text: /*
   * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
   * Copyright (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
   * Copyright (C) 2001 Peter Kelly (pmk@post.com)
   * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
   * Copyright (C) 2004-2019 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.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Library General Public License for more details.
   *
   * You should have received a copy of the GNU Library General Public License
   * along with this library; see the file COPYING.LIB.  If not, write to
   * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   * Boston, MA 02110-1301, USA.
   *
   */
  
  #pragma once
  
  #include "ExceptionOr.h"
  #include "NodeFilter.h"
  #include "ScriptWrappable.h"
  #include "Traversal.h"
  #include <wtf/IsoMalloc.h>
  #include <wtf/RefCounted.h>
  
  namespace WebCore {
  
  class TreeWalker final : public ScriptWrappable, public RefCounted<TreeWalker>, public NodeIteratorBase {
      WTF_MAKE_ISO_ALLOCATED_EXPORT(TreeWalker, WEBCORE_EXPORT);
  public:
      static Ref<TreeWalker> create(Node& rootNode, unsigned long whatToShow, RefPtr<NodeFilter>&& filter)
      {
          return adoptRef(*new TreeWalker(rootNode, whatToShow, WTFMove(filter)));
      }                            
  
      Node& currentNode() { return m_current.get(); }
      const Node& currentNode() const { return m_current.get(); }
  
      WEBCORE_EXPORT void setCurrentNode(Node&);
  
      WEBCORE_EXPORT ExceptionOr<Node*> parentNode();
      WEBCORE_EXPORT ExceptionOr<Node*> firstChild();
      WEBCORE_EXPORT ExceptionOr<Node*> lastChild();
      WEBCORE_EXPORT ExceptionOr<Node*> previousSibling();
      WEBCORE_EXPORT ExceptionOr<Node*> nextSibling();
      WEBCORE_EXPORT ExceptionOr<Node*> previousNode();
      WEBCORE_EXPORT ExceptionOr<Node*> nextNode();
  
  private:
      TreeWalker(Node&, unsigned long whatToShow, RefPtr<NodeFilter>&&);
  
      enum class SiblingTraversalType { Previous, Next };
      template<SiblingTraversalType> ExceptionOr<Node*> traverseSiblings();
      
      Node* setCurrent(Ref<Node>&&);
  
      Ref<Node> m_current;
  };
  
  } // namespace WebCore
  