Created
October 10, 2015 08:13
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Closure implementation with c++11 variadic template.
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| // Test in gcc 4.8.1. | |
| #include <tuple> | |
| #include <iostream> | |
| template<typename T> struct ParamTrait { typedef T& ForwardType; typedef T StoreType; }; | |
| template<> struct ParamTrait<int> { typedef int ForwardType; typedef int StoreType; }; | |
| class Closure | |
| { | |
| public: | |
| virtual ~Closure() {} | |
| virtual void Run() = 0; | |
| }; | |
| template<typename ReturnType, typename... Args> | |
| class FunctionClosure : public Closure | |
| { | |
| typedef ReturnType (*Function)(Args...); | |
| typedef ::std::tuple<typename ParamTrait<Args>::StoreType...> ArgTuple; | |
| public: | |
| explicit FunctionClosure(Function func, typename ParamTrait<Args>::ForwardType... args) | |
| : m_func(func), m_args(args...) // a copy overhead here | |
| {} | |
| virtual void Run() | |
| { | |
| typedef typename ::std::_Build_index_tuple<sizeof...(Args)>::__type _Indexes; | |
| this->call(_Indexes()); | |
| delete this; | |
| } | |
| private: | |
| template<std::size_t... _Indexes> | |
| void call(::std::_Index_tuple<_Indexes...>) | |
| { | |
| (void) (*m_func)(::std::get<_Indexes>(m_args)...); | |
| } | |
| Function m_func; | |
| ArgTuple m_args; | |
| }; | |
| template<typename ReturnType, typename... Args> | |
| Closure* NewCallback(ReturnType (*func)(Args...), typename ParamTrait<Args>::ForwardType... args) | |
| { | |
| return new FunctionClosure<ReturnType, Args...>(func, args...); | |
| } | |
| static void test_func() { ::std::cout << "test_func" << ::std::endl; } | |
| static int test_func1(int i) { ::std::cout << "test_func1" << ::std::endl; return i; } | |
| struct TestObj {}; | |
| static int test_func2(int i, TestObj) { ::std::cout << "test_func2" << ::std::endl; return i; } | |
| int main() | |
| { | |
| Closure* done = NewCallback(&test_func); | |
| done->Run(); | |
| done = NewCallback(&test_func1, 1); | |
| done->Run(); | |
| TestObj obj; | |
| done = NewCallback(&test_func2, 1, obj); | |
| done->Run(); | |
| return 0; | |
| } |
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