[開源世界]加強版的動態連接庫接口導出框架

參考： 從自動導出動態連接庫接口看C++的缺點
更新內容：
1.封裝了gDllImportList變量，刪除了DllImportAttribute.cpp文件。
2.封裝了User32類的全局變量，刪除了User32.cpp文件。
更新後的框架只須要一個 DllImportAttribute.h文件，導出函數的文件也只須要一個，減小了文件數量。

#pragma once


#include <Windows.h>


#include <list>
using namespace std;


/*
 * DllImportAttribute
 * 定義加載和卸載動態連接庫的接口
 */

class DllImportAttribute
{
public:
	// 加載動態連接庫
	virtual BOOL Init() = 0;

	// 卸載動態連接庫
	virtual BOOL Uninit() = 0;
};


/*
 * DllImportList
 * 封裝gDllImportList(全局)變量,避免使用cpp文件
 */

class DllImportList
{
protected:
	static DllImportList* m_pInstance;

public:
	static DllImportList* CreateInstance()
	{
		if (m_pInstance == NULL)
		{
			m_pInstance = new DllImportList();
		}
		return m_pInstance;
	}

	static void DeleteInstance()
	{
		if (m_pInstance != NULL)
		{
			delete m_pInstance;
			m_pInstance = NULL;
		}
	}

	list<DllImportAttribute*> gDllImportList;
};


DllImportList* DllImportList::m_pInstance = NULL;


// 加載全部庫,用在程序初始化的地方
inline BOOL DllImportInit()
{
	BOOL bSuccess = TRUE;

	auto& list = DllImportList::CreateInstance()->gDllImportList;	

	for (auto iter = list.begin(); iter != list.end(); iter++)
	{
		bSuccess &= (*iter)->Init();
	}

	return bSuccess;
}


// 卸載全部庫,用在程序退出釋放資源的地方
inline BOOL DllImportUninit()
{
	BOOL bSuccess = TRUE;

	auto& list = DllImportList::CreateInstance()->gDllImportList;	

	for (auto iter = list.begin(); iter != list.end(); iter++)
	{
		bSuccess &= (*iter)->Uninit();
	}

	// 別放了刪除DllImportList實例
	DllImportList::DeleteInstance();

	return bSuccess;
}


/*
 * DLLIMPORTCLASSBEGIN
 * 定義CLASS##Dll類的前半部分,主要是庫加載、卸載以及封裝自身實例(避免使用Cpp文件)
 * m_nOffPtr ：指示變量的位置
 */

#define DLLIMPORTCLASSBEGIN(CLASS, DLLPATH)	class CLASS##Dll : public DllImportAttribute	\
{	\
protected:	\
	HMODULE  m_hModule;	\
public:	\
	CLASS##Dll() : m_hModule(NULL) {	\
		DllImportList::CreateInstance()->gDllImportList.push_back(this);	\
	}	\
	virtual BOOL Init() {	\
		m_hModule = LoadLibraryA(DLLPATH);	\
		return (m_hModule != NULL);	\
	}	\
	virtual BOOL Uninit() {	\
		BOOL bFreeSuccess = FreeLibrary(m_hModule);	\
		CLASS##Dll::DeleteInstance();	\
		return bFreeSuccess;	\
	}	\
protected:	\
	static CLASS##Dll* m_pInstance;	\
public:	\
	static CLASS##Dll* CreateInstance()	\
	{	\
		if (m_pInstance == NULL)	\
		{	\
			m_pInstance = new CLASS##Dll();	\
			memset((BYTE*)m_pInstance + offsetof(CLASS##Dll, m_nOffPtr), 0, \
					sizeof(CLASS##Dll) - offsetof(CLASS##Dll, m_nOffPtr));	\
		}	\
		return m_pInstance;	\
	}	\
	static void DeleteInstance()	\
	{	\
		if (m_pInstance != NULL)	\
		{	\
			delete m_pInstance;	\
			m_pInstance = NULL;	\
		}	\
	}	\
protected:	\
	int m_nOffPtr;	\


/*
 * FUNCTIONENTRY
 */

#define FUNCTIONENTRY(ENTRYTYPE, ENTRYPOINT)	protected:	\
	typedef ENTRYTYPE;	\
	ENTRYPOINT ENTRYPOINT##Ptr;	\
public:	\
	ENTRYPOINT ENTRYPOINT##Func()	\
	{	\
		if (ENTRYPOINT##Ptr == NULL)	\
		{	\
			ENTRYPOINT##Ptr = (ENTRYPOINT)GetProcAddress(m_hModule, #ENTRYPOINT);	\
		}	\
		return ENTRYPOINT##Ptr;	\
	}	\


/*
 * DLLIMPORTCLASSEND
 */

#define DLLIMPORTCLASSEND(CLASS) };	\
CLASS##Dll* CLASS##Dll::m_pInstance = CLASS##Dll::CreateInstance();	\


/*
 * DLLIMPORTCALL
 */

#define DLLIMPORTCALL(CLASS, ENTRYPOINT)	CLASS##Dll::CreateInstance()->ENTRYPOINT##Func()

#pragma once


#include "DllImportAttribute.h"


DLLIMPORTCLASSBEGIN(User32, "User32.dll")
	FUNCTIONENTRY(int(WINAPI *MessageBoxA)(HWND, LPCSTR, LPCSTR, UINT), MessageBoxA)
DLLIMPORTCLASSEND(User32)

DllImportInit();

DLLIMPORTCALL(User32, MessageBoxA)(NULL, "ad", "ad", MB_OK);

DllImportUninit();