6d303d19a68eefce939f30631ad6dc88910157ca
[reactos.git] / reactos / lib / rtl / avlsupp.c
1 /*
2 * PROJECT: ReactOS Runtime Library
3 * LICENSE: BSD - See COPYING.ARM in the top level directory
4 * FILE: lib/rtl/avlsupp.c
5 * PURPOSE: AVL Tree Internal Support Routines/Main Algorithms
6 * PROGRAMMERS: ReactOS Portable Systems Group
7 */
8
9 /* INCLUDES ******************************************************************/
10
11 /* Internal header for table entries */
12 typedef struct _TABLE_ENTRY_HEADER
13 {
14 RTL_BALANCED_LINKS BalancedLinks;
15 LONGLONG UserData;
16 } TABLE_ENTRY_HEADER, *PTABLE_ENTRY_HEADER;
17
18 typedef enum _RTL_AVL_BALANCE_FACTOR
19 {
20 RtlUnbalancedAvlTree = -2,
21 RtlLeftHeavyAvlTree,
22 RtlBalancedAvlTree,
23 RtlRightHeavyAvlTree,
24 } RTL_AVL_BALANCE_FACTOR;
25
26 C_ASSERT(RtlBalancedAvlTree == 0);
27
28 /* FUNCTIONS ******************************************************************/
29
30 FORCEINLINE
31 TABLE_SEARCH_RESULT
32 RtlpFindAvlTableNodeOrParent(IN PRTL_AVL_TABLE Table,
33 IN PVOID Buffer,
34 OUT PRTL_BALANCED_LINKS *NodeOrParent)
35 {
36 PRTL_BALANCED_LINKS CurrentNode, ChildNode;
37 RTL_GENERIC_COMPARE_RESULTS Result;
38
39 /* Quick check to see if the table is empty */
40 if (!Table->NumberGenericTableElements) return TableEmptyTree;
41
42 /* Set the current node */
43 CurrentNode = RtlRightChildAvl(&Table->BalancedRoot);
44
45 /* Start compare loop */
46 while (TRUE)
47 {
48 /* Compare which side is greater */
49 Result = RtlpAvlCompareRoutine(Table,
50 Buffer,
51 &((PTABLE_ENTRY_HEADER)CurrentNode)->
52 UserData);
53 if (Result == GenericLessThan)
54 {
55 /* We're less, check if this is the left child */
56 ChildNode = RtlLeftChildAvl(CurrentNode);
57 if (ChildNode)
58 {
59 /* Continue searching from this node */
60 CurrentNode = ChildNode;
61 }
62 else
63 {
64 /* Otherwise, the element isn't in this tree */
65 *NodeOrParent = CurrentNode;
66 return TableInsertAsLeft;
67 }
68 }
69 else if (Result == GenericGreaterThan)
70 {
71 /* We're more, check if this is the right child */
72 ChildNode = RtlRightChildAvl(CurrentNode);
73 if (ChildNode)
74 {
75 /* Continue searching from this node */
76 CurrentNode = ChildNode;
77 }
78 else
79 {
80 /* Otherwise, the element isn't in this tree */
81 *NodeOrParent = CurrentNode;
82 return TableInsertAsRight;
83 }
84 }
85 else
86 {
87 /* We should've found the node */
88 ASSERT(Result == GenericEqual);
89
90 /* Return node found */
91 *NodeOrParent = CurrentNode;
92 return TableFoundNode;
93 }
94 }
95 }
96
97 FORCEINLINE
98 VOID
99 RtlPromoteAvlTreeNode(IN PRTL_BALANCED_LINKS Node)
100 {
101 PRTL_BALANCED_LINKS ParentNode, SuperParentNode;
102 PRTL_BALANCED_LINKS *SwapNode1, *SwapNode2;
103
104 /* Grab parents up to 2 levels high */
105 ParentNode = RtlParentAvl(Node);
106 SuperParentNode = RtlParentAvl(ParentNode);
107
108 /* Pick which nodes will be rotated */
109 SwapNode1 = RtlIsLeftChildAvl(Node) ? &ParentNode->LeftChild : &ParentNode->RightChild;
110 SwapNode2 = RtlIsLeftChildAvl(Node) ? &Node->RightChild : &Node->LeftChild;
111
112 /* Do the rotate, and update the parent and super-parent as needed */
113 *SwapNode1 = *SwapNode2;
114 if (*SwapNode1) RtlSetParent(*SwapNode1, ParentNode);
115 *SwapNode2 = ParentNode;
