static void rebalance (c_avl_tree_t *t, c_avl_node_t *n)
{
int b_top;
int b_bottom;
while (n != NULL)
{
b_top = BALANCE (n);
assert ((b_top >= -2) && (b_top <= 2));
if (b_top == -2)
{
assert (n->right != NULL);
b_bottom = BALANCE (n->right);
assert ((b_bottom >= -1) && (b_bottom <= 1));
if (b_bottom == 1)
n = rotate_right_left (t, n);
else
n = rotate_left (t, n);
}
else if (b_top == 2)
{
assert (n->left != NULL);
b_bottom = BALANCE (n->left);
assert ((b_bottom >= -1) && (b_bottom <= 1));
if (b_bottom == -1)
n = rotate_left_right (t, n);
else
n = rotate_right (t, n);
}
else
{
int height = calc_height (n);
if (height == n->height)
break;
n->height = height;
}
assert (n->height == calc_height (n));
n = n->parent;
} /* while (n != NULL) */
} /* void rebalance */
static gpr_avl_node *rebalance(const gpr_avl_vtable *vtable, void *key,
void *value, gpr_avl_node *left,
gpr_avl_node *right) {
switch (node_height(left) - node_height(right)) {
case 2:
if (node_height(left->left) - node_height(left->right) == -1) {
return assert_invariants(
rotate_left_right(vtable, key, value, left, right));
} else {
return assert_invariants(rotate_right(vtable, key, value, left, right));
}
case -2:
if (node_height(right->left) - node_height(right->right) == 1) {
return assert_invariants(
rotate_right_left(vtable, key, value, left, right));
} else {
return assert_invariants(rotate_left(vtable, key, value, left, right));
}
default:
return assert_invariants(new_node(key, value, left, right));
}
}
ZIX_PRIVATE ZixTreeNode*
zix_tree_rebalance(ZixTree* t, ZixTreeNode* node, int* height_change)
{
#ifdef ZIX_TREE_HYPER_VERIFY
const size_t old_height = height(node);
#endif
DEBUG_PRINTF("REBALANCE %ld (%d)\n", (intptr_t)node->data, node->balance);
*height_change = 0;
const bool is_root = !node->parent;
assert((is_root && t->root == node) || (!is_root && t->root != node));
ZixTreeNode* replacement = node;
if (node->balance == -2) {
assert(node->left);
if (node->left->balance == 1) {
replacement = rotate_left_right(node, height_change);
} else {
replacement = rotate_right(node, height_change);
}
} else if (node->balance == 2) {
assert(node->right);
if (node->right->balance == -1) {
replacement = rotate_right_left(node, height_change);
} else {
replacement = rotate_left(node, height_change);
}
}
if (is_root) {
assert(!replacement->parent);
t->root = replacement;
}
DUMP(t);
#ifdef ZIX_TREE_HYPER_VERIFY
assert(old_height + *height_change == height(replacement));
#endif
return replacement;
}
