GPXSee/src/common/rtree.h

// TITLE
//
//    R-TREES: A DYNAMIC INDEX STRUCTURE FOR SPATIAL SEARCHING
//
// DESCRIPTION
//
//    A C++ templated version of the RTree algorithm.
//    For more information please read the comments in RTree.h
//
// AUTHORS
//
//    * 1983 Original algorithm and test code by Antonin Guttman
//      and Michael Stonebraker, UC Berkely
//    * 1994 ANSI C ported from original test code by Melinda Green
//      (melinda@superliminal.com)
//    * 1995 Sphere volume fix for degeneracy problem submitted by Paul Brook
//    * 2004 Templated C++ port by Greg Douglas
//    * 2018 Iterator fix and Qt macros by Martin Tuma
//
// LICENSE:
//
//    Entirely free for all uses. Enjoy!

#ifndef RTREE_H
#define RTREE_H

#include <cmath>
#include <cstdlib>
#include <QtGlobal>


#define RTREE_TEMPLATE template<class DATATYPE, class ELEMTYPE, int NUMDIMS, \
  class ELEMTYPEREAL, int TMAXNODES, int TMINNODES>
#define RTREE_QUAL RTree<DATATYPE, ELEMTYPE, NUMDIMS, ELEMTYPEREAL, TMAXNODES, \
  TMINNODES>

// This version does not contain a fixed memory allocator, fill in lines with
// EXAMPLE to implement one.
#define RTREE_DONT_USE_MEMPOOLS 
// Better split classification, may be slower on some systems
#define RTREE_USE_SPHERICAL_VOLUME


/// \class RTree
///
/// Implementation of RTree, a multidimensional bounding rectangle tree.
/// Example usage: For a 3-dimensional tree use RTree<Object*, float, 3> myTree;
///
/// This modified, templated C++ version by Greg Douglas at Auran
/// (http://www.auran.com)
///
/// \c DATATYPE Referenced data, should be int, void*, obj* etc. no larger than
///    sizeof<void*> and simple type
/// \c ELEMTYPE Type of element such as int or float
/// \c NUMDIMS Number of dimensions such as 2 or 3
/// \c ELEMTYPEREAL Type of element that allows fractional and large values such
///    as float or double, for use in volume calcs
///
/// NOTES: Inserting and removing data requires the knowledge of its constant
/// Minimal Bounding Rectangle. This version uses new/delete for nodes,
/// I recommend using a fixed size allocator for efficiency. Instead of using
/// a callback function for returned results, I recommend and efficient
/// pre-sized, grow-only memory array similar to MFC CArray or STL Vector for
/// returning search query result.
///
template<class DATATYPE, class ELEMTYPE, int NUMDIMS,
class ELEMTYPEREAL = ELEMTYPE, int TMAXNODES = 8, int TMINNODES = TMAXNODES / 2>
class RTree
{
protected: 
	struct Node;  // Fwd decl.  Used by other internal structs and iterator

public:
	enum
	{
		MAXNODES = TMAXNODES, ///< Max elements in node
		MINNODES = TMINNODES, ///< Min elements in node
	};

public:

	RTree();
	RTree(const RTree &) = delete;
	virtual ~RTree();

	/// Insert entry
	/// \param a_min Min of bounding rect
	/// \param a_max Max of bounding rect
	/// \param a_dataId Positive Id of data.  Maybe zero, but negative numbers
	///   not allowed.
	void Insert(const ELEMTYPE a_min[NUMDIMS], const ELEMTYPE a_max[NUMDIMS],
	  const DATATYPE& a_dataId);

	/// Remove entry
	/// \param a_min Min of bounding rect
	/// \param a_max Max of bounding rect
	/// \param a_dataId Positive Id of data.  Maybe zero, but negative numbers
	///   not allowed.
	void Remove(const ELEMTYPE a_min[NUMDIMS], const ELEMTYPE a_max[NUMDIMS],
	  const DATATYPE& a_dataId);

	/// Find all within search rectangle
	/// \param a_min Min of search bounding rect
	/// \param a_max Max of search bounding rect
	/// \param a_resultCallback Callback function to return result.  Callback
	///   should return 'true' to continue searching
	/// \param a_context User context to pass as parameter to a_resultCallback
	/// \return Returns the number of entries found
	int Search(const ELEMTYPE a_min[NUMDIMS], const ELEMTYPE a_max[NUMDIMS],
	  bool a_resultCallback(DATATYPE a_data, void* a_context),
	  void* a_context) const;

	/// Remove all entries from tree
	void RemoveAll();

	/// Count the data elements in this container.  This is slow as no internal
	/// counter is maintained.
	int Count();


	/// Iterator is not remove safe.
	class Iterator
	{
	private:
		// Max stack size. Allows almost n^32 where n is number of branches in
		// node
		enum { MAX_STACK = 32 }; 

		struct StackElement
		{
			Node* m_node;
			int m_branchIndex;
		};

	public:
		Iterator() { Init(); }

		~Iterator() { }

		/// Is iterator invalid
		bool IsNull() { return (m_tos <= 0); }

		/// Is iterator pointing to valid data
		bool IsNotNull() { return (m_tos > 0); }

		/// Access the current data element.
		DATATYPE& operator*()
		{
			Q_ASSERT(IsNotNull());
			StackElement& curTos = m_stack[m_tos - 1];
			return curTos.m_node->m_branch[curTos.m_branchIndex].m_data;
		} 

