non-floating) object and positive otherwise.

RETURN VALUE

       On success, these functions return 0 or a positive integer. On failure, they return a
       negative errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           The slot parameter is NULL.

       -ECHILD
           The bus connection has been created in a different process, library or module
           instance.

       -ESTALE
           The bus object the specified bus slot object is associated with has already been
           freed, and hence no change in the floating state can be made anymore.

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