ReGameDLL_CS/regamedll/public/utlrbtree.h

/*
*
*   This program is free software; you can redistribute it and/or modify it
*   under the terms of the GNU General Public License as published by the
*   Free Software Foundation; either version 2 of the License, or (at
*   your option) any later version.
*
*   This program is distributed in the hope that it will be useful, but
*   WITHOUT ANY WARRANTY; without even the implied warranty of
*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*   General Public License for more details.
*
*   You should have received a copy of the GNU General Public License
*   along with this program; if not, write to the Free Software Foundation,
*   Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
*   In addition, as a special exception, the author gives permission to
*   link the code of this program with the Half-Life Game Engine ("HL
*   Engine") and Modified Game Libraries ("MODs") developed by Valve,
*   L.L.C ("Valve").  You must obey the GNU General Public License in all
*   respects for all of the code used other than the HL Engine and MODs
*   from Valve.  If you modify this file, you may extend this exception
*   to your version of the file, but you are not obligated to do so.  If
*   you do not wish to do so, delete this exception statement from your
*   version.
*
*/

#pragma once

#include "utlmemory.h"

// Tool to generate a default compare function for any type that implements
// operator<, including all simple types
template <typename T>
class CDefOps
{
public:
	static bool LessFunc(const T &lhs, const T &rhs) { return (lhs < rhs); }
};

#define DefLessFunc(type) CDefOps<type>::LessFunc

inline bool StringLessThan(const char * const &lhs, const char * const &rhs)         { return (strcmp(lhs, rhs) < 0);   }
inline bool CaselessStringLessThan(const char * const &lhs, const char * const &rhs) { return (_stricmp(lhs, rhs) < 0); }

// inline these two templates to stop multiple definitions of the same code
template <> inline bool CDefOps<const char *>::LessFunc(const char * const &lhs, const char * const &rhs) { return StringLessThan(lhs, rhs); }
template <> inline bool CDefOps<char *>::LessFunc(char * const &lhs, char * const &rhs)                   { return StringLessThan(lhs, rhs); }

template <typename RBTREE_T>
void SetDefLessFunc(RBTREE_T &RBTree)
{
	RBTree.SetLessFunc(DefLessFunc(typename RBTREE_T::KeyType_t));
}

// A red-black binary search tree
template <class I>
struct UtlRBTreeLinks_t
{
	I m_Left;
	I m_Right;
	I m_Parent;
	I m_Tag;
};

template <class T, class I>
struct UtlRBTreeNode_t: public UtlRBTreeLinks_t<I>
{
	T m_Data;
};

// A red-black binary search tree
template <class T, class I = unsigned short, typename L = bool (*)(const T &, const T &), class M = CUtlMemory<UtlRBTreeNode_t<T, I>, I>>
class CUtlRBTree
{
public:
	typedef T KeyType_t;
	typedef T ElemType_t;
	typedef I IndexType_t;

	// Less func typedef
	// Returns true if the first parameter is "less" than the second
	typedef L LessFunc_t;

	// constructor, destructor
	// Left at growSize = 0, the memory will first allocate 1 element and double in size
	// at each increment.
	// LessFunc_t is required, but may be set after the constructor using SetLessFunc() below
	CUtlRBTree(int growSize = 0, int initSize = 0, LessFunc_t lessfunc = 0);
	~CUtlRBTree();

	// gets particular elements
	T&       Element(I i);
	T const& Element(I i) const;
	T&       operator[](I i);
	T const& operator[](I i) const;

	// Gets the root
	I Root() const;

	// Num elements
	unsigned int Count() const;

	// Max "size" of the vector
	I MaxElement() const;

	// Gets the children
	I Parent(I i) const;
	I LeftChild(I i) const;
	I RightChild(I i) const;

	// Tests if a node is a left or right child
	bool IsLeftChild(I i) const;
	bool IsRightChild(I i) const;

	// Tests if root or leaf
	bool IsRoot(I i) const;
	bool IsLeaf(I i) const;

	// Checks if a node is valid and in the tree
	bool IsValidIndex(I i) const;

	// Checks if the tree as a whole is valid
	bool IsValid() const;

	// Invalid index
	static I InvalidIndex();

	// returns the tree depth (not a very fast operation)
	int Depth(I node) const;
	int Depth() const;

