tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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prefetch-helper.js (2688B)

      1 setup(_ => {
      2  assert_implements_optional(
      3    document.createElement('link').relList.supports('prefetch'),
      4    "Browser supports prefetch.");
      5  assert_implements_optional(
      6    "PerformanceResourceTiming" in window,
      7    "Browser supports performance APIs.");
      8 });
      9 
     10 function assert_resource_not_downloaded(test, url) {
     11  // CSP failures generate resource timing entries, so let's make sure that
     12  // download sizes are 0.
     13  const entries = performance.getEntriesByName(url, 'resource');
     14  for (const entry of entries) {
     15    assert_equals(entry.transferSize, 0, 'transferSize');
     16    assert_equals(entry.encodedBodySize, 0, 'encodedBodySize');
     17    assert_equals(entry.decodedBodySize, 0, 'decodedBodySize');
     18  }
     19 }
     20 
     21 function assert_link_prefetches(test, link) {
     22  assert_no_csp_event_for_url(test, link.href);
     23 
     24  link.onerror = test.unreached_func('onerror should not fire.');
     25 
     26  // Test is finished when either the `load` event fires, or we get a performance
     27  // entry showing that the resource loaded successfully.
     28  link.onload = test.step_func(test.step_func_done());
     29  waitUntilResourceDownloaded(link.href).then(test.step_func_done());
     30 
     31  document.head.appendChild(link);
     32 }
     33 
     34 function assert_link_does_not_prefetch(test, link) {
     35  let cspEvent = false;
     36  let errorEvent = false;
     37 
     38  waitUntilCSPEventForURL(test, link.href)
     39      .then(test.step_func(e => {
     40        cspEvent = true;
     41        assert_equals(e.violatedDirective, "prefetch-src");
     42        assert_equals(e.effectiveDirective, "prefetch-src");
     43 
     44        if (errorEvent)
     45          test.done();
     46      }));
     47 
     48  link.onerror = test.step_func(e => {
     49    errorEvent = true;
     50    if (cspEvent)
     51      test.done();
     52  });
     53  link.onload = test.unreached_func('onload should not fire.');
     54 
     55  document.head.appendChild(link);
     56 }
     57 
     58 async function try_to_prefetch(href, test) {
     59  const url = new URL(href, location.href);
     60  url.searchParams.set(
     61      'pipe',
     62      '|header(Cache-Control, max-age=604800)' +
     63          '|header(Access-Control-Allow-Origin, *)' +
     64          '|header(Timing-Allow-Origin, *)');
     65  url.searchParams.set('uuid', token());
     66 
     67  const link = document.createElement('link');
     68  link.rel = 'prefetch';
     69  link.href = url.toString();
     70  link.crossOrigin = 'anonymous';
     71  test.add_cleanup(() => link.remove());
     72 
     73  const didPrefetch = new Promise(resolve => {
     74    const observer = new PerformanceObserver(list => {
     75      const entries = list.getEntriesByName(link.href);
     76      if (entries.length) {
     77        resolve(entries[0]);
     78      }
     79    });
     80    observer.observe({entryTypes: ['resource']})
     81  });
     82  document.head.appendChild(link);
     83  const entry = await didPrefetch;
     84  return entry.requestStart > 0 && entry.decodedBodySize > 0;
     85 }