cpToWstr, wstrToUtf8

std::wstring Language::cpToWstr(const std::string& src)
{
    if (src.empty())
        return L"";
#ifdef _WIN32
    int size = MultiByteToWideChar(CP_ACP, 0, &src[0], (int)src.size(), NULL, 0);
    std::wstring wstr(size, 0);
    MultiByteToWideChar(CP_ACP, 0, &src[0], (int)src.size(), &wstr[0], size);
    return wstr;
#else
    const int MAX = 500;
    wchar_t buffer[MAX + 1];
    setlocale(LC_ALL, "");
    size_t len = mbstowcs(buffer, src.c_str(), MAX);
    setlocale(LC_ALL, "C");
    if (len == (size_t)-1)
        return L"?";
    return std::wstring(buffer, len);
#endif
}

std::string Language::wstrToUtf8(const std::wstring& src)
{
    if (src.empty())
        return "";
#ifdef _WIN32
    int size = WideCharToMultiByte(CP_UTF8, 0, &src[0], (int)src.size(), NULL, 0, NULL, NULL);
    std::string str(size, 0);
    WideCharToMultiByte(CP_UTF8, 0, &src[0], (int)src.size(), &str[0], size, NULL, NULL);
    return str;
#else
    std::string out;
    unsigned int codepoint = 0;
    for (std::wstring::const_iterator i = src.begin(); i != src.end(); ++i)
    {
        wchar_t ch = *i;
        if (ch >= 0xd800 && ch <= 0xdbff)
            codepoint = ((ch - 0xd800) << 10) + 0x10000;
        else
        {
            if (ch >= 0xdc00 && ch <= 0xdfff)
                codepoint |= ch - 0xdc00;
            else
                codepoint = ch;

            if (codepoint <= 0x7f)
                out.append(1, static_cast<char>(codepoint));
            else if (codepoint <= 0x7ff)
            {
                out.append(1, static_cast<char>(0xc0 | ((codepoint >> 6) & 0x1f)));
                out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
            }
            else if (codepoint <= 0xffff)
            {
                out.append(1, static_cast<char>(0xe0 | ((codepoint >> 12) & 0x0f)));
                out.append(1, static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f)));
                out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
            }
            else
            {
                out.append(1, static_cast<char>(0xf0 | ((codepoint >> 18) & 0x07)));
                out.append(1, static_cast<char>(0x80 | ((codepoint >> 12) & 0x3f)));
                out.append(1, static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f)));
                out.append(1, static_cast<char>(0x80 | (codepoint & 0x3f)));
            }
            codepoint = 0;
        }
    }
    return out;
#endif
}