		/// Access the current data element.
		const DATATYPE& operator*() const
		{
			Q_ASSERT(IsNotNull());
			StackElement& curTos = m_stack[m_tos - 1];
			return curTos.m_node->m_branch[curTos.m_branchIndex].m_data;
		} 

		/// Find the next data element
		bool operator++() { return FindNextData(); }

		/// Get the bounds for this node
		void GetBounds(ELEMTYPE a_min[NUMDIMS], ELEMTYPE a_max[NUMDIMS])
		{
			Q_ASSERT(IsNotNull());
			StackElement& curTos = m_stack[m_tos - 1];
			Branch& curBranch = curTos.m_node->m_branch[curTos.m_branchIndex];

			for (int index = 0; index < NUMDIMS; ++index) {
				a_min[index] = curBranch.m_rect.m_min[index];
				a_max[index] = curBranch.m_rect.m_max[index];
			}
		}

	private:
		// Reset iterator
		void Init() { m_tos = 0; }

		// Find the next data element in the tree (For internal use only)
		bool FindNextData()
		{
			for (;;) {
				if (m_tos <= 0)
					return false;

				// Copy stack top cause it may change as we use it
				StackElement curTos = Pop();

				if (curTos.m_node->IsLeaf()) {
					// Keep walking through data while we can
					if (curTos.m_branchIndex+1 < curTos.m_node->m_count) {
						// There is more data, just point to the next one
						Push(curTos.m_node, curTos.m_branchIndex + 1);
						return true;
					}
					// No more data, so it will fall back to previous level
				} else {
					if (curTos.m_branchIndex+1 < curTos.m_node->m_count) {
						// Push sibling on for future tree walk
						// This is the 'fall back' node when we finish with
						// the current level
						Push(curTos.m_node, curTos.m_branchIndex + 1);
					}
					// Since cur node is not a leaf, push first of next level to
					// get deeper into the tree
					Node* nextLevelnode = curTos.m_node->m_branch[curTos.m_branchIndex].m_child;
					Push(nextLevelnode, 0);
					
					// If we pushed on a new leaf, exit as the data is ready at
					// TOS
					if (nextLevelnode->IsLeaf())
						return true;
				}
			}
		}

		// Push node and branch onto iteration stack
		void Push(Node* a_node, int a_branchIndex)
		{
			m_stack[m_tos].m_node = a_node;
			m_stack[m_tos].m_branchIndex = a_branchIndex;
			++m_tos;
			Q_ASSERT(m_tos <= MAX_STACK);
		}

		// Pop element off iteration stack
		StackElement& Pop()
		{
			Q_ASSERT(m_tos > 0);
			--m_tos;
			return m_stack[m_tos];
		}

		// Stack as we are doing iteration instead of recursion
		StackElement m_stack[MAX_STACK];
		// Top Of Stack index
		int m_tos;

		friend class RTree;
	};

	// Get 'first' for iteration
	void GetFirst(Iterator& a_it)
	{
		a_it.Init();
		Node* first = m_root;

		while (first) {
			if (first->IsInternalNode() && first->m_count > 1) {
				a_it.Push(first, 1); // Descend sibling branch later
			} else if(first->IsLeaf()) {
				if(first->m_count) {
					a_it.Push(first, 0);
				}
				break;
			}
			first = first->m_branch[0].m_child;
		}
	}

	// Get Next for iteration
	void GetNext(Iterator& a_it) { ++a_it; }

	// Is iterator NULL, or at end?
	bool IsNull(Iterator& a_it) { return a_it.IsNull(); }

	// Get object at iterator position
	DATATYPE& GetAt(Iterator& a_it) { return *a_it; }

protected:
	// Minimal bounding rectangle (n-dimensional)
	struct Rect
	{
		ELEMTYPE m_min[NUMDIMS];   ///< Min dimensions of bounding box 
		ELEMTYPE m_max[NUMDIMS];   ///< Max dimensions of bounding box 
	};

	/// May be data or may be another subtree
	/// The parents level determines this.
	/// If the parents level is 0, then this is data
	struct Branch
	{
		Rect m_rect;               ///< Bounds
		union
		{
			Node* m_child;         ///< Child node
			DATATYPE m_data;       ///< Data Id or Ptr
		};
	};

	/// Node for each branch level
	struct Node
	{
		// Not a leaf, but a internal node
		bool IsInternalNode() { return (m_level > 0); }
		// A leaf, contains data
		bool IsLeaf() { return (m_level == 0); }

		int m_count;               ///< Count
		int m_level;               ///< Leaf is zero, others positive
		Branch m_branch[MAXNODES]; ///< Branch
	};

	/// A link list of nodes for reinsertion after a delete operation
	struct ListNode
	{
		ListNode* m_next;          ///< Next in list
		Node* m_node;              ///< Node
	};

	/// Variables for finding a split partition
	struct PartitionVars
	{
		int m_partition[MAXNODES+1];
		int m_total;
		int m_minFill;
		int m_taken[MAXNODES+1];
		int m_count[2];
		Rect m_cover[2];
		ELEMTYPEREAL m_area[2];

		Branch m_branchBuf[MAXNODES+1];
		int m_branchCount;
		Rect m_coverSplit;
		ELEMTYPEREAL m_coverSplitArea;
	}; 