	// Sets the less func
	void SetLessFunc(LessFunc_t func);

	// Allocation method
	I NewNode();

	// Insert method (inserts in order)
	I Insert(T const &insert);
	void Insert(const T *pArray, int nItems);

	// Find method
	I Find(T const &search) const;

	// Remove methods
	void RemoveAt(I i);
	bool Remove(T const &remove);
	void RemoveAll();
	void Purge();

	// Allocation, deletion
	void FreeNode(I i);

	// Iteration
	I FirstInorder() const;
	I NextInorder(I i) const;
	I PrevInorder(I i) const;
	I LastInorder() const;

	I FirstPreorder() const;
	I NextPreorder(I i) const;
	I PrevPreorder(I i) const;
	I LastPreorder() const;

	I FirstPostorder() const;
	I NextPostorder(I i) const;

	// If you change the search key, this can be used to reinsert the
	// element into the tree.
	void Reinsert(I elem);

private:
	// Can't copy the tree this way!
	CUtlRBTree<T, I, L, M> &operator=(const CUtlRBTree<T, I, L, M> &other);

protected:
	enum NodeColor_t
	{
		RED = 0,
		BLACK
	};

	typedef UtlRBTreeNode_t<T, I> Node_t;
	typedef UtlRBTreeLinks_t<I> Links_t;

	// Sets the children
	void SetParent(I i, I parent);
	void SetLeftChild(I i, I child);
	void SetRightChild(I i, I child);
	void LinkToParent(I i, I parent, bool isLeft);

	// Gets at the links
	Links_t const& Links(I i) const;
	Links_t&       Links(I i);

	// Checks if a link is red or black
	bool IsRed(I i) const;
	bool IsBlack(I i) const;

	// Sets/gets node color
	NodeColor_t Color(I i) const;
	void SetColor(I i, NodeColor_t c);

	// operations required to preserve tree balance
	void RotateLeft(I i);
	void RotateRight(I i);
	void InsertRebalance(I i);
	void RemoveRebalance(I i);

	// Insertion, removal
	I InsertAt(I parent, bool leftchild);

	// copy constructors not allowed
	CUtlRBTree(CUtlRBTree<T, I, L, M> const &tree);

	// Inserts a node into the tree, doesn't copy the data in.
	void FindInsertionPosition(T const &insert, I &parent, bool &leftchild);

	// Remove and add back an element in the tree.
	void Unlink(I elem);
	void Link(I elem);

	// Used for sorting.
	LessFunc_t m_LessFunc;

	M m_Elements;
	I m_Root;
	I m_NumElements;
	I m_FirstFree;
	I m_TotalElements;
};

// Constructor, Destructor
template <class T, class I, typename L, class M>
CUtlRBTree<T, I, L, M>::CUtlRBTree(int growSize, int initSize, LessFunc_t lessfunc) :
	m_LessFunc(lessfunc),
	m_Elements(growSize, initSize),
	m_Root(InvalidIndex()),
	m_NumElements(0),
	m_FirstFree(InvalidIndex()),
	m_TotalElements(0)
{
}

template <class T, class I, typename L, class M>
CUtlRBTree<T, I, L, M>::~CUtlRBTree()
{
}

// Gets particular elements
template <class T, class I, typename L, class M>
inline T &CUtlRBTree<T, I, L, M>::Element(I i)
{
	return m_Elements[i].m_Data;
}

template <class T, class I, typename L, class M>
inline T const &CUtlRBTree<T, I, L, M>::Element(I i) const
{
	return m_Elements[i].m_Data;
}

template <class T, class I, typename L, class M>
inline T &CUtlRBTree<T, I, L, M>::operator[](I i)
{
	return Element(i);
}

template <class T, class I, typename L, class M>
inline T const &CUtlRBTree<T, I, L, M>::operator[](I i) const
{
	return Element(i);
}

// Gets the root
template <class T, class I, typename L, class M>
inline I CUtlRBTree<T, I, L, M>::Root() const
{
	return m_Root;
}

// Num elements
template <class T, class I, typename L, class M>
inline unsigned int CUtlRBTree<T, I, L, M>::Count() const
{
	return (unsigned int)m_NumElements;
}

