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///////////////////////////////////////////////////////////////////////////
//
/// @file NodeManager.h
///
/// @author Ken Museth
///
/// @brief NodeManager produces linear arrays of all tree nodes
/// allowing for efficient threading and bottom-up processing.
///
/// @note A NodeManager can be constructed from a Tree or LeafManager.
/// The latter is slightly more efficient since the cached leaf nodes will be reused.

#ifndef OPENVDB_TREE_NODEMANAGER_HAS_BEEN_INCLUDED
#define OPENVDB_TREE_NODEMANAGER_HAS_BEEN_INCLUDED

#include <tbb/parallel_for.h>
#include <openvdb/Types.h>
#include <deque>

namespace openvdb {
OPENVDB_USE_VERSION_NAMESPACE
namespace OPENVDB_VERSION_NAME {
namespace tree {

// Produce linear arrays of all tree nodes, to facilitate efficient threading
// and bottom-up processing.
template<typename TreeOrLeafManagerT, Index LEVELS = TreeOrLeafManagerT::RootNodeType::LEVEL>
class NodeManager;


////////////////////////////////////////


/// @brief This class caches tree nodes of a specific type in a linear array.
///
/// @note It is for internal use and should rarely be used directly.
template<typename NodeT>
class NodeList
{
public:
    typedef NodeT* value_type;
    typedef std::deque<value_type> ListT;

    NodeList() {}

    void push_back(NodeT* node) { mList.push_back(node); }

    NodeT& operator()(size_t n) const { assert(n<mList.size()); return *(mList[n]); }

    NodeT*& operator[](size_t n) { assert(n<mList.size()); return mList[n]; }

    Index64 nodeCount() const { return mList.size(); }

    void clear() { mList.clear(); }

    void resize(size_t n) { mList.resize(n); }

    class NodeRange
    {
    public:

        NodeRange(size_t begin, size_t end, const NodeList& nodeList, size_t grainSize=1):
            mEnd(end), mBegin(begin), mGrainSize(grainSize), mNodeList(nodeList) {}

        NodeRange(NodeRange& r, tbb::split):
            mEnd(r.mEnd), mBegin(doSplit(r)), mGrainSize(r.mGrainSize),
            mNodeList(r.mNodeList) {}

        size_t size() const { return mEnd - mBegin; }

        size_t grainsize() const { return mGrainSize; }

        const NodeList& nodeList() const { return mNodeList; }

        bool empty() const {return !(mBegin < mEnd);}

        bool is_divisible() const {return mGrainSize < this->size();}

        class Iterator
        {
        public:
            Iterator(const NodeRange& range, size_t pos): mRange(range), mPos(pos)
            {
                assert(this->isValid());
            }
            Iterator& operator=(const Iterator& other)
            {
                mRange = other.mRange; mPos = other.mPos; return *this;
            }
            /// Advance to the next node.
            Iterator& operator++() { ++mPos; return *this; }
            /// Return a reference to the node to which this iterator is pointing.
            NodeT& operator*() const { return mRange.mNodeList(mPos); }
            /// Return a pointer to the node to which this iterator is pointing.
            NodeT* operator->() const { return &(this->operator*()); }
            /// Return the index into the list of the current node.
            size_t pos() const { return mPos; }
            bool isValid() const { return mPos>=mRange.mBegin && mPos<=mRange.mEnd; }
            /// Return @c true if this iterator is not yet exhausted.
            bool test() const { return mPos < mRange.mEnd; }
            /// Return @c true if this iterator is not yet exhausted.
            operator bool() const { return this->test(); }
            /// Return @c true if this iterator is exhausted.
            bool empty() const { return !this->test(); }
            bool operator!=(const Iterator& other) const
            {
                return (mPos != other.mPos) || (&mRange != &other.mRange);
            }
            bool operator==(const Iterator& other) const { return !(*this != other); }
            const NodeRange& nodeRange() const { return mRange; }

        private:
            const NodeRange& mRange;
            size_t mPos;
        };// NodeList::NodeRange::Iterator

