Extending the NthIndexCache to support caching for the type of index.

Source/core/dom/NthIndexCache.h

Index: Source/core/dom/NthIndexCache.h
diff --git a/Source/core/dom/NthIndexCache.h b/Source/core/dom/NthIndexCache.h
index 94f715957f73fd388bf8c6d8ac40ea0760523251..651548a7acc8ff204b77055ecb19b8f53da3e0ea 100644
--- a/Source/core/dom/NthIndexCache.h
+++ b/Source/core/dom/NthIndexCache.h
@@ -24,7 +24,9 @@ public:
     ~NthIndexCache();
 
     inline unsigned nthChildIndex(Element&);
+    inline unsigned nthChildIndexOfType(Element&, const QualifiedName&);
     inline unsigned nthLastChildIndex(Element&);
+    inline unsigned nthLastChildIndexOfType(Element&, const QualifiedName&);
 
 private:
     class NthIndexData final : public NoBaseWillBeGarbageCollected<NthIndexData> {
@@ -34,9 +36,12 @@ private:
         NthIndexData() { }
 
         inline unsigned nthIndex(Element&);
+        inline unsigned nthIndexOfType(Element&, const QualifiedName&);
         inline unsigned nthLastIndex(Element&);
+        inline unsigned nthLastIndexOfType(Element&, const QualifiedName&);
 
         unsigned cacheNthIndices(Element&);
+        unsigned cacheNthIndicesOfType(Element&, const QualifiedName&);
 
         WillBeHeapHashMap<RawPtrWillBeMember<Element>, unsigned> m_elementIndexMap;
         unsigned m_count = 0;
@@ -44,12 +49,30 @@ private:
         DECLARE_TRACE();
     };
 
-    NthIndexData& ensureNthIndexDataFor(Node&);
+    class HasTagName {

[esprehn, 2015/04/30 04:55:05]

This already exists elsewhere in the code. Just use that? Also I don't think all
this needs to be inline. We should move all the methods to be out of line in a
separate patch.

+    public:
+        explicit HasTagName(const QualifiedName& tagName) : m_tagName(tagName) { }
+        bool operator() (const Element& element) const { return element.hasTagName(m_tagName); }
+    private:
+        const QualifiedName m_tagName;
+    };
+
     inline unsigned nthIndex(Element&);
 
     using ParentMap = WillBeHeapHashMap<RefPtrWillBeMember<Node>, OwnPtrWillBeMember<NthIndexData>>;
-
     OwnPtrWillBeMember<ParentMap> m_parentMap;
+
+    using ElementTagNameAndNthIndexMap = WillBeHeapHashMap<String, OwnPtrWillBeMember<NthIndexData>>;
+    OwnPtrWillBeMember<ElementTagNameAndNthIndexMap> m_elementTagNameAndNthIndexMap;
+
+    using ParentMapForType = WillBeHeapHashMap<RefPtrWillBeMember<Node>, OwnPtrWillBeMember<ElementTagNameAndNthIndexMap>>;
+    OwnPtrWillBeMember<ParentMapForType> m_parentMapForType;
+
+
+    NthIndexData& ensureNthIndexDataFor(Node&);
+    NthIndexCache::ElementTagNameAndNthIndexMap& ensureElementTagNameAndNthIndexMapForType(Node&);
+
+    NthIndexCache::NthIndexData& nthIndexDataWithTagName(ElementTagNameAndNthIndexMap&, Element&);
     RawPtrWillBeMember<Document> m_document;
     uint64_t m_domTreeVersion;
 };
@@ -68,24 +91,56 @@ inline unsigned NthIndexCache::NthIndexData::nthIndex(Element& element)
     return index;
 }
 
+inline unsigned NthIndexCache::NthIndexData::nthIndexOfType(Element& element, const QualifiedName& type)
+{
+    if (!m_count)

[esprehn, 2015/04/30 04:55:05]

This will need the same pseudo element fix from rune@ other patch.

+        return cacheNthIndicesOfType(element, type);
+    unsigned index = 0;
+    for (Element* sibling = &element; sibling; sibling = ElementTraversal::previousSibling(*sibling, HasTagName(type)), index++) {
+        auto it = m_elementIndexMap.find(sibling);
+        if (it != m_elementIndexMap.end())
+            return it->value + index;
+    }
+    return index;
+}
+
 inline unsigned NthIndexCache::NthIndexData::nthLastIndex(Element& element)
 {
     unsigned index = nthIndex(element);
     return m_count - index + 1;
 }
 
+inline unsigned NthIndexCache::NthIndexData::nthLastIndexOfType(Element& element, const QualifiedName& type)
+{
+    unsigned index = nthIndexOfType(element, type);
+    return m_count - index + 1;
+}
+
 inline unsigned NthIndexCache::nthChildIndex(Element& element)
 {
     ASSERT(element.parentNode());
     return ensureNthIndexDataFor(*element.parentNode()).nthIndex(element);
 }
 
+inline unsigned NthIndexCache::nthChildIndexOfType(Element& element, const QualifiedName& type)
+{
+    ASSERT(element.parentNode());
+    return nthIndexDataWithTagName(ensureElementTagNameAndNthIndexMapForType(*element.parentNode()), element).nthIndexOfType(element, type);

[esprehn, 2015/04/30 04:55:05]

nthIndexDataWithTagName should call ensureElementTagNameAndNthIndexMapForType
internally.

+}
+
 inline unsigned NthIndexCache::nthLastChildIndex(Element& element)
 {
     ASSERT(element.parentNode());
     return ensureNthIndexDataFor(*element.parentNode()).nthLastIndex(element);
 }
 
+inline unsigned NthIndexCache::nthLastChildIndexOfType(Element& element, const QualifiedName& type)
+{
+    ASSERT(element.parentNode());
+    return nthIndexDataWithTagName(ensureElementTagNameAndNthIndexMapForType(*element.parentNode()), element).nthLastIndexOfType(element, type);

[esprehn, 2015/04/30 04:55:05]

ditto

+}
+
+
 } // namespace blink
 
 #endif // NthIndexCache_h