The Tor Browser / file revision

 function handleRequest(request, response)

 {

   var file;

   getObjectState("SERVER_ROOT", function(serverRoot)

   {

     var ref = request.getHeader("Referer").split("?")[0];

     // 8 is "https://".length which is the longest string before the host.

     var pathStart = ref.indexOf("/", 8) + 1;

     var pathEnd = ref.lastIndexOf("/") + 1;

     file = serverRoot.getFile(ref.substring(pathStart, pathEnd) + "x");

   });

   response.setHeader("Content-Type", "text/plain", false);

   response.write(file.path.substr(0, file.path.length-1));

 }