code: public byte []
  getBase64(boolean required) throws IOException {
  	String s = remainingStrings();
  	if (s == null) {
  		if (required)
  			throw exception("expected base64 encoded string");
  		else
  			return null;
  	}
  	byte [] array = base64.fromString(s);
  	if (array == null)
  		throw exception("invalid base64 encoding");
  	return array;
  }
docs: Gets the remaining string tokens until an EOL/EOF is seen, concatenates
  them together, and converts the base64 encoded data to a byte array.
  @param required If true, an exception will be thrown if no strings remain;
  otherwise null be be returned.
  @return The byte array containing the decoded strings, or null if there
  were no strings to decode.
  @throws TextParseException The input was invalid.
  @throws IOException An I/O error occurred.