/**
  * Create an InputStream from the specified Document
  *
  * @param document the Document to be read
  */
 public DocumentInputStream(POIFSDocument document) {
   _current_offset = 0;
   _marked_offset = 0;
   _document_size = document.getSize();
   _closed = false;
   _document = document;
   _currentBlock = getDataInputBlock(0);
 }
 private DataInputBlock getDataInputBlock(int offset) {
   return _document.getDataInputBlock(offset);
 }