	Node* AllocNode();
	void FreeNode(Node* a_node);
	void InitNode(Node* a_node);
	void InitRect(Rect* a_rect);
	bool InsertRectRec(Rect* a_rect, const DATATYPE& a_id, Node* a_node,
	  Node** a_newNode, int a_level);
	bool InsertRect(Rect* a_rect, const DATATYPE& a_id, Node** a_root,
	  int a_level);
	Rect NodeCover(Node* a_node);
	bool AddBranch(Branch* a_branch, Node* a_node, Node** a_newNode);
	void DisconnectBranch(Node* a_node, int a_index);
	int PickBranch(Rect* a_rect, Node* a_node);
	Rect CombineRect(Rect* a_rectA, Rect* a_rectB);
	void SplitNode(Node* a_node, Branch* a_branch, Node** a_newNode);
	ELEMTYPEREAL RectSphericalVolume(Rect* a_rect);
	ELEMTYPEREAL RectVolume(Rect* a_rect);
	ELEMTYPEREAL CalcRectVolume(Rect* a_rect);
	void GetBranches(Node* a_node, Branch* a_branch, PartitionVars* a_parVars);
	void ChoosePartition(PartitionVars* a_parVars, int a_minFill);
	void LoadNodes(Node* a_nodeA, Node* a_nodeB, PartitionVars* a_parVars);
	void InitParVars(PartitionVars* a_parVars, int a_maxRects, int a_minFill);
	void PickSeeds(PartitionVars* a_parVars);
	void Classify(int a_index, int a_group, PartitionVars* a_parVars);
	bool RemoveRect(Rect* a_rect, const DATATYPE& a_id, Node** a_root);
	bool RemoveRectRec(Rect* a_rect, const DATATYPE& a_id, Node* a_node,
	  ListNode** a_listNode);
	ListNode* AllocListNode();
	void FreeListNode(ListNode* a_listNode);
	bool Overlap(Rect* a_rectA, Rect* a_rectB) const;
	void ReInsert(Node* a_node, ListNode** a_listNode);
	bool Search(Node* a_node, Rect* a_rect, int& a_foundCount,
	  bool a_resultCallback(DATATYPE a_data, void* a_context),
	  void* a_context) const;
	void RemoveAllRec(Node* a_node);
	void Reset();
	void CountRec(Node* a_node, int& a_count);

	/// Root of tree
	Node* m_root;
	/// Unit sphere constant for required number of dimensions
	ELEMTYPEREAL m_unitSphereVolume;
};


RTREE_TEMPLATE
RTREE_QUAL::RTree()
{
	Q_ASSERT(MAXNODES > MINNODES);
	Q_ASSERT(MINNODES > 0);

	// We only support machine word size simple data type eg. integer index or
	// object pointer. Since we are storing as union with non data branch
	Q_ASSERT(sizeof(DATATYPE) == sizeof(void*) || sizeof(DATATYPE) == sizeof(int));

	// Precomputed volumes of the unit spheres for the first few dimensions
	const float UNIT_SPHERE_VOLUMES[] = {
		0.000000f, 2.000000f, 3.141593f, // Dimension  0,1,2
		4.188790f, 4.934802f, 5.263789f, // Dimension  3,4,5
		5.167713f, 4.724766f, 4.058712f, // Dimension  6,7,8
		3.298509f, 2.550164f, 1.884104f, // Dimension  9,10,11
		1.335263f, 0.910629f, 0.599265f, // Dimension  12,13,14
		0.381443f, 0.235331f, 0.140981f, // Dimension  15,16,17
		0.082146f, 0.046622f, 0.025807f, // Dimension  18,19,20 
	};

	m_root = AllocNode();
	m_root->m_level = 0;
	m_unitSphereVolume = (ELEMTYPEREAL)UNIT_SPHERE_VOLUMES[NUMDIMS];
}


RTREE_TEMPLATE
RTREE_QUAL::~RTree()
{
	Reset(); // Free, or reset node memory
}


RTREE_TEMPLATE
void RTREE_QUAL::Insert(const ELEMTYPE a_min[NUMDIMS],
  const ELEMTYPE a_max[NUMDIMS], const DATATYPE& a_dataId)
{
	#ifndef QT_NO_DEBUG
	for (int index=0; index<NUMDIMS; ++index)
		Q_ASSERT(a_min[index] <= a_max[index]);
	#endif // QT_NO_DEBUG

	Rect rect;

	for (int axis=0; axis<NUMDIMS; ++axis) {
		rect.m_min[axis] = a_min[axis];
		rect.m_max[axis] = a_max[axis];
	}

	InsertRect(&rect, a_dataId, &m_root, 0);
}


RTREE_TEMPLATE
void RTREE_QUAL::Remove(const ELEMTYPE a_min[NUMDIMS],
  const ELEMTYPE a_max[NUMDIMS], const DATATYPE& a_dataId)
{
	#ifndef QT_NO_DEBUG
	for (int index=0; index<NUMDIMS; ++index)
		Q_ASSERT(a_min[index] <= a_max[index]);
	#endif // QT_NO_DEBUG

	Rect rect;

	for (int axis=0; axis<NUMDIMS; ++axis) {
		rect.m_min[axis] = a_min[axis];
		rect.m_max[axis] = a_max[axis];
	}

	RemoveRect(&rect, a_dataId, &m_root);
}


RTREE_TEMPLATE
int RTREE_QUAL::Search(const ELEMTYPE a_min[NUMDIMS], const ELEMTYPE a_max[NUMDIMS],
  bool a_resultCallback(DATATYPE a_data, void* a_context), void* a_context) const
{
	#ifndef QT_NO_DEBUG
	for (int index=0; index<NUMDIMS; ++index)
		Q_ASSERT(a_min[index] <= a_max[index]);
	#endif // QT_NO_DEBUG

	Rect rect;

	for (int axis=0; axis<NUMDIMS; ++axis) {
		rect.m_min[axis] = a_min[axis];
		rect.m_max[axis] = a_max[axis];
	}

