329 lines
9.1 KiB
C
329 lines
9.1 KiB
C
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#include <precomp.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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Copyright (C) Microsoft, 1998.
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2/98, modified this version of redblack.c for debug symbol lookups.
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*/
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#ifndef PATCH_APPLY_CODE_ONLY
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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 SYMBOL_NODE SymRBEmptyNode = { RBNIL, RBNIL };
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VOID
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SymRBInitTree(
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IN OUT PSYMBOL_TREE Tree,
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IN HANDLE SubAllocator
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)
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{
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#if defined( DEBUG ) || defined( DBG ) || defined( TESTCODE )
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Tree->CountNodes = 0;
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Tree->DeletedAny = FALSE;
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#endif
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Tree->Root = RBNIL;
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Tree->SubAllocator = SubAllocator;
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}
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PSYMBOL_NODE
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SymRBFind(
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IN PSYMBOL_TREE Tree,
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IN LPSTR SymbolName
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)
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{
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PSYMBOL_NODE Node = Tree->Root;
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ULONG Hash;
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int Compare;
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Hash = HashName( SymbolName );
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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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Compare = strcmp( SymbolName, Node->SymbolName );
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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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}
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return NULL;
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}
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PSYMBOL_NODE
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SymRBInsert(
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IN OUT PSYMBOL_TREE Tree,
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IN LPSTR SymbolName,
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IN ULONG Rva
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)
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{
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PSYMBOL_NODE * Stack[ MAX_DEPTH ];
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PSYMBOL_NODE **StackPointer = Stack;
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PSYMBOL_NODE * Link;
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PSYMBOL_NODE Node;
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PSYMBOL_NODE Sibling;
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PSYMBOL_NODE Parent;
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PSYMBOL_NODE Child;
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PSYMBOL_NODE NewNode;
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ULONG NameLength;
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ULONG Hash;
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int Compare;
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ASSERT( ! Tree->DeletedAny );
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Hash = HashName( SymbolName );
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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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*StackPointer++ = &Tree->Root;
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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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*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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Compare = strcmp( SymbolName, Node->SymbolName );
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if ( Compare == 0 ) {
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//
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// Found a matching symbol.
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//
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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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}
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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.
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//
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NameLength = (ULONG) strlen( SymbolName ) + 1;
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NewNode = SubAllocate( Tree->SubAllocator, ( sizeof( SYMBOL_NODE ) + NameLength ));
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if ( NewNode == NULL ) {
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return NULL;
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}
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#if defined( DEBUG ) || defined( DBG ) || defined( TESTCODE )
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Tree->CountNodes++;
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#endif
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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->RvaWithStatusBits = Rva | 0x80000000; // make new node RED, not hit
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memcpy( NewNode->SymbolName, SymbolName, 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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#endif // ! PATCH_APPLY_CODE_ONLY
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