34.3. Operations

34.3.1. Decomposing and Recomposing an Object Id

Services are provided to decompose an object Id into its subordinate components. The following services are used to do this:

• rtems_object_id_get_api

• rtems_object_id_get_class

• rtems_object_id_get_node

• rtems_object_id_get_index

The following C language example illustrates the decomposition of an Id and printing the values.

void printObjectId(rtems_id id)
{
    printf(
        "API=%d Class=%" PRIu32 " Node=%" PRIu32 " Index=%" PRIu16 "\n",
        rtems_object_id_get_api(id),
        rtems_object_id_get_class(id),
        rtems_object_id_get_node(id),
        rtems_object_id_get_index(id)
    );
}

This prints the components of the Ids as integers.

It is also possible to construct an arbitrary Id using the rtems_build_id service. The following C language example illustrates how to construct the “next Id.”

rtems_id nextObjectId(rtems_id id)
{
    return rtems_build_id(
                rtems_object_id_get_api(id),
                rtems_object_id_get_class(id),
                rtems_object_id_get_node(id),
                rtems_object_id_get_index(id) + 1
           );
}

Note that this Id may not be valid in this system or associated with an allocated object.

34.3.2. Printing an Object Id

RTEMS also provides services to associate the API and Class portions of an Object Id with strings. This allows the application developer to provide more information about an object in diagnostic messages.

In the following C language example, an Id is decomposed into its constituent parts and “pretty-printed.”

void prettyPrintObjectId(rtems_id id)
{
    int tmpAPI;
    uint32_t tmpClass;

    tmpAPI   = rtems_object_id_get_api(id),
    tmpClass = rtems_object_id_get_class(id),

    printf(
        "API=%s Class=%s Node=%" PRIu32 " Index=%" PRIu16 "\n",
        rtems_object_get_api_name(tmpAPI),
        rtems_object_get_api_class_name(tmpAPI, tmpClass),
        rtems_object_id_get_node(id),
        rtems_object_id_get_index(id)
    );
}