insert_at
len = insert_at(bb, 0, &bad);
len = insert_at(bb, 0, &bad);
len = insert_at(bb, prev + 1, &bad);
r = insert_at(sizeof(uint64_t), n, index,
r = insert_at(info->value_type.size, n, index,
r = insert_at(sizeof(__le64), pn, parent_index + 1,
r = insert_at(sizeof(__le64), pn, middle_index,