public DiskRangeList extract() {
      DiskRangeList result = head;
      head = null;
      return result;
    }
This class provides just a simplistic iterator interface (check {@link DiskRangeList}).
Thus, for equality/hashcode just check the actual DiskRange content.
@return hashcode
storage-api/src/java/org/apache/hadoop/hive/common/io/DiskRangeList.java