The Tor Browser / file revision

 var DEBUG = true;

 var clientID = "javascript";

 var nsICache = Components.interfaces.nsICache;

 function getCacheService()

 {

     var nsCacheService = Components.classes["@mozilla.org/network/cache-service;1"];

     var service = nsCacheService.getService(Components.interfaces.nsICacheService);

     return service;

 }

 function createCacheSession(clientID, storagePolicy, streamable)

 {

     var service = getCacheService();

     var session = service.createSession(clientID, storagePolicy, streamable);

     return session;

 }

 function openCacheEntry(url, mode)

 {

     var session = createCacheSession(clientID, nsICache.STORE_ON_DISK, true);

     var entry = session.openCacheEntry(url, mode);

     return entry;

 }

 function wrapInputStream(input)

 {

     var nsIScriptableInputStream = Components.interfaces.nsIScriptableInputStream;

     var factory = Components.classes["@mozilla.org/scriptableinputstream;1"];

     var wrapper = factory.createInstance(nsIScriptableInputStream);

     wrapper.init(input);

     return wrapper;

 }

 function getIOService()

 {

     var CID = Components.classes["@mozilla.org/network/io-service;1"];

     var service = CID.getService(Components.interfaces.nsIIOService);

     return service;

 }

 function downloadHTTP(spec)

 {

     var ioService = getIOService();

     var uri = ioService.newURI(spec, null, null);

     var channel = ioService.newChannelFromURI(uri);

     var input = wrapInputStream(channel.open());

     var data = input.read(input.available());

     input.close();

     return data;

 }

 function download(url)

 {

     var data = "";

     var buffer = java.lang.reflect.Array.newInstance(java.lang.Byte.TYPE, 65536);

     var stream = url.getContent();

     while (true) {

         var count = stream.read(buffer);

         if (count <= 0)

             break;

         var str = new java.lang.String(buffer, 0, count);

         data += str;

     }

     stream.close();

     return data;

 }

 function write(url, data)

 {

     var key = url.toString();

     var outputEntry = openCacheEntry(key, nsICache.ACCESS_WRITE);

     var output = outputEntry.transport.openOutputStream(0, -1, 0);

     var count = output.write(data, data.length);

     // store some metadata.

     outputEntry.setMetaDataElement("size", data.length);

     output.close();

     outputEntry.markValid();

     outputEntry.close();

     return count;

 }

 function read(url)

 {

     var key = url.toString();

     var inputEntry = openCacheEntry(key, nsICache.ACCESS_READ);

     var input = wrapInputStream(inputEntry.transport.openInputStream(0, -1, 0));

     var data = input.read(input.available());

     input.close();

     inputEntry.close();

     return data;

 }

 function readMetaData(url, element)

 {

     var key = url.toString();

     var inputEntry = openCacheEntry(key, nsICache.ACCESS_READ);

     var metadata = inputEntry.getMetaDataElement(element);

     inputEntry.close();

     return metadata;

 }

 function doom(url)

 {

     var key = url.toString();

     var doomedEntry = openCacheEntry(key, nsICache.ACCESS_READ_WRITE);

     doomedEntry.doom();

     doomedEntry.close();

 }

 function test()

 {

     // download some real content from the network.

     var url = new java.net.URL("http://www.mozilla.org");

     var key = url.toString();

     var data = download(url);

     if (write(url, data) == data.length)

         print("disk cache write works!");

     else

         print("disk cache write broken!");

     if (read(url) == data)

         print("disk cache read works!");

     else

         print("disk cache read broken!");

     if (readMetaData(url, "size") == data.length)

         print("disk cache metadata works!");

     else

         print("disk cache metadata broken!");

 }

 function median(array)

 {

     var cmp = function(x, y) { return x - y; }

     array.sort(cmp);

     var middle = Math.floor(array.length / 2);

     return array[middle];

 }

 function sum(array)

 {

     var s = 0;

     var len = array.length;

     for (var i = 0; i < len; ++i)

         s += array[i];

     return s;

 }

 function time()

 {

     var N = 50;

     var System = java.lang.System;

     var url = new java.net.URL("http://www.mozilla.org");

     var downloadTimes = new Array();

     for (var i = 0; i < N; ++i) {

         var begin = System.currentTimeMillis();

         download(url);

         var end = System.currentTimeMillis();

         downloadTimes.push(end - begin);

     }

     var downloadTotal = sum(downloadTimes);

     var downloadMean = downloadTotal / N;

     var downloadMedian = median(downloadTimes);

     print("" + N + " downloads took " + downloadTotal + " milliseconds.");

     print("mean = " + downloadMean + " milliseconds.");

     print("median = " + downloadMedian + " milliseconds.");

     var readTimes = new Array();

     for (var i = 0; i < N; ++i) {

         var begin = System.currentTimeMillis();

         read(url);

         var end = System.currentTimeMillis();

         readTimes.push(end - begin);

     }

     var readTotal = sum(readTimes);

     var readMean = readTotal / N;

     var readMedian = median(readTimes);

     print("" + N + " reads took " + readTotal + " milliseconds.");

     print("mean = " + readMean + " milliseconds.");

     print("median = " + readMedian + " milliseconds.");

 }

 // load the cache service before doing anything with Java...

 getCacheService();

 if (DEBUG) {

     print("cache service loaded.");

 } else {

     print("running disk cache test.");

     test();

     print("disk cache test complete.");

 }