IndexHeader

This struct is trailed by two arrays of length indexes_len of integers, whose integer size is determined by indexes_len. These arrays are indexed by constrainIndex(hash). The entryIndexes array contains the index in the dense backing store where the entry's data can be found. Entries which are not in use have their index value set to emptySentinel(I). The entryDistances array stores the distance between an entry and its ideal hash bucket. This is used when adding elements to balance the maximum scan length.