        Iterator begin() const {return Iterator(*this, mBegin);}

        Iterator end() const {return Iterator(*this, mEnd);}

    private:
        size_t mEnd, mBegin, mGrainSize;
        const NodeList& mNodeList;

        static size_t doSplit(NodeRange& r)
        {
            assert(r.is_divisible());
            size_t middle = r.mBegin + (r.mEnd - r.mBegin) / 2u;
            r.mEnd = middle;
            return middle;
        }
    };// NodeList::NodeRange

    /// Return a TBB-compatible NodeRange.
    NodeRange nodeRange(size_t grainsize = 1) const
    {
        return NodeRange(0, this->nodeCount(), *this, grainsize);
    }

    template<typename NodeOp>
    struct NodeTransformer
    {
        NodeTransformer(const NodeOp& nodeOp) : mNodeOp(nodeOp) {}
        void run(const NodeRange& range, bool threaded = true)
        {
            threaded ? tbb::parallel_for(range, *this) : (*this)(range);
        }
        void operator()(const NodeRange& range) const
        {
            for (typename NodeRange::Iterator it = range.begin(); it; ++it) mNodeOp(*it);
        }
        const NodeOp mNodeOp;
    };// NodeRange

    template<typename NodeOp>
    void foreach(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        NodeTransformer<NodeOp> transform(op);
        transform.run(this->nodeRange(grainSize), threaded);
    }

protected:
    ListT mList;
};// NodeList


/////////////////////////////////////////////


/// @brief This class is a link in a chain that each caches tree nodes
/// of a specific type in a linear array.
///
/// @note It is for internal use and should rarely be used directly.
template<typename NodeT, Index LEVEL>
class NodeManagerLink
{
public:
    NodeManagerLink() {}

    virtual ~NodeManagerLink() {}

    void clear() { mList.clear(); mNext.clear(); }

    template<typename ParentT, typename TreeOrLeafManagerT>
    void init(ParentT& parent, TreeOrLeafManagerT& tree)
    {
        parent.getNodes(mList);
        for (size_t i=0, n=mList.nodeCount(); i<n; ++i) mNext.init(mList(i), tree);
    }

    template<typename ParentT>
    void rebuild(ParentT& parent)
    {
        mList.clear();
        parent.getNodes(mList);
        for (size_t i=0, n=mList.nodeCount(); i<n; ++i) mNext.rebuild(mList(i));
    }

    Index64 nodeCount() const { return mList.nodeCount() + mNext.nodeCount(); }

    Index64 nodeCount(Index i) const
    {
        return i==NodeT::LEVEL ? mList.nodeCount() : mNext.nodeCount(i);
    }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded, size_t grainSize)
    {
        mNext.processBottomUp(op, threaded, grainSize);
        mList.foreach(op, threaded, grainSize);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded, size_t grainSize)
    {
        mList.foreach(op, threaded, grainSize);
        mNext.processTopDown(op, threaded, grainSize);
    }

protected:
    NodeList<NodeT> mList;
    NodeManagerLink<typename NodeT::ChildNodeType, LEVEL-1> mNext;
};// NodeManagerLink class


////////////////////////////////////////


/// @brief Specialization that terminates the chain of cached tree nodes
///
/// @note It is for internal use and should rarely be used directly.
template<typename NodeT>
class NodeManagerLink<NodeT, 0>
{
public:
    NodeManagerLink() {}

    virtual ~NodeManagerLink() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mList.clear(); }

    template<typename ParentT>
    void rebuild(ParentT& parent) { mList.clear(); parent.getNodes(mList); }

