occupied

An integer specifying the total number of allocated cache buckets (minus one). During method lookup, the Objective-C runtime uses this field to determine the index at which to begin a linear search of the buckets array. A pointer to a method’s selector is masked against this field using a logical AND operation (index = (mask & selector)). This serves as a simple hashing algorithm.

An array of pointers to Method data structures. This array may contain no more than mask + 1 items. Note that pointers may be NULL, indicating that the cache bucket is unoccupied, and occupied buckets may not be contiguous. This array may grow over time.