запросить или опубликовать известное имя службы на шине (request or release a well-known service name on a bus)
Имя (Name)
sd_bus_request_name, sd_bus_request_name_async,
sd_bus_release_name, sd_bus_release_name_async - Request or
release a well-known service name on a bus
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
typedef int (*sd_bus_message_handler_t)(sd_bus_message *m,
void *userdata,
sd_bus_error *ret_error);
int sd_bus_request_name(sd_bus *bus, const char *name,
uint64_t flags);
int sd_bus_request_name_async(sd_bus *bus, sd_bus_slot **slot,
const char *name, uint64_t flags,
sd_bus_message_handler_t callback,
void *userdata);
int sd_bus_release_name(sd_bus *bus, const char *name);
int sd_bus_release_name_async(sd_bus *bus, sd_bus_slot **slot,
const char *name,
sd_bus_message_handler_t callback,
void *userdata);
Описание (Description)
sd_bus_request_name() requests a well-known service name on a
bus. It takes a bus connection, a valid bus name, and a flags
parameter. The flags parameter is a combination of zero or more
of the following flags:
SD_BUS_NAME_ALLOW_REPLACEMENT
After acquiring the name successfully, permit other peers to
take over the name when they try to acquire it with the
SD_BUS_NAME_REPLACE_EXISTING flag set. If
SD_BUS_NAME_ALLOW_REPLACEMENT is not set on the original
request, such a request by other peers will be denied.
SD_BUS_NAME_REPLACE_EXISTING
Take over the name if it was already acquired by another
peer, and that other peer has permitted takeover by setting
SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring it.
SD_BUS_NAME_QUEUE
Queue the acquisition of the name when the name is already
taken.
sd_bus_request_name() operates in a synchronous fashion: a
message requesting the name is sent to the bus broker, and the
call waits until the broker responds.
sd_bus_request_name_async() is an asynchronous version of
sd_bus_request_name(). Instead of waiting for the request to
complete, the request message is enqueued. The specified callback
will be called when the broker's response is received. If the
parameter is specified as NULL a default implementation is used
instead which will terminate the connection when the name cannot
be acquired. The function returns a slot object in its slot
parameter — if it is passed as non-NULL — which may be used as a
reference to the name request operation. Use sd_bus_slot_unref(3)
to destroy this reference. Note that destroying the reference
will not unregister the name, but simply ensure the specified
callback is no longer called.
sd_bus_release_name() releases an acquired well-known name. It
takes a bus connection and a valid bus name as parameters. This
function operates synchronously, sending a release request
message to the bus broker and waiting for it to reply.
sd_bus_release_name_async() is an asynchronous version of
sd_bus_release_name(). The specified callback function is called
when the name has been released successfully. If specified as
NULL a generic implementation is used that ignores the result of
the operation. As above, the slot (if non-NULL) is set to an
object that may be used to reference the operation.
These functions are supported only on bus connections, i.e.
connections to a bus broker and not on direct connections.
Возвращаемое значение (Return value)
On success, these calls return 0 or a positive integer. On
failure, these calls return a negative errno-style error code.
If SD_BUS_NAME_QUEUE is specified, sd_bus_request_name() will
return 0 when the name is already taken by another peer and the
client has been added to the queue for the name. In that case,
the caller can subscribe to "NameOwnerChanged" signals to be
notified when the name is successfully acquired.
sd_bus_request_name() returns > 0 when the name has immediately
been acquired successfully.
Errors
Returned errors may indicate the following problems:
-EALREADY
The caller already is the owner of the specified name.
-EEXIST
The name has already been acquired by a different peer, and
SD_BUS_NAME_REPLACE_EXISTING was not specified or the other
peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while
acquiring the name.
-ESRCH
It was attempted to release a name that is currently not
registered on the bus.
-EADDRINUSE
It was attempted to release a name that is owned by a
different peer on the bus.
-EINVAL
A specified parameter is invalid. This is also generated when
the requested name is a special service name reserved by the
D-Bus specification, or when the operation is requested on a
connection that does not refer to a bus.
-ENOTCONN
The bus connection has been disconnected.
-ECHILD
The bus connection has been created in a different process
than the current one.
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_new(3), sd_bus_slot_unref(3)