    Index64 nodeCount() const { return mList.nodeCount(); }

    Index64 nodeCount(Index) const { return mList.nodeCount(); }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded, size_t grainSize)
    {
        mList.foreach(op, threaded, grainSize);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded, size_t grainSize)
    {
        mList.foreach(op, threaded, grainSize);
    }

    template<typename ParentT, typename TreeOrLeafManagerT>
    void init(ParentT& parent, TreeOrLeafManagerT& tree)
    {
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_BEGIN
        if (TreeOrLeafManagerT::DEPTH == 2 && NodeT::LEVEL == 0) {
            tree.getNodes(mList);
        } else {
            parent.getNodes(mList);
        }
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_END
    }
protected:
    NodeList<NodeT> mList;
};// NodeManagerLink class


////////////////////////////////////////


/// @brief To facilitate threading over the nodes of a tree, cache
/// node pointers in linear arrays, one for each level of the tree.
///
/// @details This implementation works with trees of any depth, but
/// optimized specializations are provided for the most typical tree depths.
template<typename TreeOrLeafManagerT, Index _LEVELS>
class NodeManager
{
public:
    static const Index LEVELS = _LEVELS;
    BOOST_STATIC_ASSERT(LEVELS > 0);//special implementation below
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    BOOST_STATIC_ASSERT(RootNodeType::LEVEL >= LEVELS);

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root()) { mChain.init(mRoot, tree); }

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mChain.clear(); }

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild() { mChain.rebuild(mRoot); }

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const { return mChain.nodeCount(); }

    /// @brief Return the number of cached nodes at level @a i, where
    /// 0 corresponds to the lowest level.
    Index64 nodeCount(Index i) const { return mChain.nodeCount(i); }

    //@{
    /// @brief   Threaded method that applies a user-supplied functor
    ///          to all the nodes in the tree.
    ///
    /// @param op        user-supplied functor, see examples for interface details.
    /// @param threaded  optional toggle to disable threading, on by default.
    /// @param grainSize optional parameter to specify the grainsize
    ///                  for threading, one by default.
    ///
    /// @warning The functor object is deep-copied to create TBB tasks.
    ///
    /// @par Example:
    /// @code
    /// // Functor to offset all the inactive values of a tree. Note
    /// // this implementation also illustrates how different
    /// // computation can be applied to the different node types.
    /// template<typename TreeType>
    /// struct OffsetOp
    /// {
    ///     typedef typename TreeT::ValueType    ValueT;
    ///     typedef typename TreeT::RootNodeType RootT;
    ///     typedef typename TreeT::LeafNodeType LeafT;
    ///     OffsetOp(const ValueT& v) : mOffset(v) {}
    ///
    ///     // Processes the root node. Required by the NodeManager
    ///     void operator()(RootT& root) const
    ///     {
    ///         for (typename RootT::ValueOffIter i = root.beginValueOff(); i; ++i) *i += mOffset;
    ///     }
    ///     // Processes the leaf nodes. Required by the NodeManager
    ///     void operator()(LeafT& leaf) const
    ///     {
    ///         for (typename LeafT::ValueOffIter i = leaf.beginValueOff(); i; ++i) *i += mOffset;
    ///     }
    ///     // Processes the internal nodes. Required by the NodeManager
    ///     template<typename NodeT>
    ///     void operator()(NodeT& node) const
    ///     {
    ///         for (typename NodeT::ValueOffIter i = node.beginValueOff(); i; ++i) *i += mOffset;
    ///     }
    /// private:
    ///     const ValueT mOffset;
    /// };
    ///
    /// // usage:
    /// OffsetOp<FloatTree> op(tree);
    /// tree::NodeManager<FloatTree> nodes(tree);
    /// nodes.processBottomUp(op);
    ///
    /// // or for better performance
    /// typedef tree::LeafManager<FloatTree> T;
    /// OffsetOp<T> op(leafManager);
    /// tree::NodeManager<T> nodes(leafManager);
    /// nodes.processBottomUp(op);
    ///
    /// @endcode
    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        mChain.processBottomUp(op, threaded, grainSize);
        op(mRoot);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        op(mRoot);
        mChain.processTopDown(op, threaded, grainSize);
    }
    //@}

protected:
    RootNodeType& mRoot;
    NodeManagerLink<typename RootNodeType::ChildNodeType, LEVELS-1> mChain;

private:
    NodeManager(const NodeManager&) {}//disallow copy-construction
};// NodeManager class


