Method queryNs

src/SFML/Network/Dns.cpp:568–633

///////////////////////////////////////////////////////

////////////////////////////////////////////////////////////
std::vector<sf::String> Dns::queryNs(const String& hostname, const std::vector<IpAddress>& servers, std::optional<Time> timeout)
{
    std::vector<sf::String> nsRecords;

    if (hostname.isEmpty())
        return nsRecords;

    auto encoded = encodeHostname(hostname);

    // On Android the libc provided resolv API doesn't work, we will have to do the work ourselves
#if defined(SFML_SYSTEM_ANDROID)
    const auto& serversToQuery = servers.empty() ? getAndroidServers() : servers;
#else
    const auto& serversToQuery = servers;
#endif

    if (!serversToQuery.empty())
    {
        queryDns(
            [&](const char* data, std::size_t length, const char* messageBegin, std::uint16_t responseType, std::uint16_t responseClass)
            {
                // NS, IN
                if ((responseType != 2) || (responseClass != 1))
                    return;

                if (auto nameserver = readName(data, data + length, messageBegin); !nameserver.empty())
                    nsRecords.emplace_back(decodeHostname(nameserver));
            },
            timeout,
            {{serversToQuery,
              2, // NS
              1, // IN
              encoded}});

        return nsRecords;
    }

#if defined(SFML_SYSTEM_WINDOWS)
    const auto records = getRecords(encoded, DNS_TYPE_NS);
    for (const auto* ptr = records.get(); ptr; ptr = ptr->pNext)
    {
        if ((ptr->wType == DNS_TYPE_NS) && (ptr->Data.NS.pNameHost != nullptr))
            nsRecords.emplace_back(decodeHostname(sf::String(ptr->Data.NS.pNameHost).toAnsiString()));
    }
#else
    getRecords(encoded,
               ns_t_ns,
               [&nsRecords](const ns_msg& handle, const ns_rr& record)
               {
                   std::array<char, NS_MAXCDNAME> nameserver{};

                   if (const auto result = dn_expand(ns_msg_base(handle),
                                                     ns_msg_end(handle),
                                                     ns_rr_rdata(record),
                                                     nameserver.data(),
                                                     nameserver.size());
                       result >= 0)
                   {