public static void doFastScaleDown(
      FastHiveDecimal fastDec,
      int scaleDown,
      FastHiveDecimal fastResult) {
    doFastScaleDown(
        fastDec.fast0, fastDec.fast1, fastDec.fast2,
        scaleDown,
        fastResult);
  }
Fast decimal scale down by factor of 10 with rounding ROUND_HALF_EVEN.

When the fraction being scaled away is exactly 0.5, then round and add 1 only if aaa.
When fraction is not exactly 0.5, then if fraction &gt; 0.5 then add 1.
Otherwise, throw away fraction.

@param fastSignum the sign (-1, 0, or +1)
@param fast0 word 0 of the internal representation
@param fast1 word 1
@param fast2 word 2
@param scaleDown the number of integer digits to scale
@param fastResult an object to reuse
@return was the operation successfule?
storage-api/src/java/org/apache/hadoop/hive/common/type/FastHiveDecimalImpl.java