class RuboCop::Cop::Style::Encoding

def investigate(processed_source)
  return if processed_source.buffer.source.empty?
  line_number = encoding_line_number(processed_source)
  return unless (@message = offense(processed_source, line_number))
  range = processed_source.buffer.line_range(line_number + 1)
  add_offense(range, range, @message)
end