code: public Result readCacheIdsByRange(int index, int length) {
          Result result = readByRange(CACHE_ID_DATA, index, length, CHECK_EXPIRED, FILTER);
          return result;
      }
docs: ***********************************************************************
  readCacheIdsByRange()
  This method is used by CacheMonitor to retrive the cache ids from the disk.
  If index = 0, it starts the beginning. If index = 1, it means "next". If Index = -1, it means "previous".
  The length of the max number of templates to be read. If length = -1, it reads all templates until the end.
  ***********************************************************************