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
