473 lines
14 KiB
C++
473 lines
14 KiB
C++
// Copyright (C) 2007 Id Software, Inc.
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//
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#ifndef __BTREE_H__
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#define __BTREE_H__
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/*
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===============================================================================
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Balanced Search Tree
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===============================================================================
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*/
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//#define BTREE_CHECK
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template< class objType, class keyType >
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class idBTreeNode {
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public:
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keyType key; // key used for sorting
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objType * object; // if != NULL pointer to object stored in leaf node
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idBTreeNode * parent; // parent node
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idBTreeNode * next; // next sibling
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idBTreeNode * prev; // prev sibling
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int numChildren; // number of children
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idBTreeNode * firstChild; // first child
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idBTreeNode * lastChild; // last child
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};
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template< class objType, class keyType, int maxChildrenPerNode >
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class idBTree {
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public:
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idBTree( void );
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~idBTree( void );
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void Init( void );
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void Shutdown( void );
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idBTreeNode<objType,keyType> * Add( objType *object, keyType key ); // add an object to the tree
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void Remove( idBTreeNode<objType,keyType> *node ); // remove an object node from the tree
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objType * Find( keyType key ) const; // find an object using the given key
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objType * FindSmallestLargerEqual( keyType key ) const; // find an object with the smallest key larger equal the given key
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idBTreeNode<objType,keyType> * GetRoot( void ) const; // returns the root node of the tree
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int GetNodeCount( void ) const; // returns the total number of nodes in the tree
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idBTreeNode<objType,keyType> * GetNext( idBTreeNode<objType,keyType> *node ) const; // goes through all nodes of the tree
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idBTreeNode<objType,keyType> * GetNextLeaf( idBTreeNode<objType,keyType> *node ) const; // goes through all leaf nodes of the tree
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private:
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idBTreeNode<objType,keyType> * root;
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idBlockAlloc<idBTreeNode<objType,keyType>,128> nodeAllocator;
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idBTreeNode<objType,keyType> * AllocNode( void );
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void FreeNode( idBTreeNode<objType,keyType> *node );
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void SplitNode( idBTreeNode<objType,keyType> *node );
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idBTreeNode<objType,keyType> * MergeNodes( idBTreeNode<objType,keyType> *node1, idBTreeNode<objType,keyType> *node2 );
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void CheckTree_r( idBTreeNode<objType,keyType> *node, int &numNodes ) const;
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void CheckTree( void ) const;
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};
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTree<objType,keyType,maxChildrenPerNode>::idBTree( void ) {
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assert( maxChildrenPerNode >= 4 );
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root = NULL;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTree<objType,keyType,maxChildrenPerNode>::~idBTree( void ) {
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Shutdown();
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::Init( void ) {
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root = AllocNode();
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::Shutdown( void ) {
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nodeAllocator.Shutdown();
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root = NULL;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::Add( objType *object, keyType key ) {
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idBTreeNode<objType,keyType> *node, *child, *newNode;
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if ( root->numChildren >= maxChildrenPerNode ) {
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newNode = AllocNode();
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newNode->key = root->key;
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newNode->firstChild = root;
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newNode->lastChild = root;
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newNode->numChildren = 1;
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root->parent = newNode;
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SplitNode( root );
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root = newNode;
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}
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newNode = AllocNode();
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newNode->key = key;
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newNode->object = object;
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for ( node = root; node->firstChild != NULL; node = child ) {
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if ( key > node->key ) {
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node->key = key;
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}
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// find the first child with a key larger equal to the key of the new node
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for( child = node->firstChild; child->next; child = child->next ) {
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if ( key <= child->key ) {
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break;
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}
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}
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if ( child->object ) {
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if ( key <= child->key ) {
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// insert new node before child
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if ( child->prev ) {
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child->prev->next = newNode;
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} else {
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node->firstChild = newNode;
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}
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newNode->prev = child->prev;
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newNode->next = child;
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child->prev = newNode;
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} else {
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// insert new node after child
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if ( child->next ) {
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child->next->prev = newNode;
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} else {
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node->lastChild = newNode;
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}
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newNode->prev = child;
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newNode->next = child->next;
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child->next = newNode;
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}
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newNode->parent = node;
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node->numChildren++;
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#ifdef BTREE_CHECK
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CheckTree();
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#endif
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return newNode;
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}
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// make sure the child has room to store another node
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if ( child->numChildren >= maxChildrenPerNode ) {
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SplitNode( child );
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if ( key <= child->prev->key ) {
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child = child->prev;
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}
