summaryrefslogtreecommitdiffstats
path: root/devtools/shared/heapsnapshot/census-tree-node.js
blob: 73dbe391ad5f978caaaf6ea0e04578811444c225 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
/* 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/. */
"use strict";

// CensusTreeNode is an intermediate representation of a census report that
// exists between after a report is generated by taking a census and before the
// report is rendered in the DOM. It must be dead simple to render, with no
// further data processing or massaging needed before rendering DOM nodes. Our
// goal is to do the census report to CensusTreeNode transformation in the
// HeapAnalysesWorker, and ensure that the **only** work that the main thread
// has to do is strictly DOM rendering work.

const {
  Visitor,
  walk,
  basisTotalBytes,
  basisTotalCount,
} = require("resource://devtools/shared/heapsnapshot/CensusUtils.js");

// Monotonically increasing integer for CensusTreeNode `id`s.
let censusTreeNodeIdCounter = 0;

/**
 * Return true if the given object is a SavedFrame stack object, false otherwise.
 *
 * @param {any} obj
 * @returns {Boolean}
 */
function isSavedFrame(obj) {
  return Object.prototype.toString.call(obj) === "[object SavedFrame]";
}

/**
 * A CensusTreeNodeCache maps from SavedFrames to CensusTreeNodes. It is used when
 * aggregating multiple SavedFrame allocation stack keys into a tree of many
 * CensusTreeNodes. Each stack may share older frames, and we want to preserve
 * this sharing when converting to CensusTreeNode, so before creating a new
 * CensusTreeNode, we look for an existing one in one of our CensusTreeNodeCaches.
 */
function CensusTreeNodeCache() {}
CensusTreeNodeCache.prototype = null;

/**
 * The value of a single entry stored in a CensusTreeNodeCache. It is a pair of
 * the CensusTreeNode for this cache value, and the subsequent
 * CensusTreeNodeCache for this node's children.
 *
 * @param {SavedFrame} frame
 *        The frame being cached.
 */
function CensusTreeNodeCacheValue() {
  // The CensusTreeNode for this cache value.
  this.node = undefined;
  // The CensusTreeNodeCache for this frame's children.
  this.children = undefined;
}

CensusTreeNodeCacheValue.prototype = null;

/**
 * Create a unique string for the given SavedFrame (ignoring the frame's parent
 * chain) that can be used as a hash to key this frame within a CensusTreeNodeCache.
 *
 * NB: We manually hash rather than using an ES6 Map because we are purposely
 * ignoring the parent chain and wish to consider frames with everything the
 * same except their parents as the same.
 *
 * @param {SavedFrame} frame
 *        The SavedFrame object we would like to lookup in or insert into a
 *        CensusTreeNodeCache.
 *
 * @returns {String}
 *          The unique string that can be used as a key in a CensusTreeNodeCache.
 */
CensusTreeNodeCache.hashFrame = function (frame) {
  // eslint-disable-next-line max-len
  return `FRAME,${frame.functionDisplayName},${frame.source},${frame.line},${frame.column},${frame.asyncCause}`;
};

/**
 * Create a unique string for the given CensusTreeNode **with regards to
 * siblings at the current depth of the tree, not within the whole tree.** It
 * can be used as a hash to key this node within a CensusTreeNodeCache.
 *
 * @param {CensusTreeNode} node
 *        The node we would like to lookup in or insert into a cache.
 *
 * @returns {String}
 *          The unique string that can be used as a key in a CensusTreeNodeCache.
 */
CensusTreeNodeCache.hashNode = function (node) {
  return isSavedFrame(node.name)
    ? CensusTreeNodeCache.hashFrame(node.name)
    : `NODE,${node.name}`;
};

/**
 * Insert the given CensusTreeNodeCacheValue whose node.name is a SavedFrame
 * object in the given cache.
 *
 * @param {CensusTreeNodeCache} cache
 * @param {CensusTreeNodeCacheValue} value
 */
CensusTreeNodeCache.insertFrame = function (cache, value) {
  cache[CensusTreeNodeCache.hashFrame(value.node.name)] = value;
};

