mirror of
https://github.com/reactos/reactos.git
synced 2024-09-13 22:31:34 +00:00
560 lines
17 KiB
C
560 lines
17 KiB
C
/*
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* COPYRIGHT: See COPYING in the top level directory
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* PROJECT: ReactOS system libraries
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* PURPOSE: Splay-Tree implementation
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* FILE: lib/rtl/splaytree.c
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* PROGRAMMER: Alex Ionescu (alex@relsoft.net)
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*/
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/* INCLUDES *****************************************************************/
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#include <rtl.h>
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#define NDEBUG
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#include <debug.h>
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/* FUNCTIONS ***************************************************************/
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VOID
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SwapSplayLinks(PRTL_SPLAY_LINKS LinkA,
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PRTL_SPLAY_LINKS LinkB)
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{
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DPRINT1("UNIMPLEMENTED!\n");
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlDelete(PRTL_SPLAY_LINKS Links)
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{
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PRTL_SPLAY_LINKS N, P, C, SP;
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N = Links;
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/* Check if we have two children */
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if ((RtlLeftChild(N)) && (RtlRightChild(N)))
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{
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/* Get the predecessor */
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SP = RtlSubtreePredecessor(N);
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/* Swap it with N, this will guarantee that N will have only a child */
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SwapSplayLinks(SP, N);
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}
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/* Check if we have no children */
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if (!(RtlLeftChild(N)) && !(RtlRightChild(N)))
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{
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/* If we are also the root, then the tree is gone */
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if (RtlIsRoot(N)) return NULL;
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/* Get our parent */
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P = RtlParent(N);
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/* Find out who is referencing us and delete the reference */
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if (RtlIsLeftChild(N))
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{
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/* N was a left child, so erase its parent's left child link */
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RtlLeftChild(RtlParent(N)) = NULL;
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}
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else
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{
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/* N was a right child, so erase its parent's right child link */
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RtlRightChild(RtlParent(N)) = NULL;
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}
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/* And finally splay the parent */
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return RtlSplay(P);
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}
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/* If we got here, we have a child (not two: we swapped above!) */
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if (RtlLeftChild(N))
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{
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/* We have a left child, so get it */
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C = RtlLeftChild(N);
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}
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else
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{
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/* We have a right child, get him instead */
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C = RtlRightChild(N);
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}
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/* Check if we are the root entry */
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if (RtlIsRoot(N))
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{
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/* Our child is now root, return him */
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C->Parent = C;
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return C;
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}
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/* Find out who is referencing us and link to our child instead */
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if (RtlIsLeftChild(N))
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{
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/* N was a left child, so set its parent's left child as our child */
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RtlLeftChild(RtlParent(N)) = C;
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}
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else
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{
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/* N was a right child, so set its parent's right child as our child */
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RtlRightChild(RtlParent(N)) = C;
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}
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/* Finally, inherit our parent and splay the parent */
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C->Parent = N->Parent;
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return RtlSplay(RtlParent(C));
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}
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/*
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* @unimplemented
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*/
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VOID
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NTAPI
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RtlDeleteNoSplay(PRTL_SPLAY_LINKS Links,
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PRTL_SPLAY_LINKS *Root)
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{
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UNIMPLEMENTED;
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlRealPredecessor(PRTL_SPLAY_LINKS Links)
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{
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PRTL_SPLAY_LINKS Child;
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/* Get the left child */
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Child = RtlLeftChild(Links);
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if (Child)
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{
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/* Get right-most child */
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while (RtlRightChild(Child)) Child = RtlRightChild(Child);
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return Child;
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}
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/* We don't have a left child, keep looping until we find our parent */
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Child = Links;
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while (RtlIsLeftChild(Child)) Child = RtlParent(Child);
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/* The parent should be a right child, return the real predecessor */
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if (RtlIsRightChild(Child)) return RtlParent(Child);
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/* The parent isn't a right child, so no real precessor for us */
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return NULL;
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlRealSuccessor(PRTL_SPLAY_LINKS Links)
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{
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PRTL_SPLAY_LINKS Child;
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/* Get the right child */
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Child = RtlRightChild(Links);
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if (Child)
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{
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/* Get left-most child */
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while (RtlLeftChild(Child)) Child = RtlLeftChild(Child);
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return Child;
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}
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/* We don't have a right child, keep looping until we find our parent */
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Child = Links;
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while (RtlIsRightChild(Child)) Child = RtlParent(Child);
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/* The parent should be a left child, return the real successor */
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if (RtlIsLeftChild(Child)) return RtlParent(Child);
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/* The parent isn't a right child, so no real successor for us */
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return NULL;
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlSplay(PRTL_SPLAY_LINKS Links)
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{
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/*
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* Implementation Notes (http://en.wikipedia.org/wiki/Splay_tree):
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*
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* To do a splay, we carry out a sequence of rotations,
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* each of which moves the target node N closer to the root.
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*
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* Each particular step depends on only two factors:
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* - Whether N is the left or right child of its parent node, P,
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* - Whether P is the left or right child of its parent, G (for grandparent node).