////////////////////////////////////////////


/// Template specialization of the NodeManager with no caching of nodes
template<typename TreeOrLeafManagerT>
class NodeManager<TreeOrLeafManagerT, 0>
{
public:
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    static const Index LEVELS = 0;

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root()) {}

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() {}

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild() {}

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const { return 0; }

    Index64 nodeCount(Index) const { return 0; }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool, size_t) { op(mRoot); }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool, size_t) { op(mRoot); }

protected:
    RootNodeType& mRoot;

private:
    NodeManager(const NodeManager&) {} // disallow copy-construction
}; // NodeManager<0>


////////////////////////////////////////////


/// Template specialization of the NodeManager with one level of nodes
template<typename TreeOrLeafManagerT>
class NodeManager<TreeOrLeafManagerT, 1>
{
public:
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    BOOST_STATIC_ASSERT(RootNodeType::LEVEL > 0);
    static const Index LEVELS = 1;

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root())
    {
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_BEGIN
        if (TreeOrLeafManagerT::DEPTH == 2 && NodeT0::LEVEL == 0) {
            tree.getNodes(mList0);
        } else {
            mRoot.getNodes(mList0);
        }
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_END
    }

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mList0.clear(); }

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild() { mList0.clear(); mRoot.getNodes(mList0); }

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const { return mList0.nodeCount(); }

    /// @brief Return the number of cached nodes at level @a i, where
    /// 0 corresponds to the lowest level.
    Index64 nodeCount(Index i) const { return i==0 ? mList0.nodeCount() : 0; }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        mList0.foreach(op, threaded, grainSize);
        op(mRoot);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        op(mRoot);
        mList0.foreach(op, threaded, grainSize);
    }

protected:
    typedef RootNodeType                   NodeT1;
    typedef typename NodeT1::ChildNodeType NodeT0;
    typedef NodeList<NodeT0>               ListT0;

    NodeT1& mRoot;
    ListT0 mList0;

private:
    NodeManager(const NodeManager&) {} // disallow copy-construction
}; // NodeManager<1>


////////////////////////////////////////////


/// Template specialization of the NodeManager with two levels of nodes
template<typename TreeOrLeafManagerT>
class NodeManager<TreeOrLeafManagerT, 2>
{
public:
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    BOOST_STATIC_ASSERT(RootNodeType::LEVEL > 1);
    static const Index LEVELS = 2;

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root())
    {
        mRoot.getNodes(mList1);

        OPENVDB_NO_UNREACHABLE_CODE_WARNING_BEGIN
        if (TreeOrLeafManagerT::DEPTH == 2 && NodeT0::LEVEL == 0) {
            tree.getNodes(mList0);
        } else {
            for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
        }
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_END
    }

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mList0.clear(); mList1.clear(); }

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild()
    {
        this->clear();
        mRoot.getNodes(mList1);
        for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
    }

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const { return mList0.nodeCount() + mList1.nodeCount(); }

    /// @brief Return the number of cached nodes at level @a i, where
    /// 0 corresponds to the lowest level.
    Index64 nodeCount(Index i) const
    {
        return i==0 ? mList0.nodeCount() : i==1 ? mList1.nodeCount() : 0;
    }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        mList0.foreach(op, threaded, grainSize);
        mList1.foreach(op, threaded, grainSize);
        op(mRoot);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        op(mRoot);
        mList1.foreach(op, threaded, grainSize);
        mList0.foreach(op, threaded, grainSize);
    }

protected:
    typedef RootNodeType                   NodeT2;
    typedef typename NodeT2::ChildNodeType NodeT1;//upper level
    typedef typename NodeT1::ChildNodeType NodeT0;//lower level

    typedef NodeList<NodeT1>               ListT1;//upper level
    typedef NodeList<NodeT0>               ListT0;//lower level

