str::string和wchar_t*相互转化

虽然已经默默的在不断告诉自己，非万不得已不要使用c++，但还是会有一些时候需要，尤其是这种接口函数。

#include <windows.h>
#include <locale.h>

// wchar_t to string
void Wchar_tToString(std::string& szDst, wchar_t *wchar)
{
	wchar_t * wText = wchar;
	DWORD dwNum = WideCharToMultiByte(CP_OEMCP,NULL,wText,-1,NULL,0,NULL,FALSE);// WideCharToMultiByteµƒ‘À”√
	char *psText; // psTextŒ™char*µƒ¡Ÿ ± ˝◊È£¨◊˜Œ™∏≥÷µ∏¯std::stringµƒ÷–º‰±‰¡ø
	psText = new char[dwNum];
	WideCharToMultiByte (CP_OEMCP,NULL,wText,-1,psText,dwNum,NULL,FALSE);// WideCharToMultiByteµƒ‘Ÿ¥Œ‘À”√
	szDst = psText;// std::string∏≥÷µ
	delete []psText;// psTextµƒ«Â≥˝
}

//Converting a WChar string to a Ansi string   
std::string WChar2Ansi(LPCWSTR pwszSrc)  
{  
	int nLen = WideCharToMultiByte(CP_ACP, 0, pwszSrc, -1, NULL, 0, NULL, NULL);  
	if (nLen<= 0) return std::string("");  
	char* pszDst = new char[nLen];  
	if (NULL == pszDst) return std::string("");  
	WideCharToMultiByte(CP_ACP, 0, pwszSrc, -1, pszDst, nLen, NULL, NULL);  
	pszDst[nLen -1] = 0;  
	std::string strTemp(pszDst);  
	delete [] pszDst;  
	return strTemp;  
} 
std::string ws2s(std::wstring& inputws)
{ 
	return WChar2Ansi(inputws.c_str()); 
} 

//Converting a Ansi string to WChar string   
std::wstring Ansi2WChar(LPCSTR pszSrc, int nLen)  
{  
	int nSize = MultiByteToWideChar(CP_ACP, 0, (LPCSTR)pszSrc, nLen, 0, 0);  
	if(nSize <= 0) return NULL;  
	WCHAR *pwszDst = new WCHAR[nSize+1];  
	if( NULL == pwszDst) return NULL;  
	MultiByteToWideChar(CP_ACP, 0,(LPCSTR)pszSrc, nLen, pwszDst, nSize);  
	pwszDst[nSize] = 0;  
	if( pwszDst[0] == 0xFEFF) // skip Oxfeff   
	for(int i = 0; i < nSize; i ++)   
	pwszDst[i] = pwszDst[i+1];   
	std::wstring wcharString(pwszDst);  
	delete pwszDst;  
	return wcharString;  
}  
std::wstring s2ws(const std::string& s)
{ 
	return Ansi2WChar(s.c_str(),s.size());
}  

用法：

//const wchar_t * to std::string
const wchar_t* _file;
std::string fileName;
Wchar_tToString(fileName, const_cast<wchar_t*>(_file));

//std::string to std::wstring
std::wstring str = s2ws(fileName);