Stores and iterate on sorted integers in compressed form in RAM.
The code for compressing the differences between ascending integers was borrowed from {@link org.apache.lucene.store.IndexInput} and{@link org.apache.lucene.store.IndexOutput}.
NOTE: this class assumes the stored integers are doc Ids (hence why it extends {@link DocIdSet}). Therefore its {@link #iterator()} assumes {@link DocIdSetIterator#NO_MORE_DOCS} can be used as sentinel. If you intent to usethis value, then make sure it's not used during search flow.