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  1. #include <iostream>
  2. #include <cstdlib>
  3. #include <functional>
  4.  
  5. // C library with some callbacks
  6.  
  7. typedef void (*CallbackTypeOne)(void* userdata, double arg1);
  8. typedef void (*CallbackTypeTwo)(void* userdata, int arg1);
  9. typedef void (*CallbackTypeThree)(void* userdata, int arg1, float arg2);
  10.  
  11. typedef void(*GenericCallback)();
  12.  
  13. void registerAndCallCallback(int typeID, GenericCallback callback, void* userdata)
  14. {
  15.     switch (typeID) {
  16.     case 0: ((CallbackTypeOne)callback)(userdata, 3.14); break;
  17.     case 1: ((CallbackTypeTwo)callback)(userdata, 42); break;
  18.     case 2: ((CallbackTypeThree)callback)(userdata, 42, 3.14f); break;
  19.     };
  20. }
  21.  
  22. // C++ app using the above library
  23.  
  24. template <const size_t TypeID, typename T, typename RetType, typename... Args>
  25. struct FunctionFactory
  26. {
  27. public:
  28.     static void bind(RetType(T::*f)(Args...)) {
  29.         instance().fn_ = [f](T* t, Args&&... args) {
  30.             return (t->*f)(std::forward<Args>(args)...);
  31.         };
  32.     }
  33.  
  34.     static RetType invoke(void* userdata, Args... args) {
  35.         T * t = reinterpret_cast<T*>(userdata);
  36.         return instance().fn_(t, args...);
  37.     }
  38.  
  39.     typedef decltype(&FunctionFactory::invoke) pointer_type;
  40.     static pointer_type ptr() {
  41.         return &invoke;
  42.     }
  43.  
  44. private:
  45.     static FunctionFactory & instance() {
  46.         static FunctionFactory inst_;
  47.         return inst_;
  48.     }
  49.  
  50.     FunctionFactory() = default;
  51.  
  52.     std::function<RetType(T*, Args...)> fn_;
  53. };
  54.  
  55. template <const size_t TypeID, typename T, typename RetType, typename... Args>
  56. typename FunctionFactory<TypeID, T, RetType, Args...>::pointer_type
  57. getFunctionPtr(RetType(T::*f)(Args...))
  58. {
  59.     FunctionFactory<TypeID, T, RetType, Args...>::bind(f);
  60.     return FunctionFactory<TypeID, T, RetType, Args...>::ptr();
  61. }
  62.  
  63. class MyClass
  64. {
  65. public:
  66.     MyClass() {
  67.         registerAndCallCallback(0, reinterpret_cast<GenericCallback>(getFunctionPtr<0>(&MyClass::callbackOne)), this);
  68.         registerAndCallCallback(1, reinterpret_cast<GenericCallback>(getFunctionPtr<1>(&MyClass::callbackTwo)), this);
  69.         registerAndCallCallback(2, reinterpret_cast<GenericCallback>(getFunctionPtr<2>(&MyClass::callbackThree)), this);
  70.     }
  71.  
  72.     void callbackOne(double arg1) { std::cout << "callback 1 called: " << arg1 << std::endl; }
  73.     void callbackTwo(int arg1) { std::cout << "callback 2 called: " << arg1 << std::endl; }
  74.     void callbackThree(int arg1, float arg2) { std:: cout << "callback 3 called: " << arg1 << ", " << arg2 << std::endl; }
  75. };
  76.  
  77. int main()
  78. {
  79.     MyClass myclass;
  80.     return 0;
  81. }
  82.  
Success #stdin #stdout 0s 4396KB
comments (?)
stdin
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Standard input is empty
stdout
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callback 1 called: 3.14
callback 2 called: 42
callback 3 called: 42, 3.14
https://ideone.com/Kk7x14
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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