Function queryDns

src/SFML/Network/Dns.cpp:245–416

template <typename Handler>
void queryDns(const Handler& handler, std::optional<sf::Time> timeout, const std::vector<Query>& queries)
{
    const auto hasIpV6 = std::any_of(queries.begin(),
                                     queries.end(),
                                     [](const auto& query) {
                                         return std::any_of(query.servers.begin(),
                                                            query.servers.end(),
                                                            [](const auto& server) { return server.isV6(); });
                                     });

    sf::UdpSocket socket;
    if (socket.bind(sf::Socket::AnyPort, hasIpV6 ? sf::IpAddress::AnyV6 : sf::IpAddress::AnyV4) != sf::Socket::Status::Done)
        return;

    static std::atomic_uint16_t nextTransactionId{1};
    const auto                  transactionId = nextTransactionId.fetch_add(1);

    const auto parseResponse = [&](const std::vector<char>& buffer)
    {
        const auto* begin = buffer.data();
        const auto* ptr   = begin;
        const auto* end   = ptr + buffer.size();

        // Verify matching transaction ID
        if (const auto responseTransactionId = readU16(ptr, end); responseTransactionId != transactionId)
            return false;

        // Ensure response and no error
        if (const auto flags = readU16(ptr, end); !(flags & 0x8000) || (flags & 0x000F))
            return false;

        const auto questions = readU16(ptr, end);
        const auto answers   = readU16(ptr, end);
        readU16(ptr, end); // Authority RRs
        readU16(ptr, end); // Additional RRs

        for (auto i = 0u; (i < questions) && (ptr < end); ++i)
        {
            readName(ptr, end, begin);
            readU16(ptr, end); // Type
            readU16(ptr, end); // Class
        }

        auto handled = false;

        for (auto i = 0u; (i < answers) && (ptr < end); ++i)
        {
            readU16(ptr, end); // Name
            const auto responseType  = readU16(ptr, end);
            const auto responseClass = readU16(ptr, end);
            readU32(ptr, end); // TTL
            const auto length = readU16(ptr, end);

            if (length == 0)
                continue;

            if (ptr + length <= end)
            {