mirror of
https://github.com/reactos/reactos.git
synced 2024-06-30 18:01:07 +00:00
797 lines
24 KiB
C
797 lines
24 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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//#define VERIFY_SWAP_SPLAY_LINKS
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/* FUNCTIONS ***************************************************************/
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static
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VOID
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FixupChildLinks(PRTL_SPLAY_LINKS Links, BOOLEAN Root, BOOLEAN LeftChild)
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{
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if (RtlLeftChild(Links))
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{
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RtlInsertAsLeftChild(Links, RtlLeftChild(Links));
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}
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if (RtlRightChild(Links))
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{
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RtlInsertAsRightChild(Links, RtlRightChild(Links));
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}
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if (!Root)
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{
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if (LeftChild)
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{
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RtlInsertAsLeftChild(RtlParent(Links), Links);
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}
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else
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{
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RtlInsertAsRightChild(RtlParent(Links), Links);
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}
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}
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}
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/*
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Given the tree:
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D
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B F
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A C E G
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Swap(Q,S):
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Q S Q.P Q.L Q.R S.P S.L S.R
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A C S.P S.L S.R Q.P Q.L Q.R
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B A S S.L S.R Q.P Q Q.R
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B C S S.L S.R Q.P Q.L Q
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D A S.P S.L S.R S Q.L Q.R
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D B S S.L S.R S Q Q.R
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D F S S.L S.R S Q.L Q
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When Q is the immediate parent of S,
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Set Q's parent to S, and the proper child ptr of S to Q
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When Q is the root,
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Set S's parent to S
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*/
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static
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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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if (RtlParent(LinkA) == LinkB || RtlIsRoot(LinkB))
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{
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PRTL_SPLAY_LINKS Tmp = LinkA;
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LinkA = LinkB;
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LinkB = Tmp;
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}
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{
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RTL_SPLAY_LINKS Ta = *LinkA, Tb = *LinkB;
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BOOLEAN RootA = RtlIsRoot(LinkA),
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LeftA = RtlIsLeftChild(LinkA),
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LeftB = RtlIsLeftChild(LinkB);
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*LinkB = Ta; *LinkA = Tb;
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// A was parent of B is a special case: A->Parent is now B
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if (RtlParent(&Tb) == LinkA)
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{
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if (!RootA)
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{
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if (LeftA)
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{
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RtlInsertAsLeftChild(RtlParent(&Ta), LinkB);
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}
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else
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{
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RtlInsertAsRightChild(RtlParent(&Ta), LinkB);
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}
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}
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if (LeftB)
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{
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RtlInsertAsLeftChild(LinkB, LinkA);
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}
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else
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{
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RtlInsertAsRightChild(LinkB, LinkA);
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}
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}
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FixupChildLinks(LinkA, FALSE, LeftB);
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FixupChildLinks(LinkB, RootA, LeftA);
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// A was root is a special case: B->Parent is now B
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if (RootA)
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RtlParent(LinkB) = LinkB;
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#ifdef VERIFY_SWAP_SPLAY_LINKS
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// Verify the distinct cases of node swap
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if (RootA)
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{
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if (RtlParent(&Tb) == LinkA)
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{
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// LinkA = D, LinkB = B
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// D B S S.L S.R S Q Q.R
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ASSERT(RtlParent(LinkA) == LinkB);
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ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
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ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
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ASSERT(RtlParent(LinkB) == LinkB);
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ASSERT(RtlLeftChild(LinkB) == (LeftB ? LinkA : RtlLeftChild(&Ta)));
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ASSERT(RtlRightChild(LinkB) == (LeftB ? RtlRightChild(&Ta) : LinkA));
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}
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else
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{
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// LinkA = D, LinkB = A
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// D A S.P S.L S.R S Q.L Q.R
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ASSERT(RtlParent(LinkA) == RtlParent(&Tb));
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ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
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ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
