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6.2   Classes

Each Simics class implemented by a module must be registered with Simics. Remember that classes registered in a module should be listed in the MODULE_CLASSES variable in the module's Makefile. This allows Simics to automatically load the required modules when reading a configuration file.

Registering a class is done by creating and filling a class_data_t structure, and then call the function SIM_register_class with the new class name and the class_data_t structure that describes it. The members in the class_data_t structure are:

new_instance

A function called when creating an instance of the class. This function will be described in objects below.

finalize_instance

This function is called once new_instance has returned, and all attributes in a configuration have been set.

description

A string that should contain a description of the class.

kind

The class kind tells Simics whether objects of this class should be saved when a checkpoint is created. Valid values are:

Sim_Class_Kind_Vanilla

class instances will be saved as part of checkpoints (this is the default if kind is not given any value.)

Sim_Class_Kind_Pseudo

class instances will never be saved.

Sim_Class_Kind_Session

is not used for the time being, and thus has the same meaning as Sim_Class_Kind_Pseudo.

C/C++

In C/C++, registration of classes is usually done from within the mandatory init_local() function. The C definition of class_data_t and SIM_register_class() is the following:

typedef struct class_data {
        conf_object_t *(*new_instance)(parse_object_t *parse_obj);
        int            (*delete_instance)(conf_object_t *obj);
        void           (*finalize_instance)(conf_object_t *obj);
        const char      *description;
        class_kind_t     kind;
} class_data_t;

conf_class_t *
SIM_register_class(const char *name, class_data_t *class_data);

SIM_register_class() returns a pointer to a conf_class_t structure which is used internally by Simics to keep track of the class information. This pointer can be used when referring to the class in calls to other functions.

A simple init_local() initialization function could look like this:

void
init_local(void)
{
        class_data_t cdata;
        conf_class_t *my_class;

        memset(&cdata, 0, sizeof(cdata));
        cdata.new_instance = my_new_instance;
        cdata.description = "This is my class";
        cdata.kind = Sim_Class_Kind_Session;

        my_class = SIM_register_class("my-class", &cdata);

        // Other initializations...
}

Python

In Python, the registration is done when the global statements of the module are executed (at load time):

def new_instance(parse_obj):
    ...

def finalize_instance(obj):
    ...

class_data = class_data_t()
class_data.new_instance = new_instance
class_data.finalize_instance = finalize_instance
class_data.description = """
    A sample class used for documentation purposes only.""";
SIM_register_class("sample-doc-class", class_data)

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