sd_bus_slot_set_floating, sd_bus_slot_get_floating — Control whether a bus slot object is "floating"
#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); |
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.
On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style error code.
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.