The Tor Browser / file revision

 /* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=8 sts=2 et sw=2 tw=80: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /* dash_detect_stream_switch.sjs

  *

  * Parses requests for DASH manifests and ensures stream switching takes place

  * by verifying the subsegments downloaded and the streams they belong to.

  * If unexpected subsegments (byte ranges) are requested, the script will

  * will respond with a 404.

  */

 var DEBUG = false;

 function parseQuery(request, key) {

   var params = request.queryString.split('&');

   if (DEBUG) {

     dump("DASH-SJS: request params = \"" + params + "\"\n");

   }

   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;

 }

 function handleRequest(request, response)

 {

   try {

     var name = parseQuery(request, "name");

     var range = request.hasHeader("Range") ? request.getHeader("Range")

                                            : undefined;

     // Should not get request for 1st subsegment from 2nd stream, nor 2nd

     // subsegment from 1st stream.

     if (name == "dash-webm-video-320x180.webm" && range == "bytes=25514-32767" ||

         name == "dash-webm-video-428x240.webm" && range == "bytes=228-35852") 

     {

       throw "Should not request " + name + " with byte-range " + range;

     } else {

       var rangeSplit = range.split("=");

       if (rangeSplit.length != 2) {

         throw "DASH-SJS: ERROR: invalid number of tokens (" + rangeSplit.length +

               ") delimited by \'=\' in \'Range\' header.";

       }

       var offsets = rangeSplit[1].split("-");

       if (offsets.length != 2) {

         throw "DASH-SJS: ERROR: invalid number of tokens (" + offsets.length +

               ") delimited by \'-\' in \'Range\' header.";

       }

       var startOffset = parseInt(offsets[0]);

       var endOffset = parseInt(offsets[1]);

       var file = Components.classes["@mozilla.org/file/directory_service;1"].

                             getService(Components.interfaces.nsIProperties).

                             get("CurWorkD", Components.interfaces.nsILocalFile);

       var fis  = Components.classes['@mozilla.org/network/file-input-stream;1'].

                             createInstance(Components.interfaces.nsIFileInputStream);

       var bis  = Components.classes["@mozilla.org/binaryinputstream;1"].

                             createInstance(Components.interfaces.nsIBinaryInputStream);

       var paths = "tests/content/media/test/" + name;

       var split = paths.split("/");

       for (var i = 0; i < split.length; ++i) {

         file.append(split[i]);

       }

       fis.init(file, -1, -1, false);

       // Exception: start offset should be within file bounds.

       if (startOffset > file.fileSize) {

         throw "Starting offset [" + startOffset + "] is after end of file [" +

               file.fileSize + "].";

       }

       // End offset may be too large in the MPD. Real world HTTP servers just

       // return what data they can; do the same here - reduce the end offset.

       if (endOffset >= file.fileSize) {

         if (DEBUG) {

           dump("DASH-SJS: reducing endOffset [" + endOffset + "] to fileSize [" +

                (file.fileSize-1) + "]\n");

         }

         endOffset = file.fileSize-1;

       }

       fis.seek(Components.interfaces.nsISeekableStream.NS_SEEK_SET, startOffset);

       bis.setInputStream(fis);

       var byteLengthToRead = endOffset + 1 - startOffset;

       var totalBytesExpected = byteLengthToRead + startOffset;

       if (DEBUG) {

         dump("DASH-SJS: byteLengthToRead = " + byteLengthToRead +

              " byteLengthToRead+startOffset = " + totalBytesExpected +

              " fileSize = " + file.fileSize + "\n");

       }

       var bytes = bis.readBytes(byteLengthToRead);

       response.setStatusLine(request.httpVersion, 206, "Partial Content");

       response.setHeader("Content-Length", ""+bytes.length, false);

       response.setHeader("Content-Type", "application/dash+xml", false);

       var contentRange = "bytes " + startOffset + "-" + endOffset + "/" +

                          file.fileSize;

       response.setHeader("Content-Range", contentRange, false);

       response.write(bytes, bytes.length);

       bis.close();

     }

   } catch (e) {

     dump ("DASH-SJS-ERROR: " + e + "\n");

     response.setStatusLine(request.httpVersion, 404, "Not found");

   }

 }