UTF-8与Unicode互转

以后应该会用到，在这里备份一下，感谢原作者。

需要注意的是，MultiByteToWideChar和WideCharToMultiByte函数只能在Windows系统下使用。

void ConvertGBKToUtf8(CString& strGBK)
{
	int len = MultiByteToWideChar(CP_ACP, 0, (LPCTSTR)strGBK, -1, NULL, 0);
	unsigned short *wszUtf8 = new unsigned short[len + 1];
	memset(wszUtf8, 0, len * 2 + 2);
	MultiByteToWideChar(CP_ACP, 0, (LPCTSTR)strGBK, -1, wszUtf8, len);
	len = WideCharToMultiByte(CP_UTF8, 0, wszUtf8, -1, NULL, 0, NULL, NULL);
	char *szUtf8 = new char[len + 1];
	memset(szUtf8, 0, len + 1);
	WideCharToMultiByte(CP_UTF8, 0, wszUtf8, -1, szUtf8, len, NULL, NULL);
	strGBK = szUtf8;
	delete[] szUtf8;
	delete[] wszUtf8;
}

void ConvertUtf8ToGBK(CString& strUtf8)
{
	int len = MultiByteToWideChar(CP_UTF8, 0, (LPCTSTR)strUtf8, -1, NULL, 0);
	unsigned short *wszGBK = new unsigned short[len + 1];
	memset(wszGBK, 0, len * 2 + 2);
	MultiByteToWideChar(CP_UTF8, 0, (LPCTSTR)strUtf8, -1, wszGBK, len);
	len = WideCharToMultiByte(CP_ACP, 0, wszGBK, -1, NULL, 0, NULL, NULL);
	char *szGBK = new char[len + 1];
	memset(szGBK, 0, len + 1);
	WideCharToMultiByte(CP_ACP, 0, wszGBK, -1, szGBK, len, NULL, NULL);
	strUtf8 = szGBK;
	delete[] szGBK;
	delete[] wszGBK;
}