function handleRequest(request, response) { let { NetUtil } = ChromeUtils.importESModule( "resource://gre/modules/NetUtil.sys.mjs" ); let query = new URLSearchParams(request.queryString); response.setHeader("Cross-Origin-Opener-Policy", "same-origin", false); response.setHeader("Cross-Origin-Embedder-Policy", "require-corp", false); var fileRoot = query.get("fileRoot"); // Get the desired file var file; getObjectState("SERVER_ROOT", function (serverRoot) { file = serverRoot.getFile(fileRoot); }); // Set up the file streams to read in the file as UTF-8 let fstream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance( Ci.nsIFileInputStream ); fstream.init(file, -1, 0, 0); // Read the file let available = fstream.available(); let data = available > 0 ? NetUtil.readInputStreamToString(fstream, available) : ""; fstream.close(); response.write(data); }