/**
 * Insert the given value in the cache.
 *
 * @param {CensusTreeNodeCache} cache
 * @param {CensusTreeNodeCacheValue} value
 */
CensusTreeNodeCache.insertNode = function (cache, value) {
  if (isSavedFrame(value.node.name)) {
    CensusTreeNodeCache.insertFrame(cache, value);
  } else {
    cache[CensusTreeNodeCache.hashNode(value.node)] = value;
  }
};

/**
 * Lookup `frame` in `cache` and return its value if it exists.
 *
 * @param {CensusTreeNodeCache} cache
 * @param {SavedFrame} frame
 *
 * @returns {undefined|CensusTreeNodeCacheValue}
 */
CensusTreeNodeCache.lookupFrame = function (cache, frame) {
  return cache[CensusTreeNodeCache.hashFrame(frame)];
};

/**
 * Lookup `node` in `cache` and return its value if it exists.
 *
 * @param {CensusTreeNodeCache} cache
 * @param {CensusTreeNode} node
 *
 * @returns {undefined|CensusTreeNodeCacheValue}
 */
CensusTreeNodeCache.lookupNode = function (cache, node) {
  return isSavedFrame(node.name)
    ? CensusTreeNodeCache.lookupFrame(cache, node.name)
    : cache[CensusTreeNodeCache.hashNode(node)];
};

/**
 * Add `child` to `parent`'s set of children and store the parent ID
 * on the child.
 *
 * @param {CensusTreeNode} parent
 * @param {CensusTreeNode} child
 */
function addChild(parent, child) {
  if (!parent.children) {
    parent.children = [];
  }
  child.parent = parent.id;
  parent.children.push(child);
}

/**
 * Get an array of each frame in the provided stack.
 *
 * @param {SavedFrame} stack
 * @returns {Array<SavedFrame>}
 */
function getArrayOfFrames(stack) {
  const frames = [];
  let frame = stack;
  while (frame) {
    frames.push(frame);
    frame = frame.parent;
  }
  frames.reverse();
  return frames;
}

/**
 * Given an `edge` to a sub-`report` whose structure is described by
 * `breakdown`, create a CensusTreeNode tree.
 *
 * @param {Object} breakdown
 *        The breakdown specifying the structure of the given report.
 *
 * @param {Object} report
 *        The census report.
 *
 * @param {null|String|SavedFrame} edge
 *        The edge leading to this report from the parent report.
 *
 * @param {CensusTreeNodeCache} cache
 *        The cache of CensusTreeNodes we have already made for the siblings of
 *        the node being created. The existing nodes are reused when possible.
 *
 * @param {Object} outParams
 *        The return values are attached to this object after this function
 *        returns. Because we create a CensusTreeNode for each frame in a
 *        SavedFrame stack edge, there may multiple nodes per sub-report.
 *
 *          - top: The deepest node in the CensusTreeNode subtree created.
 *
 *          - bottom: The shallowest node in the CensusTreeNode subtree created.
 *                    This is null if the shallowest node in the subtree was
 *                    found in the `cache` and reused.
 *
 *        Note that top and bottom are not necessarily different. In the case
 *        where there is a 1:1 correspondence between an edge in the report and
 *        a CensusTreeNode, top and bottom refer to the same node.
 */
function makeCensusTreeNodeSubTree(breakdown, report, edge, cache, outParams) {
  if (!isSavedFrame(edge)) {
    const node = new CensusTreeNode(edge);
    outParams.top = outParams.bottom = node;
    return;
  }

  const frames = getArrayOfFrames(edge);
  let currentCache = cache;
  let prevNode;
  for (let i = 0, length = frames.length; i < length; i++) {
    const frame = frames[i];

    // Get or create the CensusTreeNodeCacheValue for this frame. If we already
    // have a CensusTreeNodeCacheValue (and hence a CensusTreeNode) for this
    // frame, we don't need to add the node to the previous node's children as
    // we have already done that. If we don't have a CensusTreeNodeCacheValue
    // and CensusTreeNode for this frame, then create one and make sure to hook
    // it up as a child of the previous node.
    let isNewNode = false;
    let val = CensusTreeNodeCache.lookupFrame(currentCache, frame);
    if (!val) {
      isNewNode = true;
      val = new CensusTreeNodeCacheValue();
      val.node = new CensusTreeNode(frame);

