Written by Gil Tene of Azul Systems, and released to the public domain,
as explained at http://creativecommons.org/publicdomain/zero/1.0/
Used for iterating through histogram values using the finest granularity steps supported by the underlying
representation. The iteration steps through all possible unit value levels, regardless of whether or not
there were recorded values for that value level, and terminates when all recorded histogram values are exhausted.
Reset iterator for re-use in a fresh iteration over the same histogram data set.
histogram The histogram this iterator will operate on