public int read(byte[] buf,int offset,int length) throws IOException {
  if (_is == null)   return -1;
  int len=_is.read(buf,offset,length);
  return len;
}

public int read ( byte [ ] buf , int offset , int length ) throws IOException { if ( _is == null ) return - 1 ; int len = _is . read ( buf , offset , length ) ; return len ; }
reads bytes from the file .
