step

Description

The step interface is typically implemented by processors, but can be implemented by other objects as well. Its purpose is to handle step events using a queue.

The current number of steps for the queue is returned when calling get_step_count.

The post_step function will schedule an event that will occur after steps (which must be nonnegative) counted from local current step at queue. An event previously posted can be removed by calling cancel_step. The cancel_step function takes a function pred as argument which is called when a matching event is found. The event is only removed if pred returns 1. The find_next_step takes the same arguments as cancel_step but only returns the number of cycles before the event will occur. The evclass is the event class, obj is the object posting the event, and user_data is pointer to data used as a parameter when calling the callback function defined in the evclass. If no matching event was found, find_next_step returns −1.

The events method returns a list of all pending events in expiration order. Each element is a four-element list containing the event object, the event class name, the expiration time counted in steps as an integer and the event description as given by the event class describe method, or nil for events whose event class do not define that method.

The advance function will increment the number of steps for the queue, decrementing the number of steps to the first event to the value defined by steps. The number of steps remaining to the next event is returned. It is an error to advance beyond the next pending event, so the return value is never negative.

The implementor of the step interface can use any checkpoint representation. The name field in the event class data structure is unique, and the attribute setter function for checkpoint restore can use VT_get_event_class to get the event class structure corresponding to an event class name.

SIM_INTERFACE(step) {
        pc_step_t (*get_step_count)(conf_object_t *NOTNULL queue);
        void (*post_step)(
                conf_object_t *NOTNULL queue,
                event_class_t *NOTNULL evclass,
                conf_object_t *NOTNULL obj,
                pc_step_t steps,
                lang_void *user_data);
        void (*cancel_step)(
                conf_object_t *NOTNULL queue,
                event_class_t *NOTNULL evclass,
                conf_object_t *NOTNULL obj,
                int (*pred)(lang_void *data, lang_void *match_data),
                lang_void *match_data);
        pc_step_t (*find_next_step)(
                conf_object_t *NOTNULL queue,
                event_class_t *NOTNULL evclass,
                conf_object_t *NOTNULL obj,
                int (*pred)(lang_void *data, lang_void *match_data),
                lang_void *match_data);

        attr_value_t (*events)(conf_object_t *NOTNULL obj);

        pc_step_t (*advance)(conf_object_t *queue, pc_step_t steps);
};

#define STEP_INTERFACE "step"

Execution Context

Cell Context for all methods.