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397 lines
11 KiB
397 lines
11 KiB
/**********************************************************************/
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/** Microsoft Windows/NT **/
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/** Copyright(c) Microsoft Corporation, 1998 - 2002 **/
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/**********************************************************************/
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#include "stdafx.h"
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#include "redblack.h"
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/*
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redblack.c
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Implementation of red-black binary tree insertion, deletion, and search.
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This algorithm efficiently guarantees that the tree depth will never exceed
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2*Lg(N), so a one million node tree would have a worst case depth of 40.
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This insertion implementation is non-recursive and very efficient (the
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average insertion speed is less than twice the average search speed).
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Author: Tom McGuire (tommcg) 1/98
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2/98, modified this version of redblack.c for debug symbol lookups.
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8/98, modified this version of redblack.h for generic name table.
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*/
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//
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// Rather than storing NULL links as NULL, we point NULL links to a special
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// "Empty" node which is always black and its children links point to itself.
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// We do this to simplify the color testing for children and grandchildren
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// such that any link can be dereferenced and even double-dereferenced without
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// explicitly checking for NULL. The empty node must be colored black.
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//
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const NAME_NODE NameRbEmptyNode = { RBNIL, RBNIL };
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extern PVOID __fastcall SubAllocate(IN HANDLE hAllocator, IN ULONG Size);
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ULONG
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__fastcall
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NameRbHash(
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IN LPCSTR Name,
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IN ULONG Length
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)
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{
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ULONG Hash = ~Length;
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while ( Length-- ) {
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Hash = _rotl( Hash, 3 ) ^ *Name++;
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}
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return Hash;
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}
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VOID
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NameRbInitTree(
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IN OUT PNAME_TREE Tree,
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IN HANDLE SubAllocator
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)
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{
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Tree->Root = RBNIL;
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Tree->SubAllocator = SubAllocator;
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}
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PNAME_NODE
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NameRbFind(
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IN PNAME_TREE Tree,
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IN LPCSTR Name
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)
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{
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PNAME_NODE Node;
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ULONG NameLength;
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ULONG Hash;
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int Compare;
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NameLength = strlen( Name );
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Hash = NameRbHash( Name, NameLength );
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Node = Tree->Root;
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while ( Node != RBNIL ) {
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if ( Hash < Node->Hash ) {
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Node = Node->Left;
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}
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else if ( Hash > Node->Hash ) {
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Node = Node->Right;
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}
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else {
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//
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// Hashes equal, switch to strlen
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//
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do {
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if ( NameLength < Node->NameLength ) {
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Node = Node->Left;
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}
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else if ( NameLength > Node->NameLength ) {
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Node = Node->Right;
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}
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else {
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//
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// Lengths equal, switch to memcmp
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//
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do {
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Compare = memcmp( Name, Node->Name, NameLength );
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if ( Compare == 0 ) {
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return Node;
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}
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else if ( Compare < 0 ) {
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Node = Node->Left;
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}
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else {
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Node = Node->Right;
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}
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}
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while ( Node != RBNIL );
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}
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}
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while ( Node != RBNIL );
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}
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}
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return NULL;
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}
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PNAME_NODE
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NameRbInsert(
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IN OUT PNAME_TREE Tree,
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IN LPCSTR Name
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)
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{
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PNAME_NODE * Stack[ MAX_DEPTH ];
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PNAME_NODE **StackPointer = Stack;
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PNAME_NODE * Link;
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PNAME_NODE Node;
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PNAME_NODE Sibling;
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PNAME_NODE Parent;
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PNAME_NODE Child;
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PNAME_NODE NewNode;
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ULONG NameLength;
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ULONG Hash;
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int Compare;
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NameLength = strlen( Name );
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Hash = NameRbHash( Name, NameLength );
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*StackPointer++ = &Tree->Root;
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Node = Tree->Root;
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//
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// Walk down the tree to find either an existing node with the same key
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// (in which case we simply return) or the insertion point for the new
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// node. At each traversal we need to store the address of the link to
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// the next node so we can retrace the traversal path for balancing.
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// The speed of insertion is highly dependent on traversing the tree
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// quickly, so all balancing operations are deferred until after the
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// traversal is complete.
