一种通用 RAII 对象模板类

该类主要方便写单行的利用RAII思想进行析构的对象，

两种功能（1）通过Func（xxx）形式释放（2）通过obj->Func(xxx)形式释放

使用了比较猥琐的__if_exist语法

 

 

#include 
#include 

#pragma warning(disable:4996)

namespace XYZ
{

	class __CsRaiiRss_global_dummy_class
	{
	public:
		//定义一个变量用来判断一个模板能否是__CsRaiiRss_global_dummy_class参数
		BOOL __CsRaiiRss_global_dummy_class__test_exist_member_201907011318__abc__this_variable_is_too_speciall_so_ithink_other_class_doesntHasIt__mmm;
	};
	template
	class CSimpleRAIIResource
	{
	public:
		T* m_p;

		CSimpleRAIIResource(T* from, FREE_FUN_TYPE fnFree, IN_CLASS_TYPE* thiz = 0)
		{
			if (!fnFree)
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr");
			}

			m_p = from;
			m_fnFree = fnFree;
			m_thiz = thiz;
		}
		~CSimpleRAIIResource() {
			self_destroy();
		}
		operator T*() const {
			return m_p;
		}
		bool operator !() {
			return (m_p == defVal);
		}
		CSimpleRAIIResource& operator = (T* p)
		{
			if (!(m_p == p))
			{
				self_destroy();
				m_p = p;
			}

			return *this;
		}
	private:
		void self_destroy()
		{
			if (m_p)
			{
				if (m_fnFree)
				{
					if (m_thiz)
					{
						__if_not_exists(IN_CLASS_TYPE::__CsRaiiRss_global_dummy_class__test_exist_member_201907011318__abc__this_variable_is_too_speciall_so_ithink_other_class_doesntHasIt__mmm)
						{
							((*m_thiz).*m_fnFree)(m_p);
						}
					}
					else
					{
						__if_exists(IN_CLASS_TYPE::__CsRaiiRss_global_dummy_class__test_exist_member_201907011318__abc__this_variable_is_too_speciall_so_ithink_other_class_doesntHasIt__mmm)
						{
							m_fnFree(m_p);
						}
					}
				}
				else
				{
					assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr, m_p will leak");
				}

				m_p = NULL;
			}
		}
		FREE_FUN_TYPE m_fnFree;
		IN_CLASS_TYPE* m_thiz;
	};


};


class MyClass
{
public:

	void Test()
	{

	}
	HANDLE GetFile()
	{
		return CreateFileW(L"C:\\aa.txt", GENERIC_WRITE | GENERIC_READ, 0, 0, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
	}
	void ReleaseFile(HANDLE h)
	{
		CloseHandle(h);
	}

};


int main()
{
	std::cout << "Hello World!\n";
	MyClass myClass;

	{
		XYZ::CSimpleRAIIResource spFile
			(
				myClass.GetFile(),
				&MyClass::ReleaseFile,
				&myClass
			);
		if (spFile)
		{
			DWORD dwWrite = 0;
			WriteFile(spFile, L"HelloWorld", 20, &dwWrite, 0);
		}
	}
	{
		XYZ::CSimpleRAIIResource spFile(_wfopen(L"C:\\bb.txt", L"wb+"), fclose);
		if (spFile)
		{
			fwrite(L"HelloWorlK", 2, 10, spFile);
		}

		spFile = _wfopen(L"C:\\cc.txt", L"wb+");
		if (spFile)
		{
			fwrite(L"HelloWorlN", 2, 10, spFile);
		}

	}



}

若不用if——exist，则目前C++不支持同名类模板的参数重载，那么只能实现两个不同名字的类模板

namespace EFG
{
	template 
	class __CSimpleRAIIResource__base_xxx
	{
	public:
		T* m_p;
		__CSimpleRAIIResource__base_xxx(T* from)
		{
			m_p = from;
		}
		~__CSimpleRAIIResource__base_xxx()
		{
			self_destroy();
		}
		operator T*() const {
			return m_p;
		}
		bool operator !() {
			return (m_p == defVal);
		}
		TBASE& operator = (T* p)
		{
			if (!(m_p == p))
			{
				self_destroy();
				m_p = p;
			}

			return *this;
		}

	private:
		void self_destroy()
		{
			if (m_p)
			{
				((TBASE*)this)->Do_Free();
				m_p = NULL;
			}
		}
	};

	template
	class CSimpleRAIIResource : public __CSimpleRAIIResource__base_xxx >
	{
	public:
		CSimpleRAIIResource(T* from, FREE_FUN_TYPE fnFree, IN_CLASS_TYPE* thiz) :m_p(from)
		{
			if (!fnFree)
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr");
			}

			m_fnFree = fnFree;
			m_thiz = thiz;
		}

		CSimpleRAIIResource(T* from, FREE_FUN_TYPE fnFree) :m_p(from)
		{
			if (!fnFree)
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr");
			}

			m_fnFree = fnFree;
			m_thiz = 0;
		}

		void Do_Free()
		{
			if (m_fnFree)
			{
				//最难的就是这里，统一个指针的不同语法式
				if (m_thiz)
				{
					((*m_thiz).*m_fnFree)(m_p);
				}
				else
				{
					assert(0 && "code error m_thiz=null !");
				}
			}
			else
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr, m_p will leak");
			}
		}

	private:
		FREE_FUN_TYPE m_fnFree;
		IN_CLASS_TYPE* m_thiz;
	};

	template
	class CSimpleRAIIResourceFromGlobal : public __CSimpleRAIIResource__base_xxx >
	{
	public:
		CSimpleRAIIResourceFromGlobal(T* from, FREE_FUN_TYPE fnFree) :m_p(from)
		{
			if (!fnFree)
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr");
			}

			m_fnFree = fnFree;
		}

		void Do_Free()
		{
			if (m_fnFree)
			{
				m_fnFree(m_p);
			}
			else
			{
				assert(0 && "Invalid Useage of CSimpleRAIIResource, fnFree cannot = nullptr, m_p will leak");
			}
		}

	private:
		FREE_FUN_TYPE m_fnFree;
	};



};