    NodeT2& mRoot;
    ListT1 mList1;
    ListT0 mList0;

private:
    NodeManager(const NodeManager&) {} // disallow copy-construction
}; // NodeManager<2>


////////////////////////////////////////////


/// Template specialization of the NodeManager with three levels of nodes
template<typename TreeOrLeafManagerT>
class NodeManager<TreeOrLeafManagerT, 3>
{
public:
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    BOOST_STATIC_ASSERT(RootNodeType::LEVEL > 2);
    static const Index LEVELS = 3;

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root())
    {
        mRoot.getNodes(mList2);
        for (size_t i=0, n=mList2.nodeCount(); i<n; ++i) mList2(i).getNodes(mList1);

        OPENVDB_NO_UNREACHABLE_CODE_WARNING_BEGIN
        if (TreeOrLeafManagerT::DEPTH == 2 && NodeT0::LEVEL == 0) {
            tree.getNodes(mList0);
        } else {
            for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
        }
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_END
    }

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mList0.clear(); mList1.clear(); mList2.clear(); }

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild()
    {
        this->clear();
        mRoot.getNodes(mList2);
        for (size_t i=0, n=mList2.nodeCount(); i<n; ++i) mList2(i).getNodes(mList1);
        for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
    }

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const { return mList0.nodeCount()+mList1.nodeCount()+mList2.nodeCount(); }

    /// @brief Return the number of cached nodes at level @a i, where
    /// 0 corresponds to the lowest level.
    Index64 nodeCount(Index i) const
    {
        return i==0 ? mList0.nodeCount() : i==1 ? mList1.nodeCount()
             : i==2 ? mList2.nodeCount() : 0;
    }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        mList0.foreach(op, threaded, grainSize);
        mList1.foreach(op, threaded, grainSize);
        mList2.foreach(op, threaded, grainSize);
        op(mRoot);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        op(mRoot);
        mList2.foreach(op, threaded, grainSize);
        mList1.foreach(op, threaded, grainSize);
        mList0.foreach(op, threaded, grainSize);
    }

protected:
    typedef RootNodeType                   NodeT3;
    typedef typename NodeT3::ChildNodeType NodeT2;//upper level
    typedef typename NodeT2::ChildNodeType NodeT1;//mid level
    typedef typename NodeT1::ChildNodeType NodeT0;//lower level

    typedef NodeList<NodeT2>               ListT2;//upper level of internal nodes
    typedef NodeList<NodeT1>               ListT1;//lower level of internal nodes
    typedef NodeList<NodeT0>               ListT0;//lower level of internal nodes or leafs

    NodeT3& mRoot;
    ListT2 mList2;
    ListT1 mList1;
    ListT0 mList0;

private:
    NodeManager(const NodeManager&) {} // disallow copy-construction
}; // NodeManager<3>


////////////////////////////////////////////


/// Template specialization of the NodeManager with four levels of nodes
template<typename TreeOrLeafManagerT>
class NodeManager<TreeOrLeafManagerT, 4>
{
public:
    typedef typename TreeOrLeafManagerT::RootNodeType RootNodeType;
    BOOST_STATIC_ASSERT(RootNodeType::LEVEL > 3);
    static const Index LEVELS = 4;

    NodeManager(TreeOrLeafManagerT& tree) : mRoot(tree.root())
    {
        mRoot.getNodes(mList3);
        for (size_t i=0, n=mList3.nodeCount(); i<n; ++i) mList3(i).getNodes(mList2);
        for (size_t i=0, n=mList2.nodeCount(); i<n; ++i) mList2(i).getNodes(mList1);

