x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_MESSAGE_NEW(3) sd_bus_message_new SD_BUS_MESSAGE_NEW(3)
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
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);
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 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[1].
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.
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.
NOTES
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.
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)
NOTES
1. Clean-up Variable Attribute
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
systemd 254 SD_BUS_MESSAGE_NEW(3)
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