sd_bus_message_method_call(3) — Linux manual page


SD_BUS_MESSAGE_NEW(3)        sd_bus_message_new        SD_BUS_MESSAGE_NEW(3)

NAME         top

       sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref,
       sd_bus_message_unrefp, SD_BUS_MESSAGE_METHOD_CALL,
       SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus
       message object and create or destroy references to it

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       enum {

       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         top

       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_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[1]. See sd_bus_new(3) for an example how to use the cleanup

       sd_bus_message_ref() and sd_bus_message_unref() execute no operation
       if the passed in bus 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         top

       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.

       Returned errors may indicate the following problems:

           Specified type is invalid.

           The bus parameter bus is NULL or the bus is not connected.

           Memory allocation failed.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_new(3),
       sd_bus_message_new_method_return(3), sd_bus_message_new_signal(3)

NOTES         top

        1. Clean-up Variable Attribute

COLOPHON         top

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systemd 246                                            SD_BUS_MESSAGE_NEW(3)