      CensusTreeNodeCache.insertFrame(currentCache, val);
      if (prevNode) {
        addChild(prevNode, val.node);
      }
    }

    if (i === 0) {
      outParams.bottom = isNewNode ? val.node : null;
    }
    if (i === length - 1) {
      outParams.top = val.node;
    }

    prevNode = val.node;

    if (i !== length - 1 && !val.children) {
      // This is not the last frame and therefore this node will have
      // children, which we must cache.
      val.children = new CensusTreeNodeCache();
    }

    currentCache = val.children;
  }
}

/**
 * A Visitor that walks a census report and creates the corresponding
 * CensusTreeNode tree.
 */
function CensusTreeNodeVisitor() {
  // The root of the resulting CensusTreeNode tree.
  this._root = null;

  // The stack of CensusTreeNodes that we are in the process of building while
  // walking the census report.
  this._nodeStack = [];

  // To avoid unnecessary allocations, we reuse the same out parameter object
  // passed to `makeCensusTreeNodeSubTree` every time we call it.
  this._outParams = {
    top: null,
    bottom: null,
  };

  // The stack of `CensusTreeNodeCache`s that we use to aggregate many
  // SavedFrame stacks into a single CensusTreeNode tree.
  this._cacheStack = [new CensusTreeNodeCache()];

  // The current index in the DFS of the census report tree.
  this._index = -1;
}

CensusTreeNodeVisitor.prototype = Object.create(Visitor);

/**
 * Create the CensusTreeNode subtree for this sub-report and link it to the
 * parent CensusTreeNode.
 *
 * @overrides Visitor.prototype.enter
 */
CensusTreeNodeVisitor.prototype.enter = function (breakdown, report, edge) {
  this._index++;

  const cache = this._cacheStack[this._cacheStack.length - 1];
  makeCensusTreeNodeSubTree(breakdown, report, edge, cache, this._outParams);
  const { top, bottom } = this._outParams;

  if (!this._root) {
    this._root = bottom;
  } else if (bottom) {
    addChild(this._nodeStack[this._nodeStack.length - 1], bottom);
  }

  this._cacheStack.push(new CensusTreeNodeCache());
  this._nodeStack.push(top);
};

function values(cache) {
  return Object.keys(cache).map(k => cache[k]);
}

function isNonEmpty(node) {
  return (
    (node.children !== undefined && node.children.length) ||
    node.bytes !== 0 ||
    node.count !== 0
  );
}

/**
 * We have finished adding children to the CensusTreeNode subtree for the
 * current sub-report. Make sure that the children are sorted for every node in
 * the subtree.
 *
 * @overrides Visitor.prototype.exit
 */
CensusTreeNodeVisitor.prototype.exit = function () {
  // Ensure all children are sorted and have their counts/bytes aggregated. We
  // only need to consider cache children here, because other children
  // correspond to other sub-reports and we already fixed them up in an earlier
  // invocation of `exit`.

  function dfs(node, childrenCache) {
    if (childrenCache) {
      const childValues = values(childrenCache);
      for (let i = 0, length = childValues.length; i < length; i++) {
        dfs(childValues[i].node, childValues[i].children);
      }
    }

    node.totalCount = node.count;
    node.totalBytes = node.bytes;

    if (node.children) {
      // Prune empty leaves.
      node.children = node.children.filter(isNonEmpty);

      node.children.sort(compareByTotal);

      for (let i = 0, length = node.children.length; i < length; i++) {
        node.totalCount += node.children[i].totalCount;
        node.totalBytes += node.children[i].totalBytes;
      }
    }
  }

  const top = this._nodeStack.pop();
  const cache = this._cacheStack.pop();
  dfs(top, cache);
};

