final int bigBlockSize = POIFSConstants.BIG_BLOCK_MINIMUM_DOCUMENT_SIZE;
BufferedInputStream bis = new BufferedInputStream(stream, bigBlockSize+1);
bis.mark(bigBlockSize);
// Do we need to store as a mini stream or a full one?
if(bis.skip(bigBlockSize) < bigBlockSize) {
_stream = new NPOIFSStream(_filesystem.getMiniStore());
_block_size = _filesystem.getMiniStore().getBlockStoreBlockSize();
} else {
_stream = new NPOIFSStream(_filesystem);
_block_size = _filesystem.getBlockStoreBlockSize();