контроль того, является ли объект слота шины плавающим (Control whether a bus slot object is "floating")
Имя (Name)
sd_bus_slot_set_floating, sd_bus_slot_get_floating - Control
whether a bus slot object is "floating"
Синопсис (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);
Описание (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.
Возвращаемое значение (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.
-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.
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)
