treewalker.h

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// © Copyright 2010 - 2016 BlackTopp Studios Inc.
/* This file is part of The Mezzanine Engine.

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*/
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/*
 *
 * Software, Files, Libraries and all other items referenced in this clause refers only
 * to the contents of this file and associated documentation.
 *
 * Pugixml parser - version 1.0
 * --------------------------------------------------------
 * Copyright © 2006-2012, by Arseny Kapoulkine (arseny.kapoulkine@gmail.com)
 * Report bugs and download new versions at http://pugixml.org/
 *
 * This library is distributed under the MIT License. See notice at the end
 * of this file.
 *
 * This work is based on the pugxml parser, which is:
 * Copyright © 2003, by Kristen Wegner (kristen@tima.net)
 */
#ifndef _xmltreewalker_h
#define _xmltreewalker_h

/// @file
/// @brief This defines the TreeWalker Interface

#include "datatypes.h"
#include "XML/node.h"



namespace Mezzanine
{
    namespace XML
    {
        //////////////////////////////////////////////////////////////////////////////
        /// @brief Used to call a function OnEachNode member of the subtree of nodes descended from a specific node.
        /// @details If you want to do a deep tree traversal, you'll either have to do it via a recursive function or some
        /// equivalent method or use a TreeWalker. This provides a helper for depth-first traversal of a subtree. In order
        /// to use it, you have to implement XML::TreeWalker interface and call XML::Node::Traverse() function. \n\n
        ///  * First, TreeWalker::OnTraversalBegin() is called with traversal root as its argument.\n
        ///  * Then, TreeWalker::OnEachNode() function is called for all nodes in the traversal subtree in depth first order, excluding the traversal root. Each Node is passed as an argument.\n
        ///  * Finally, TreeWalker::OnTraversalEnd() function is called with traversal root as its argument.\n\n
        /// If TreeWalker::OnTraversalBegin(), TreeWalker::OnTraversalEnd() or any of the TreeWalker::OnEachNode() calls return false, the traversal
        /// is terminated and false is returned as the traversal result; otherwise, the traversal results in true. Note that
        /// you don't have to override begin or end functions; their default implementations return true.\n\n
        /// You can get the node's depth relative to the traversal root at any point by calling TreeWalker::Depth() function.
        class MEZZ_LIB TreeWalker
        {
                friend class Node;

            private:

                /// @internal
                /// @brief Stores How deep in the tree we are
                int TraversalDepth;

            protected:

                /// @brief How many descendants deep are we during traversal.
                /// @return This returns -1 if called from TreeWalker::OnTraversalBegin() or TreeWalker::OnTraversalEnd(), and returns 0-based depth if called from OnEachNode - depth is 0 for all children of the traversal root, 1 for all grandchildren, 2 for great-grandchildren and so on.
                int Depth() const;

            public:

                /// @brief Default constructor, initializes depth, and can do little else without a fully implemented treewalker.
                TreeWalker();

                /// @brief Virtual deconstructor. Tears down a TreeWalker
                virtual ~TreeWalker();

                /// @brief Called by the root Node of the xml subtree when traversal begins.
                /// @param node The first node the Tree to traverse
                /// @details By default this simply returns true, but is expected to be overridden with any desired behavior
                /// @return True by default. If it returns false, then traversal ends and the Node::Traverse() that was called is expected to return false.
                virtual bool OnTraversalBegin(Node& node);

                /// @brief A Pure Virtual function that is expected to be implemented to create the desired behavior.
                /// @param node The curren node being trraversed.
                /// @details This is called on every Node that is traversed except the root node of the traversed subtree. Can be used to perform sophisticated searches
                /// of a portion of the xml document, alter the document on a large scale, gather statistics, or just about any other behavior that requires touching
                /// many nodes.
                /// @return if true Traversal is expected to continue, if false, then traversal ends and the Node::Traverse() that was called is expected to return false.
                virtual bool OnEachNode(Node& node) = 0;

                /// @brief Called on the root Node of the xml subtree when traversal ends.
                /// @param node The last node the Tree to traverse
                /// @details By default this simply returns true, but is expected to be overridden with any desired behavior
                /// @return True by default. If it returns false, then traversal ends and the Node::Traverse() that was called is expected to return false.
                virtual bool OnTraversalEnd(Node& node);
        };
    }
}// /namespace Mezzanine



#endif // Include guard

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 * Software, Files, Libraries and all other items referenced in this clause refers only
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