	// NOTE: May want to return search result another way, perhaps returning
	// the number of found elements here.

	int foundCount = 0;
	Search(m_root, &rect, foundCount, a_resultCallback, a_context);

	return foundCount;
}


RTREE_TEMPLATE
int RTREE_QUAL::Count()
{
	int count = 0;
	CountRec(m_root, count);

	return count;
}


RTREE_TEMPLATE
void RTREE_QUAL::CountRec(Node* a_node, int& a_count)
{
	if (a_node->IsInternalNode()) {  // not a leaf node
		for (int index = 0; index < a_node->m_count; ++index)
			CountRec(a_node->m_branch[index].m_child, a_count);
	} else { // A leaf node
		a_count += a_node->m_count;
	}
}


RTREE_TEMPLATE
void RTREE_QUAL::RemoveAll()
{
	// Delete all existing nodes
	Reset();

	m_root = AllocNode();
	m_root->m_level = 0;
}


RTREE_TEMPLATE
void RTREE_QUAL::Reset()
{
	#ifdef RTREE_DONT_USE_MEMPOOLS
	// Delete all existing nodes
	RemoveAllRec(m_root);
	#else // RTREE_DONT_USE_MEMPOOLS
	// Just reset memory pools.  We are not using complex types
	// EXAMPLE
	#endif // RTREE_DONT_USE_MEMPOOLS
}


RTREE_TEMPLATE
void RTREE_QUAL::RemoveAllRec(Node* a_node)
{
	Q_ASSERT(a_node);
	Q_ASSERT(a_node->m_level >= 0);

	if (a_node->IsInternalNode()) { // This is an internal node in the tree
		for (int index=0; index < a_node->m_count; ++index)
			RemoveAllRec(a_node->m_branch[index].m_child);
	}
	FreeNode(a_node); 
}


RTREE_TEMPLATE
typename RTREE_QUAL::Node* RTREE_QUAL::AllocNode()
{
	Node* newNode;
	#ifdef RTREE_DONT_USE_MEMPOOLS
	newNode = new Node;
	#else // RTREE_DONT_USE_MEMPOOLS
	// EXAMPLE
	#endif // RTREE_DONT_USE_MEMPOOLS
	InitNode(newNode);
	return newNode;
}


RTREE_TEMPLATE
void RTREE_QUAL::FreeNode(Node* a_node)
{
	Q_ASSERT(a_node);

	#ifdef RTREE_DONT_USE_MEMPOOLS
	delete a_node;
	#else // RTREE_DONT_USE_MEMPOOLS
	// EXAMPLE
	#endif // RTREE_DONT_USE_MEMPOOLS
}


// Allocate space for a node in the list used in DeletRect to
// store Nodes that are too empty.
RTREE_TEMPLATE
typename RTREE_QUAL::ListNode* RTREE_QUAL::AllocListNode()
{
	#ifdef RTREE_DONT_USE_MEMPOOLS
	return new ListNode;
	#else // RTREE_DONT_USE_MEMPOOLS
	// EXAMPLE
	#endif // RTREE_DONT_USE_MEMPOOLS
}


RTREE_TEMPLATE
void RTREE_QUAL::FreeListNode(ListNode* a_listNode)
{
	#ifdef RTREE_DONT_USE_MEMPOOLS
	delete a_listNode;
	#else // RTREE_DONT_USE_MEMPOOLS
	// EXAMPLE
	#endif // RTREE_DONT_USE_MEMPOOLS
}


RTREE_TEMPLATE
void RTREE_QUAL::InitNode(Node* a_node)
{
	a_node->m_count = 0;
	a_node->m_level = -1;
}


RTREE_TEMPLATE
void RTREE_QUAL::InitRect(Rect* a_rect)
{
	for (int index = 0; index < NUMDIMS; ++index) {
		a_rect->m_min[index] = (ELEMTYPE)0;
		a_rect->m_max[index] = (ELEMTYPE)0;
	}
}


// Inserts a new data rectangle into the index structure.
// Recursively descends tree, propagates splits back up.
// Returns 0 if node was not split.  Old node updated.
// If node was split, returns 1 and sets the pointer pointed to by
// new_node to point to the new node.  Old node updated to become one of two.
// The level argument specifies the number of steps up from the leaf
// level to insert; e.g. a data rectangle goes in at level = 0.
RTREE_TEMPLATE
bool RTREE_QUAL::InsertRectRec(Rect* a_rect, const DATATYPE& a_id, Node* a_node,
  Node** a_newNode, int a_level)
{
	Q_ASSERT(a_rect && a_node && a_newNode);
	Q_ASSERT(a_level >= 0 && a_level <= a_node->m_level);

	int index;
	Branch branch;
	Node* otherNode;

	// Still above level for insertion, go down tree recursively
	if (a_node->m_level > a_level) {
		index = PickBranch(a_rect, a_node);
		if (!InsertRectRec(a_rect, a_id, a_node->m_branch[index].m_child, &otherNode, a_level)) {
			// Child was not split
			a_node->m_branch[index].m_rect = CombineRect(a_rect, &(a_node->m_branch[index].m_rect));
			return false;
		} else { // Child was split
			a_node->m_branch[index].m_rect = NodeCover(a_node->m_branch[index].m_child);
			branch.m_child = otherNode;
			branch.m_rect = NodeCover(otherNode);
			return AddBranch(&branch, a_node, a_newNode);
		}
	// Have reached level for insertion. Add rect, split if necessary
	} else if (a_node->m_level == a_level) {
		branch.m_rect = *a_rect;
		branch.m_child = (Node*) a_id;
		// Child field of leaves contains id of data record
		return AddBranch(&branch, a_node, a_newNode);
	} else {
		// Should never occur
		Q_ASSERT(0);
		return false;
	}
}