// Max "size" of the vector
template <class T, class I, typename L, class M>
inline I CUtlRBTree<T, I, L, M>::MaxElement() const
{
	return (I)m_TotalElements;
}

// Gets the children
template <class T, class I, typename L, class M>
inline I CUtlRBTree<T, I, L, M>::Parent(I i) const
{
	return Links(i).m_Parent;
}

template <class T, class I, typename L, class M>
inline I CUtlRBTree<T, I, L, M>::LeftChild(I i) const
{
	return Links(i).m_Left;
}

template <class T, class I, typename L, class M>
inline I CUtlRBTree<T, I, L, M>::RightChild(I i) const
{
	return Links(i).m_Right;
}

// Tests if a node is a left or right child
template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsLeftChild(I i) const
{
	return LeftChild(Parent(i)) == i;
}

template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsRightChild(I i) const
{
	return RightChild(Parent(i)) == i;
}

// Tests if root or leaf
template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsRoot(I i) const
{
	return i == m_Root;
}

template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsLeaf(I i) const
{
	return (LeftChild(i) == InvalidIndex()) && (RightChild(i) == InvalidIndex());
}

// Checks if a node is valid and in the tree
template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsValidIndex(I i) const
{
	return LeftChild(i) != i;
}

// Invalid index
template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::InvalidIndex()
{
	return (I)M::InvalidIndex();
}

// returns the tree depth (not a very fast operation)
template <class T, class I, typename L, class M>
inline int CUtlRBTree<T, I, L, M>::Depth() const
{
	return Depth(Root());
}

// Sets the children
template <class T, class I, typename L, class M>
inline void CUtlRBTree<T, I, L, M>::SetParent(I i, I parent)
{
	Links(i).m_Parent = parent;
}

template <class T, class I, typename L, class M>
inline void CUtlRBTree<T, I, L, M>::SetLeftChild(I i, I child)
{
	Links(i).m_Left = child;
}

template <class T, class I, typename L, class M>
inline void CUtlRBTree<T, I, L, M>::SetRightChild(I i, I child)
{
	Links(i).m_Right = child;
}

// Gets at the links
template <class T, class I, typename L, class M>
inline typename CUtlRBTree<T, I, L, M>::Links_t const &CUtlRBTree<T, I, L, M>::Links(I i) const
{
	// Sentinel node, makes life easier
	static Links_t s_Sentinel =
	{
		InvalidIndex(), InvalidIndex(), InvalidIndex(), CUtlRBTree<T, I, L, M>::BLACK
	};

	return (i != InvalidIndex()) ?
				*(Links_t*)&m_Elements[i] :
				*(Links_t*)&s_Sentinel;
}

template <class T, class I, typename L, class M>
inline typename CUtlRBTree<T, I, L, M>::Links_t &CUtlRBTree<T, I, L, M>::Links(I i)
{
	DbgAssert(i != InvalidIndex());
	return *(Links_t *)&m_Elements[i];
}

// Checks if a link is red or black
template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsRed(I i) const
{
	return (Links(i).m_Tag == RED);
}

template <class T, class I, typename L, class M>
inline bool CUtlRBTree<T, I, L, M>::IsBlack(I i) const
{
	return (Links(i).m_Tag == BLACK);
}

// Sets/gets node color
template <class T, class I, typename L, class M>
inline typename CUtlRBTree<T, I, L, M>::NodeColor_t CUtlRBTree<T, I, L, M>::Color(I i) const
{
	return (NodeColor_t)Links(i).m_Tag;
}

template <class T, class I, typename L, class M>
inline void CUtlRBTree<T, I, L, M>::SetColor(I i, typename CUtlRBTree<T, I, L, M>::NodeColor_t c)
{
	Links(i).m_Tag = (I)c;
}

// Allocates/ deallocates nodes
template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::NewNode()
{
	I newElem;

	// Nothing in the free list; add.
	if (m_FirstFree == InvalidIndex())
	{
		if (m_Elements.NumAllocated() == m_TotalElements)
			m_Elements.Grow();
		newElem = m_TotalElements++;
	}
	else
	{
		newElem = m_FirstFree;
		m_FirstFree = RightChild(m_FirstFree);
	}

#ifdef _DEBUG
	// reset links to invalid....
	Links_t &node = Links(newElem);
	node.m_Left = node.m_Right = node.m_Parent = InvalidIndex();
#endif