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//
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while ( Node != RBNIL ) {
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if ( Hash < Node->Hash ) {
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*StackPointer++ = &Node->Left;
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Node = Node->Left;
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}
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else if ( Hash > Node->Hash ) {
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*StackPointer++ = &Node->Right;
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Node = Node->Right;
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}
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else {
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//
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// Hashes equal, switch to strlen
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//
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do {
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if ( NameLength < Node->NameLength ) {
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*StackPointer++ = &Node->Left;
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Node = Node->Left;
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}
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else if ( NameLength > Node->NameLength ) {
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*StackPointer++ = &Node->Right;
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Node = Node->Right;
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}
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else {
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//
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// Lengths equal, switch to memcmp
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//
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do {
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Compare = memcmp( Name, Node->Name, NameLength );
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if ( Compare == 0 ) {
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return Node;
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}
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else if ( Compare < 0 ) {
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*StackPointer++ = &Node->Left;
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Node = Node->Left;
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}
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else {
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*StackPointer++ = &Node->Right;
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Node = Node->Right;
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}
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}
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while ( Node != RBNIL );
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}
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}
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while ( Node != RBNIL );
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}
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}
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//
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// Didn't find a matching entry, so allocate a new node and add it
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// to the tree. Note that we're not allocating space for a terminator
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// for the name data since we store the length of the name in the node.
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//
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NewNode = (PNAME_NODE)SubAllocate( Tree->SubAllocator, ( sizeof( NAME_NODE ) + NameLength ));
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if ( NewNode == NULL ) {
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return NULL;
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}
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NewNode->Left = RBNIL;
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NewNode->Right = RBNIL;
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NewNode->Hash = Hash;
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NewNode->NameLengthAndColorBit = NameLength | 0x80000000; // MARK_RED
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memcpy( NewNode->Name, Name, NameLength );
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//
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// Insert new node under last link we traversed. The top of the stack
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// contains the address of the last link we traversed.
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//
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Link = *( --StackPointer );
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*Link = NewNode;
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//
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// Now walk back up the traversal chain to see if any balancing is
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// needed. This terminates in one of three ways: we walk all the way
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// up to the root (StackPointer == Stack), or find a black node that
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// we don't need to change (no balancing needs to be done above a
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// black node), or we perform a balancing rotation (only one necessary).
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//
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Node = NewNode;
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Child = RBNIL;
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while ( StackPointer > Stack ) {
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Link = *( --StackPointer );
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Parent = *Link;
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//
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// Node is always red here.
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//
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if ( IS_BLACK( Parent )) {
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Sibling = ( Parent->Left == Node ) ? Parent->Right : Parent->Left;
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if ( IS_RED( Sibling )) {
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//
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// Both Node and its Sibling are red, so change them both to
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// black and make the Parent red. This essentially moves the
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// red link up the tree so balancing can be performed at a
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// higher level.
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//
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// Pb Pr
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// / \ ----> / \
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// Cr Sr Cb Sb
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//
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MARK_BLACK( Sibling );
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MARK_BLACK( Node );
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MARK_RED( Parent );
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}
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else {
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//
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// This is a terminal case. The Parent is black, and it's
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// not going to be changed to red. If the Node's child is
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// red, we perform an appropriate rotation to balance the
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// tree. If the Node's child is black, we're done.
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//
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if ( IS_RED( Child )) {
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if ( Node->Left == Child ) {
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if ( Parent->Left == Node ) {
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//
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// Pb Nb
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// / \ / \
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// Nr Z to Cr Pr
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// / \ / \
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// Cr Y Y Z
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//
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MARK_RED( Parent );
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Parent->Left = Node->Right;
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Node->Right = Parent;
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MARK_BLACK( Node );
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*Link = Node;
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}
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else {
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//
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// Pb Cb
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// / \ / \
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// W Nr to Pr Nr
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// / \ / \ / \
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// Cr Z W X Y Z
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// / \
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// X Y
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//
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MARK_RED( Parent );
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Parent->Right = Child->Left;
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Child->Left = Parent;
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Node->Left = Child->Right;
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Child->Right = Node;
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MARK_BLACK( Child );
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*Link = Child;
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}
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}
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else {
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if ( Parent->Right == Node ) {
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MARK_RED( Parent );
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Parent->Right = Node->Left;
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Node->Left = Parent;
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MARK_BLACK( Node );
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*Link = Node;
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}
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else {
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MARK_RED( Parent );
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Parent->Left = Child->Right;
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Child->Right = Parent;
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Node->Right = Child->Left;
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Child->Left = Node;
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MARK_BLACK( Child );
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*Link = Child;
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}
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}
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}
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return NewNode;
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}
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}
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Child = Node;
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Node = Parent;
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}
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//
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// We bubbled red up to the root -- restore it to black.
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//
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MARK_BLACK( Tree->Root );
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return NewNode;
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}
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