def register_custom_data(name, default_value = 0)
      if @custom_data_labels.include?(name)
        PEROBS.log.fatal "Custom data field #{name} has already been registered"
      end

      @custom_data_labels << name
      @custom_data_values << default_value
      @custom_data_defaults << default_value
    end
def register_custom_data(name, default_value = 0)
      if @custom_data_labels.include?(name)
        PEROBS.log.fatal "Custom data field #{name} has already been registered"
      end

      @custom_data_labels << name
      @custom_data_values << default_value
      @custom_data_defaults << default_value
    end
In addition to the standard offsets for the first entry and the first
 space any number of additional data fields can be registered. This must be
 done right after the object is instanciated and before the open() method
 is called. Each field represents a 64 bit unsigned integer.
 @param name [String] The label for this offset
 @param default_value [Integer] The default value for the offset