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ASSERT(RtlParent(LinkB) == LinkB);
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ASSERT(RtlLeftChild(LinkB) == RtlLeftChild(&Ta));
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ASSERT(RtlRightChild(LinkB) == RtlRightChild(&Ta));
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}
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}
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else
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{
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if (RtlParent(&Tb) == LinkA)
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{
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// LinkA = B, LinkB = A
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// B A S S.L S.R Q.P Q Q.R
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ASSERT(RtlParent(LinkA) == LinkB);
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ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
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ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
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ASSERT(RtlParent(LinkB) == RtlParent(&Ta));
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ASSERT(RtlLeftChild(LinkB) == (LeftB ? LinkA : RtlLeftChild(&Ta)));
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ASSERT(RtlRightChild(LinkB) == (LeftB ? RtlRightChild(&Ta) : LinkA));
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}
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else
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{
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// LinkA = A, LinkB = C
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// A C S.P S.L S.R Q.P Q.L Q.R
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ASSERT(!memcmp(LinkA, &Tb, sizeof(Tb)));
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ASSERT(!memcmp(LinkB, &Ta, sizeof(Ta)));
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}
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}
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#endif
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}
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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 only have 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(P) = 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(P) = 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 it 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 it */
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RtlParent(C) = C;
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return C;
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}
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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 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(P) = 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(P) = C;
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}
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/* Finally, inherit our parent and splay the parent */
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RtlParent(C) = P;
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return RtlSplay(P);
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}
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/*
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* @implemented
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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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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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/* If we are the root, the new root will be our predecessor after swapping */
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if (RtlIsRoot(N)) *Root = SP;
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/* Swap the predecessor with N, this will guarantee that N will only have 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))
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{
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*Root = NULL;
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return;
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}
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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(P) = 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(P) = NULL;
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}
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/* We are done */
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return;
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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 it 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 it */
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RtlParent(C) = C;
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*Root = C;
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return;
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}
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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 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(P) = 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(P) = C;
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}
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/* Finally, inherit our parent and we are done */
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RtlParent(C) = P;
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return;
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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))
|
|
{
|
|
/* G doesn't have a parent, so N will become the root! */
|
|
RtlParent(N) = N;
|
|
}
|
|
else
|
|
{
|
|
/* G has a parent, so inherit it since we take G's place */
|
|
RtlParent(N) = RtlParent(G);
|
|
|
|
/*
|
|
* Now find out who was referencing G and have it reference
|
|
* N instead, since we're taking G's place.
|
|
*/
|
|
if (RtlIsLeftChild(G))
|
|
{
|
|
/*
|
|
* G was a left child, so change its parent's left
|
|
* child link to point to N now.
|
|
*/
|
|
RtlLeftChild(RtlParent(G)) = N;
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* G was a right child, so change its parent's right
|
|
* child link to point to N now.
|
|
*/
|
|
RtlRightChild(RtlParent(G)) = N;
|
|
}
|
|
}
|
|
|
|
/* Now N is on top, so G has become its left child. */
|
|
RtlLeftChild(N) = G;
|
|
RtlParent(G) = N;
|
|
|
|
/* N is on top, G is its left child, so P is right child. */
|
|
RtlRightChild(N) = P;
|
|
RtlParent(P) = N;
|
|
}
|
|
/* "Finally" case: N doesn't have a grandparent => P is root */
|
|
else
|
|
{
|
|
/* P's left-child becomes N's right child */
|
|
RtlLeftChild(P) = RtlRightChild(N);
|
|
|
|
/* If it exists, update its parent pointer too */
|
|
if (RtlLeftChild(P)) RtlParent(RtlLeftChild(P)) = P;
|
|
|
|
/* Now make N the root, no need to worry about references */
|
|
N->Parent = N;
|
|
|
|
/* And make P its right child */
|
|
N->RightChild = P;
|
|
P->Parent = N;
|
|
}
|
|
}
|
|
/* Case 2 & 4: N is right child of P */
|
|
else
|
|
{
|
|
/* Case 2: P is the right child of G */
|
|
if (RtlIsRightChild(P))
|
|
{
|
|
/*
|
|
* P's left-child becomes G's right child and
|
|
* N's left-child becomes P's right child.
|
|
*/
|
|
RtlRightChild(G) = RtlLeftChild(P);
|
|
RtlRightChild(P) = RtlLeftChild(N);
|
|
|
|
/*
|
|
* If they exist, update their parent pointers too,
|
|
* since they've changed trees.
|
|
*/
|
|
if (RtlRightChild(G)) RtlParent(RtlRightChild(G)) = G;
|
|
if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
|
|
|
|
/*
|
|
* Now we'll shove N all the way to the top.
|
|
* Check if G is the root first.
|
|
*/
|
|
if (RtlIsRoot(G))
|
|
{
|
|
/* G doesn't have a parent, so N will become the root! */
|
|
RtlParent(N) = N;
|
|
}
|
|
else
|
|
{
|
|
/* G has a parent, so inherit it since we take G's place */
|
|
RtlParent(N) = RtlParent(G);
|
|
|
|
/*
|
|
* Now find out who was referencing G and have it reference
|
|
* N instead, since we're taking G's place.
|
|
*/
|
|
if (RtlIsLeftChild(G))
|
|
{
|
|
/*
|
|
* G was a left child, so change its parent's left
|
|
* child link to point to N now.