	Construct(&Element(newElem));
	return newElem;
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::FreeNode(I i)
{
	DbgAssert(IsValidIndex(i) && (i != InvalidIndex()));
	Destruct(&Element(i));
	SetLeftChild(i, i); // indicates it's in not in the tree
	SetRightChild(i, m_FirstFree);
	m_FirstFree = i;
}

// Rotates node i to the left
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::RotateLeft(I elem)
{
	I rightchild = RightChild(elem);
	SetRightChild(elem, LeftChild(rightchild));
	if (LeftChild(rightchild) != InvalidIndex())
		SetParent(LeftChild(rightchild), elem);

	if (rightchild != InvalidIndex())
		SetParent(rightchild, Parent(elem));
	if (!IsRoot(elem))
	{
		if (IsLeftChild(elem))
			SetLeftChild(Parent(elem), rightchild);
		else
			SetRightChild(Parent(elem), rightchild);
	}
	else
		m_Root = rightchild;

	SetLeftChild(rightchild, elem);
	if (elem != InvalidIndex())
		SetParent(elem, rightchild);
}

// Rotates node i to the right
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::RotateRight(I elem)
{
	I leftchild = LeftChild(elem);
	SetLeftChild(elem, RightChild(leftchild));
	if (RightChild(leftchild) != InvalidIndex())
		SetParent(RightChild(leftchild), elem);

	if (leftchild != InvalidIndex())
		SetParent(leftchild, Parent(elem));
	if (!IsRoot(elem))
	{
		if (IsRightChild(elem))
			SetRightChild(Parent(elem), leftchild);
		else
			SetLeftChild(Parent(elem), leftchild);
	}
	else
		m_Root = leftchild;

	SetRightChild(leftchild, elem);
	if (elem != InvalidIndex())
		SetParent(elem, leftchild);
}

// Rebalances the tree after an insertion
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::InsertRebalance(I elem)
{
	while (!IsRoot(elem) && (Color(Parent(elem)) == RED))
	{
		I parent = Parent(elem);
		I grandparent = Parent(parent);

		// we have a violation
		if (IsLeftChild(parent))
		{
			I uncle = RightChild(grandparent);
			if (IsRed(uncle))
			{
				// uncle is RED
				SetColor(parent, BLACK);
				SetColor(uncle, BLACK);
				SetColor(grandparent, RED);
				elem = grandparent;
			}
			else
			{
				// uncle is BLACK
				if (IsRightChild(elem))
				{
					// make x a left child, will change parent and grandparent
					elem = parent;
					RotateLeft(elem);
					parent = Parent(elem);
					grandparent = Parent(parent);
				}

				// recolor and rotate
				SetColor(parent, BLACK);
				SetColor(grandparent, RED);
				RotateRight(grandparent);
			}
		}
		else
		{
			// mirror image of above code
			I uncle = LeftChild(grandparent);
			if (IsRed(uncle))
			{
				// uncle is RED
				SetColor(parent, BLACK);
				SetColor(uncle, BLACK);
				SetColor(grandparent, RED);
				elem = grandparent;
			}
			else
			{
				// uncle is BLACK
				if (IsLeftChild(elem))
				{
					// make x a right child, will change parent and grandparent
					elem = parent;
					RotateRight(parent);
					parent = Parent(elem);
					grandparent = Parent(parent);
				}
				// recolor and rotate
				SetColor(parent, BLACK);
				SetColor(grandparent, RED);
				RotateLeft(grandparent);
			}
		}
	}
	SetColor(m_Root, BLACK);
}

// Insert a node into the tree
template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::InsertAt(I parent, bool leftchild)
{
	I i = NewNode();
	LinkToParent(i, parent, leftchild);
	m_NumElements++;
	return i;
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::LinkToParent(I i, I parent, bool isLeft)
{
	Links_t &elem = Links(i);
	elem.m_Parent = parent;
	elem.m_Left = elem.m_Right = InvalidIndex();
	elem.m_Tag = RED;

	// insert node in tree
	if (parent != InvalidIndex())
	{
		if (isLeft)
			Links(parent).m_Left = i;
		else
			Links(parent).m_Right = i;
	}
	else
	{
		m_Root = i;
	}

