parsedepth.html - mozsearch

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This WPT test may be referenced by the following Test IDs:
- /xml/parsedepth.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<title></title>

<script src=/resources/testharness.js></script>

<script src=/resources/testharnessreport.js></script>

<script>

function parseBlob(blob) {

  return new Promise(resolve => {

    let xhr = new XMLHttpRequest();

    xhr.open("GET", URL.createObjectURL(blob));

    xhr.onload = () => {

      resolve(xhr.responseXML);

    xhr.send();

});

promise_test(async (t) => {

  // Most browser engines, including Gecko, use 5000 as the limit, so test a

  // range around that.

  const cutoff = 5000;

  let minDepth = cutoff - 100;

  let maxDepth = cutoff + 100;

  // Generate a string with elements nested maxDepth deep.

  const openTag = "<x>";

  const closeTag = "</x>";

  let xml = openTag.repeat(maxDepth) + closeTag.repeat(maxDepth);

  // Compute where we change from opening to closing tags.

  const middle = maxDepth * openTag.length;

  // Create a blob around the string.

  let blob = new Blob([xml], { type: "application/xml" });

  while (minDepth < maxDepth) {

    // Try to parse a number of nested tags between minDepth and maxDepth.

    let test = Math.ceil((minDepth + maxDepth) / 2);

    // We need the number of opening and closing tags to be equal to the number

    // that we calculated above.

    let slice = blob.slice(middle - (test * openTag.length),

                           middle + (test * closeTag.length), blob.type);

    let responseXML = await parseBlob(slice);

    // Move either minDepth or maxDepth so that the actual limit is still in the

    // range of [minDepth-maxDepth].

    if (responseXML) {

      // Depth is ok.

      minDepth = test;

    } else {

      maxDepth = test - 1;

  assert_equals(minDepth, maxDepth);

  assert_equals(minDepth, cutoff);

},"Parsing XML fails when the nesting depth is 5000");

</script>