/*
* COPYRIGHT: See COPYING in the top level directory
* PROJECT: ReactOS system libraries
* PURPOSE: Splay-Tree implementation
* FILE: lib/rtl/splaytree.c
* PROGRAMMER: Alex Ionescu (alex@relsoft.net)
*/
/* INCLUDES *****************************************************************/
#include <rtl.h>
#define NDEBUG
#include <debug.h>
//#define VERIFY_SWAP_SPLAY_LINKS
/* FUNCTIONS ***************************************************************/
static
VOID
FixupChildLinks(PRTL_SPLAY_LINKS Links, BOOLEAN Root, BOOLEAN LeftChild)
{
if (RtlLeftChild(Links))
{
RtlInsertAsLeftChild(Links, RtlLeftChild(Links));
}
if (RtlRightChild(Links))
{
RtlInsertAsRightChild(Links, RtlRightChild(Links));
}
if (!Root)
{
if (LeftChild)
{
RtlInsertAsLeftChild(RtlParent(Links), Links);
}
else
{
RtlInsertAsRightChild(RtlParent(Links), Links);
}
}
}
/*
Given the tree:
D
B F
A C E G
Swap(Q,S):
Q S Q.P Q.L Q.R S.P S.L S.R
A C S.P S.L S.R Q.P Q.L Q.R
B A S S.L S.R Q.P Q Q.R
B C S S.L S.R Q.P Q.L Q
D A S.P S.L S.R S Q.L Q.R
D B S S.L S.R S Q Q.R
D F S S.L S.R S Q.L Q
When Q is the immediate parent of S,
Set Q's parent to S, and the proper child ptr of S to Q
When Q is the root,
Set S's parent to S
*/
static
VOID
SwapSplayLinks(PRTL_SPLAY_LINKS LinkA,
PRTL_SPLAY_LINKS LinkB)
{
if (RtlParent(LinkA) == LinkB || RtlIsRoot(LinkB))
{
PRTL_SPLAY_LINKS Tmp = LinkA;
LinkA = LinkB;
LinkB = Tmp;
}
{
RTL_SPLAY_LINKS Ta = *LinkA, Tb = *LinkB;
BOOLEAN RootA = RtlIsRoot(LinkA),
LeftA = RtlIsLeftChild(LinkA),
LeftB = RtlIsLeftChild(LinkB);
*LinkB = Ta; *LinkA = Tb;
// A was parent of B is a special case: A->Parent is now B
if (RtlParent(&Tb) == LinkA)
{
if (!RootA)
{
if (LeftA)
{
RtlInsertAsLeftChild(RtlParent(&Ta), LinkB);
}
else
{
RtlInsertAsRightChild(RtlParent(&Ta), LinkB);
}
}
if (LeftB)
{
RtlInsertAsLeftChild(LinkB, LinkA);
}
else
{
RtlInsertAsRightChild(LinkB, LinkA);
}
}
FixupChildLinks(LinkA, FALSE, LeftB);
FixupChildLinks(LinkB, RootA, LeftA);
// A was root is a special case: B->Parent is now B
if (RootA)
RtlParent(LinkB) = LinkB;
#ifdef VERIFY_SWAP_SPLAY_LINKS
// Verify the distinct cases of node swap
if (RootA)
{
if (RtlParent(&Tb) == LinkA)
{
// LinkA = D, LinkB = B
// D B S S.L S.R S Q Q.R
ASSERT(RtlParent(LinkA) == LinkB);
ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
ASSERT(RtlParent(LinkB) == LinkB);
ASSERT(RtlLeftChild(LinkB) == (LeftB ? LinkA : RtlLeftChild(&Ta)));
ASSERT(RtlRightChild(LinkB) == (LeftB ? RtlRightChild(&Ta) : LinkA));
}
else
{
// LinkA = D, LinkB = A
// D A S.P S.L S.R S Q.L Q.R
ASSERT(RtlParent(LinkA) == RtlParent(&Tb));
ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
ASSERT(RtlParent(LinkB) == LinkB);
ASSERT(RtlLeftChild(LinkB) == RtlLeftChild(&Ta));
ASSERT(RtlRightChild(LinkB) == RtlRightChild(&Ta));
}
}
else
{
if (RtlParent(&Tb) == LinkA)
{
// LinkA = B, LinkB = A
// B A S S.L S.R Q.P Q Q.R
ASSERT(RtlParent(LinkA) == LinkB);
ASSERT(RtlLeftChild(LinkA) == RtlLeftChild(&Tb));
ASSERT(RtlRightChild(LinkA) == RtlRightChild(&Tb));
ASSERT(RtlParent(LinkB) == RtlParent(&Ta));
ASSERT(RtlLeftChild(LinkB) == (LeftB ? LinkA : RtlLeftChild(&Ta)));
ASSERT(RtlRightChild(LinkB) == (LeftB ? RtlRightChild(&Ta) : LinkA));
}
else
{
// LinkA = A, LinkB = C
// A C S.P S.L S.R Q.P Q.L Q.R
ASSERT(!memcmp(LinkA, &Tb, sizeof(Tb)));
ASSERT(!memcmp(LinkB, &Ta, sizeof(Ta)));
}
}
#endif
}
}
/*
* @implemented
*/
PRTL_SPLAY_LINKS
NTAPI
RtlDelete(PRTL_SPLAY_LINKS Links)
{
PRTL_SPLAY_LINKS N, P, C, SP;
N = Links;
/* Check if we have two children */
if (RtlLeftChild(N) && RtlRightChild(N))
{
/* Get the predecessor */
SP = RtlSubtreePredecessor(N);
/* Swap it with N, this will guarantee that N will only have a child */