// Insert a data rectangle into an index structure.
// InsertRect provides for splitting the root;
// returns 1 if root was split, 0 if it was not.
// The level argument specifies the number of steps up from the leaf
// level to insert; e.g. a data rectangle goes in at level = 0.
// InsertRect2 does the recursion.
//
RTREE_TEMPLATE
bool RTREE_QUAL::InsertRect(Rect* a_rect, const DATATYPE& a_id, Node** a_root,
  int a_level)
{
	Q_ASSERT(a_rect && a_root);
	Q_ASSERT(a_level >= 0 && a_level <= (*a_root)->m_level);
	#ifndef QT_NO_DEBUG
	for (int index=0; index < NUMDIMS; ++index)
		Q_ASSERT(a_rect->m_min[index] <= a_rect->m_max[index]);
	#endif // QT_NO_DEBUG

	Node* newRoot;
	Node* newNode;
	Branch branch;

	// Root split
	if (InsertRectRec(a_rect, a_id, *a_root, &newNode, a_level)) {
		newRoot = AllocNode();  // Grow tree taller and new root
		newRoot->m_level = (*a_root)->m_level + 1;
		branch.m_rect = NodeCover(*a_root);
		branch.m_child = *a_root;
		AddBranch(&branch, newRoot, NULL);
		branch.m_rect = NodeCover(newNode);
		branch.m_child = newNode;
		AddBranch(&branch, newRoot, NULL);
		*a_root = newRoot;
		return true;
	}

	return false;
}


// Find the smallest rectangle that includes all rectangles in branches of
// a node.
RTREE_TEMPLATE
typename RTREE_QUAL::Rect RTREE_QUAL::NodeCover(Node* a_node)
{
	Q_ASSERT(a_node);

	int firstTime = true;
	Rect rect;
	InitRect(&rect);

	for (int index = 0; index < a_node->m_count; ++index) {
		if (firstTime) {
			rect = a_node->m_branch[index].m_rect;
			firstTime = false;
		} else {
			rect = CombineRect(&rect, &(a_node->m_branch[index].m_rect));
		}
	}

	return rect;
}


// Add a branch to a node.  Split the node if necessary.
// Returns 0 if node not split.  Old node updated.
// Returns 1 if node split, sets *new_node to address of new node.
// Old node updated, becomes one of two.
RTREE_TEMPLATE
bool RTREE_QUAL::AddBranch(Branch* a_branch, Node* a_node, Node** a_newNode)
{
	Q_ASSERT(a_branch);
	Q_ASSERT(a_node);

	if (a_node->m_count < MAXNODES) {  // Split won't be necessary
		a_node->m_branch[a_node->m_count] = *a_branch;
		++a_node->m_count;

		return false;
	} else {
		Q_ASSERT(a_newNode);

		SplitNode(a_node, a_branch, a_newNode);
		return true;
	}
}


// Disconnect a dependent node.
// Caller must return (or stop using iteration index) after this as count has
// changed
RTREE_TEMPLATE
void RTREE_QUAL::DisconnectBranch(Node* a_node, int a_index)
{
	Q_ASSERT(a_node && (a_index >= 0) && (a_index < MAXNODES));
	Q_ASSERT(a_node->m_count > 0);

	// Remove element by swapping with the last element to prevent gaps in array
	a_node->m_branch[a_index] = a_node->m_branch[a_node->m_count - 1];

	--a_node->m_count;
}


// Pick a branch.  Pick the one that will need the smallest increase
// in area to accomodate the new rectangle.  This will result in the
// least total area for the covering rectangles in the current node.
// In case of a tie, pick the one which was smaller before, to get
// the best resolution when searching.
RTREE_TEMPLATE
int RTREE_QUAL::PickBranch(Rect* a_rect, Node* a_node)
{
	Q_ASSERT(a_rect && a_node);

	bool firstTime = true;
	ELEMTYPEREAL increase;
	ELEMTYPEREAL bestIncr = (ELEMTYPEREAL)-1;
	ELEMTYPEREAL area;
	ELEMTYPEREAL bestArea;
	int best = 0;
	Rect tempRect;

	for (int index=0; index < a_node->m_count; ++index) {
		Rect* curRect = &a_node->m_branch[index].m_rect;
		area = CalcRectVolume(curRect);
		tempRect = CombineRect(a_rect, curRect);
		increase = CalcRectVolume(&tempRect) - area;

		if ((increase < bestIncr) || firstTime) {
			best = index;
			bestArea = area;
			bestIncr = increase;
			firstTime = false;
		} else if ((increase == bestIncr) && (area < bestArea)) {
			best = index;
			bestArea = area;
			bestIncr = increase;
		}
	}
	return best;
}


// Combine two rectangles into larger one containing both
RTREE_TEMPLATE
typename RTREE_QUAL::Rect RTREE_QUAL::CombineRect(Rect* a_rectA, Rect* a_rectB)
{
	Q_ASSERT(a_rectA && a_rectB);

	Rect newRect;

	for (int index = 0; index < NUMDIMS; ++index) {
		newRect.m_min[index] = qMin(a_rectA->m_min[index], a_rectB->m_min[index]);
		newRect.m_max[index] = qMax(a_rectA->m_max[index], a_rectB->m_max[index]);
	}

	return newRect;
}



// Split a node.
// Divides the nodes branches and the extra one between two nodes.
// Old node is one of the new ones, and one really new one is created.
// Tries more than one method for choosing a partition, uses best result.
RTREE_TEMPLATE
void RTREE_QUAL::SplitNode(Node* a_node, Branch* a_branch, Node** a_newNode)
{
	Q_ASSERT(a_node);
	Q_ASSERT(a_branch);

