/******************************************************************************
**函数名称: _btree_merge
**功 能: 合并结点
**输入参数:
** btree: B树
** node:
** brother:
**输出参数: NONE
**返 回: 0:成功 !0:失败
**实现描述:
**注意事项:
**作 者: # Qifeng.zou # 2014.03.12 #
******************************************************************************/
static int _btree_merge(btree_t *btree, btree_node_t *left, btree_node_t *right, int mid)
{
int m;
btree_node_t *parent = left->parent;
left->key[left->num] = parent->key[mid];
left->data[left->num] = parent->data[mid];
++left->num;
memcpy(left->key + left->num, right->key, right->num*sizeof(int));
memcpy(left->data + left->num, right->data, right->num*sizeof(void *));
memcpy(left->child + left->num, right->child, (right->num+1)*sizeof(btree_node_t *));
for (m=0; m<=right->num; m++) {
if (NULL != right->child[m]) {
right->child[m]->parent = left;
}
}
left->num += right->num;
for (m=mid; m<parent->num-1; m++) {
parent->key[m] = parent->key[m+1];
parent->data[m] = parent->data[m+1];
parent->child[m+1] = parent->child[m+2];
}
parent->key[m] = 0;
parent->data[m] = NULL;
parent->child[m+1] = NULL;
parent->num--;
btree->dealloc(btree->pool, right->child);
btree->dealloc(btree->pool, right->key);
btree->dealloc(btree->pool, right->data);
btree->dealloc(btree->pool, right);
/* Check */
if (parent->num < btree->min) {
return btree_merge(btree, parent);
}
return 0;
}
/******************************************************************************
**函数名称: _btree_remove
**功 能: 在指定结点删除指定关键字
**输入参数:
** btree: B树
** node: 指定结点
** idx: 将被删除的关键字在结点node中位置(0 ~ node->num - 1)
**输出参数: NONE
**返 回: 0:成功 !0:失败
**实现描述:
** 使用node->child[idx]中的最大值替代被删除的关键字,
** 并依次向下处理直至最底层结点,
** -- 其实最终其处理过程相当于是删除最底层结点的关键字
**注意事项:
**作 者: # Qifeng.zou # 2014.03.12 #
******************************************************************************/
static int _btree_remove(btree_t *btree, btree_node_t *node, int idx)
{
btree_node_t *orig = node, *child = node->child[idx];
/* 使用node->child[idx]中的最大值替代被删除的关键字 */
while (NULL != child) {
node = child;
child = node->child[child->num];
}
orig->key[idx] = node->key[node->num - 1];
orig->data[idx] = node->data[node->num - 1];
/* 最终其处理过程相当于是删除最底层结点的关键字 */
--node->num;
node->key[node->num] = 0;
node->data[node->num] = NULL;
if (node->num < btree->min) {
return btree_merge(btree, node);
}
return 0;
}
/**
* btree_delete_internal
* @access private
* @param btree struct
* @param btree node
* @param key that was requested for deletion
* @param current key
* @param data index
* @return int 1 on success, 0 on failure
*
* Removes a node at key from the btree
* Locks the entire tree until complete
*/
static int btree_delete_internal(btree_tree *t, btree_node *node, uint64_t key_to_delete, uint64_t key, uint32_t *data_idx_to_free)
{
uint32_t idx;
uint32_t data_idx;
/* if x is a leaf then
* if k is in x then
* delete k from x and return true
* else return false //k is not in subtree
*/
if (node->leaf) {
if (btree_check_key_in_node(node, key, &idx, &data_idx)) {
btree_delete_key_idx_from_node(node, idx);
btree_delete_branch_idx_from_node(node, idx);
if (key == key_to_delete) {
*data_idx_to_free = data_idx;
}
return 1;
} else {
return 0;
}
} else {
/* if k is in x then */
if (btree_check_key_in_node(node, key, &idx, &data_idx)) {
btree_node *y, *node_with_prev_key;
/* Record the data_idx for this key */
if (key == key_to_delete) {
*data_idx_to_free = data_idx;
}
/* y = the child of x that precedes k
* if y has at least t keys then
* k' = the predecessor of k (use B-Tree-FindLargest)
* Copy k' over k //i.e., replace k with k'
* B-Tree-Delete(y, k') //Note: recursive call
*/
y = btree_get_node(t, node->branch[idx]);
if (y->nr_of_keys >= BTREE_T(t)) {
node_with_prev_key = btree_find_greatest(t, y);
node->keys[idx] = node_with_prev_key->keys[y->nr_of_keys-1];
return btree_delete_internal(t, y, key_to_delete, node_with_prev_key->keys[y->nr_of_keys-1].key, data_idx_to_free);
} else {
btree_node *z, *node_with_next_key;
/* else //y has t-1 keys
* z = the child of x that follows k
* if z has at least t keys then
* k' = the successor of k
* Copy k' over k //i.e., replace k with k'
* B-Tree-Delete(z, k') //Note: recursive call
*/
z = btree_get_node(t, node->branch[idx + 1]);
if (z->nr_of_keys >= BTREE_T(t)) {
node_with_next_key = btree_find_smallest(t, z);
node->keys[idx] = node_with_next_key->keys[0];
btree_delete_internal(t, z, key_to_delete, node_with_next_key->keys[0].key, data_idx_to_free);
} else {
/* else //both y and z have t-1 keys
* merge k and all of z into y //y now contains 2t-1 keys.
