Function utfConvert

core/base/UTF8.cpp:278–316

template <typename From, typename To, typename FromTrait = ConvertTrait<From>, typename ToTrait = ConvertTrait<To>>
bool utfConvert(const std::basic_string_view<From>& from,
                std::basic_string<To>& to,
                ConversionResult (*cvtfunc)(const typename FromTrait::ArgType**,
                                            const typename FromTrait::ArgType*,
                                            typename ToTrait::ArgType**,
                                            typename ToTrait::ArgType*,
                                            ConversionFlags))
{
    static_assert(sizeof(From) == sizeof(typename FromTrait::ArgType), "Error size mismatched");
    static_assert(sizeof(To) == sizeof(typename ToTrait::ArgType), "Error size mismatched");

    if (from.empty())
    {
        to.clear();
        return true;
    }

    // See: http://unicode.org/faq/utf_bom.html#gen6
    static const int most_bytes_per_character = 4;

    const size_t maxNumberOfChars = from.length();  // all UTFs at most one element represents one character.
    const size_t numberOfOut      = maxNumberOfChars * most_bytes_per_character / sizeof(To);

    std::basic_string<To> working(numberOfOut, 0);

    auto inbeg = reinterpret_cast<const typename FromTrait::ArgType*>(&from[0]);
    auto inend = inbeg + from.length();

    auto outbeg = reinterpret_cast<typename ToTrait::ArgType*>(&working[0]);
    auto outend = outbeg + working.length();
    auto r      = cvtfunc(&inbeg, inend, &outbeg, outend, strictConversion);
    if (r != conversionOK)
        return false;

    working.resize(reinterpret_cast<To*>(outbeg) - &working[0]);
    to = std::move(working);

    return true;
};

bool UTF8ToUTF16(std::string_view utf8, std::u16string& outUtf16)
{