/*
* PROJECT: ReactOS Runtime Library
* LICENSE: BSD - See COPYING.ARM in the top level directory
* FILE: lib/rtl/avlsupp.c
* PURPOSE: AVL Tree Internal Support Routines/Main Algorithms
* PROGRAMMERS: ReactOS Portable Systems Group
*/
/* INCLUDES ******************************************************************/
/* Internal header for table entries */
typedef struct _TABLE_ENTRY_HEADER
{
RTL_BALANCED_LINKS BalancedLinks;
LONGLONG UserData;
} TABLE_ENTRY_HEADER, *PTABLE_ENTRY_HEADER;
typedef enum _RTL_AVL_BALANCE_FACTOR
{
RtlUnbalancedAvlTree = -2,
RtlLeftHeavyAvlTree,
RtlBalancedAvlTree,
RtlRightHeavyAvlTree,
} RTL_AVL_BALANCE_FACTOR;
C_ASSERT(RtlBalancedAvlTree == 0);
/* FUNCTIONS ******************************************************************/
FORCEINLINE
TABLE_SEARCH_RESULT
RtlpFindAvlTableNodeOrParent(IN PRTL_AVL_TABLE Table,
IN PVOID Buffer,
OUT PRTL_BALANCED_LINKS *NodeOrParent)
{
PRTL_BALANCED_LINKS CurrentNode, ChildNode;
RTL_GENERIC_COMPARE_RESULTS Result;
/* Quick check to see if the table is empty */
if (!Table->NumberGenericTableElements) return TableEmptyTree;
/* Set the current node */
CurrentNode = RtlRightChildAvl(&Table->BalancedRoot);
/* Start compare loop */
while (TRUE)
{
/* Compare which side is greater */
Result = RtlpAvlCompareRoutine(Table,
Buffer,
&((PTABLE_ENTRY_HEADER)CurrentNode)->
UserData);
if (Result == GenericLessThan)
{
/* We're less, check if this is the left child */
ChildNode = RtlLeftChildAvl(CurrentNode);
if (ChildNode)
{
/* Continue searching from this node */
CurrentNode = ChildNode;
}
else
{
/* Otherwise, the element isn't in this tree */
*NodeOrParent = CurrentNode;
return TableInsertAsLeft;
}
}
else if (Result == GenericGreaterThan)
{
/* We're more, check if this is the right child */
ChildNode = RtlRightChildAvl(CurrentNode);
if (ChildNode)
{
/* Continue searching from this node */
CurrentNode = ChildNode;
}
else
{
/* Otherwise, the element isn't in this tree */
*NodeOrParent = CurrentNode;
return TableInsertAsRight;
}
}
else
{
/* We should've found the node */
ASSERT(Result == GenericEqual);
/* Return node found */
*NodeOrParent = CurrentNode;
return TableFoundNode;
}
}
}
FORCEINLINE
VOID
RtlpPromoteAvlTreeNode(IN PRTL_BALANCED_LINKS Node)
{
PRTL_BALANCED_LINKS ParentNode, SuperParentNode;
PRTL_BALANCED_LINKS *SwapNode1, *SwapNode2;
/* Grab parents up to 2 levels high */
ParentNode = RtlParentAvl(Node);
SuperParentNode = RtlParentAvl(ParentNode);
/* Pick which nodes will be rotated */
SwapNode1 = RtlIsLeftChildAvl(Node) ? &ParentNode->LeftChild : &ParentNode->RightChild;
SwapNode2 = RtlIsLeftChildAvl(Node) ? &Node->RightChild : &Node->LeftChild;
/* Do the rotate, and update the parent and super-parent as needed */
*SwapNode1 = *SwapNode2;
if (*SwapNode1) RtlSetParent(*SwapNode1, ParentNode);
*SwapNode2 = ParentNode;
RtlSetParent(ParentNode, Node);
/* Now update the super-parent child link, and make it parent of the node*/
SwapNode1 = (RtlLeftChildAvl(SuperParentNode) == ParentNode) ?
&SuperParentNode->LeftChild: &SuperParentNode->RightChild;
*SwapNode1 = Node;
RtlSetParent(Node, SuperParentNode);
}
FORCEINLINE
BOOLEAN
RtlpRebalanceAvlTreeNode(IN PRTL_BALANCED_LINKS Node)
{
PRTL_BALANCED_LINKS ChildNode, SubChildNode;
CHAR Balance;
ASSERT(RtlParentAvl(Node) != Node);
/* Get the balance, and figure out which child node to go down on */
Balance = RtlBalance(Node);
ChildNode = (Balance == RtlRightHeavyAvlTree) ?
