Bug 1384661 - Part 2: Add class nsParentNodeChildContentList. r=smaug

--HG--
extra : rebase_source : d5a5c93ba62c03e01fffaade0fd20b934732e095

dom/base/FragmentOrElement.cpp

@@ -570,6 +570,77 @@ nsAttrChildContentList::IndexOf(nsIContent* aContent)
   return -1;
 }
 
+//----------------------------------------------------------------------
+NS_IMETHODIMP
+nsParentNodeChildContentList::GetLength(uint32_t* aLength)
+{
+  if (!mIsCacheValid && !ValidateCache()) {
+    *aLength = 0;
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(mIsCacheValid);
+
+  *aLength = mCachedChildArray.Length();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsParentNodeChildContentList::Item(uint32_t aIndex, nsIDOMNode** aReturn)
+{
+  nsINode* node = Item(aIndex);
+  if (!node) {
+    *aReturn = nullptr;
+    return NS_OK;
+  }
+
+  return CallQueryInterface(node, aReturn);
+}
+
+nsIContent*
+nsParentNodeChildContentList::Item(uint32_t aIndex)
+{
+  if (!mIsCacheValid && !ValidateCache()) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(mIsCacheValid);
+
+  return mCachedChildArray.SafeElementAt(aIndex, nullptr);
+}
+
+int32_t
+nsParentNodeChildContentList::IndexOf(nsIContent* aContent)
+{
+  if (!mIsCacheValid && !ValidateCache()) {
+    return -1;
+  }
+
+  MOZ_ASSERT(mIsCacheValid);
+
+  return mCachedChildArray.IndexOf(aContent);
+}
+
+bool
+nsParentNodeChildContentList::ValidateCache()
+{
+  MOZ_ASSERT(!mIsCacheValid);
+  MOZ_ASSERT(mCachedChildArray.IsEmpty());
+
+  nsINode* parent = GetParentObject();
+  if (!parent) {
+    return false;
+  }
+
+  for (nsIContent* node = parent->GetFirstChild(); node;
+       node = node->GetNextSibling()) {
+    mCachedChildArray.AppendElement(node);
+  }
+  mIsCacheValid = true;
+
+  return true;
+}
+
 //----------------------------------------------------------------------
 
 nsIHTMLCollection*

dom/base/nsChildContentList.h

@@ -8,7 +8,7 @@
 #define nsChildContentList_h__
 
 #include "nsISupportsImpl.h"
-#include "nsINodeList.h"            // base class
+#include "nsINodeList.h"      // base class
 #include "js/TypeDecls.h"     // for Handle, Value, JSObject, JSContext
 
 class nsIContent;
@@ -20,7 +20,7 @@ class nsINode;
  * and Item to its existing child list.
  * @see nsIDOMNodeList
  */
-class nsAttrChildContentList final : public nsINodeList
+class nsAttrChildContentList : public nsINodeList
 {
 public:
   explicit nsAttrChildContentList(nsINode* aNode)
@@ -42,7 +42,7 @@ public:
   virtual int32_t IndexOf(nsIContent* aContent) override;
   virtual nsIContent* Item(uint32_t aIndex) override;
 
-  void DropReference()
+  virtual void DropReference()
   {
     mNode = nullptr;
   }
@@ -52,13 +52,56 @@ public:
     return mNode;
   }
 
-private:
+protected:
-  ~nsAttrChildContentList() {}
+  virtual ~nsAttrChildContentList() {}
 
+private:
   // The node whose children make up the list.
   // This is a non-owning ref which is safe because it's set to nullptr by
   // DropReference() by the node slots get destroyed.
   nsINode* MOZ_NON_OWNING_REF mNode;
 };
 
+class nsParentNodeChildContentList final : public nsAttrChildContentList
+{
+public:
+  explicit nsParentNodeChildContentList(nsINode* aNode)
+    : nsAttrChildContentList(aNode)
+    , mIsCacheValid(false)
+  {
+    ValidateCache();
+  }
+
+  // nsIDOMNodeList interface
+  NS_DECL_NSIDOMNODELIST
+
+  // nsINodeList interface
+  virtual int32_t IndexOf(nsIContent* aContent) override;
+  virtual nsIContent* Item(uint32_t aIndex) override;
+
+  void DropReference() override
+  {
+    InvalidateCache();
+    nsAttrChildContentList::DropReference();
+  }
+
+  void InvalidateCache()
+  {
+    mIsCacheValid = false;
+    mCachedChildArray.Clear();
+  }
+
+private:
+  ~nsParentNodeChildContentList() {}
+
+  // 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__ */