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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. #include <map>
  5.  
  6. template<typename T>
  7. class Base
  8. {
  9. public:    
  10.     typedef void (T::*PFunc)(void);
  11.     typedef void (*PHandler)(void*);
  12.  
  13.     using method_map_t = map< string, PHandler >;
  14.     static method_map_t& methods( ) {
  15.         static method_map_t* map_of_methods{};
  16.         if( ! map_of_methods ) map_of_methods = new method_map_t;
  17.         return *map_of_methods;
  18.     }
  19.  
  20.     static void register_method( string name, PHandler handler ) {
  21.         methods()[name] = handler;
  22.     }
  23.  
  24.     // generic trampoline
  25.     template<PFunc sig>
  26.     static void Handler( void* pInstance ) {
  27.         T* f = reinterpret_cast<T*>(pInstance);
  28.         (f ->* sig)();
  29.     }
  30. };
  31.  
  32. class Final : Base<Final>
  33. {
  34. public:
  35.     void Foo(){cout<<"got foo";}
  36.     void Bar(){cout<<"got bar";}
  37.  
  38.     static void init(){
  39.         // register_method populates a table of "extern C" function pointers.
  40.         register_method( "foo", static_cast<PHandler>( &Handler<&Final::Foo> ) );
  41.         register_method( "bar", static_cast<PHandler>( &Handler<&Final::Bar> ) );
  42.     }
  43. };
  44.  
  45. void InvokeFromC(void* inst, string name) {
  46. 	Base<Final>::PHandler h = Base<Final>::methods()[name];
  47. 	(*h)(inst);
  48. }
  49.  
  50. int main() {
  51. 	Final* f = new Final{};
  52. 	f->init();
  53. 	// simulate invoking from C 
  54. 	InvokeFromC( f, "foo" );
  55.  
  56. 	// your code goes here
  57. 	return 0;
  58. }
Success #stdin #stdout 0s 3432KB
comments (?)
stdin
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Standard input is empty
stdout
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got foo
https://ideone.com/vOtbcD
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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