（16）std::wstring

std::wstring主要用于 UTF-16编码的字符,
std::string主要用于存储单字节的字符( ASCII字符集 )，但是也可以用来保存UTF-8编码的字符。
UTF-8和UTF-16是UNICODE字符集的两种不同的字符编码。

std::string ws2s(const std::wstring &ws)
{
    size_t i;
    std::string curLocale = setlocale(LC_ALL, NULL);
    setlocale(LC_ALL, "chs");
    const wchar_t* _source = ws.c_str();
    size_t _dsize = 2 * ws.size() + 1;
    char* _dest = new char[_dsize];
    memset(_dest, 0x0, _dsize);
    wcstombs_s(&i, _dest, _dsize, _source, _dsize);
    std::string result = _dest;
    delete[] _dest;
    setlocale(LC_ALL, curLocale.c_str());
    return result;
}

std::wstring s2ws(const std::string &s)
{
    size_t i;
    std::string curLocale = setlocale(LC_ALL, NULL);
    setlocale(LC_ALL, "chs");
    const char* _source = s.c_str();
    size_t _dsize = s.size() + 1;
    wchar_t* _dest = new wchar_t[_dsize];
    wmemset(_dest, 0x0, _dsize);
    mbstowcs_s(&i, _dest, _dsize, _source, _dsize);
    std::wstring result = _dest;
    delete[] _dest;
    setlocale(LC_ALL, curLocale.c_str());
    return result;
}