# File lib/rack/utils.rb, line 247
    def set_cookie_header!(header, key, value)
      case value
      when Hash
        domain  = "; domain="  + value[:domain] if value[:domain]
        path    = "; path="    + value[:path]   if value[:path]
        max_age = "; max-age=" + value[:max_age] if value[:max_age]
        # There is an RFC mess in the area of date formatting for Cookies. Not
        # only are there contradicting RFCs and examples within RFC text, but
        # there are also numerous conflicting names of fields and partially
        # cross-applicable specifications.
        #
        # These are best described in RFC 2616 3.3.1. This RFC text also
        # specifies that RFC 822 as updated by RFC 1123 is preferred. That is a
        # fixed length format with space-date delimeted fields.
        #
        # See also RFC 1123 section 5.2.14.
        #
        # RFC 6265 also specifies "sane-cookie-date" as RFC 1123 date, defined
        # in RFC 2616 3.3.1. RFC 6265 also gives examples that clearly denote
        # the space delimited format. These formats are compliant with RFC 2822.
        #
        # For reference, all involved RFCs are:
        # RFC 822
        # RFC 1123
        # RFC 2109
        # RFC 2616
        # RFC 2822
        # RFC 2965
        # RFC 6265
        expires = "; expires=" +
          rfc2822(value[:expires].clone.gmtime) if value[:expires]
        secure = "; secure"  if value[:secure]
        httponly = "; HttpOnly" if value[:httponly]
        value = value[:value]
      end
      value = [value] unless Array === value
      cookie = escape(key) + "=" +
        value.map { |v| escape v }.join("&") +
        "#{domain}#{path}#{max_age}#{expires}#{secure}#{httponly}"

      case header["Set-Cookie"]
      when nil, ''
        header["Set-Cookie"] = cookie
      when String
        header["Set-Cookie"] = [header["Set-Cookie"], cookie].join("\n")
      when Array
        header["Set-Cookie"] = (header["Set-Cookie"] + [cookie]).join("\n")
      end

      nil
    end