SwapSplayLinks(SP, N);
}
/* Check if we have no children */
if (!RtlLeftChild(N) && !RtlRightChild(N))
{
/* If we are also the root, then the tree is gone */
if (RtlIsRoot(N)) return NULL;
/* Get our parent */
P = RtlParent(N);
/* Find out who is referencing us and delete the reference */
if (RtlIsLeftChild(N))
{
/* N was a left child, so erase its parent's left child link */
RtlLeftChild(P) = NULL;
}
else
{
/* N was a right child, so erase its parent's right child link */
RtlRightChild(P) = NULL;
}
/* And finally splay the parent */
return RtlSplay(P);
}
/* If we got here, we have a child (not two: we swapped above!) */
if (RtlLeftChild(N))
{
/* We have a left child, so get it */
C = RtlLeftChild(N);
}
else
{
/* We have a right child, get it instead */
C = RtlRightChild(N);
}
/* Check if we are the root entry */
if (RtlIsRoot(N))
{
/* Our child is now root, return it */
RtlParent(C) = C;
return C;
}
/* Get our parent */
P = RtlParent(N);
/* Find out who is referencing us and link to our child instead */
if (RtlIsLeftChild(N))
{
/* N was a left child, so set its parent's left child as our child */
RtlLeftChild(P) = C;
}
else
{
/* N was a right child, so set its parent's right child as our child */
RtlRightChild(P) = C;
}
/* Finally, inherit our parent and splay the parent */
RtlParent(C) = P;
return RtlSplay(P);
}
/*
* @implemented
*/
VOID
NTAPI
RtlDeleteNoSplay(PRTL_SPLAY_LINKS Links,
PRTL_SPLAY_LINKS *Root)
{
PRTL_SPLAY_LINKS N, P, C, SP;
N = Links;
/* Check if we have two children */
if (RtlLeftChild(N) && RtlRightChild(N))
{
/* Get the predecessor */
SP = RtlSubtreePredecessor(N);
/* If we are the root, the new root will be our predecessor after swapping */
if (RtlIsRoot(N)) *Root = SP;
/* Swap the predecessor with N, this will guarantee that N will only have a child */
SwapSplayLinks(SP, N);
}
/* Check if we have no children */
if (!RtlLeftChild(N) && !RtlRightChild(N))
{
/* If we are also the root, then the tree is gone */
if (RtlIsRoot(N))
{
*Root = NULL;
return;
}
/* Get our parent */
P = RtlParent(N);
/* Find out who is referencing us and delete the reference */
if (RtlIsLeftChild(N))
{
/* N was a left child, so erase its parent's left child link */
RtlLeftChild(P) = NULL;
}
else
{
/* N was a right child, so erase its parent's right child link */
RtlRightChild(P) = NULL;
}
/* We are done */
return;
}
/* If we got here, we have a child (not two: we swapped above!) */
if (RtlLeftChild(N))
{
/* We have a left child, so get it */
C = RtlLeftChild(N);
}
else
{
/* We have a right child, get it instead */
C = RtlRightChild(N);
}
/* Check if we are the root entry */
if (RtlIsRoot(N))
{
/* Our child is now root, return it */
RtlParent(C) = C;
*Root = C;
return;
}
/* Get our parent */
P = RtlParent(N);
/* Find out who is referencing us and link to our child instead */
if (RtlIsLeftChild(N))
{
/* N was a left child, so set its parent's left child as our child */
RtlLeftChild(P) = C;
}
else
{
/* N was a right child, so set its parent's right child as our child */
RtlRightChild(P) = C;
}
/* Finally, inherit our parent and we are done */
RtlParent(C) = P;
return;
}
/*
* @implemented
*/
PRTL_SPLAY_LINKS
NTAPI
RtlRealPredecessor(PRTL_SPLAY_LINKS Links)
{
PRTL_SPLAY_LINKS Child;
/* Get the left child */
Child = RtlLeftChild(Links);
if (Child)
{
/* Get right-most child */
while (RtlRightChild(Child)) Child = RtlRightChild(Child);
return Child;
}
/* We don't have a left child, keep looping until we find our parent */
Child = Links;
while (RtlIsLeftChild(Child)) Child = RtlParent(Child);
/* The parent should be a right child, return the real predecessor */
if (RtlIsRightChild(Child)) return RtlParent(Child);
