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
#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); |
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 internal reference counter of
m by one.
sd_bus_message_unref() decreases the internal 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. See
sd_bus_new(3)
for an example how to use the cleanup 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.
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.
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.
sd_bus_message_new(),
sd_bus_message_ref(),
sd_bus_message_unref(),
sd_bus_message_unrefp(), and
sd_bus_message_get_bus() were added in version 240.