* //k and the pointer to z will be deleted from x.
* B-Tree-Delete(y, k) //Note: recursive call
*/
btree_merge(t, y, node, idx, z);
btree_delete_key_idx_from_node(node, idx);
btree_delete_branch_idx_from_node(node, idx + 1);
btree_delete_internal(t, y, key_to_delete, key, data_idx_to_free);
if (t->root->nr_of_keys == 0 && !t->root->leaf) {
t->root = btree_get_node(t, t->root->branch[0]);
}
}
}
} else {
btree_node *c;
uint32_t i;
c = btree_find_branch(t, node, key, &i);
if (c->nr_of_keys <= BTREE_T(t) - 1) {
btree_node *z, *node_with_prev_key, *node_with_next_key;
btree_key tmp_key;
/* Is there a left sibling with T or more keys? */
if (i > 0) { /* otherwise there is no left sibling */
z = btree_get_node(t, node->branch[i - 1]);
if (z->nr_of_keys > BTREE_T(t) - 1) {
node_with_prev_key = btree_find_greatest(t, z);
btree_node_insert_key(t, c, 0, node_with_prev_key->keys[z->nr_of_keys-1]);
btree_delete_internal(t, z, key_to_delete, node_with_prev_key->keys[z->nr_of_keys-1].key, data_idx_to_free);
/* Swap parent and first key in C */
tmp_key = node->keys[i-1];
node->keys[i-1] = c->keys[0];
c->keys[0] = tmp_key;
goto proceed;
}
}
/* Is there a left sibling with T or more keys? */
if (i < node->nr_of_keys) { /* otherwise there is no right sibling */
z = btree_get_node(t, node->branch[i + 1]);
if (z->nr_of_keys > BTREE_T(t) - 1) {
node_with_next_key = btree_find_smallest(t, z);
btree_node_insert_key(t, c, c->nr_of_keys, node_with_next_key->keys[0]);
btree_delete_internal(t, z, key_to_delete, node_with_next_key->keys[0].key, data_idx_to_free);
/* Swap parent and last key in C */
tmp_key = node->keys[i];
node->keys[i] = c->keys[c->nr_of_keys - 1];
c->keys[c->nr_of_keys - 1] = tmp_key;
goto proceed;
}
}
/* No siblings, so we need to merge. */
/* Is there a left sibling? */
if (i > 0) { /* otherwise there is no left sibling */
z = btree_get_node(t, node->branch[i - 1]);
btree_merge(t, z, node, i - 1, c);
btree_delete_branch_idx_from_node(node, i);
btree_delete_key_idx_from_node(node, i - 1);
if (t->root->nr_of_keys == 0 && !t->root->leaf) {
t->root = btree_get_node(t, t->root->branch[0]);
}
return btree_delete_internal(t, z, key_to_delete, key, data_idx_to_free);
}
/* Is there a right sibling? */
if (i < node->nr_of_keys) { /* otherwise there is no right sibling */
z = btree_get_node(t, node->branch[i + 1]);
btree_merge(t, c, node, i, z);
btree_delete_branch_idx_from_node(node, i + 1);
btree_delete_key_idx_from_node(node, i);
if (t->root->nr_of_keys == 0 && !t->root->leaf) {
t->root = btree_get_node(t, t->root->branch[0]);
}
return btree_delete_internal(t, c, key_to_delete, key, data_idx_to_free);
}
}
proceed:
return btree_delete_internal(t, c, key_to_delete, key, data_idx_to_free);
}
}
return 0;
}
