fork download
copy 
  1. #include <iostream>
  2. #include <typeinfo>
  3. #include <typeindex>
  4. #include <unordered_map>
  5.  
  6.  
  7. struct Base {
  8.     virtual ~Base() = default;  
  9. };
  10.  
  11. struct E1 : Base {int i;};
  12. struct E2 : Base {};
  13.  
  14. struct Data {
  15.     std::size_t id;
  16.     std::size_t size;
  17. };
  18.  
  19. struct CCollection
  20. {
  21.     template <typename T>
  22.     std::size_t toId() {
  23.         auto it = info.find(typeid(T));
  24.         if (it == info.end()) {
  25.             it = info.insert({typeid(T), {count++, sizeof(T)}}).first;
  26.         }
  27.         return it->second.id;   
  28.     }
  29.  
  30.     std::size_t sizeOf(const Base& base) const {
  31.         const auto& data = info.at(typeid(base));
  32.         return data.size;   
  33.     }
  34.  
  35.     std::size_t count = 0;
  36.     std::unordered_map<std::type_index, Data> info;
  37. };
  38.  
  39. int main()
  40. {
  41.     CCollection c;
  42.  
  43.     const auto e1Id = c.toId<E1>();
  44.     const auto e1Size = c.sizeOf(E1{});
  45.  
  46.     std::cout << e1Id << " " << e1Size << std::endl;
  47.  
  48.     const auto e2Id = c.toId<E2>();
  49.     const auto e2Size = c.sizeOf(E2{});
  50.  
  51.     std::cout << e2Id << " " << e2Size << std::endl;
  52.  
  53. }
  54.  
Success #stdin #stdout 0s 3472KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
0 8
1 4
https://ideone.com/28xFOy
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!