116 RtlSetParent(ParentNode, Node);
117
118 /* Now update the super-parent child link, and make it parent of the node*/
119 SwapNode1 = (RtlLeftChildAvl(SuperParentNode) == ParentNode) ?
120 &SuperParentNode->LeftChild: &SuperParentNode->RightChild;
121 *SwapNode1 = Node;
122 RtlSetParent(Node, SuperParentNode);
123 }
124
125 FORCEINLINE
126 BOOLEAN
127 RtlpRebalanceAvlTreeNode(IN PRTL_BALANCED_LINKS Node)
128 {
129 PRTL_BALANCED_LINKS ChildNode, SubChildNode;
130 CHAR Balance;
131 ASSERT(RtlParentAvl(Node) != Node);
132
133 /* Get the balance, and figure out which child node to go down on */
134 Balance = RtlBalance(Node);
135 ChildNode = (Balance == RtlRightHeavyAvlTree) ?
136 RtlRightChildAvl(Node) : RtlLeftChildAvl(Node);
137
138 /* The child and node have the same balance, promote the child upwards */
139 if (RtlBalance(ChildNode) == Balance)
140 {
141 /* This performs the rotation described in Knuth A8-A10 for Case 1 */
142 RtlPromoteAvlTreeNode(ChildNode);
143
144 /* The nodes are now balanced */
145 RtlSetBalance(ChildNode, RtlBalancedAvlTree);
146 RtlSetBalance(Node, RtlBalancedAvlTree);
147 return FALSE;
148 }
149
150 /* The child has the opposite balance, a double promotion of the child's child must happen */
151 if (RtlBalance(ChildNode) == -Balance)
152 {
153 /* Pick which sub-child to use based on the balance */
154 SubChildNode = (Balance == RtlRightHeavyAvlTree) ?
155 RtlLeftChildAvl(ChildNode) : RtlRightChildAvl(ChildNode);
156
157 /* Do the double-rotation described in Knuth A8-A10 for Case 2 */
158 RtlPromoteAvlTreeNode(SubChildNode);
159 RtlPromoteAvlTreeNode(SubChildNode);
160
161 /* Was the sub-child sharing the same balance as the node? */
162 if (RtlBalance(SubChildNode) == Balance)
163 {
164 /* Then the subchild is now balanced, and the node's weight is inversed */
165 RtlSetBalance(ChildNode, RtlBalancedAvlTree);
166 RtlSetBalance(Node, -Balance);
167 }
168 else if (RtlBalance(SubChildNode) == -Balance)
169 {
170 /*
171 * In this case, the sub-child weight was the inverse of the node, so
172 * the child now shares the node's balance original weight, while the
173 * node becomes balanced.
174 */
175 RtlSetBalance(ChildNode, Balance);
176 RtlSetBalance(Node, RtlBalancedAvlTree);
177 }
178 else
179 {
180 /*
181 * Otherwise, the sub-child was unbalanced, so both the child and node
182 * now become balanced.
