code: public void sendBlocksBeingWrittenReport(DatanodeProtocol node,
        int namespaceId, DatanodeRegistration nsRegistration) throws IOException {
      Block[] blocks = data.getBlocksBeingWrittenReport(namespaceId);
      if (blocks != null && blocks.length != 0) {
        long[] blocksAsLong =
          BlockListAsLongs.convertToArrayLongs(blocks);
        BlockReport bbwReport = new BlockReport(blocksAsLong);
        node.blocksBeingWrittenReport(nsRegistration, bbwReport);
      }
    }
docs: Sends a 'Blocks Being Written' report to the given node.
  
  @param node the node to send the report to
  @throws IOException