xor_byte_strings

# File actionpack/lib/action_controller/metal/request_forgery_protection.rb, line 423
      def xor_byte_strings(s1, s2) # :doc:
        s2 = s2.dup
        size = s1.bytesize
        i = 0
        while i < size
          s2.setbyte(i, s1.getbyte(i) ^ s2.getbyte(i))
          i += 1
        end
        s2
      end