code: String
  rrToString() {
  	StringBuffer sb = new StringBuffer();
  	sb.append(footprint);
  	sb.append(" ");
  	sb.append(alg);
  	sb.append(" ");
  	sb.append(digestid);
  	if (digest != null) {
  		sb.append(" ");
  		sb.append(base16.toString(digest));
  	}
  
  	return sb.toString();
  }
docs: Converts rdata to a String