in spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/DefaultSource.scala [750:755]
def compareRange(left: Array[Byte], right: Array[Byte]): Int = {
if (left == null && right == null) 0
else if (left == null && right != null) 1
else if (left != null && right == null) -1
else Bytes.compareTo(left, right)
}