/**
 * @overrides Visitor.prototype.count
 */
CensusTreeNodeVisitor.prototype.count = function (breakdown, report) {
  const node = this._nodeStack[this._nodeStack.length - 1];
  node.reportLeafIndex = this._index;

  if (breakdown.count) {
    node.count = report.count;
  }

  if (breakdown.bytes) {
    node.bytes = report.bytes;
  }
};

/**
 * Get the root of the resulting CensusTreeNode tree.
 *
 * @returns {CensusTreeNode}
 */
CensusTreeNodeVisitor.prototype.root = function () {
  if (!this._root) {
    throw new Error(
      "Attempt to get the root before walking the census report!"
    );
  }

  if (this._nodeStack.length) {
    throw new Error("Attempt to get the root while walking the census report!");
  }

  return this._root;
};

/**
 * Create a single, uninitialized CensusTreeNode.
 *
 * @param {null|String|SavedFrame} name
 */
function CensusTreeNode(name) {
  // Display name for this CensusTreeNode. Either null, a string, or a
  // SavedFrame.
  this.name = name;

  // The number of bytes occupied by matching things in the heap snapshot.
  this.bytes = 0;

  // The sum of `this.bytes` and `child.totalBytes` for each child in
  // `this.children`.
  this.totalBytes = 0;

  // The number of things in the heap snapshot that match this node in the
  // census tree.
  this.count = 0;

  // The sum of `this.count` and `child.totalCount` for each child in
  // `this.children`.
  this.totalCount = 0;

  // An array of this node's children, or undefined if it has no children.
  this.children = undefined;

  // The unique ID of this node.
  this.id = ++censusTreeNodeIdCounter;

  // If present, the unique ID of this node's parent. If this node does not have
  // a parent, then undefined.
  this.parent = undefined;

  // The `reportLeafIndex` property allows mapping a CensusTreeNode node back to
  // a leaf in the census report it was generated from. It is always one of the
  // following variants:
  //
  // * A `Number` index pointing a leaf report in a pre-order DFS traversal of
  //   this CensusTreeNode's census report.
  //
  // * A `Set` object containing such indices, when this is part of an inverted
  //   CensusTreeNode tree and multiple leaves in the report map onto this node.
  //
  // * Finally, `undefined` when no leaves in the census report correspond with
  //   this node.
  //
  // The first and third cases are the common cases. The second case is rather
  // uncommon, and to avoid doubling the number of allocations when creating
  // CensusTreeNode trees, and objects that get structured cloned when sending
  // such trees from the HeapAnalysesWorker to the main thread, we only allocate
  // a Set object once a node actually does have multiple leaves it corresponds
  // to.
  this.reportLeafIndex = undefined;
}

CensusTreeNode.prototype = null;

/**
 * Compare the given nodes by their `totalBytes` properties, and breaking ties
 * with the `totalCount`, `bytes`, and `count` properties (in that order).
 *
 * @param {CensusTreeNode} node1
 * @param {CensusTreeNode} node2
 *
 * @returns {Number}
 *          A number suitable for using with Array.prototype.sort.
 */
function compareByTotal(node1, node2) {
  return (
    Math.abs(node2.totalBytes) - Math.abs(node1.totalBytes) ||
    Math.abs(node2.totalCount) - Math.abs(node1.totalCount) ||
    Math.abs(node2.bytes) - Math.abs(node1.bytes) ||
    Math.abs(node2.count) - Math.abs(node1.count)
  );
}

/**
 * Compare the given nodes by their `bytes` properties, and breaking ties with
 * the `count`, `totalBytes`, and `totalCount` properties (in that order).
 *
 * @param {CensusTreeNode} node1
 * @param {CensusTreeNode} node2
 *
 * @returns {Number}
 *          A number suitable for using with Array.prototype.sort.
 */
function compareBySelf(node1, node2) {
  return (
    Math.abs(node2.bytes) - Math.abs(node1.bytes) ||
    Math.abs(node2.count) - Math.abs(node1.count) ||
    Math.abs(node2.totalBytes) - Math.abs(node1.totalBytes) ||
    Math.abs(node2.totalCount) - Math.abs(node1.totalCount)
  );
}

