code: private static boolean isHttpSeparator(final char c) {
          if (c < 0x20 || c >= 0x7f) {
              if (c != 0x09) {
                  throw UndertowMessages.MESSAGES.invalidControlCharacter(Integer.toString(c));
              }
          }
  
          return HTTP_SEPARATOR_FLAGS[c];
      }
docs: Returns true if the byte is a separator as defined by V1 of the cookie
  spec, RFC2109.
  @throws IllegalArgumentException if a control character was supplied as
  input