Remove complexity related to m_cachedElementsArrayOffset from LiveNodeListBase

Source/core/html/HTMLFormControlsCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 19 matching lines @@
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 // Since the collections are to be "live", we have to do the
 // calculation every time if anything has changed.
 
 HTMLFormControlsCollection::HTMLFormControlsCollection(Node* ownerNode)
     : HTMLCollection(ownerNode, FormControls, OverridesItemAfter)
+    , m_cachedElement(0)
+    , m_cachedElementOffsetInArray(0)
 {
     ASSERT(ownerNode->hasTagName(formTag) || ownerNode->hasTagName(fieldsetTag));
     ScriptWrappable::init(this);
 }
 
 PassRefPtr<HTMLFormControlsCollection> HTMLFormControlsCollection::create(Node* ownerNode, CollectionType)
 {
     return adoptRef(new HTMLFormControlsCollection(ownerNode));
 }
 
 HTMLFormControlsCollection::~HTMLFormControlsCollection()
 {
 }
 
 const Vector<FormAssociatedElement*>& HTMLFormControlsCollection::formControlElements() const
 {
     ASSERT(ownerNode());
     ASSERT(ownerNode()->hasTagName(formTag) || ownerNode()->hasTagName(fieldsetTag));
     if (ownerNode()->hasTagName(formTag))
         return toHTMLFormElement(ownerNode())->associatedElements();
     return toHTMLFieldSetElement(ownerNode())->associatedElements();
 }
 
 const Vector<HTMLImageElement*>& HTMLFormControlsCollection::formImageElements() const
 {
     ASSERT(ownerNode());
     return toHTMLFormElement(ownerNode())->imageElements();
 }
 
-Element* HTMLFormControlsCollection::virtualItemAfter(unsigned& offset, Element* previousItem) const
+static unsigned findFormAssociatedElement(const Vector<FormAssociatedElement*>& associatedElements, Element* element)
 {
-    const Vector<FormAssociatedElement*>& elementsArray = formControlElements();
-    if (previousItem)
-        offset++;
-    while (offset < elementsArray.size()) {
-        FormAssociatedElement* element = elementsArray[offset];
-        if (element->isEnumeratable())
-            return toHTMLElement(element);
-        offset++;
+    unsigned i = 0;
+    for (; i < associatedElements.size(); ++i) {
+        FormAssociatedElement* associatedElement = associatedElements[i];
+        if (associatedElement->isEnumeratable() && toHTMLElement(associatedElement) == element)
+            break;
+    }
+    return i;
+}
+
+Element* HTMLFormControlsCollection::virtualItemAfter(Element* previous) const
+{
+    const Vector<FormAssociatedElement*>& associatedElements = formControlElements();
+    unsigned offset;
+    if (!previous)
+        offset = 0;
+    else if (m_cachedElement == previous)
+        offset = m_cachedElementOffsetInArray + 1;
+    else
+        offset = findFormAssociatedElement(associatedElements, previous) + 1;
+
+    for (unsigned i = offset; i < associatedElements.size(); ++i) {
+        FormAssociatedElement* associatedElement = associatedElements[i];
+        if (associatedElement->isEnumeratable()) {
+            m_cachedElement = toHTMLElement(associatedElement);
+            m_cachedElementOffsetInArray = i;
+            return m_cachedElement;
+        }
     }
     return 0;
 }
 
+void HTMLFormControlsCollection::invalidateCache() const
+{
+    HTMLCollection::invalidateCache();
+    m_cachedElement = 0;
+    m_cachedElementOffsetInArray = 0;
+}
+
 static HTMLElement* firstNamedItem(const Vector<FormAssociatedElement*>& elementsArray,
     const Vector<HTMLImageElement*>* imageElementsArray, const QualifiedName& attrName, const String& name)
 {
     ASSERT(attrName == idAttr || attrName == nameAttr);
 
     for (unsigned i = 0; i < elementsArray.size(); ++i) {
         HTMLElement* element = toHTMLElement(elementsArray[i]);
         if (elementsArray[i]->isEnumeratable() && element->fastGetAttribute(attrName) == name)
             return element;
     }
@@ skipping 78 matching lines @@
         returnValue1Enabled = true;
         returnValue1 = namedItems.at(0);
         return;
     }
 
     returnValue0Enabled = true;
     returnValue0 = this->ownerNode()->radioNodeList(name);
 }
 
 }