Guessing the encoding of given string by trying only Japanese major encodings.

gistfile1.rb

def ugly_guess_jp str
  %w[UTF-8 EUC-JP Shift_JIS eucJP-ms Windows-31J].find do |encoding|
    begin
      tested = str.force_encoding(encoding)
      tested.valid_encoding? && tested.encode('UTF-8').valid_encoding?
    rescue Encoding::UndefinedConversionError => e
      nil
    end
  end
end