def data=(data)
      data, *extra = data.split(/([#{CODEA+CODEB+CODEC}])/n)
      @data = data || ''
      self.extra = extra.join unless extra.empty?
    end
def data=(data)
      data, *extra = data.split(/([#{CODEA+CODEB+CODEC}])/n)
      @data = data || ''
      self.extra = extra.join unless extra.empty?
    end
Set the data for this barcode. If the barcode changes
character set, an extra will be created.