@Override public void write(byte[] buffer,int offset,int length) throws IOException {
  _crc=Crc64.generate(_crc,buffer,offset,length);
  _next.write(buffer,offset,length);
}

@ Override public void write ( byte [ ] buffer , int offset , int length ) throws IOException { _crc = Crc64 . generate ( _crc , buffer , offset , length ) ; _next . write ( buffer , offset , length ) ; }
writes a buffer to the underlying stream .