/**
 * Given a parent cache value from a tree we are building and a child node from
 * a tree we are basing the new tree off of, if we already have a corresponding
 * node in the parent's children cache, merge this node's counts with
 * it. Otherwise, create the corresponding node, add it to the parent's children
 * cache, and create the parent->child edge.
 *
 * @param {CensusTreeNodeCacheValue} parentCachevalue
 * @param {CensusTreeNode} node
 *
 * @returns {CensusTreeNodeCacheValue}
 *          The new or extant child node's corresponding cache value.
 */
function insertOrMergeNode(parentCacheValue, node) {
  if (!parentCacheValue.children) {
    parentCacheValue.children = new CensusTreeNodeCache();
  }

  let val = CensusTreeNodeCache.lookupNode(parentCacheValue.children, node);

  if (val) {
    // When inverting, it is possible that multiple leaves in the census report
    // get merged into a single CensusTreeNode node. When this occurs, switch
    // from a single index to a set of indices.
    if (
      val.node.reportLeafIndex !== undefined &&
      val.node.reportLeafIndex !== node.reportLeafIndex
    ) {
      if (typeof val.node.reportLeafIndex === "number") {
        const oldIndex = val.node.reportLeafIndex;
        val.node.reportLeafIndex = new Set();
        val.node.reportLeafIndex.add(oldIndex);
        val.node.reportLeafIndex.add(node.reportLeafIndex);
      } else {
        val.node.reportLeafIndex.add(node.reportLeafIndex);
      }
    }

    val.node.count += node.count;
    val.node.bytes += node.bytes;
  } else {
    val = new CensusTreeNodeCacheValue();

    val.node = new CensusTreeNode(node.name);
    val.node.reportLeafIndex = node.reportLeafIndex;
    val.node.count = node.count;
    val.node.totalCount = node.totalCount;
    val.node.bytes = node.bytes;
    val.node.totalBytes = node.totalBytes;

    addChild(parentCacheValue.node, val.node);
    CensusTreeNodeCache.insertNode(parentCacheValue.children, val);
  }

  return val;
}

/**
 * Given an un-inverted CensusTreeNode tree, return the corresponding inverted
 * CensusTreeNode tree. The input tree is not modified. The resulting inverted
 * tree is sorted by self bytes rather than by total bytes.
 *
 * @param {CensusTreeNode} tree
 *        The un-inverted tree.
 *
 * @returns {CensusTreeNode}
 *          The corresponding inverted tree.
 */
function invert(tree) {
  const inverted = new CensusTreeNodeCacheValue();
  inverted.node = new CensusTreeNode(null);

  // Do a depth-first search of the un-inverted tree. As we reach each leaf,
  // take the path from the old root to the leaf, reverse that path, and add it
  // to the new, inverted tree's root.

  const path = [];
  (function addInvertedPaths(node) {
    path.push(node);

    if (node.children) {
      for (let i = 0, length = node.children.length; i < length; i++) {
        addInvertedPaths(node.children[i]);
      }
    } else {
      // We found a leaf node, add the reverse path to the inverted tree.
      let currentCacheValue = inverted;
      for (let i = path.length - 1; i >= 0; i--) {
        currentCacheValue = insertOrMergeNode(currentCacheValue, path[i]);
      }
    }

    path.pop();
  })(tree);

  // Ensure that the root node always has the totals.
  inverted.node.totalBytes = tree.totalBytes;
  inverted.node.totalCount = tree.totalCount;

  return inverted.node;
}

/**
 * Given a CensusTreeNode tree and predicate function, create the tree
 * containing only the nodes in any path `(node_0, node_1, ..., node_n-1)` in
 * the given tree where `predicate(node_j)` is true for `0 <= j < n`, `node_0`
 * is the given tree's root, and `node_n-1` is a leaf in the given tree. The
 * given tree is left unmodified.
 *
 * @param {CensusTreeNode} tree
 * @param {Function} predicate
 *
 * @returns {CensusTreeNode}
 */
function filter(tree, predicate) {
  const filtered = new CensusTreeNodeCacheValue();
  filtered.node = new CensusTreeNode(null);

