gecko-dev/dom/media/test/dynamic_resource.sjs

function parseQuery(request, key) {
  var params = request.queryString.split("&");
  for (var j = 0; j < params.length; ++j) {
    var p = params[j];
    if (p == key) {
      return true;
    }
    if (p.indexOf(key + "=") == 0) {
      return p.substring(key.length + 1);
    }
    if (p.indexOf("=") < 0 && key == "") {
      return p;
    }
  }
  return false;
}

// Return resource1 file content for the first request with a given key.
// All subsequent requests return resource2. Both must be video/ogg.
function handleRequest(request, response) {
  var key = parseQuery(request, "key");
  var resource1 = parseQuery(request, "res1");
  var resource2 = parseQuery(request, "res2");

  var resource = getState(key) == "2" ? resource2 : resource1;
  setState(key, "2");

  var file = Cc["@mozilla.org/file/directory_service;1"]
    .getService(Ci.nsIProperties)
    .get("CurWorkD", Ci.nsIFile);
  var fis = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
    Ci.nsIFileInputStream
  );
  var bis = Cc["@mozilla.org/binaryinputstream;1"].createInstance(
    Ci.nsIBinaryInputStream
  );
  var paths = "tests/dom/media/test/" + resource;
  var split = paths.split("/");
  for (var i = 0; i < split.length; ++i) {
    file.append(split[i]);
  }
  fis.init(file, -1, -1, false);
  dump("file=" + file + "\n");
  bis.setInputStream(fis);
  var bytes = bis.readBytes(bis.available());
  response.setStatusLine(request.httpVersion, 206, "Partial Content");
  response.setHeader(
    "Content-Range",
    "bytes 0-" + (bytes.length - 1) + "/" + bytes.length
  );
  response.setHeader("Content-Length", "" + bytes.length, false);
  response.setHeader("Content-Type", "video/ogg", false);
  response.write(bytes, bytes.length);
  bis.close();
}