STL数组和com数组相互转换的做法

作者：朱金灿

来源：http://blog.csdn.net/clever101

STL的泛型数组是vetor，com的泛型数组类型是VARIANT。二者怎样能相互转化呢？就是说怎么把一个vector对象封装进VARIANT对象，又怎么将VARIANT对象封装进vector对象。经过一番研究，找到了办法。需要注意的是，数值数组和字符串数组是需要单独处理的。首先谈谈数组类型的数组如何转换，比如std::vector<int>转换为一个VARIANT对象。需要一个模板类来实现，代码如下：

template<class T>

class CVariantPack

{

private:

	CVariantPack(void){};

	~CVariantPack(void){};

public:

	static bool SetTPtrVariant(VARENUM ElementType,const std::vector<T>& vecData,VARIANT &vdata)

	{

		try

		{

			if(vecData.empty())

			{

				return false;

			}

			SAFEARRAYBOUND rgsabound[1];

			rgsabound[0].lLbound = 0;

			rgsabound[0].cElements = (ULONG)vecData.size();

			SAFEARRAY *psa = SafeArrayCreate(ElementType,1, rgsabound );

			if( psa )

			{

				for( long i=0; i<(long)vecData.size(); i++ )

				{

					SafeArrayPutElement( psa, &i, (void *)(&vecData[i]));

				}

				vdata.vt = VT_ARRAY|ElementType;

				vdata.parray = psa;

				SafeArrayUnaccessData( psa );

				return true;

			}

			else

			{

				return false;

			}

		}

		catch(...)

		{

			return false;

		}

	}

	static int GetTPtrVariant (VARENUM ElementType,std::vector<T>& vecData,const VARIANT vdata)

	{

		try

		{

			if( vdata.vt==VT_NULL || vdata.vt==VT_EMPTY )

			{

				return -1;

			}

			if( !(vdata.vt & VT_ARRAY)  )

			{

				return -2;

			}

			SAFEARRAY *psa = vdata.parray;

			UINT nDims = SafeArrayGetDim( psa );

			if( nDims != 1 )

			{

				return -3;

			}

			//检查数组元素类型

			VARTYPE vt = 0;

			SafeArrayGetVartype( psa, &vt );

			if( vt != ElementType )

			{

				return -4;

			}

			//检查数组上下限和元素个数是否为偶数个

			LONG lUBound =0, lLBound = 0;

			SafeArrayGetUBound( psa, 1, &lUBound );

			SafeArrayGetLBound( psa, 1, &lLBound );

			int lElements = lUBound - lLBound + 1;

			if( lElements <= 0 )

			{

				return -5;

			}

			T *pTmp = NULL;

			SafeArrayAccessData( psa, (void **)&pTmp );

			if( NULL == pTmp )

			{

				return -6;

			}

			for (int i = 0;i<lElements;i++)

			{

                 vecData.push_back(*(pTmp+i));

			}

			SafeArrayUnaccessData( psa );

			return lElements;

		}

		catch(...)

		{

			return -1;

		};

	}

};

测试函数如下：

bool TestVariantPack1(void)

{

	std::vector<long> a;

a.push_back(1);

a.push_back(2);

a.push_back(3);

	VARIANT vdata;

	//long 数组封装到variant

	if( !CVariantPack<long>::packtptrvariant(v_long,a,3,vdata))

	{

		return false;

	}

	std::vector<long> b;

	//从variant获取long数组数据

	int num= CVariantPack<long>::GetTPtrVariant(VT_I4,b,vdata);

	if( num<=0 )

	{

		return false;

	}

}

下面再谈谈字符串数组的相互转换。

// std::vector< std::wstring>转换为一个VARIANT对象

	bool StringArrayToVariant(const std::vector< std::wstring >& vecData,VARIANT& vdata)

	{

		if(vecData.empty())

		{

			return false;

		}

		SAFEARRAY *psa;

		SAFEARRAYBOUND rgsabound;

		rgsabound.cElements = (ULONG)vecData.size();

		rgsabound.lLbound = 0;

		psa = SafeArrayCreate(VT_BSTR, 1, &rgsabound);//设置为一位BSTR数组

		if( psa )

		{

			BSTR* bstrArray;

			::SafeArrayAccessData(psa,(void**)&bstrArray);//将数据引出进行操作，并加锁

			for (int i = 0 ; i < vecData.size(); ++i)

			{

// bstrArray[i] =  arExport[i].AllocSysString(); // 如果是std::vector<CString>，请用这句代码

				bstrArray[i] =  const_cast<TCHAR*>(vecData[i].c_str());

			}

			vdata.vt = VT_ARRAY|VT_BSTR;

			vdata.parray = psa;

			::SafeArrayUnaccessData(psa);

			return true;

		}

		return false;

	}

//VARIANT对象转换为std::vector< std::wstring>

	int VariantToStringArray(const VARIANT& vdata,std::vector<std::wstring >& vecData)

	{

		if( vdata.vt==VT_NULL || vdata.vt==VT_EMPTY )

		{

			return -1;

		}

		if( !(vdata.vt & VT_ARRAY)  )

		{

			return -2;

		}

		SAFEARRAY *psa = vdata.parray;

		UINT nDims = SafeArrayGetDim( psa );

		if( nDims != 1 )

		{

			return -3;

		}

		//检查数组元素类型

		VARTYPE vt = 0;

		SafeArrayGetVartype( psa, &vt );

		if( vt != VT_BSTR )

		{

			return -4;

		}

		//检查数组上下限和元素个数是否为偶数个

		LONG lUBound =0, lLBound = 0;

		SafeArrayGetUBound( psa, 1, &lUBound );

		SafeArrayGetLBound( psa, 1, &lLBound );

		int lElements = lUBound - lLBound + 1;

		if( lElements <= 0 )

		{

			return -5;

		}

		BSTR* pTmp = NULL;

		SafeArrayAccessData( psa, (void **)&pTmp );

		if( NULL == pTmp )

		{

			return -6;

		}

		for (int i = 0;i<lElements;i++)

		{

			vecData.push_back(*(pTmp+i));

		}

		SafeArrayUnaccessData( psa );

		return lElements;

	}

这里需要注意的是，com只支持unicode字符，所以对应的stl字符串数组类型为std::vector<std::wstring>。

测试函数如下：

bool TestVariantPack(void)

{

	std::vector<std::wstring> vecString;

    vecString.push_back(_T("HelloWorld"));

    vecString.push_back(_T(","));

    vecString.push_back(_T("I am from China!"));

	VARIANT vdata;

	// std::vector<std::wstring> 数组封装到variant

	if( !SysUtility::StringArrayToVariant(vecString,vdata))

	{

		return false;

	}

	std::vector<std::wstring> vecString2;

	//从variant获取std::vector<std::wstring>数组数据

	int num= SysUtility::VariantToStringArray(vdata,vecString2);

	if( num<=0 )

	{

		return false;

	}

	return true;

}

参考文献：

1. 关于在C#中调用MFC编写Activex控件中传入字符串数组的有关问题

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