@Override
    public boolean isEmpty() {
      return seeker.isEmpty();
    }
Adds a new entry in the root block index. Only used when reading.
@param key      Last key in the block
@param offset   file offset where the block is stored
@param dataSize the uncompressed data size
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java