class RuboCop::Cop::Style::Encoding

def offense(processed_source, line_number)
  line = processed_source[line_number]
  encoding_present = line =~ ENCODING_PATTERN
  ascii_only = processed_source.buffer.source.ascii_only?
  always_encode = style == :always
  never_encode = style == :never
  encoding_omitable = never_encode || (!always_encode && ascii_only)
  if !encoding_present && !encoding_omitable
    MSG_MISSING
  elsif encoding_present && encoding_omitable
    MSG_UNNECESSARY
  end
end