class Mail::Multibyte::Chars

def translate_offset(byte_offset) #:nodoc:
  return nil if byte_offset.nil?
  return 0   if @wrapped_string == ''
  if @wrapped_string.respond_to?(:force_encoding)
    @wrapped_string = @wrapped_string.dup.force_encoding(Encoding::ASCII_8BIT)
  end
  begin
    @wrapped_string[0...byte_offset].unpack('U*').length
  rescue ArgumentError
    byte_offset -= 1
    retry
  end
end