extract_parts

# File activesupport/lib/active_support/message_encryptor.rb, line 350
      def extract_parts(encrypted_message)
        parts = []
        rindex = encrypted_message.length

        if aead_mode?
          parts << extract_part(encrypted_message, rindex, length_of_encoded_auth_tag)
          rindex -= SEPARATOR.length + length_of_encoded_auth_tag
        end

        parts << extract_part(encrypted_message, rindex, length_of_encoded_iv)
        rindex -= SEPARATOR.length + length_of_encoded_iv

        parts << encrypted_message[0, rindex]

        parts.reverse!.map! { |part| decode(part) }
      end