183 */
184 RtlSetBalance(ChildNode, RtlBalancedAvlTree);
185 RtlSetBalance(Node, RtlBalancedAvlTree);
186 }
187
188 /* In all cases, the sub-child is now balanced */
189 RtlSetBalance(SubChildNode, RtlBalancedAvlTree);
190 return FALSE;
191 }
192
193 /*
194 * The case that remains is that the child was already balanced, so this is
195 * This is the rotation required for Case 3 in Knuth A8-A10
196 */
197 RtlPromoteAvlTreeNode(ChildNode);
198
199 /* Now the child has the opposite weight of the node */
200 RtlSetBalance(ChildNode, -Balance);
201
202 /* This only happens on deletion, so we return TRUE to terminate the delete */
203 return TRUE;
204 }
205
206 FORCEINLINE
207 VOID
208 RtlpInsertAvlTreeNode(IN PRTL_AVL_TABLE Table,
209 IN PRTL_BALANCED_LINKS NewNode,
210 IN OUT PVOID NodeOrParent,
211 IN OUT TABLE_SEARCH_RESULT SearchResult)
212 {
213 CHAR Balance;
214
215 /* Initialize the new inserted element */
216 MI_ASSERT(SearchResult != TableFoundNode);
217 NewNode->LeftChild = NewNode->RightChild = NULL;
218 RtlSetBalance(NewNode, RtlBalancedAvlTree);
219
220 /* Increase element count */
221 Table->NumberGenericTableElements++;
222
223 /* Check where we should insert the entry */
224 if (SearchResult == TableEmptyTree)
225 {
226 /* This is the new root node */
227 RtlInsertAsRightChildAvl(&Table->BalancedRoot, NewNode);
228
229 /* On AVL trees, we also update the depth */
230 ASSERT(Table->DepthOfTree == 0);
231 Table->DepthOfTree = 1;
232 return;
233 }
234 else if (SearchResult == TableInsertAsLeft)
235 {
236 /* Insert it left */
237 RtlInsertAsLeftChildAvl(NodeOrParent, NewNode);
238 }
239 else
240 {
241 /* Right node */
242 RtlInsertAsRightChildAvl(NodeOrParent, NewNode);
243 }
244
245 /* Little cheat to save on loop processing, taken from Timo */
246 RtlSetBalance(&Table->BalancedRoot, RtlLeftHeavyAvlTree);
247
248 /*
249 * This implements A6-A7 from Knuth based on http://coding.derkeiler.com
250 * /pdf/Archive/C_CPP/comp.lang.c/2004-01/1812.pdf, however the algorithm
251 * is slightly modified to follow the tree based on the Parent Node such
252 * as the Windows algorithm does it, instead of following the nodes down.
253 */
254 while (TRUE)
255 {
256 /* Calculate which side to balance on */
257 Balance = RtlIsLeftChildAvl(NewNode) ? RtlLeftHeavyAvlTree : RtlRightHeavyAvlTree;
258
259 /* Check if the parent node was balanced */
260 if (RtlBalance(NodeOrParent) == RtlBalancedAvlTree)
261 {
262 /* It's not balanced anymore (heavy on one side) */
263 RtlSetBalance(NodeOrParent, Balance);
264
265 /* Move up */
266 NewNode = NodeOrParent;
267 NodeOrParent = RtlParentAvl(NodeOrParent);
268 }
269 else if (RtlBalance(NodeOrParent) != Balance)
270 {
271 /* The parent's balance is opposite, so the tree is balanced now */
272 RtlSetBalance(NodeOrParent, RtlBalancedAvlTree);
273
274 /* Check if this is the root (the cheat applied earlier gets us here) */
275 if (RtlBalance(&Table->BalancedRoot) == RtlBalancedAvlTree)
276 {
277 /* The depth has thus increased */
278 Table->DepthOfTree++;
279 }
280
281 /* We reached the root or a balanced node, so we're done */
282 break;
283 }
284 else
285 {
286 /* The tree is now unbalanced, so AVL rebalancing must happen */
287 RtlpRebalanceAvlTreeNode(NodeOrParent);
288 break;
289 }
290 }
291 }
292
293 FORCEINLINE
294 VOID
295 RtlpDeleteAvlTreeNode(IN PRTL_AVL_TABLE Table,
296 IN PRTL_BALANCED_LINKS Node)
297 {
298 PRTL_BALANCED_LINKS DeleteNode = NULL, ParentNode;
299 PRTL_BALANCED_LINKS *Node1, *Node2;
300 CHAR Balance;
