aligned_storage

aligned_storage

通过union 将存储和访问分开，并将存储数据的内存作为整体进行对齐

#include <vector>
#include <iostream>
#include <type_traits>

template <typename T>
using Vec = std::vector<T>;

template <typename T, size_t N>
struct GetAlignedData {
  using type = typename std::aligned_storage<sizeof(T) * N, sizeof(T) * N>::type;
};

template <typename T, size_t N>
using AlignedType = typename GetAlignedData<T, N>::type;

template <typename T, size_t N>
union PackData {
  AlignedType<T, N> storage;
  T elem[N];
};

int main() {
  PackData<int, 4> data;
  int x[4] = {1, 2, 3, 4};
  data.storage = *(reinterpret_cast <AlignedType<int, 4>* >(x));
  for(auto z : data.elem) {
    std::cout << "z: " << z << std::endl;
  }
  return 0;
}