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*
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* Thus, there are four cases:
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* - Case 1: N is the left child of P and P is the left child of G.
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* In this case we perform a double right rotation, so that
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* P becomes N's right child, and G becomes P's right child.
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*
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* - Case 2: N is the right child of P and P is the right child of G.
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* In this case we perform a double left rotation, so that
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* P becomes N's left child, and G becomes P's left child.
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*
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* - Case 3: N is the left child of P and P is the right child of G.
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* In this case we perform a rotation so that
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* G becomes N's left child, and P becomes N's right child.
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*
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* - Case 4: N is the right child of P and P is the left child of G.
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* In this case we perform a rotation so that
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* P becomes N's left child, and G becomes N's right child.
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*
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* Finally, if N doesn't have a grandparent node, we simply perform a
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* left or right rotation to move it to the root.
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*
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* By performing a splay on the node of interest after every operation,
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* we keep recently accessed nodes near the root and keep the tree
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* roughly balanced, so that we achieve the desired amortized time bounds.
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*/
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PRTL_SPLAY_LINKS N, P, G;
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/* N is the item we'll be playing with */
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N = Links;
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/* Let the algorithm run until N becomes the root entry */
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while (!RtlIsRoot(N))
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{
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/* Now get the parent and grand-parent */
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P = RtlParent(N);
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G = RtlParent(P);
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/* Case 1 & 3: N is left child of P */
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if (RtlIsLeftChild(N))
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{
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/* Case 1: P is the left child of G */
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if (RtlIsLeftChild(P))
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{
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/*
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* N's right-child becomes P's left child and
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* P's right-child becomes G's left child.
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*/
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RtlLeftChild(P) = RtlRightChild(N);
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RtlLeftChild(G) = RtlRightChild(P);
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/*
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* If they exist, update their parent pointers too,
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* since they've changed trees.
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*/
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if (RtlLeftChild(P)) RtlParent(RtlLeftChild(P)) = P;
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if (RtlLeftChild(G)) RtlParent(RtlLeftChild(G)) = G;
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/*
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* Now we'll shove N all the way to the top.
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* Check if G is the root first.
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*/
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if (RtlIsRoot(G))
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{
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/* G doesn't have a parent, so N will become the root! */
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RtlParent(N) = N;
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}
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else
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{
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/* G has a parent, so inherit it since we take G's place */
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RtlParent(N) = RtlParent(G);
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/*
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* Now find out who was referencing G and have it reference
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* N instead, since we're taking G's place.
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*/
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if (RtlIsLeftChild(G))
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{
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/*
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* G was a left child, so change its parent's left
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* child link to point to N now.
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*/
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RtlLeftChild(RtlParent(G)) = N;
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}
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else
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{
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/*
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* G was a right child, so change its parent's right
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* child link to point to N now.
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*/
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RtlRightChild(RtlParent(G)) = N;
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}
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}
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/* Now N is on top, so P has become its child. */
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RtlRightChild(N) = P;
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RtlParent(P) = N;
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/* N is on top, P is its child, so G is grandchild. */
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RtlRightChild(P) = G;
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RtlParent(G) = P;
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}
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/* Case 3: P is the right child of G */
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else if (RtlIsRightChild(P))
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{
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/*
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* N's left-child becomes G's right child and
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* N's right-child becomes P's left child.
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*/
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RtlRightChild(G) = RtlLeftChild(N);
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RtlLeftChild(P) = RtlRightChild(N);
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/*
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* If they exist, update their parent pointers too,
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* since they've changed trees.
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*/
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if (RtlRightChild(G)) RtlParent(RtlRightChild(G)) = G;
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if (RtlLeftChild(P)) RtlParent(RtlLeftChild(P)) = P;
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/*
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* Now we'll shove N all the way to the top.
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* Check if G is the root first.
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*/
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if (RtlIsRoot(G))
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{
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/* G doesn't have a parent, so N will become the root! */
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RtlParent(N) = N;
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}
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else
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{
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/* G has a parent, so inherit it since we take G's place */
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RtlParent(N) = RtlParent(G);
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/*
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* Now find out who was referencing G and have it reference
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* N instead, since we're taking G's place.
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*/
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if (RtlIsLeftChild(G))
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{
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/*
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* G was a left child, so change its parent's left
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* child link to point to N now.
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*/
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RtlLeftChild(RtlParent(G)) = N;
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}
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else
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{
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/*
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* G was a right child, so change its parent's right
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* child link to point to N now.
