public int getRootBlockDataSize(int i) {
      return blockDataSizes[i];
    }
@param i zero-based index of a root-level block
@return the on-disk size of the root-level block for version 2, or the uncompressed size for
        version 1
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java