protected String fastToString(
      byte[] scratchBuffer) {
    return
        FastHiveDecimalImpl.fastToString(
            fastSignum, fast0, fast1, fast2,
            fastIntegerDigitCount, fastScale, -1,
            scratchBuffer);
  }
FastHiveDecimal is a mutable fast decimal object.  It is the base class for both the
   HiveDecimal and HiveDecimalWritable classes.  All fast* methods are protected so they
   cannot be accessed by clients of HiveDecimal and HiveDecimalWritable.  HiveDecimal ensures
   it creates new objects when the value changes since it provides immutable semantics;
   HiveDecimalWritable does not create new objects since it provides mutable semantics.

   The methods in this class are shells that pickup the member variables from FastHiveDecimal
   parameters and pass them as individual parameters to static methods in the FastHiveDecimalImpl
   class that do the real work.

   NOTE: The rationale for fast decimal is in FastHiveDecimalImpl.
storage-api/src/java/org/apache/hadoop/hive/common/type/FastHiveDecimal.java