1 files changed, 83 insertions, 0 deletions
diff --git a/dom/base/nsChildContentList.h b/dom/base/nsChildContentList.h
new file mode 100644
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+++ b/dom/base/nsChildContentList.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef nsChildContentList_h__
+#define nsChildContentList_h__
+
+#include "mozilla/RefPtr.h"
+#include "nsISupportsImpl.h"
+#include "nsINodeList.h"   // base class
+#include "js/TypeDecls.h"  // for Handle, Value, JSObject, JSContext
+
+class nsIContent;
+class nsINode;
+
+/**
+ * Class that implements the nsINodeList interface (a list of children of
+ * the content), by holding a reference to the content and delegating Length
+ * and Item to its existing child list.
+ * @see nsINodeList
+ */
+class nsAttrChildContentList : public nsINodeList {
+ public:
+  explicit nsAttrChildContentList(nsINode* aNode) : mNode(aNode) {}
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SKIPPABLE_WRAPPERCACHE_CLASS(nsAttrChildContentList)
+
+  // nsWrapperCache
+  virtual JSObject* WrapObject(JSContext* cx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  // nsINodeList interface
+  virtual int32_t IndexOf(nsIContent* aContent) override;
+  virtual nsIContent* Item(uint32_t aIndex) override;
+  uint32_t Length() override;
+  nsINode* GetParentObject() final { return mNode; }
+
+  virtual void InvalidateCacheIfAvailable() {}
+
+ protected:
+  virtual ~nsAttrChildContentList() = default;
+
+ private:
+  // The node whose children make up the list.
+  RefPtr<nsINode> mNode;
+};
+
+class nsParentNodeChildContentList final : public nsAttrChildContentList {
+ public:
+  explicit nsParentNodeChildContentList(nsINode* aNode)
+      : nsAttrChildContentList(aNode), mIsCacheValid(false) {
+    ValidateCache();
+  }
+
+  // nsINodeList interface
+  virtual int32_t IndexOf(nsIContent* aContent) override;
+  virtual nsIContent* Item(uint32_t aIndex) override;
+  uint32_t Length() override;
+
+  void InvalidateCacheIfAvailable() final { InvalidateCache(); }
+
+  void InvalidateCache() {
+    mIsCacheValid = false;
+    mCachedChildArray.Clear();
+  }
+
+ private:
+  ~nsParentNodeChildContentList() = default;
+
+  // Return true if validation succeeds, false otherwise
+  bool ValidateCache();
+
+  // Whether cached array of child nodes is valid
+  bool mIsCacheValid;
+
+  // Cached array of child nodes
+  AutoTArray<nsIContent*, 8> mCachedChildArray;
+};
+
+#endif /* nsChildContentList_h__ */