        OPENVDB_NO_UNREACHABLE_CODE_WARNING_BEGIN
        if (TreeOrLeafManagerT::DEPTH == 2 && NodeT0::LEVEL == 0) {
            tree.getNodes(mList0);
        } else {
            for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
        }
        OPENVDB_NO_UNREACHABLE_CODE_WARNING_END
    }

    virtual ~NodeManager() {}

    /// @brief Clear all the cached tree nodes
    void clear() { mList0.clear(); mList1.clear(); mList2.clear(); mList3.clear; }

    /// @brief Clear and recache all the tree nodes from the
    /// tree. This is required if tree nodes have been added or removed.
    void rebuild()
    {
        this->clear();
        mRoot.getNodes(mList3);
        for (size_t i=0, n=mList3.nodeCount(); i<n; ++i) mList3(i).getNodes(mList2);
        for (size_t i=0, n=mList2.nodeCount(); i<n; ++i) mList2(i).getNodes(mList1);
        for (size_t i=0, n=mList1.nodeCount(); i<n; ++i) mList1(i).getNodes(mList0);
    }

    /// @brief Return a reference to the root node.
    const RootNodeType& root() const { return mRoot; }

    /// @brief Return the total number of cached nodes (excluding the root node)
    Index64 nodeCount() const
    {
        return mList0.nodeCount() + mList1.nodeCount()
             + mList2.nodeCount() + mList3.nodeCount();
    }

    /// @brief Return the number of cached nodes at level @a i, where
    /// 0 corresponds to the lowest level.
    Index64 nodeCount(Index i) const
    {
        return i==0 ? mList0.nodeCount() : i==1 ? mList1.nodeCount() :
               i==2 ? mList2.nodeCount() : i==3 ? mList3.nodeCount() : 0;
    }

    template<typename NodeOp>
    void processBottomUp(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        mList0.foreach(op, threaded, grainSize);
        mList1.foreach(op, threaded, grainSize);
        mList2.foreach(op, threaded, grainSize);
        mList3.foreach(op, threaded, grainSize);
        op(mRoot);
    }

    template<typename NodeOp>
    void processTopDown(const NodeOp& op, bool threaded = true, size_t grainSize=1)
    {
        op(mRoot);
        mList3.foreach(op, threaded, grainSize);
        mList2.foreach(op, threaded, grainSize);
        mList1.foreach(op, threaded, grainSize);
        mList0.foreach(op, threaded, grainSize);
    }

protected:
    typedef RootNodeType                   NodeT4;
    typedef typename NodeT4::ChildNodeType NodeT3;//upper level
    typedef typename NodeT3::ChildNodeType NodeT2;//upper mid level
    typedef typename NodeT2::ChildNodeType NodeT1;//lower mid level
    typedef typename NodeT1::ChildNodeType NodeT0;//lower level

    typedef NodeList<NodeT3>               ListT3;//upper level of internal nodes
    typedef NodeList<NodeT2>               ListT2;//upper mid level of internal nodes
    typedef NodeList<NodeT1>               ListT1;//lower mid level of internal nodes
    typedef NodeList<NodeT0>               ListT0;//lower level of internal nodes or leafs

    NodeT4& mRoot;
    ListT3  mList3;
    ListT2  mList2;
    ListT1  mList1;
    ListT0  mList0;

private:
    NodeManager(const NodeManager&) {} // disallow copy-construction
}; // NodeManager<4>

} // namespace tree
} // namespace OPENVDB_VERSION_NAME
} // namespace openvdb

#endif // OPENVDB_TREE_NODEMANAGER_HAS_BEEN_INCLUDED

// Copyright (c) 2012-2015 DreamWorks Animation LLC
// All rights reserved. This software is distributed under the
// Mozilla Public License 2.0 ( http://www.mozilla.org/MPL/2.0/ )
