调用示例
size_t capacity = 100U;
size_t total_size = capacity * sizeof(int64_t) + sizeof(ContinuousVector);
auto holder = std::unique_ptr<uint8_t[]>(new (std::nothrow) uint8_t[total_size]);
reinterpret_cast<ContinuousVector *>(holder.get())->Init(capacity); // 100U