	// Could just use local here, but member or external is faster since it is
	// reused
	PartitionVars localVars;
	PartitionVars* parVars = &localVars;
	int level;

	// Load all the branches into a buffer, initialize old node
	level = a_node->m_level;
	GetBranches(a_node, a_branch, parVars);

	// Find partition
	ChoosePartition(parVars, MINNODES);

	// Put branches from buffer into 2 nodes according to chosen partition
	*a_newNode = AllocNode();
	(*a_newNode)->m_level = a_node->m_level = level;
	LoadNodes(a_node, *a_newNode, parVars);

	Q_ASSERT((a_node->m_count + (*a_newNode)->m_count) == parVars->m_total);
}


// Calculate the n-dimensional volume of a rectangle
RTREE_TEMPLATE
ELEMTYPEREAL RTREE_QUAL::RectVolume(Rect* a_rect)
{
	Q_ASSERT(a_rect);

	ELEMTYPEREAL volume = (ELEMTYPEREAL)1;

	for (int index=0; index<NUMDIMS; ++index)
		volume *= a_rect->m_max[index] - a_rect->m_min[index];

	Q_ASSERT(volume >= (ELEMTYPEREAL)0);

	return volume;
}


// The exact volume of the bounding sphere for the given Rect
RTREE_TEMPLATE
ELEMTYPEREAL RTREE_QUAL::RectSphericalVolume(Rect* a_rect)
{
	Q_ASSERT(a_rect);

	ELEMTYPEREAL sumOfSquares = (ELEMTYPEREAL)0;
	ELEMTYPEREAL radius;

	for (int index=0; index < NUMDIMS; ++index) {
		ELEMTYPEREAL halfExtent = ((ELEMTYPEREAL)a_rect->m_max[index]
		  - (ELEMTYPEREAL)a_rect->m_min[index]) * 0.5f;
		sumOfSquares += halfExtent * halfExtent;
	}

	radius = (ELEMTYPEREAL)sqrt(sumOfSquares);

	// Pow maybe slow, so test for common dims like 2,3 and just use x*x, x*x*x.
	if (NUMDIMS == 3)
		return (radius * radius * radius * m_unitSphereVolume);
	else if (NUMDIMS == 2)
		return (radius * radius * m_unitSphereVolume);
	else
		return (ELEMTYPEREAL)(pow(radius, NUMDIMS) * m_unitSphereVolume);
}


// Use one of the methods to calculate retangle volume
RTREE_TEMPLATE
ELEMTYPEREAL RTREE_QUAL::CalcRectVolume(Rect* a_rect)
{
	#ifdef RTREE_USE_SPHERICAL_VOLUME
	return RectSphericalVolume(a_rect); // Slower but helps certain merge cases
	#else // RTREE_USE_SPHERICAL_VOLUME
	return RectVolume(a_rect); // Faster but can cause poor merges
	#endif // RTREE_USE_SPHERICAL_VOLUME  
}


// Load branch buffer with branches from full node plus the extra branch.
RTREE_TEMPLATE
void RTREE_QUAL::GetBranches(Node* a_node, Branch* a_branch,
  PartitionVars* a_parVars)
{
	Q_ASSERT(a_node);
	Q_ASSERT(a_branch);

	Q_ASSERT(a_node->m_count == MAXNODES);

	// Load the branch buffer
	for (int index=0; index < MAXNODES; ++index)
		a_parVars->m_branchBuf[index] = a_node->m_branch[index];
	a_parVars->m_branchBuf[MAXNODES] = *a_branch;
	a_parVars->m_branchCount = MAXNODES + 1;

	// Calculate rect containing all in the set
	a_parVars->m_coverSplit = a_parVars->m_branchBuf[0].m_rect;
	for (int index=1; index < MAXNODES+1; ++index)
		a_parVars->m_coverSplit = CombineRect(&a_parVars->m_coverSplit,
		  &a_parVars->m_branchBuf[index].m_rect);
	a_parVars->m_coverSplitArea = CalcRectVolume(&a_parVars->m_coverSplit);

	InitNode(a_node);
}


// Method #0 for choosing a partition:
// As the seeds for the two groups, pick the two rects that would waste the
// most area if covered by a single rectangle, i.e. evidently the worst pair
// to have in the same group.
// Of the remaining, one at a time is chosen to be put in one of the two groups.
// The one chosen is the one with the greatest difference in area expansion
// depending on which group - the rect most strongly attracted to one group
// and repelled from the other.
// If one group gets too full (more would force other group to violate min
// fill requirement) then other group gets the rest.
// These last are the ones that can go in either group most easily.
RTREE_TEMPLATE
void RTREE_QUAL::ChoosePartition(PartitionVars* a_parVars, int a_minFill)
{
	Q_ASSERT(a_parVars);

	ELEMTYPEREAL biggestDiff;
	int group, chosen = 0, betterGroup = 0;