	InsertRebalance(i);

	DbgAssert(IsValid());
}

// Rebalance the tree after a deletion
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::RemoveRebalance(I elem)
{
	while (elem != m_Root && IsBlack(elem))
	{
		I parent = Parent(elem);

		// If elem is the left child of the parent
		if (elem == LeftChild(parent))
		{
			// Get our sibling
			I sibling = RightChild(parent);
			if (IsRed(sibling))
			{
				SetColor(sibling, BLACK);
				SetColor(parent, RED);
				RotateLeft(parent);

				// We may have a new parent now
				parent = Parent(elem);
				sibling = RightChild(parent);
			}
			if ((IsBlack(LeftChild(sibling))) && (IsBlack(RightChild(sibling))))
			{
				if (sibling != InvalidIndex())
					SetColor(sibling, RED);
				elem = parent;
			}
			else
			{
				if (IsBlack(RightChild(sibling)))
				{
					SetColor(LeftChild(sibling), BLACK);
					SetColor(sibling, RED);
					RotateRight(sibling);

					// rotation may have changed this
					parent = Parent(elem);
					sibling = RightChild(parent);
				}
				SetColor(sibling, Color(parent));
				SetColor(parent, BLACK);
				SetColor(RightChild(sibling), BLACK);
				RotateLeft(parent);
				elem = m_Root;
			}
		}
		else
		{
			// Elem is the right child of the parent
			I sibling = LeftChild(parent);
			if (IsRed(sibling))
			{
				SetColor(sibling, BLACK);
				SetColor(parent, RED);
				RotateRight(parent);

				// We may have a new parent now
				parent = Parent(elem);
				sibling = LeftChild(parent);
			}
			if ((IsBlack(RightChild(sibling))) && (IsBlack(LeftChild(sibling))))
			{
				if (sibling != InvalidIndex())
					SetColor(sibling, RED);
				elem = parent;
			}
			else
			{
				if (IsBlack(LeftChild(sibling)))
				{
					SetColor(RightChild(sibling), BLACK);
					SetColor(sibling, RED);
					RotateLeft(sibling);

					// rotation may have changed this
					parent = Parent(elem);
					sibling = LeftChild(parent);
				}
				SetColor(sibling, Color(parent));
				SetColor(parent, BLACK);
				SetColor(LeftChild(sibling), BLACK);
				RotateRight(parent);
				elem = m_Root;
			}
		}
	}
	SetColor(elem, BLACK);
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::Unlink(I elem)
{
	if (elem != InvalidIndex())
	{
		I x, y;

		if ((LeftChild(elem) == InvalidIndex()) ||
			(RightChild(elem) == InvalidIndex()))
		{
			// y has a NIL node as a child
			y = elem;
		}
		else
		{
			// find tree successor with a NIL node as a child
			y = RightChild(elem);
			while (LeftChild(y) != InvalidIndex())
				y = LeftChild(y);
		}

		// x is y's only child
		if (LeftChild(y) != InvalidIndex())
			x = LeftChild(y);
		else
			x = RightChild(y);

		// remove y from the parent chain
		if (x != InvalidIndex())
			SetParent(x, Parent(y));
		if (!IsRoot(y))
		{
			if (IsLeftChild(y))
				SetLeftChild(Parent(y), x);
			else
				SetRightChild(Parent(y), x);
		}
		else
			m_Root = x;

		// need to store this off now, we'll be resetting y's color
		NodeColor_t ycolor = Color(y);
		if (y != elem)
		{
			// Standard implementations copy the data around, we cannot here.
			// Hook in y to link to the same stuff elem used to.
			SetParent(y, Parent(elem));
			SetRightChild(y, RightChild(elem));
			SetLeftChild(y, LeftChild(elem));

			if (!IsRoot(elem))
				if (IsLeftChild(elem))
					SetLeftChild(Parent(elem), y);
				else
					SetRightChild(Parent(elem), y);
				else
					m_Root = y;

				if (LeftChild(y) != InvalidIndex())
					SetParent(LeftChild(y), y);
				if (RightChild(y) != InvalidIndex())
					SetParent(RightChild(y), y);

