code: function getCookieToken(res) {
  		var value = res.req.cookies[cookieName(res.req)];
  		if (!value)
  			return false;
  
  		var parts = value.split('|');
  
  		// If the existing cookie is invalid, reject it.
  		if (parts.length !== 3)
  			return false;
  
  		// If the user data doesn't match this request's user, reject the cookie
  		if (parts[1] !== getUserData(res.req))
  			return false;
  
  		var hasher = crypto.createHmac(options.algorithm, cookieKey);
  		hasher.update(parts[0]);
  		hasher.update("|");	// Don't confuse longer or shorter userDatas
  		hasher.update(parts[1]);
  
  		// If the hash doesn't match, reject the cookie
  		if (parts[2] !== hasher.digest('base64'))
  			return false;
  
  		return parts[0];
  	}
docs: Private function that finds an existing cookie token and returns its salt value