detect_encoding.rb

require 'charlock_holmes'
 
def is_utf8?(data)
  data.force_encoding('UTF-8').valid_encoding?
end
 
def detect_with_charlock_holmes(data)
  detection = CharlockHolmes::EncodingDetector.detect(data)
  return detection[:encoding]
end
 
def detect_with_brut_force(data)
  Encoding.list.each do |enc|
    test_data = data.force_encoding(enc.name)
    next unless test_data.valid_encoding?
    begin
      converter = Encoding::Converter.new(enc.name, 'UTF-8')
      converted_string = converter.convert(test_data)
      return enc.name if converted_string.valid_encoding?
    rescue Encoding::InvalidByteSequenceError, Encoding::UndefinedConversionError, Encoding::ConverterNotFoundError
      next
    end
  end
end
 
def detect(data)
  if is_utf8?(data)
    return 'UTF-8'
  else
    encoding = detect_with_charlock_holmes(data)
    encoding ||= detect_with_brut_force(data)
    return encoding
  end
end
 
data = ARGF.read
puts detect(data)