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comments + fixes

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donnaskiez 2024-06-16 20:31:06 +10:00
parent 0ba98fa9d5
commit 424f1e9a63
1 changed files with 56 additions and 11 deletions
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67
driver/containers/tree.c
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@ -1,12 +1,53 @@
#include "tree.h" #include "tree.h"
/* /*
* Basic red-black tree implementation. Currently the enumeration routines are * Basic red-black tree implementation. Currently, the enumeration routines are
* recursive which maybe isnt the best idea given the environment this is meant * recursive, which may not be the best idea given the environment this is meant
* for (kernel mode). We can always fix that up later though :). * for (kernel mode). We can always fix that up later though :).
* *
* Example of a Red-Black Tree:
*
* grandparent(B)
* |
* +--------+--------+
* | |
* parent(R) uncle(R)
* |
* +-----+-----+
* | |
* Node(R) sibling(B)
* |
* +-----+
* | |
* child ...
*
* Legend:
* - 'B' represents a Black node
* - 'R' represents a Red node
*
* Labels for components during insert and delete fix-up:
*
* - Node: The newly inserted node that may cause a violation.
* - Parent: The parent of the newly inserted node.
* - Grandparent: The grandparent of the newly inserted node.
* - Uncle: The sibling of the parent node.
* - Sibling: The sibling of the node to be deleted or fixed.
* - Child: The child of the node to be deleted or fixed.
*
* In this example:
* - Each 'B' is a black node.
* - Each 'R' is a red node.
* - The labels illustrate a typical structure that might be encountered during
* the insertion or deletion process, where the new node, its parent,
* grandparent, uncle, sibling, and child are involved in the rebalancing
* operations.
*
* Resources used:
* https://www.kernel.org/doc/Documentation/rbtree.txt * https://www.kernel.org/doc/Documentation/rbtree.txt
* https://github.com/torvalds/linux/blob/master/lib/rbtree.c * https://github.com/torvalds/linux/blob/master/lib/rbtree.c
* https://www.osronline.com/article.cfm%5Earticle=516.htm
* https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-_rtl_avl_table (for structure ideas)
*
*/ */
/** /**
@ -357,9 +398,9 @@ RtlpRbTreeFixupDelete(_In_ PRB_TREE Tree, _In_ PRB_TREE_NODE Node)
else { else {
if (sibling && if (sibling &&
(!sibling->right || sibling->right->colour == black)) { (!sibling->right || sibling->right->colour == black)) {
if (sibling->left) { if (sibling->left)
sibling->left->colour = black; sibling->left->colour = black;
}
sibling->colour = red; sibling->colour = red;
RtlpRbTreeRotateRight(Tree, sibling); RtlpRbTreeRotateRight(Tree, sibling);
sibling = Node->parent->right; sibling = Node->parent->right;
@ -368,11 +409,13 @@ RtlpRbTreeFixupDelete(_In_ PRB_TREE Tree, _In_ PRB_TREE_NODE Node)
if (sibling) { if (sibling) {
sibling->colour = Node->parent->colour; sibling->colour = Node->parent->colour;
Node->parent->colour = black; Node->parent->colour = black;
if (sibling->right) {
if (sibling->right)
sibling->right->colour = black; sibling->right->colour = black;
}
RtlpRbTreeRotateLeft(Tree, Node->parent); RtlpRbTreeRotateLeft(Tree, Node->parent);
} }
Node = Tree->root; Node = Tree->root;
} }
} }
@ -395,9 +438,9 @@ RtlpRbTreeFixupDelete(_In_ PRB_TREE Tree, _In_ PRB_TREE_NODE Node)
else { else {
if (sibling && if (sibling &&
(!sibling->left || sibling->left->colour == black)) { (!sibling->left || sibling->left->colour == black)) {
if (sibling->right) { if (sibling->right)
sibling->right->colour = black; sibling->right->colour = black;
}
sibling->colour = red; sibling->colour = red;
RtlpRbTreeRotateLeft(Tree, sibling); RtlpRbTreeRotateLeft(Tree, sibling);
sibling = Node->parent->left; sibling = Node->parent->left;
@ -406,11 +449,13 @@ RtlpRbTreeFixupDelete(_In_ PRB_TREE Tree, _In_ PRB_TREE_NODE Node)
if (sibling) { if (sibling) {
sibling->colour = Node->parent->colour; sibling->colour = Node->parent->colour;
Node->parent->colour = black; Node->parent->colour = black;
if (sibling->left) {
if (sibling->left)
sibling->left->colour = black; sibling->left->colour = black;
}
RtlpRbTreeRotateRight(Tree, Node->parent); RtlpRbTreeRotateRight(Tree, Node->parent);
} }
Node = Tree->root; Node = Tree->root;
} }
} }