void splay_insert_top(splay_tree_t *tree, splay_node_t *node) {
node->prev = node->next = node->left = node->right = node->parent = NULL;
tree->head = tree->tail = tree->root = node;
void splay_insert_top(splay_tree_t *tree, splay_node_t *node) {
node->prev = node->next = node->left = node->right = node->parent = NULL;
tree->head = tree->tail = tree->root = node;