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}
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}
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// we only end up here if the root node is empty
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newNode->parent = root;
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root->key = key;
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root->firstChild = newNode;
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root->lastChild = newNode;
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root->numChildren++;
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#ifdef BTREE_CHECK
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CheckTree();
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#endif
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return newNode;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::Remove( idBTreeNode<objType,keyType> *node ) {
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idBTreeNode<objType,keyType> *parent;
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assert( node->object != NULL );
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// unlink the node from it's parent
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if ( node->prev ) {
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node->prev->next = node->next;
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} else {
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node->parent->firstChild = node->next;
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}
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if ( node->next ) {
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node->next->prev = node->prev;
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} else {
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node->parent->lastChild = node->prev;
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}
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node->parent->numChildren--;
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// make sure there are no parent nodes with a single child
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for ( parent = node->parent; parent != root && parent->numChildren <= 1; parent = parent->parent ) {
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if ( parent->next ) {
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parent = MergeNodes( parent, parent->next );
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} else if ( parent->prev ) {
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parent = MergeNodes( parent->prev, parent );
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}
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// a parent may not use a key higher than the key of it's last child
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if ( parent->key > parent->lastChild->key ) {
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parent->key = parent->lastChild->key;
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}
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if ( parent->numChildren > maxChildrenPerNode ) {
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SplitNode( parent );
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break;
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}
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}
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for ( ; parent != NULL && parent->lastChild != NULL; parent = parent->parent ) {
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// a parent may not use a key higher than the key of it's last child
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if ( parent->key > parent->lastChild->key ) {
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parent->key = parent->lastChild->key;
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}
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}
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// free the node
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FreeNode( node );
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// remove the root node if it has a single internal node as child
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if ( root->numChildren == 1 && root->firstChild->object == NULL ) {
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idBTreeNode<objType,keyType> *oldRoot = root;
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root->firstChild->parent = NULL;
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root = root->firstChild;
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FreeNode( oldRoot );
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}
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#ifdef BTREE_CHECK
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CheckTree();
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#endif
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE objType *idBTree<objType,keyType,maxChildrenPerNode>::Find( keyType key ) const {
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idBTreeNode<objType,keyType> *node;
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for ( node = root->firstChild; node != NULL; node = node->firstChild ) {
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while( node->next ) {
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if ( node->key >= key ) {
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break;
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}
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node = node->next;
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}
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if ( node->object ) {
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if ( node->key == key ) {
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return node->object;
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} else {
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return NULL;
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}
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}
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}
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return NULL;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE objType *idBTree<objType,keyType,maxChildrenPerNode>::FindSmallestLargerEqual( keyType key ) const {
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idBTreeNode<objType,keyType> *node;
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for ( node = root->firstChild; node != NULL; node = node->firstChild ) {
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while( node->next ) {
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if ( node->key >= key ) {
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break;
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}
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node = node->next;
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}
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if ( node->object ) {
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if ( node->key >= key ) {
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return node->object;
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} else {
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return NULL;
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}
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}
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}
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return NULL;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::GetRoot( void ) const {
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return root;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE int idBTree<objType,keyType,maxChildrenPerNode>::GetNodeCount( void ) const {
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return nodeAllocator.GetAllocCount();
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::GetNext( idBTreeNode<objType,keyType> *node ) const {
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if ( node->firstChild ) {
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return node->firstChild;
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} else {
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while( node && node->next == NULL ) {
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node = node->parent;
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}
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return node;
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}
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::GetNextLeaf( idBTreeNode<objType,keyType> *node ) const {
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if ( node->firstChild ) {
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while ( node->firstChild ) {
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node = node->firstChild;
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}
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return node;
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} else {
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while( node && node->next == NULL ) {
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node = node->parent;
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}
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if ( node ) {
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node = node->next;
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while ( node->firstChild ) {
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node = node->firstChild;
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}
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return node;
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} else {
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return NULL;
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}