	InitParVars(a_parVars, a_parVars->m_branchCount, a_minFill);
	PickSeeds(a_parVars);

	while (((a_parVars->m_count[0] + a_parVars->m_count[1]) < a_parVars->m_total)
		&& (a_parVars->m_count[0] < (a_parVars->m_total - a_parVars->m_minFill))
		&& (a_parVars->m_count[1] < (a_parVars->m_total - a_parVars->m_minFill))) {
		biggestDiff = (ELEMTYPEREAL) -1;

		for (int index=0; index<a_parVars->m_total; ++index) {
			if (!a_parVars->m_taken[index]) {
				Rect* curRect = &a_parVars->m_branchBuf[index].m_rect;
				Rect rect0 = CombineRect(curRect, &a_parVars->m_cover[0]);
				Rect rect1 = CombineRect(curRect, &a_parVars->m_cover[1]);
				ELEMTYPEREAL growth0 = CalcRectVolume(&rect0) - a_parVars->m_area[0];
				ELEMTYPEREAL growth1 = CalcRectVolume(&rect1) - a_parVars->m_area[1];
				ELEMTYPEREAL diff = growth1 - growth0;

				if (diff >= 0) {
					group = 0;
				} else {
					group = 1;
					diff = -diff;
				}

				if (diff > biggestDiff) {
					biggestDiff = diff;
					chosen = index;
					betterGroup = group;
				} else if ((diff == biggestDiff) && (a_parVars->m_count[group]
				  < a_parVars->m_count[betterGroup])) {
					chosen = index;
					betterGroup = group;
				}
			}
		}
		Classify(chosen, betterGroup, a_parVars);
	}

	// If one group too full, put remaining rects in the other
	if ((a_parVars->m_count[0] + a_parVars->m_count[1]) < a_parVars->m_total) {
		if (a_parVars->m_count[0] >= a_parVars->m_total - a_parVars->m_minFill)
			group = 1;
		else
			group = 0;

		for (int index=0; index<a_parVars->m_total; ++index) {
			if (!a_parVars->m_taken[index])
				Classify(index, group, a_parVars);
		}
	}

	Q_ASSERT((a_parVars->m_count[0] + a_parVars->m_count[1]) == a_parVars->m_total);
	Q_ASSERT((a_parVars->m_count[0] >= a_parVars->m_minFill) &&
	(a_parVars->m_count[1] >= a_parVars->m_minFill));
}


// Copy branches from the buffer into two nodes according to the partition.
RTREE_TEMPLATE
void RTREE_QUAL::LoadNodes(Node* a_nodeA, Node* a_nodeB, PartitionVars* a_parVars)
{
	Q_ASSERT(a_nodeA);
	Q_ASSERT(a_nodeB);
	Q_ASSERT(a_parVars);

	for (int index=0; index < a_parVars->m_total; ++index) {
		Q_ASSERT(a_parVars->m_partition[index] == 0 || a_parVars->m_partition[index] == 1);

		if (a_parVars->m_partition[index] == 0)
			AddBranch(&a_parVars->m_branchBuf[index], a_nodeA, NULL);
		else if (a_parVars->m_partition[index] == 1)
			AddBranch(&a_parVars->m_branchBuf[index], a_nodeB, NULL);
	}
}


// Initialize a PartitionVars structure.
RTREE_TEMPLATE
void RTREE_QUAL::InitParVars(PartitionVars* a_parVars, int a_maxRects,
  int a_minFill)
{
	Q_ASSERT(a_parVars);

	a_parVars->m_count[0] = a_parVars->m_count[1] = 0;
	a_parVars->m_area[0] = a_parVars->m_area[1] = (ELEMTYPEREAL)0;
	a_parVars->m_total = a_maxRects;
	a_parVars->m_minFill = a_minFill;

	for (int index=0; index < a_maxRects; ++index) {
		a_parVars->m_taken[index] = false;
		a_parVars->m_partition[index] = -1;
	}
}


RTREE_TEMPLATE
void RTREE_QUAL::PickSeeds(PartitionVars* a_parVars)
{
	int seed0 = 0, seed1 = 0;
	ELEMTYPEREAL worst, waste;
	ELEMTYPEREAL area[MAXNODES+1];

	for (int index=0; index<a_parVars->m_total; ++index)
		area[index] = CalcRectVolume(&a_parVars->m_branchBuf[index].m_rect);

	worst = -a_parVars->m_coverSplitArea - 1;
	for (int indexA=0; indexA < a_parVars->m_total-1; ++indexA) {
		for (int indexB = indexA+1; indexB < a_parVars->m_total; ++indexB) {
			Rect oneRect = CombineRect(&a_parVars->m_branchBuf[indexA].m_rect,
			  &a_parVars->m_branchBuf[indexB].m_rect);
			waste = CalcRectVolume(&oneRect) - area[indexA] - area[indexB];
			if (waste > worst) {
				worst = waste;
				seed0 = indexA;
				seed1 = indexB;
			}
		}
	}
	Classify(seed0, 0, a_parVars);
	Classify(seed1, 1, a_parVars);
}


// Put a branch in one of the groups.
RTREE_TEMPLATE
void RTREE_QUAL::Classify(int a_index, int a_group, PartitionVars* a_parVars)
{
	Q_ASSERT(a_parVars);
	Q_ASSERT(!a_parVars->m_taken[a_index]);

	a_parVars->m_partition[a_index] = a_group;
	a_parVars->m_taken[a_index] = true;

	if (a_parVars->m_count[a_group] == 0)
		a_parVars->m_cover[a_group] = a_parVars->m_branchBuf[a_index].m_rect;
	else
		a_parVars->m_cover[a_group] = CombineRect(
		  &a_parVars->m_branchBuf[a_index].m_rect, &a_parVars->m_cover[a_group]);

	a_parVars->m_area[a_group] = CalcRectVolume(&a_parVars->m_cover[a_group]);
	++a_parVars->m_count[a_group];
}