RtlRightChildAvl(Node) : RtlLeftChildAvl(Node);
/* The child and node have the same balance, promote the child upwards */
if (RtlBalance(ChildNode) == Balance)
{
/* This performs the rotation described in Knuth A8-A10 for Case 1 */
RtlpPromoteAvlTreeNode(ChildNode);
/* The nodes are now balanced */
RtlSetBalance(ChildNode, RtlBalancedAvlTree);
RtlSetBalance(Node, RtlBalancedAvlTree);
return FALSE;
}
/* The child has the opposite balance, a double promotion of the child's child must happen */
if (RtlBalance(ChildNode) == -Balance)
{
/* Pick which sub-child to use based on the balance */
SubChildNode = (Balance == RtlRightHeavyAvlTree) ?
RtlLeftChildAvl(ChildNode) : RtlRightChildAvl(ChildNode);
/* Do the double-rotation described in Knuth A8-A10 for Case 2 */
RtlpPromoteAvlTreeNode(SubChildNode);
RtlpPromoteAvlTreeNode(SubChildNode);
/* Was the sub-child sharing the same balance as the node? */
if (RtlBalance(SubChildNode) == Balance)
{
/* Then the subchild is now balanced, and the node's weight is inversed */
RtlSetBalance(ChildNode, RtlBalancedAvlTree);
RtlSetBalance(Node, -Balance);
}
else if (RtlBalance(SubChildNode) == -Balance)
{
/*
* In this case, the sub-child weight was the inverse of the node, so
* the child now shares the node's balance original weight, while the
* node becomes balanced.
*/
RtlSetBalance(ChildNode, Balance);
RtlSetBalance(Node, RtlBalancedAvlTree);
}
else
{
/*
* Otherwise, the sub-child was unbalanced, so both the child and node
* now become balanced.
*/
RtlSetBalance(ChildNode, RtlBalancedAvlTree);
RtlSetBalance(Node, RtlBalancedAvlTree);
}
/* In all cases, the sub-child is now balanced */
RtlSetBalance(SubChildNode, RtlBalancedAvlTree);
return FALSE;
}
/*
* The case that remains is that the child was already balanced, so this is
* This is the rotation required for Case 3 in Knuth A8-A10
*/
RtlpPromoteAvlTreeNode(ChildNode);
/* Now the child has the opposite weight of the node */
RtlSetBalance(ChildNode, -Balance);
/* This only happens on deletion, so we return TRUE to terminate the delete */
return TRUE;
}
FORCEINLINE
VOID
RtlpInsertAvlTreeNode(IN PRTL_AVL_TABLE Table,
IN PRTL_BALANCED_LINKS NewNode,
IN OUT PVOID NodeOrParent,
IN OUT TABLE_SEARCH_RESULT SearchResult)
{
CHAR Balance;
/* Initialize the new inserted element */
MI_ASSERT(SearchResult != TableFoundNode);
NewNode->LeftChild = NewNode->RightChild = NULL;
RtlSetBalance(NewNode, RtlBalancedAvlTree);
/* Increase element count */
Table->NumberGenericTableElements++;
/* Check where we should insert the entry */
if (SearchResult == TableEmptyTree)
{
/* This is the new root node */
RtlInsertAsRightChildAvl(&Table->BalancedRoot, NewNode);
/* On AVL trees, we also update the depth */
ASSERT(Table->DepthOfTree == 0);
Table->DepthOfTree = 1;
return;
}
else if (SearchResult == TableInsertAsLeft)
{
/* Insert it left */
RtlInsertAsLeftChildAvl(NodeOrParent, NewNode);
}
else
{
/* Right node */
RtlInsertAsRightChildAvl(NodeOrParent, NewNode);
}
/* Little cheat to save on loop processing, taken from Timo */
RtlSetBalance(&Table->BalancedRoot, RtlLeftHeavyAvlTree);
/*
* This implements A6-A7 from Knuth based on http://coding.derkeiler.com
* /pdf/Archive/C_CPP/comp.lang.c/2004-01/1812.pdf, however the algorithm
* is slightly modified to follow the tree based on the Parent Node such
* as the Windows algorithm does it, instead of following the nodes down.