				SetColor(y, Color(elem));
		}

		if ((x != InvalidIndex()) && (ycolor == BLACK))
			RemoveRebalance(x);
	}
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::Link(I elem)
{
	if (elem != InvalidIndex())
	{
		I parent;
		bool leftchild;
		FindInsertionPosition(Element(elem), parent, leftchild);
		LinkToParent(elem, parent, leftchild);
	}
}

// Delete a node from the tree
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::RemoveAt(I elem)
{
	if (elem != InvalidIndex())
	{
		Unlink(elem);

		FreeNode(elem);
		m_NumElements--;
	}
}

// remove a node in the tree
template <class T, class I, typename L, class M>
bool CUtlRBTree<T, I, L, M>::Remove(T const &search)
{
	I node = Find(search);
	if (node != InvalidIndex())
	{
		RemoveAt(node);
		return true;
	}
	return false;
}

// Removes all nodes from the tree
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::RemoveAll()
{
	// Just iterate through the whole list and add to free list
	// much faster than doing all of the rebalancing
	// also, do it so the free list is pointing to stuff in order
	// to get better cache coherence when re-adding stuff to this tree.
	I prev = InvalidIndex();
	for (int i = (int)m_TotalElements; --i >= 0;)
	{
		I idx = (I)i;
		if (IsValidIndex(idx))
			Destruct(&Element(idx));
		SetRightChild(idx, prev);
		SetLeftChild(idx, idx);
		prev = idx;
	}
	m_FirstFree = m_TotalElements ? (I)0 : InvalidIndex();
	m_Root = InvalidIndex();
	m_NumElements = 0;
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::Purge()
{
	RemoveAll();
	m_FirstFree = InvalidIndex();
	m_TotalElements = 0;
	m_Elements.Purge();
}

// Iteration
template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::FirstInorder() const
{
	I i = m_Root;
	while (LeftChild(i) != InvalidIndex())
		i = LeftChild(i);
	return i;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::NextInorder(I i) const
{
	DbgAssert(IsValidIndex(i));

	if (RightChild(i) != InvalidIndex())
	{
		i = RightChild(i);
		while (LeftChild(i) != InvalidIndex())
			i = LeftChild(i);
		return i;
	}

	I parent = Parent(i);
	while (IsRightChild(i))
	{
		i = parent;
		if (i == InvalidIndex()) break;
		parent = Parent(i);
	}
	return parent;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::PrevInorder(I i) const
{
	DbgAssert(IsValidIndex(i));

	if (LeftChild(i) != InvalidIndex())
	{
		i = LeftChild(i);
		while (RightChild(i) != InvalidIndex())
			i = RightChild(i);
		return i;
	}

	I parent = Parent(i);
	while (IsLeftChild(i))
	{
		i = parent;
		if (i == InvalidIndex()) break;
		parent = Parent(i);
	}
	return parent;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::LastInorder() const
{
	I i = m_Root;
	while (RightChild(i) != InvalidIndex())
		i = RightChild(i);
	return i;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::FirstPreorder() const
{
	return m_Root;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::NextPreorder(I i) const
{
	if (LeftChild(i) != InvalidIndex())
		return LeftChild(i);

	if (RightChild(i) != InvalidIndex())
		return RightChild(i);

	I parent = Parent(i);
	while(parent != InvalidIndex())
	{
		if (IsLeftChild(i) && (RightChild(parent) != InvalidIndex()))
			return RightChild(parent);
		i = parent;
		parent = Parent(parent);
	}
	return InvalidIndex();
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::PrevPreorder(I i) const
{
	DbgAssert(0); // Not implemented yet
	return InvalidIndex();
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::LastPreorder() const
{
	I i = m_Root;
	while (1)
	{
		while (RightChild(i) != InvalidIndex())
			i = RightChild(i);

		if (LeftChild(i) != InvalidIndex())
			i = LeftChild(i);
		else
			break;
	}
	return i;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::FirstPostorder() const
{
	I i = m_Root;
	while (!IsLeaf(i))
	{
		if (LeftChild(i))
			i = LeftChild(i);
		else
			i = RightChild(i);
	}
	return i;
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::NextPostorder(I i) const
{
	I parent = Parent(i);
	if (parent == InvalidIndex())
		return InvalidIndex();

	if (IsRightChild(i))
		return parent;

	if (RightChild(parent) == InvalidIndex())
		return parent;

	i = RightChild(parent);
	while (!IsLeaf(i))
	{
		if (LeftChild(i))
			i = LeftChild(i);
		else
			i = RightChild(i);
	}
	return i;
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::Reinsert(I elem)
{
	Unlink(elem);
	Link(elem);
}

