Const.LEAF_BYTESIZE is the INITIAL size for
BufArrayOutputStream's buffer which can still grow as needed
*/
bary_outs = new BufArrayOutputStream(
filehdr.getTreeLeafByteSize() );
data_outs = new MixedDataOutputStream( bary_outs );
treedir = new TreeDir();
node_blockptr = null;
// Write the initialized Header to Disk