|
|
*/
|
|
RtlLeftChild(RtlParent(G)) = N;
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* G was a right child, so change its parent's right
|
|
* child link to point to N now.
|
|
*/
|
|
RtlRightChild(RtlParent(G)) = N;
|
|
}
|
|
}
|
|
|
|
/* Now N is on top, so P has become its child. */
|
|
RtlLeftChild(N) = P;
|
|
RtlParent(P) = N;
|
|
|
|
/* N is on top, P is its child, so G is grandchild. */
|
|
RtlLeftChild(P) = G;
|
|
RtlParent(G) = P;
|
|
}
|
|
/* Case 4: P is the left child of G */
|
|
else if (RtlIsLeftChild(P))
|
|
{
|
|
/*
|
|
* N's left-child becomes G's right child and
|
|
* N's right-child becomes P's left child.
|
|
*/
|
|
RtlRightChild(P) = RtlLeftChild(N);
|
|
RtlLeftChild(G) = RtlRightChild(N);
|
|
|
|
/*
|
|
* If they exist, update their parent pointers too,
|
|
* since they've changed trees.
|
|
*/
|
|
if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
|
|
if (RtlLeftChild(G)) RtlParent(RtlLeftChild(G)) = G;
|
|
|
|
/*
|
|
* Now we'll shove N all the way to the top.
|
|
* Check if G is the root first.
|
|
*/
|
|
if (RtlIsRoot(G))
|
|
{
|
|
/* G doesn't have a parent, so N will become the root! */
|
|
RtlParent(N) = N;
|
|
}
|
|
else
|
|
{
|
|
/* G has a parent, so inherit it since we take G's place */
|
|
RtlParent(N) = RtlParent(G);
|
|
|
|
/*
|
|
* Now find out who was referencing G and have it reference
|
|
* N instead, since we're taking G's place.
|
|
*/
|
|
if (RtlIsLeftChild(G))
|
|
{
|
|
/*
|
|
* G was a left child, so change its parent's left
|
|
* child link to point to N now.
|
|
*/
|
|
RtlLeftChild(RtlParent(G)) = N;
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* G was a right child, so change its parent's right
|
|
* child link to point to N now.
|
|
*/
|
|
RtlRightChild(RtlParent(G)) = N;
|
|
}
|
|
}
|
|
|
|
/* Now N is on top, so P has become its left child. */
|
|
RtlLeftChild(N) = P;
|
|
RtlParent(G) = N;
|
|
|
|
/* N is on top, P is its left child, so G is right child. */
|
|
RtlRightChild(N) = G;
|
|
RtlParent(P) = N;
|
|
}
|
|
/* "Finally" case: N doesn't have a grandparent => P is root */
|
|
else
|
|
{
|
|
/* P's right-child becomes N's left child */
|
|
RtlRightChild(P) = RtlLeftChild(N);
|
|
|
|
/* If it exists, update its parent pointer too */
|
|
if (RtlRightChild(P)) RtlParent(RtlRightChild(P)) = P;
|
|
|
|
/* Now make N the root, no need to worry about references */
|
|
N->Parent = N;
|
|
|
|
/* And make P its left child */
|
|
N->LeftChild = P;
|
|
P->Parent = N;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Return the root entry */
|
|
ASSERT(RtlIsRoot(N));
|
|
return N;
|
|
}
|
|
|
|
/*
|
|
* @implemented
|
|
*/
|
|
PRTL_SPLAY_LINKS
|
|
NTAPI
|
|
RtlSubtreePredecessor(IN PRTL_SPLAY_LINKS Links)
|
|
{
|
|
PRTL_SPLAY_LINKS Child;
|
|
|
|
/* Get the left child */
|
|
Child = RtlLeftChild(Links);
|
|
if (!Child) return NULL;
|
|
|
|
/* Get right-most child */
|
|
while (RtlRightChild(Child)) Child = RtlRightChild(Child);
|
|
|
|
/* Return it */
|
|
return Child;
|
|
}
|
|
|
|
/*
|
|
* @implemented
|
|
*/
|
|
PRTL_SPLAY_LINKS
|
|
NTAPI
|
|
RtlSubtreeSuccessor(IN PRTL_SPLAY_LINKS Links)
|
|
{
|
|
PRTL_SPLAY_LINKS Child;
|
|
|
|
/* Get the right child */
|
|
Child = RtlRightChild(Links);
|
|
if (!Child) return NULL;
|
|
|
|
/* Get left-most child */
|
|
while (RtlLeftChild(Child)) Child = RtlLeftChild(Child);
|
|
|
|
/* Return it */
|
|
return Child;
|
|
}
|
|
|
|
/* EOF */
|