| SD_BUS_SLOT_SET_FLOATING(3) | sd_bus_slot_set_floating | SD_BUS_SLOT_SET_FLOATING(3) |
.SH "NAME" sd_bus_slot_set_floating, sd_bus_slot_get_floating -
Control whether a bus slot object is "floating"
.SH "SYNOPSIS"
#include <systemd/sd-bus.h>
.HP 696u int
sd_bus_slot_set_floating(sd_bus_slot *slot,
int b);
.HP 696u int
sd_bus_slot_get_floating(sd_bus_slot *slot);
.SH "DESCRIPTION"
.PP 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 made into a regular
(non-floating) slot object, otherwise it is made into a floating slot
object.
.PP 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.
.PP 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.
.SH "RETURN VALUE"
.PP On success, these functions return 0 or a positive integer. On failure,
they return a negative errno-style error code.
.SS "Errors"
.PP Returned errors may indicate the following problems:
.PP -EINVAL
The slot parameter is NULL.
.RE
.PP -ECHILD
The bus connection has been created in a different process, library or module
instance.
.RE
.PP -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.
.RE
.SH "NOTES"
.PP Functions described here are available as a shared library, which can be
compiled against and linked to with the
libsystemd pkg-config(1) file.
.PP All functions listed here are thread-agnostic and only a single thread
may operate on a given object at any given time. Different threads may
access the same object at different times. Multiple independent objects may
be used from different threads in parallel.
.PP 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.
.SH "HISTORY"
.PP sd_bus_slot_set_floating() and sd_bus_slot_get_floating()
were added in version 239.
.SH "SEE ALSO"
.PP systemd(1), sd-bus(3),
sd_bus_slot_set_destroy_callback(3), sd_bus_add_match(3)
| systemd 262.2 |