/* The parent isn't a right child, so no real precessor for us */
return NULL;
}
/*
* @implemented
*/
PRTL_SPLAY_LINKS
NTAPI
RtlRealSuccessor(PRTL_SPLAY_LINKS Links)
{
PRTL_SPLAY_LINKS Child;
/* Get the right child */
Child = RtlRightChild(Links);
if (Child)
{
/* Get left-most child */
while (RtlLeftChild(Child)) Child = RtlLeftChild(Child);
return Child;
}
/* We don't have a right child, keep looping until we find our parent */
Child = Links;
while (RtlIsRightChild(Child)) Child = RtlParent(Child);
/* The parent should be a left child, return the real successor */
if (RtlIsLeftChild(Child)) return RtlParent(Child);
/* The parent isn't a right child, so no real successor for us */
return NULL;
}
/*
* @implemented
*/
PRTL_SPLAY_LINKS
NTAPI
RtlSplay(PRTL_SPLAY_LINKS Links)
{
/*
* Implementation Notes (http://en.wikipedia.org/wiki/Splay_tree):
*
* To do a splay, we carry out a sequence of rotations,
* each of which moves the target node N closer to the root.
*
* Each particular step depends on only two factors:
* - Whether N is the left or right child of its parent node, P,
* - Whether P is the left or right child of its parent, G (for grandparent node).
*
* Thus, there are four cases:
* - Case 1: N is the left child of P and P is the left child of G.
* In this case we perform a double right rotation, so that
* P becomes N's right child, and G becomes P's right child.
*
* - Case 2: N is the right child of P and P is the right child of G.
* In this case we perform a double left rotation, so that
* P becomes N's left child, and G becomes P's left child.
*
* - Case 3: N is the left child of P and P is the right child of G.
* In this case we perform a rotation so that
* G becomes N's left child, and P becomes N's right child.
*
* - Case 4: N is the right child of P and P is the left child of G.
* In this case we perform a rotation so that
* P becomes N's left child, and G becomes N's right child.
*
* Finally, if N doesn't have a grandparent node, we simply perform a
* left or right rotation to move it to the root.
*
* By performing a splay on the node of interest after every operation,
* we keep recently accessed nodes near the root and keep the tree
* roughly balanced, so that we achieve the desired amortized time bounds.
*/
PRTL_SPLAY_LINKS N, P, G;
/* N is the item we'll be playing with */
N = Links;
/* Let the algorithm run until N becomes the root entry */
while (!RtlIsRoot(N))
{
/* Now get the parent and grand-parent */
P = RtlParent(N);
G = RtlParent(P);
/* Case 1 & 3: N is left child of P */
if (RtlIsLeftChild(N))
{
/* Case 1: P is the left child of G */
if (RtlIsLeftChild(P))
{
/*
* N's right-child becomes P's left child and
* P's right-child becomes G's left child.
*/
RtlLeftChild(P) = RtlRightChild(N);
RtlLeftChild(G) = RtlRightChild(P);
/*
* If they exist, update their parent pointers too,
* since they've changed trees.
*/
if (RtlLeftChild(P)) RtlParent(RtlLeftChild(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 child. */
RtlRightChild(N) = P;
RtlParent(P) = N;
/* N is on top, P is its child, so G is grandchild. */
RtlRightChild(P) = G;
RtlParent(G) = P;
}
/* Case 3: P is the right child of G */
else if (RtlIsRightChild(P))
{
/*
* N's left-child becomes G's right child and
* N's right-child becomes P's left child.
*/
RtlRightChild(G) = RtlLeftChild(N);
RtlLeftChild(P) = RtlRightChild(N);
/*
* If they exist, update their parent pointers too,
* since they've changed trees.
*/
if (RtlRightChild(G)) RtlParent(RtlRightChild(G)) = G;
if (RtlLeftChild(P)) RtlParent(RtlLeftChild(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 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 */