*/
while (TRUE)
{
/* Calculate which side to balance on */
Balance = RtlIsLeftChildAvl(NewNode) ? RtlLeftHeavyAvlTree : RtlRightHeavyAvlTree;
/* Check if the parent node was balanced */
if (RtlBalance(NodeOrParent) == RtlBalancedAvlTree)
{
/* It's not balanced anymore (heavy on one side) */
RtlSetBalance(NodeOrParent, Balance);
/* Move up */
NewNode = NodeOrParent;
NodeOrParent = RtlParentAvl(NodeOrParent);
}
else if (RtlBalance(NodeOrParent) != Balance)
{
/* The parent's balance is opposite, so the tree is balanced now */
RtlSetBalance(NodeOrParent, RtlBalancedAvlTree);
/* Check if this is the root (the cheat applied earlier gets us here) */
if (RtlBalance(&Table->BalancedRoot) == RtlBalancedAvlTree)
{
/* The depth has thus increased */
Table->DepthOfTree++;
}
/* We reached the root or a balanced node, so we're done */
break;
}
else
{
/* The tree is now unbalanced, so AVL rebalancing must happen */
RtlpRebalanceAvlTreeNode(NodeOrParent);
break;
}
}
}
FORCEINLINE
VOID
RtlpDeleteAvlTreeNode(IN PRTL_AVL_TABLE Table,
IN PRTL_BALANCED_LINKS Node)
{
PRTL_BALANCED_LINKS DeleteNode = NULL, ParentNode;
PRTL_BALANCED_LINKS *Node1, *Node2;
CHAR Balance;
/* Take one of the children if possible */
if (!(RtlLeftChildAvl(Node)) || !(RtlRightChildAvl(Node))) DeleteNode = Node;
/* Otherwise, check if one side is longer */
if (!(DeleteNode) && (RtlBalance(Node) >= RtlBalancedAvlTree))
{
/* Pick the successor which will be the longest side in this case */
DeleteNode = RtlRightChildAvl(Node);
while (RtlLeftChildAvl(DeleteNode)) DeleteNode = RtlLeftChildAvl(DeleteNode);
}
else if (!DeleteNode)
{
/* Pick the predecessor which will be the longest side in this case */
DeleteNode = RtlLeftChildAvl(Node);
while (RtlRightChildAvl(DeleteNode)) DeleteNode = RtlRightChildAvl(DeleteNode);
}
/* Get the parent node */
ParentNode = RtlParentAvl(DeleteNode);
DPRINT("Parent: %p\n", ParentNode);
/* Pick which now to use based on whether or not we have a left child */
Node1 = RtlLeftChildAvl(DeleteNode) ? &DeleteNode->LeftChild : &DeleteNode->RightChild;
DPRINT("Node 1: %p %p\n", Node1, *Node1);
/* Pick which node to swap based on if we're already a left child or not */
Node2 = RtlIsLeftChildAvl(DeleteNode) ? &ParentNode->LeftChild : &ParentNode->RightChild;
DPRINT("Node 2: %p %p\n", Node2, *Node2);
/* Pick the correct balance depending on which side will get heavier */
Balance = RtlIsLeftChildAvl(DeleteNode) ? RtlLeftHeavyAvlTree : RtlRightHeavyAvlTree;
DPRINT("Balance: %lx\n", Balance);
/* Swap the children nodes, making one side heavier */
*Node2 = *Node1;
/* If the node has a child now, update its parent */
if (*Node1) RtlSetParent(*Node1, ParentNode);
/* Assume balanced root for loop optimization */
RtlSetBalance(&Table->BalancedRoot, RtlBalancedAvlTree);
/* Loop up the tree by parents */
while (TRUE)
{
/* Check if the tree's balance increased */
if (RtlBalance(ParentNode) == Balance)
{
/* Now the tree is balanced */
RtlSetBalance(ParentNode, RtlBalancedAvlTree);
}
else if (RtlBalance(ParentNode) == RtlBalancedAvlTree)
{
/* The tree has now become less balanced, since it was balanced */
RtlSetBalance(ParentNode, -Balance);
/* Deal with the loop optimization to detect loss of a tree level */
if (RtlBalance(&Table->BalancedRoot) != RtlBalancedAvlTree) Table->DepthOfTree--;
break;
}
else
{
/* The tree has become unbalanced, so a rebalance is needed */
if (RtlpRebalanceAvlTreeNode(ParentNode)) break;
/* Get the new parent after the balance */
ParentNode = RtlParentAvl(ParentNode);
}
/* Choose which balance factor to use based on which side we're on */
Balance = RtlIsRightChild(ParentNode) ?
RtlRightHeavyAvlTree : RtlLeftHeavyAvlTree;
/* Iterate up the tree */
ParentNode = RtlParentAvl(ParentNode);
}
/* Check if this isn't the node we ended up deleting directly */
if (Node == DeleteNode) return;
/* Copy the deleted node itself */
RtlpCopyAvlNodeData(DeleteNode, Node);
/* Pick the right node to unlink */
Node1 = RtlIsLeftChildAvl(Node) ?
&(RtlParentAvl(DeleteNode))->LeftChild : &(RtlParentAvl(DeleteNode))->RightChild;
*Node1 = DeleteNode;
/* Reparent as appropriate */
if (RtlLeftChildAvl(DeleteNode)) RtlSetParent(RtlLeftChildAvl(DeleteNode), DeleteNode);
if (RtlRightChildAvl(DeleteNode)) RtlSetParent(RtlRightChildAvl(DeleteNode), DeleteNode);
}
/* EOF */