public static boolean fastMultiplyFullInternal(
      FastHiveDecimal fastLeft,
      FastHiveDecimal fastRight,
      long[] result) {
    return
        fastMultiplyFullInternal(
            fastLeft.fast0, fastLeft.fast1, fastLeft.fast2,
            fastRight.fast0, fastRight.fast1, fastRight.fast2,
            result);
  }
Fast decimal multiplication on two decimals that have been already scaled and whose results
will fit in 38 digits.

The caller is responsible checking for overflow within the highword and determining
if scale down appropriate.

@return  Returns false if the multiplication resulted in large overflow.  Values in result are
         undefined in that case.
storage-api/src/java/org/apache/hadoop/hive/common/type/FastHiveDecimalImpl.java