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*/
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RtlRightChild(RtlParent(G)) = N;
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}
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}
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/* Now N is on top, so G has become its left child. */
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RtlLeftChild(N) = G;
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RtlParent(G) = N;
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/* N is on top, G is its left child, so P is right child. */
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RtlRightChild(N) = P;
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RtlParent(P) = N;
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}
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/* "Finally" case: N doesn't have a grandparent => P is root */
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else
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{
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/* P's left-child becomes N's right child */
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RtlLeftChild(P) = RtlRightChild(N);
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/* If it exists, update its parent pointer too */
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if (RtlLeftChild(P)) RtlParent(RtlLeftChild(P)) = P;
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/* Now make N the root, no need to worry about references */
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N->Parent = N;
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/* And make P its right child */
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N->RightChild = P;
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P->Parent = N;
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}
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}
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/* Case 2 & 4: N is right child of P */
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else
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{
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/* Case 2: P is the right child of G */
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if (RtlIsRightChild(P))
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{
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/*
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* P's left-child becomes G's right child and
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* N's left-child becomes P's right child.
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*/
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RtlRightChild(G) = RtlLeftChild(P);
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RtlRightChild(P) = RtlLeftChild(N);
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/*
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* If they exist, update their parent pointers too,
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* since they've changed trees.
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*/
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if (RtlRightChild(G)) RtlParent(RtlRightChild(G)) = G;
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if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
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/*
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* Now we'll shove N all the way to the top.
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* Check if G is the root first.
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*/
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if (RtlIsRoot(G))
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{
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/* G doesn't have a parent, so N will become the root! */
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RtlParent(N) = N;
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}
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else
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{
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/* G has a parent, so inherit it since we take G's place */
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RtlParent(N) = RtlParent(G);
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/*
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* Now find out who was referencing G and have it reference
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* N instead, since we're taking G's place.
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*/
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if (RtlIsLeftChild(G))
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{
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/*
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* G was a left child, so change its parent's left
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* child link to point to N now.
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*/
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RtlLeftChild(RtlParent(G)) = N;
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}
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else
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{
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/*
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* G was a right child, so change its parent's right
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* child link to point to N now.
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*/
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RtlRightChild(RtlParent(G)) = N;
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}
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}
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/* Now N is on top, so P has become its child. */
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RtlLeftChild(N) = P;
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RtlParent(P) = N;
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/* N is on top, P is its child, so G is grandchild. */
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RtlLeftChild(P) = G;
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RtlParent(G) = P;
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}
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/* Case 4: P is the left child of G */
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else if (RtlIsLeftChild(P))
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{
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/*
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* N's left-child becomes G's right child and
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* N's right-child becomes P's left child.
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*/
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RtlRightChild(P) = RtlLeftChild(N);
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RtlLeftChild(G) = RtlRightChild(N);
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/*
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* If they exist, update their parent pointers too,
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* since they've changed trees.
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*/
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if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
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if (RtlLeftChild(G)) RtlParent(RtlLeftChild(G)) = G;
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/*
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* Now we'll shove N all the way to the top.
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* Check if G is the root first.
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*/
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if (RtlIsRoot(G))
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{
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/* G doesn't have a parent, so N will become the root! */
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RtlParent(N) = N;
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}
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else
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{
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/* G has a parent, so inherit it since we take G's place */
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RtlParent(N) = RtlParent(G);
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/*
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* Now find out who was referencing G and have it reference
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* N instead, since we're taking G's place.
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*/
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if (RtlIsLeftChild(G))
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{
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/*
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* G was a left child, so change its parent's left
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* child link to point to N now.
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*/
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RtlLeftChild(RtlParent(G)) = N;
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}
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else
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{
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/*
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* G was a right child, so change its parent's right
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* child link to point to N now.
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*/
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RtlRightChild(RtlParent(G)) = N;
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}
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}
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/* Now N is on top, so P has become its left child. */
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RtlLeftChild(N) = P;
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RtlParent(G) = N;
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/* N is on top, P is its left child, so G is right child. */
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RtlRightChild(N) = G;
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RtlParent(P) = N;
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}
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/* "Finally" case: N doesn't have a grandparent => P is root */
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else
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{
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/* P's right-child becomes N's left child */
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RtlRightChild(P) = RtlLeftChild(N);
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/* If it exists, update its parent pointer too */
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if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
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/* Now make N the root, no need to worry about references */
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N->Parent = N;
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/* And make P its left child */
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N->LeftChild = P;
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P->Parent = N;
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}
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}
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}
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/* Return the root entry */
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return N;
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlSubtreePredecessor(IN PRTL_SPLAY_LINKS Links)
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{
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PRTL_SPLAY_LINKS Child;
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/* Get the left child */
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Child = RtlLeftChild(Links);
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if (!Child) return NULL;
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/* Get right-most child */
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while (RtlRightChild(Child)) Child = RtlRightChild(Child);
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/* Return it */
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return Child;
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}
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/*
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* @implemented
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*/
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PRTL_SPLAY_LINKS
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NTAPI
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RtlSubtreeSuccessor(IN PRTL_SPLAY_LINKS Links)
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{
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PRTL_SPLAY_LINKS Child;
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/* Get the right child */
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Child = RtlRightChild(Links);
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if (!Child) return NULL;
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/* Get left-most child */
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while (RtlLeftChild(Child)) Child = RtlLeftChild(Child);
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/* Return it */
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return Child;
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}
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/* EOF */
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