// Delete a data rectangle from an index structure.
// Pass in a pointer to a Rect, the tid of the record, ptr to ptr to root node.
// Returns 1 if record not found, 0 if success.
// RemoveRect provides for eliminating the root.
RTREE_TEMPLATE
bool RTREE_QUAL::RemoveRect(Rect* a_rect, const DATATYPE& a_id, Node** a_root)
{
	Q_ASSERT(a_rect && a_root);
	Q_ASSERT(*a_root);

	Node* tempNode;
	ListNode* reInsertList = NULL;

	if (!RemoveRectRec(a_rect, a_id, *a_root, &reInsertList)) {
		// Found and deleted a data item
		// Reinsert any branches from eliminated nodes
		while (reInsertList) {
			tempNode = reInsertList->m_node;

			for (int index = 0; index < tempNode->m_count; ++index)
				InsertRect(&(tempNode->m_branch[index].m_rect),
				  tempNode->m_branch[index].m_data, a_root, tempNode->m_level);

			ListNode* remLNode = reInsertList;
			reInsertList = reInsertList->m_next;

			FreeNode(remLNode->m_node);
			FreeListNode(remLNode);
		}

		// Check for redundant root (not leaf, 1 child) and eliminate
		if ((*a_root)->m_count == 1 && (*a_root)->IsInternalNode()) {
			tempNode = (*a_root)->m_branch[0].m_child;

			Q_ASSERT(tempNode);
			FreeNode(*a_root);
			*a_root = tempNode;
		}
		return false;
	} else {
		return true;
	}
}


// Delete a rectangle from non-root part of an index structure.
// Called by RemoveRect.  Descends tree recursively,
// merges branches on the way back up.
// Returns 1 if record not found, 0 if success.
RTREE_TEMPLATE
bool RTREE_QUAL::RemoveRectRec(Rect* a_rect, const DATATYPE& a_id, Node* a_node,
  ListNode** a_listNode)
{
	Q_ASSERT(a_rect && a_node && a_listNode);
	Q_ASSERT(a_node->m_level >= 0);

	if (a_node->IsInternalNode()) {  // not a leaf node
		for (int index = 0; index < a_node->m_count; ++index) {
			if (Overlap(a_rect, &(a_node->m_branch[index].m_rect))) {
				if (!RemoveRectRec(a_rect, a_id, a_node->m_branch[index].m_child, a_listNode)) {
					if (a_node->m_branch[index].m_child->m_count >= MINNODES) {
						// child removed, just resize parent rect
						a_node->m_branch[index].m_rect = NodeCover(a_node->m_branch[index].m_child);
					} else {
						// child removed, not enough entries in node, eliminate
						// node
						ReInsert(a_node->m_branch[index].m_child, a_listNode);
						DisconnectBranch(a_node, index);
						// Must return after this call as count has changed
					}
					return false;
				}
			}
		}
		return true;
	} else { // A leaf node
		for (int index = 0; index < a_node->m_count; ++index)
		{
			if (a_node->m_branch[index].m_child == (Node*)a_id)
			{
				DisconnectBranch(a_node, index);
				// Must return after this call as count has changed
				return false;
			}
		}
		return true;
	}
}


// Decide whether two rectangles overlap.
RTREE_TEMPLATE
bool RTREE_QUAL::Overlap(Rect* a_rectA, Rect* a_rectB) const
{
	Q_ASSERT(a_rectA && a_rectB);

	for (int index=0; index < NUMDIMS; ++index) {
		if (a_rectA->m_min[index] > a_rectB->m_max[index] ||
			a_rectB->m_min[index] > a_rectA->m_max[index]) {
			return false;
		}
	}
	return true;
}


// Add a node to the reinsertion list.  All its branches will later
// be reinserted into the index structure.
RTREE_TEMPLATE
void RTREE_QUAL::ReInsert(Node* a_node, ListNode** a_listNode)
{
	ListNode* newListNode;

	newListNode = AllocListNode();
	newListNode->m_node = a_node;
	newListNode->m_next = *a_listNode;
	*a_listNode = newListNode;
}


// Search in an index tree or subtree for all data retangles that overlap
// the argument rectangle.
RTREE_TEMPLATE
bool RTREE_QUAL::Search(Node* a_node, Rect* a_rect, int& a_foundCount,
  bool (*a_resultCallback)(DATATYPE a_data, void* a_context),
  void* a_context) const
{
	Q_ASSERT(a_node);
	Q_ASSERT(a_node->m_level >= 0);
	Q_ASSERT(a_rect);

	if (a_node->IsInternalNode()) { // This is an internal node in the tree
		for (int index=0; index < a_node->m_count; ++index) {
			if (Overlap(a_rect, &a_node->m_branch[index].m_rect)) {
				if (!Search(a_node->m_branch[index].m_child, a_rect,
				  a_foundCount, a_resultCallback, a_context)) {
					return false; // Don't continue searching
				}
			}
		}
	} else { // This is a leaf node
		for (int index=0; index < a_node->m_count; ++index) {
			if (Overlap(a_rect, &a_node->m_branch[index].m_rect)) {
				DATATYPE& id = a_node->m_branch[index].m_data;

				// NOTE: There are different ways to return results.
				// Here's where to modify
				if (a_resultCallback) {
					++a_foundCount;
					if (!a_resultCallback(id, a_context))
						return false; // Don't continue searching
				}
			}
		}
	}

	return true; // Continue searching
}


#undef RTREE_TEMPLATE
#undef RTREE_QUAL

#endif //RTREE_H