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  1. #include <iostream>
  2.  
  3. struct shared_buffer {};
  4.  
  5. shared_buffer do_pack(int arg);
  6. shared_buffer do_pack(double arg);
  7.  
  8. struct foo {
  9. 	friend shared_buffer do_pack(foo const& arg);
  10. };
  11.  
  12.  
  13. struct somestruct {
  14.     template<typename... Args>
  15.     shared_buffer pack(const Args&... args) {
  16.     	// convert arg pack to array of pack functions and arguments
  17.     	arg_pack_fn fns[] = { &wrap_do_pack<Args>... };
  18.     	void const* data[] = { std::addressof(args)... };
  19.  
  20.         return pack2(fns, data, sizeof...(Args));
  21.     }
  22.  
  23. private:
  24.     using arg_pack_fn = shared_buffer (*)(void const* arg);
  25.  
  26. 	// actual do_pack for each arg type
  27.     template<typename T>
  28.     static shared_buffer wrap_do_pack(void const* arg) {
  29.         return do_pack(*static_cast<T const*>(arg));
  30.     }
  31.  
  32.     shared_buffer pack2(arg_pack_fn pack_fns[], void const* args[], size_t count);
  33. };
  34.  
  35. // implementation in .cpp
  36.  
  37. shared_buffer do_pack(int arg) {
  38. 	std::cout << arg << ' ';
  39. }
  40.  
  41. shared_buffer do_pack(double arg) {
  42. 	std::cout << arg << ' ';
  43. }
  44.  
  45. shared_buffer do_pack(foo const& arg) {
  46. 	std::cout << "foo ";
  47. }
  48.  
  49. shared_buffer somestruct::pack2(arg_pack_fn pack_fns[], void const* args[], size_t count) {
  50. 	for (size_t i = 0; i != count; ++i)
  51. 	{
  52. 		pack_fns[i](args[i]);
  53. 	}
  54. }
  55.  
  56. int main() {
  57. 	somestruct	ss;
  58. 	ss.pack(foo{}, 1, 3.14);
  59. }
Success #stdin #stdout 0s 3468KB
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Standard input is empty
stdout
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foo 1 3.14
https://ideone.com/Ol1KUx
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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