301
302 /* Take one of the children if possible */
303 if (!(RtlLeftChildAvl(Node)) || !(RtlRightChildAvl(Node))) DeleteNode = Node;
304
305 /* Otherwise, check if one side is longer */
306 if (!(DeleteNode) && (RtlBalance(Node) >= RtlBalancedAvlTree))
307 {
308 /* Pick the successor which will be the longest side in this case */
309 DeleteNode = RtlRightChildAvl(Node);
310 while (RtlLeftChildAvl(DeleteNode)) DeleteNode = RtlLeftChildAvl(DeleteNode);
311 }
312 else if (!DeleteNode)
313 {
314 /* Pick the predecessor which will be the longest side in this case */
315 DeleteNode = RtlLeftChildAvl(Node);
316 while (RtlRightChildAvl(DeleteNode)) DeleteNode = RtlRightChildAvl(DeleteNode);
317 }
318
319 /* Get the parent node */
320 ParentNode = RtlParentAvl(DeleteNode);
321 DPRINT("Parent: %p\n", ParentNode);
322
323 /* Pick which now to use based on whether or not we have a left child */
324 Node1 = RtlLeftChildAvl(DeleteNode) ? &DeleteNode->LeftChild : &DeleteNode->RightChild;
325 DPRINT("Node 1: %p %p\n", Node1, *Node1);
326
327 /* Pick which node to swap based on if we're already a left child or not */
328 Node2 = RtlIsLeftChildAvl(DeleteNode) ? &ParentNode->LeftChild : &ParentNode->RightChild;
329 DPRINT("Node 2: %p %p\n", Node2, *Node2);
330
331 /* Pick the correct balance depending on which side will get heavier */
332 Balance = RtlIsLeftChildAvl(DeleteNode) ? RtlLeftHeavyAvlTree : RtlRightHeavyAvlTree;
333 DPRINT("Balance: %lx\n", Balance);
334
335 /* Swap the children nodes, making one side heavier */
336 *Node2 = *Node1;
337
338 /* If the node has a child now, update its parent */
339 if (*Node1) RtlSetParent(*Node1, ParentNode);
340
341 /* Assume balanced root for loop optimization */
342 RtlSetBalance(&Table->BalancedRoot, RtlBalancedAvlTree);
343
344 /* Loop up the tree by parents */
345 while (TRUE)
346 {
347 /* Check if the tree's balance increased */
348 if (RtlBalance(ParentNode) == Balance)
349 {
350 /* Now the tree is balanced */
351 RtlSetBalance(ParentNode, RtlBalancedAvlTree);
352 }
353 else if (RtlBalance(ParentNode) == RtlBalancedAvlTree)
354 {
355 /* The tree has now become less balanced, since it was balanced */
356 RtlSetBalance(ParentNode, -Balance);
357
358 /* Deal with the loop optimization to detect loss of a tree level */
359 if (RtlBalance(&Table->BalancedRoot) != RtlBalancedAvlTree) Table->DepthOfTree--;
360 break;
361 }
362 else
363 {
364 /* The tree has become unbalanced, so a rebalance is needed */
365 if (RtlpRebalanceAvlTreeNode(ParentNode)) break;
366
367 /* Get the new parent after the balance */
368 ParentNode = RtlParentAvl(ParentNode);
369 }
370
371 /* Choose which balance factor to use based on which side we're on */
372 Balance = RtlIsRightChild(ParentNode) ?
373 RtlRightHeavyAvlTree : RtlLeftHeavyAvlTree;
374
375 /* Iterate up the tree */
376 ParentNode = RtlParentAvl(ParentNode);
377 }
378
379 /* Check if this isn't the node we ended up deleting directly */
380 if (Node == DeleteNode) return;
381
382 /* Copy the deleted node itself */
383 RtlpCopyAvlNodeData(DeleteNode, Node);
384
385 /* Pick the right node to unlink */
386 Node1 = RtlIsLeftChildAvl(Node) ?
387 &(RtlParentAvl(DeleteNode))->LeftChild : &(RtlParentAvl(DeleteNode))->RightChild;
388 *Node1 = DeleteNode;
389
390 /* Reparent as appropriate */
391 if (RtlLeftChildAvl(DeleteNode)) RtlSetParent(RtlLeftChildAvl(DeleteNode), DeleteNode);
392 if (RtlRightChildAvl(DeleteNode)) RtlSetParent(RtlRightChildAvl(DeleteNode), DeleteNode);
393 }
394
395 /* EOF */