  // Do a DFS over the given tree. If the predicate returns true for any node,
  // add that node and its whole subtree to the filtered tree.

  const path = [];
  let match = false;

  function addMatchingNodes(node) {
    path.push(node);

    const oldMatch = match;
    if (!match && predicate(node)) {
      match = true;
    }

    if (node.children) {
      for (let i = 0, length = node.children.length; i < length; i++) {
        addMatchingNodes(node.children[i]);
      }
    } else if (match) {
      // We found a matching leaf node, add it to the filtered tree.
      let currentCacheValue = filtered;
      for (let i = 0, length = path.length; i < length; i++) {
        currentCacheValue = insertOrMergeNode(currentCacheValue, path[i]);
      }
    }

    match = oldMatch;
    path.pop();
  }

  if (tree.children) {
    for (let i = 0, length = tree.children.length; i < length; i++) {
      addMatchingNodes(tree.children[i]);
    }
  }

  filtered.node.count = tree.count;
  filtered.node.totalCount = tree.totalCount;
  filtered.node.bytes = tree.bytes;
  filtered.node.totalBytes = tree.totalBytes;

  return filtered.node;
}

/**
 * Given a filter string, return a predicate function that takes a node and
 * returns true iff the node matches the filter.
 *
 * @param {String} filterString
 * @returns {Function}
 */
function makeFilterPredicate(filterString) {
  return function (node) {
    if (!node.name) {
      return false;
    }

    if (isSavedFrame(node.name)) {
      return (
        node.name.source.includes(filterString) ||
        (node.name.functionDisplayName || "").includes(filterString) ||
        (node.name.asyncCause || "").includes(filterString)
      );
    }

    return String(node.name).includes(filterString);
  };
}

/**
 * Takes a report from a census (`dbg.memory.takeCensus()`) and the breakdown
 * used to generate the census and returns a structure used to render
 * a tree to display the data.
 *
 * Returns a recursive "CensusTreeNode" object, looking like:
 *
 * CensusTreeNode = {
 *   // `children` if it exists, is sorted by `bytes`, if they are leaf nodes.
 *   children: ?[<CensusTreeNode...>],
 *   name: <?String>
 *   count: <?Number>
 *   bytes: <?Number>
 *   id: <?Number>
 *   parent: <?Number>
 * }
 *
 * @param {Object} breakdown
 *        The breakdown used to generate the census report.
 *
 * @param {Object} report
 *        The census report generated with the specified breakdown.
 *
 * @param {Object} options
 *        Configuration options.
 *          - invert: Whether to invert the resulting tree or not. Defaults to
 *                    false, ie uninverted.
 *
 * @returns {CensusTreeNode}
 */
exports.censusReportToCensusTreeNode = function (
  breakdown,
  report,
  options = {
    invert: false,
    filter: null,
  }
) {
  // Reset the counter so that turning the same census report into a
  // CensusTreeNode tree repeatedly is idempotent.
  censusTreeNodeIdCounter = 0;

  const visitor = new CensusTreeNodeVisitor();
  walk(breakdown, report, visitor);
  let result = visitor.root();

  if (options.invert) {
    result = invert(result);
  }

  if (typeof options.filter === "string") {
    result = filter(result, makeFilterPredicate(options.filter));
  }

  // If the report is a delta report that was generated by diffing two other
  // reports, make sure to use the basis totals rather than the totals of the
  // difference.
  if (typeof report[basisTotalBytes] === "number") {
    result.totalBytes = report[basisTotalBytes];
    result.totalCount = report[basisTotalCount];
  }

  // Inverting and filtering could have messed up the sort order, so do a
  // depth-first search of the tree and ensure that siblings are sorted.
  const comparator = options.invert ? compareBySelf : compareByTotal;
  (function ensureSorted(node) {
    if (node.children) {
      node.children.sort(comparator);
      for (let i = 0, length = node.children.length; i < length; i++) {
        ensureSorted(node.children[i]);
      }
    }
  })(result);

  return result;
};