// Returns the tree depth (not a very fast operation)
template <class T, class I, typename L, class M>
int CUtlRBTree<T, I, L, M>::Depth(I node) const
{
	if (node == InvalidIndex())
		return 0;

	int depthright = Depth(RightChild(node));
	int depthleft = Depth(LeftChild(node));
	return max(depthright, depthleft) + 1;
}

// Makes sure the tree is valid after every operation
template <class T, class I, typename L, class M>
bool CUtlRBTree<T, I, L, M>::IsValid() const
{
	if (!Count())
		return true;

	if ((Root() >= MaxElement()) || (Parent(Root()) != InvalidIndex()))
		goto InvalidTree;

#ifdef UTLTREE_PARANOID

	// First check to see that mNumEntries matches reality.
	// count items on the free list
	int numFree = 0;
	int curr = m_FirstFree;
	while (curr != InvalidIndex())
	{
		numFree++;
		curr = RightChild(curr);
		if ((curr > MaxElement()) && (curr != InvalidIndex()))
			goto InvalidTree;
	}
	if (MaxElement() - numFree != Count())
		goto InvalidTree;

	// Iterate over all elements, looking for validity
	// based on the self pointers
	int numFree2 = 0;
	for (curr = 0; curr < MaxElement(); curr++)
	{
		if (!IsValidIndex(curr))
			numFree2++;
		else
		{
			int right = RightChild(curr);
			int left = LeftChild(curr);
			if ((right == left) && (right != InvalidIndex()))
				goto InvalidTree;

			if (right != InvalidIndex())
			{
				if (!IsValidIndex(right))
					goto InvalidTree;
				if (Parent(right) != curr)
					goto InvalidTree;
				if (IsRed(curr) && IsRed(right))
					goto InvalidTree;
			}

			if (left != InvalidIndex())
			{
				if (!IsValidIndex(left))
					goto InvalidTree;
				if (Parent(left) != curr)
					goto InvalidTree;
				if (IsRed(curr) && IsRed(left))
					goto InvalidTree;
			}
		}
	}
	if (numFree2 != numFree)
		goto InvalidTree;

#endif // UTLTREE_PARANOID

	return true;

InvalidTree:
	return false;
}

// Sets the less func
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::SetLessFunc(typename CUtlRBTree<T, I, L, M>::LessFunc_t func)
{
	if (!m_LessFunc)
		m_LessFunc = func;
	else
	{
		// Need to re-sort the tree here....
		Assert(0);
	}
}

// Inserts a node into the tree, doesn't copy the data in.
template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::FindInsertionPosition(T const &insert, I &parent, bool &leftchild)
{
	DbgAssert(m_LessFunc);

	// Find where node belongs
	I current = m_Root;
	parent = InvalidIndex();
	leftchild = false;
	while (current != InvalidIndex())
	{
		parent = current;
		if (m_LessFunc(insert, Element(current)))
		{
			leftchild = true;
			current = LeftChild(current);
		}
		else
		{
			leftchild = false;
			current = RightChild(current);
		}
	}
}

template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::Insert(T const &insert)
{
	// Use copy constructor to copy it in
	I parent;
	bool leftchild;
	FindInsertionPosition(insert, parent, leftchild);
	I newNode = InsertAt(parent, leftchild);
	CopyConstruct(&Element(newNode), insert);
	return newNode;
}

template <class T, class I, typename L, class M>
void CUtlRBTree<T, I, L, M>::Insert(const T *pArray, int nItems)
{
	while (nItems--)
	{
		Insert(*pArray++);
	}
}

// Finds a node in the tree
template <class T, class I, typename L, class M>
I CUtlRBTree<T, I, L, M>::Find(T const &search) const
{
	DbgAssert(m_LessFunc);

	I current = m_Root;
	while (current != InvalidIndex())
	{
		if (m_LessFunc(search, Element(current)))
			current = LeftChild(current);
		else if (m_LessFunc(Element(current), search))
			current = RightChild(current);
		else
			break;
	}
	return current;
}