STD:C++ 03替代:Aligndl存储

可以实现 alignof 在C++ 03中,对于大多数类型,例如有一个很长的解释。 this page 。

有了它,您可以使用一些模板专门化来使用具有这种对齐方式的存储类型:

#include<iostream>

struct alignment {};

template<>
struct alignment<1> {
  typedef char type;
  static const unsigned div_v=sizeof(type);
  static const unsigned add_v=div_v-1;
};
template<>
struct alignment<2> {
  typedef short type;
  static const unsigned div_v=sizeof(type);
  static const unsigned add_v=div_v-1;
};
template<>
struct alignment<4> {
  typedef int type;
  static const unsigned div_v=sizeof(type);
  static const unsigned add_v=div_v-1;
};
template<>
struct alignment<8> {
  typedef double type;
  static const unsigned div_v=sizeof(type);
  static const unsigned add_v=div_v-1;
};

template<typename T>
struct align_store {
  typedef alignment<__alignof(T)> ah;

  typename ah::type data[(ah::add_v + sizeof(T))/ah::div_v];
};

int main() {
  std::cout << __alignof(align_store<int>) << std::endl;
  std::cout << __alignof(align_store<double>) << std::endl;
}