/*
* check balances and rotate as required.
*/
static void rebalance(cp_avlnode **node)
{
if ((*node)->balance == -2)
{
if ((*node)->left->balance == 1)
left_right_rotate(node);
else
right_rotate(node);
}
else if ((*node)->balance == 2)
{
if ((*node)->right->balance == -1)
right_left_rotate(node);
else
left_rotate(node);
}
}
/*******************************************************************************
* Fixes the tree in order to balance it. Basically, we start from 'p_entry' *
* go up the chain towards parents. If a parent is disbalanced, a set of *
* rotations are applied. If 'insertion_mode' is on, it means that previous *
* modification was insertion of an entry. In such a case we need to perform *
* only one rotation. If 'insertion_mode' is off, the last operation was *
* removal and we need to go up until the root node. *
*******************************************************************************/
static void fix_after_modification(map* p_map,
map_entry* entry,
bool insertion_mode)
{
map_entry* parent = entry->parent;
map_entry* grand_parent;
map_entry* sub_tree;
while (parent)
{
if (height(parent->left) == height(parent->right) + 2)
{
grand_parent = parent->parent;
if (height(parent->left->left) >= height(parent->left->right))
{
sub_tree = right_rotate(parent);
}
else
{
sub_tree = left_right_rotate(parent);
}
if (!grand_parent)
{
p_map->root = sub_tree;
}
else if (grand_parent->left == parent)
{
grand_parent->left = sub_tree;
}
else
{
grand_parent->right = sub_tree;
}
if (grand_parent)
{
grand_parent->height =
max(height(grand_parent->left),
height(grand_parent->right)) + 1;
}
/* Fixing after insertion requires only one rotation. */
if (insertion_mode)
{
return;
}
}
else if (height(parent->right) == height(parent->left) + 2)
{
grand_parent = parent->parent;
if (height(parent->right->right) >= height(parent->right->left))
{
sub_tree = left_rotate(parent);
}
else
{
sub_tree = right_left_rotate(parent);
}
if (!grand_parent)
{
p_map->root = sub_tree;
}
else if (grand_parent->left == parent)
{
grand_parent->left = sub_tree;
}
else
{
grand_parent->right = sub_tree;
}
if (grand_parent)
{
grand_parent->height =
max(height(grand_parent->left),
height(grand_parent->right)) + 1;
}
/* Fixing after insertion requires only one rotation. */
if (insertion_mode)
{
return;
}
}
parent->height = max(height(parent->left),
height(parent->right)) + 1;
parent = parent->parent;
}
}
