发信人: RoachCock (穷鬼), 信区: Programming 标 题: .net中的 delegate的标准C++模拟 发信站: BBS 水木清华站 (Mon Mar 18 21:11:30 2002)
用模板的偏特化和成员模板，重载函数调用运算符成功的实现了delegate,既可以绑定普通函数，也可以绑定对象及其成员函数在cygnuwin下编译通过, 还不支持一个delegate包含多个函数的用法,不过相信很简单，从std::list派生一个类 就可以了 我用的cygun有些毛病， my_delegate d2=my_delegate(t,&Test::f); ^如果写成&t，就会导致编译器内部错误，没办法了 我本来写程序是加空行的，贴到BBS上就没了，忍受一下吧 Win32下的各种调用约定很讨厌，没有考虑，不过实现起来不费什么脑筋，就是麻烦， 不管了 // Test.cpp : Defines the entry point for the console application. // #include <stddef.h> template<class T>
//函数traits,用来提取函数的返回类型
struct function_traits { }; template<class RT> struct function_traits< RT(*)() > { typedef RT result_type; }; template<class RT,class AT> struct function_traits< RT(*)(AT) > { typedef RT result_type; typedef AT argument_type; }; template<class RT,class AT1,class AT2> struct function_traits< RT(*)(AT1,AT2) > { typedef RT result_type; typedef AT1 first_argument_type; typedef AT2 second_argument_type; };
// 函数traits,用来提取类成员函数的返回类型
template<class RT, class OT> struct function_traits< RT (OT::*)() > { typedef OT object_type; typedef RT result_type; }; template<class RT, class OT, class AT> struct function_traits< RT (OT::*)(AT) > { typedef OT object_type; typedef RT result_type; typedef AT argument_type; typedef AT first_argument_type; }; template<class RT,class OT,class AT1,class AT2> struct function_traits< RT (OT::*)(AT1,AT2) > { typedef OT object_type; typedef RT result_type; typedef AT1 first_argument_type; typedef AT2 second_argument_type; };
// 把一个普通函数类向转化为类型兼容的指定类的成员函数类型 template <typename OT, typename PFT> struct to_member_function_pointer { }; template <typename OT,typename RT> struct to_member_function_pointer< OT, RT(*)() > { typedef RT (OT::*type)(); }; template <typename OT, typename RT, typename AT> struct to_member_function_pointer< OT, RT(*)(AT) > { typedef RT (OT::*type)(AT); }; template <typename OT, typename RT, typename AT1, typename AT2> struct to_member_function_pointer< OT, RT(*)(AT1,AT2) > { typedef RT (OT::*type)(AT1,AT2); }; template <typename OT, typename RT, typename AT1, typename AT2, typename AT3> struct to_member_function_pointer< OT, RT(*)(AT1,AT2,AT3) > { typedef RT (OT::*type)(AT1,AT2,AT3); };
// 转化为const 成员函数
template <typename OT, typename PFT> struct to_const_member_function_pointer { }; template <typename OT, typename RT> struct to_const_member_function_pointer< OT, RT(*)() > { typedef RT (OT::*type)() const; }; template <typename OT, typename RT, typename AT> struct to_const_member_function_pointer< OT, RT(*)(AT) > { typedef RT (OT::*type)(AT) const; }; template <typename OT, typename RT, typename AT1, typename AT2> struct to_const_member_function_pointer< OT, RT(*)(AT1,AT2) > { typedef RT (OT::*type)(AT1,AT2) const; }; template <typename OT, typename RT, typename AT1, typename AT2, typename AT3> struct to_const_member_function_pointer< OT, RT(*)(AT1,AT2,AT3) > { typedef RT (OT::*type)(AT1,AT2,AT3) const; };
// delegate的实现
template <typename PFT> class delegate { class object { }*m_pObject; // 对象指针，是一个代理对象 typedef typename to_member_function_pointer<object, PFT>::type object_member_fuunction_pointer; union { PFT m_pf; object_member_function_pointer m_pmf; }; // 函数指针和成员函数指针的联合体 public: typedef typename function_traits<PFT>::result_type result_type; delegate() { m_pObject=NULL; m_pf=NULL; } delegate(PFT pf) { operator=(pf); } template<typename OT> delegate( OT *pObject, typename to_member_function_pointer<OT, PFT>::type pmf ) { m_pObject=reinterpret_cast<object*>(pObject); m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); } template<typename OT> delegate( OT &pObject, typename to_member_function_pointer<OT, PFT>::type pmf ) { m_pObject=reinterpret_cast<object*>(&pObject); m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); } template<typename OT> delegate( const OT *pObject, typename to_const_member_function_pointer<OT, PFT>::type pmf ) { m_pObject=const_cast<object*>(reinterpret_cast<object*>(pObject)); m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); } template<typename OT> delegate( const OT &pObject, typename to_const_member_function_pointer<OT, PFT>::type pmf ) { m_pObject=const_cast<object*>(reinterpret_cast<object*>(&pObject)); m_pmf=*(reinterpret_cast<object_member_function_pointer*>(&pmf)); } delegate & operator=(PFT pf) { m_pf=pf; m_pObject=0; return *this; } template<int> :gcc的函数模板不许无参数，加了个占位的"int"才能通过 result_type operator()() { if(m_pObject) return (m_pObject->*m_pmf)(); else return m_pf(); } template<typename AT> result_type operator()( AT a1 ) { if(m_pObject) return (m_pObject->*m_pmf)(a1); else return m_pf(a1); } template<typename AT1, typename AT2> result_type operator()( AT1 a1, AT2 a2 ) { if(m_pObject) return (m_pObject->*m_pmf)(a1,a2); else return m_pf(a1,a2); } template<typename AT1, typename AT2, typename AT3> result_type operator()( AT1 a1, AT2 a2, AT3 a3 ) { if(m_pObject) return (m_pObject->*m_pmf)(a1,a2,a3); else return m_pf(a1,a2,a3); } }; int gf(int) { return 0; } class Test { public: int f(int){return 0;} }; typedef delegate < int (*)(int) > my_delegate; int main() { Test t;
my_delegate d1=&gf; // 普通函数 my_delegate d2=my_delegate(t,&Test::f); //对象和类成员函数 d1(0); //调用 d2(2); } -- 要钱没有,要命也没有
