1 files changed, 140 insertions, 0 deletions
diff --git a/devtools/shared/heapsnapshot/DominatorTree.cpp b/devtools/shared/heapsnapshot/DominatorTree.cpp
new file mode 100644
index 000000000..e53c196cf
--- /dev/null
+++ b/devtools/shared/heapsnapshot/DominatorTree.cpp
@@ -0,0 +1,140 @@
+/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* 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/. */
+
+#include "mozilla/devtools/DominatorTree.h"
+#include "mozilla/dom/DominatorTreeBinding.h"
+
+namespace mozilla {
+namespace devtools {
+
+dom::Nullable<uint64_t>
+DominatorTree::GetRetainedSize(uint64_t aNodeId, ErrorResult& aRv)
+{
+  JS::ubi::Node::Id id(aNodeId);
+  auto node = mHeapSnapshot->getNodeById(id);
+  if (node.isNothing())
+    return dom::Nullable<uint64_t>();
+
+  auto mallocSizeOf = GetCurrentThreadDebuggerMallocSizeOf();
+  JS::ubi::Node::Size size = 0;
+  if (!mDominatorTree.getRetainedSize(*node, mallocSizeOf, size)) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return dom::Nullable<uint64_t>();
+  }
+
+  MOZ_ASSERT(size != 0,
+             "The node should not have been unknown since we got it from the heap snapshot.");
+  return dom::Nullable<uint64_t>(size);
+}
+
+struct NodeAndRetainedSize
+{
+  JS::ubi::Node mNode;
+  JS::ubi::Node::Size mSize;
+
+  NodeAndRetainedSize(const JS::ubi::Node& aNode, JS::ubi::Node::Size aSize)
+    : mNode(aNode)
+    , mSize(aSize)
+  { }
+
+  struct Comparator
+  {
+    static bool
+    Equals(const NodeAndRetainedSize& aLhs, const NodeAndRetainedSize& aRhs)
+    {
+      return aLhs.mSize == aRhs.mSize;
+    }
+
+    static bool
+    LessThan(const NodeAndRetainedSize& aLhs, const NodeAndRetainedSize& aRhs)
+    {
+      // Use > because we want to sort from greatest to least retained size.
+      return aLhs.mSize > aRhs.mSize;
+    }
+  };
+};
+
+void
+DominatorTree::GetImmediatelyDominated(uint64_t aNodeId,
+                                       dom::Nullable<nsTArray<uint64_t>>& aOutResult,
+                                       ErrorResult& aRv)
+{
+  MOZ_ASSERT(aOutResult.IsNull());
+
+  JS::ubi::Node::Id id(aNodeId);
+  Maybe<JS::ubi::Node> node = mHeapSnapshot->getNodeById(id);
+  if (node.isNothing())
+    return;
+
+  // Get all immediately dominated nodes and their retained sizes.
+  MallocSizeOf mallocSizeOf = GetCurrentThreadDebuggerMallocSizeOf();
+  Maybe<JS::ubi::DominatorTree::DominatedSetRange> range = mDominatorTree.getDominatedSet(*node);
+  MOZ_ASSERT(range.isSome(), "The node should be known, since we got it from the heap snapshot.");
+  size_t length = range->length();
+  nsTArray<NodeAndRetainedSize> dominatedNodes(length);
+  for (const JS::ubi::Node& dominatedNode : *range) {
+    JS::ubi::Node::Size retainedSize = 0;
+    if (NS_WARN_IF(!mDominatorTree.getRetainedSize(dominatedNode, mallocSizeOf, retainedSize))) {
+      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+      return;
+    }
+    MOZ_ASSERT(retainedSize != 0,
+               "retainedSize should not be zero since we know the node is in the dominator tree.");
+
+    dominatedNodes.AppendElement(NodeAndRetainedSize(dominatedNode, retainedSize));
+  }
+
+  // Sort them by retained size.
+  NodeAndRetainedSize::Comparator comparator;
+  dominatedNodes.Sort(comparator);
+
+  // Fill the result with the nodes' ids.
+  JS::ubi::Node root = mDominatorTree.root();
+  aOutResult.SetValue(nsTArray<uint64_t>(length));
+  for (const NodeAndRetainedSize& entry : dominatedNodes) {
+    // The root dominates itself, but we don't want to expose that to JS.
+    if (entry.mNode == root)
+      continue;
+
+    aOutResult.Value().AppendElement(entry.mNode.identifier());
+  }
+}
+
+dom::Nullable<uint64_t>
+DominatorTree::GetImmediateDominator(uint64_t aNodeId) const
+{
+  JS::ubi::Node::Id id(aNodeId);
+  Maybe<JS::ubi::Node> node = mHeapSnapshot->getNodeById(id);
+  if (node.isNothing())
+    return dom::Nullable<uint64_t>();
+
+  JS::ubi::Node dominator = mDominatorTree.getImmediateDominator(*node);
+  if (!dominator || dominator == *node)
+    return dom::Nullable<uint64_t>();
+
+  return dom::Nullable<uint64_t>(dominator.identifier());
+}
+
+
+/*** Cycle Collection Boilerplate *****************************************************************/
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(DominatorTree, mParent, mHeapSnapshot)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(DominatorTree)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(DominatorTree)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DominatorTree)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/* virtual */ JSObject*
+DominatorTree::WrapObject(JSContext* aCx, JS::HandleObject aGivenProto)
+{
+  return dom::DominatorTreeBinding::Wrap(aCx, this, aGivenProto);
+}
+
+} // namespace devtools
+} // namespace mozilla