создать новый объект сообщения шины и создать или уничтожить ссылки на него (create a new bus message object and create or destroy references to it)
Дубль
(статьи:
sd_bus_message_get_bus - создать новый объект сообщения шины и создать или уничтожить ссылки на него )
Имя (Name)
sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref,
sd_bus_message_unrefp, SD_BUS_MESSAGE_METHOD_CALL,
SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR,
SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus
message object and create or destroy references to it
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
enum {
SD_BUS_MESSAGE_METHOD_CALL,
SD_BUS_MESSAGE_METHOD_RETURN,
SD_BUS_MESSAGE_METHOD_ERROR,
SD_BUS_MESSAGE_SIGNAL,
};
int sd_bus_message_new(sd_bus *bus, sd_bus_message **m,
uint8_t type);
sd_bus_message *sd_bus_message_ref(sd_bus_message *m);
sd_bus_message *sd_bus_message_unref(sd_bus_message *m);
void sd_bus_message_unrefp(sd_bus_message **mp);
sd_bus *sd_bus_message_get_bus(sd_bus_message *m);
Описание (Description)
sd_bus_message_new() creates a new bus message object attached to
the bus bus and returns it in the output parameter m. This object
is reference-counted, and will be destroyed when all references
are gone. Initially, the caller of this function owns the sole
reference to the message object. Note that the message object
holds a reference to the bus object, so the bus object will not
be destroyed as long as the message exists.
Note: this is a low-level call. In most cases functions like
sd_bus_message_new_method_call(3),
sd_bus_message_new_method_error(3),
sd_bus_message_new_method_return(3), and
sd_bus_message_new_signal(3) that create a message of a certain
type and initialize various fields are easier to use.
The type parameter specifies the type of the message. It must be
one of SD_BUS_MESSAGE_METHOD_CALL — a method call,
SD_BUS_MESSAGE_METHOD_RETURN — a method call reply,
SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call,
SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply.
The flag to allow interactive authorization is initialized based
on the current value set in the bus object, see
sd_bus_set_allow_interactive_authorization(3). This may be
changed using
sd_bus_message_set_allow_interactive_authorization(3).
sd_bus_message_ref() increases the reference counter of m by one.
sd_bus_message_unref() decreases the reference counter of m by
one. Once the reference count has dropped to zero, message object
is destroyed and cannot be used anymore, so further calls to
sd_bus_message_ref() or sd_bus_message_unref() are illegal.
sd_bus_message_unrefp() is similar to sd_bus_message_unref() but
takes a pointer to a pointer to an sd_bus_message object. This
call is useful in conjunction with GCC's and LLVM's Clean-up
Variable Attribute
sd_bus_message_ref() and sd_bus_message_unref() execute no
operation if the passed in bus message object address is NULL.
sd_bus_message_unrefp() will first dereference its argument,
which must not be NULL, and will execute no operation if that is
NULL.
sd_bus_message_get_bus() returns the bus object that message m is
attached to.
Возвращаемое значение (Return value)
On success, sd_bus_message_new() returns 0 or a positive integer.
On failure, it returns a negative errno-style error code.
sd_bus_message_ref() always returns the argument.
sd_bus_message_unref() always returns NULL.
sd_bus_message_get_bus() always returns the bus object.
Errors
Returned errors may indicate the following problems:
-EINVAL
Specified type is invalid.
-ENOTCONN
The bus parameter bus is NULL or the bus is not connected.
-ENOMEM
Memory allocation failed.
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_message_new_method_call(3),
sd_bus_message_new_method_error(3),
sd_bus_message_new_method_return(3), sd_bus_message_new_signal(3)
Примечание (Note)
1. Clean-up Variable Attribute
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