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}
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::AllocNode( void ) {
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idBTreeNode<objType,keyType> *node = nodeAllocator.Alloc();
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node->key = 0;
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node->parent = NULL;
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node->next = NULL;
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node->prev = NULL;
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node->numChildren = 0;
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node->firstChild = NULL;
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node->lastChild = NULL;
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node->object = NULL;
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return node;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::FreeNode( idBTreeNode<objType,keyType> *node ) {
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nodeAllocator.Free( node );
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::SplitNode( idBTreeNode<objType,keyType> *node ) {
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int i;
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idBTreeNode<objType,keyType> *child, *newNode;
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// allocate a new node
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newNode = AllocNode();
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newNode->parent = node->parent;
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// divide the children over the two nodes
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child = node->firstChild;
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child->parent = newNode;
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for ( i = 3; i < node->numChildren; i += 2 ) {
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child = child->next;
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child->parent = newNode;
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}
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newNode->key = child->key;
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newNode->numChildren = node->numChildren / 2;
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newNode->firstChild = node->firstChild;
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newNode->lastChild = child;
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node->numChildren -= newNode->numChildren;
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node->firstChild = child->next;
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child->next->prev = NULL;
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child->next = NULL;
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// add the new child to the parent before the split node
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assert( node->parent->numChildren < maxChildrenPerNode );
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if ( node->prev ) {
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node->prev->next = newNode;
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} else {
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node->parent->firstChild = newNode;
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}
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newNode->prev = node->prev;
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newNode->next = node;
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node->prev = newNode;
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node->parent->numChildren++;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE idBTreeNode<objType,keyType> *idBTree<objType,keyType,maxChildrenPerNode>::MergeNodes( idBTreeNode<objType,keyType> *node1, idBTreeNode<objType,keyType> *node2 ) {
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idBTreeNode<objType,keyType> *child;
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assert( node1->parent == node2->parent );
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assert( node1->next == node2 && node2->prev == node1 );
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assert( node1->object == NULL && node2->object == NULL );
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assert( node1->numChildren >= 1 && node2->numChildren >= 1 );
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for ( child = node1->firstChild; child->next; child = child->next ) {
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child->parent = node2;
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}
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child->parent = node2;
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child->next = node2->firstChild;
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node2->firstChild->prev = child;
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node2->firstChild = node1->firstChild;
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node2->numChildren += node1->numChildren;
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// unlink the first node from the parent
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if ( node1->prev ) {
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node1->prev->next = node2;
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} else {
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node1->parent->firstChild = node2;
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}
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node2->prev = node1->prev;
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node2->parent->numChildren--;
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FreeNode( node1 );
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return node2;
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::CheckTree_r( idBTreeNode<objType,keyType> *node, int &numNodes ) const {
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int numChildren;
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idBTreeNode<objType,keyType> *child;
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numNodes++;
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// the root node may have zero children and leaf nodes always have zero children, all other nodes should have at least 2 and at most maxChildrenPerNode children
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assert( ( node == root ) || ( node->object != NULL && node->numChildren == 0 ) || ( node->numChildren >= 2 && node->numChildren <= maxChildrenPerNode ) );
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// the key of a node may never be larger than the key of it's last child
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assert( ( node->lastChild == NULL ) || ( node->key <= node->lastChild->key ) );
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numChildren = 0;
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for ( child = node->firstChild; child; child = child->next ) {
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numChildren++;
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// make sure the children are properly linked
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if ( child->prev == NULL ) {
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assert( node->firstChild == child );
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} else {
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assert( child->prev->next == child );
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}
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if ( child->next == NULL ) {
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assert( node->lastChild == child );
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} else {
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assert( child->next->prev == child );
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}
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// recurse down the tree
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CheckTree_r( child, numNodes );
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}
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// the number of children should equal the number of linked children
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assert( numChildren == node->numChildren );
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}
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template< class objType, class keyType, int maxChildrenPerNode >
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ID_INLINE void idBTree<objType,keyType,maxChildrenPerNode>::CheckTree( void ) const {
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int numNodes = 0;
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idBTreeNode<objType,keyType> *node, *lastNode;
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CheckTree_r( root, numNodes );
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// the number of nodes in the tree should equal the number of allocated nodes
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assert( numNodes == nodeAllocator.GetAllocCount() );
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// all the leaf nodes should be ordered
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lastNode = GetNextLeaf( GetRoot() );
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if ( lastNode ) {
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for ( node = GetNextLeaf( lastNode ); node; lastNode = node, node = GetNextLeaf( node ) ) {
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assert( lastNode->key <= node->key );
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}
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}
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}
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#endif /* !__BTREE_H__ */
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