third_party/web_platform_tests/XMLHttpRequest/progress-events-response-data-gzip.htm

<!doctype html>
<html>
  <head>
    <title>XMLHttpRequest: progress events and GZIP encoding</title>
    <meta name="timeout" content="long">
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
    <link rel="help" href="https://xhr.spec.whatwg.org/#firing-events-using-the-progressevent-interface-for-http" data-tested-assertations="following::p[contains(text(),'content-encodings')]" />
    <!-- TODO: find better spec reference when https://www.w3.org/Bugs/Public/show_bug.cgi?id=25587 is fixed -->
  </head>
  <body>
    <div id="log"></div>
    <script>
      var test = async_test()
      test.step(function() {
        var client = new XMLHttpRequest()
        /*

          Two behaviours are considered acceptable, so there are two ways to
          pass this test

          a) Set data for the compressed resource:
            * event.total reflects the Content-length of the gzipp'ed resource
            * event.loaded how many gzipped bytes have arrived over the wire so far
            * lengthComputable is true

          or

          b) If the implementation does not provide progress details for the compressed
          resource, set
            * lengthComputable to false
            * event.total to 0
            * event.loaded to the number of bytes available so far after gzip decoding

          Implications of this are tested here as follows:

          * If lengthComputable is true:
              * Event.total must match Content-length header
              * event.loaded should be a smaller number while resource is loading
                and match Content-length when loading is finished
              * Setting event.loaded to equal event.total for each progress event if the
                resource is not fully downloaded would be cheating

          * If lengthComputable is false:
              * event.total should be 0
              * event.loaded should be the length of the decompressed content, i.e.
                bigger than Content-length header value when finished loading

        */
        client.addEventListener('loadend', test.step_func(function(e){
          var len = parseInt(client.getResponseHeader('content-length'), 10)
          if(e.lengthComputable){
            assert_equals(e.total, len, 'event.total is content-length')
            assert_equals(e.loaded, len, 'event.loaded should be content-length at loadend')
          }else{
            assert_equals(e.total, 0, 'if implementation can\'t compute event.total for gzipped content it is 0')
            assert_true(e.loaded >= len, 'event.loaded should be set even if total is not computable')
          }
          test.done();
        }), false)
        client.addEventListener('progress', test.step_func(function(e){
          if(e.lengthComputable && e.total && e.loaded && e.target.readyState < 4){
            assert_not_equals(e.total, e.loaded, 'total should not equal loaded while download/decode is incomplete')
            // We should only do this assertation once
            // it's theoretically possible that all the data would get in
            // and a progress event fire before the readyState switches from 3 to 4 -
            // in this case we might report bogus and random failures. Better to remove the event listener again..
            client.removeEventListener('progress', arguments.callee, false);
          }
        }), false)
        // image.gif is 165375 bytes compressed. Sending 45000 bytes at a time with 1 second delay will load it in 4 seconds
        client.open("GET", "resources/image.gif?pipe=gzip|trickle(45000:d1:r2)", true)
        client.send()
      })
    </script>
  </body>
</html>