Committable

A hashmap with delta entries that enables quick revert of the recent changes. Implementation-wise, the hashmap keeps a delta map that records the additional changes on a base map. The user can call DeltaHashMap::commit to merge the additional changes into the base map. However, if the user is unsatisfied with the result of the specific layer of operation, the changes that happens after the layer can be discarded on demand.

See DeltaHashMap::commit and DeltaHashMap::cocommit for more information.