Method queryMx

src/SFML/Network/Dns.cpp:637–710

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

////////////////////////////////////////////////////////////
std::vector<Dns::MxRecord> Dns::queryMx(const String& hostname, const std::vector<IpAddress>& servers, std::optional<Time> timeout)
{
    std::vector<MxRecord> mxRecords;

    if (hostname.isEmpty())
        return mxRecords;

    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)
            {
                // MX, IN
                if ((responseType != 15) || (responseClass != 1))
                    return;

                const auto preference = readU16(data, data + length);
                auto       exchange   = readName(data, data + length, messageBegin);

                if (!exchange.empty())
                    mxRecords.emplace_back(MxRecord{decodeHostname(exchange), preference});
            },
            timeout,
            {{serversToQuery,
              15, // MX
              1,  // IN
              encoded}});

        return mxRecords;
    }

#if defined(SFML_SYSTEM_WINDOWS)
    const auto records = getRecords(encoded, DNS_TYPE_MX);
    for (const auto* ptr = records.get(); ptr; ptr = ptr->pNext)
    {
        if ((ptr->wType == DNS_TYPE_MX) && (ptr->Data.MX.pNameExchange != nullptr))
        {
            mxRecords.emplace_back(
                MxRecord{decodeHostname(sf::String(ptr->Data.MX.pNameExchange).toAnsiString()), ptr->Data.MX.wPreference});
        }
    }
#else
    getRecords(encoded,
               ns_t_mx,
               [&mxRecords](const ns_msg& handle, const ns_rr& record)
               {
                   const auto preference = static_cast<std::uint16_t>(ns_get16(ns_rr_rdata(record) + 0 * NS_INT16SZ));

                   std::array<char, NS_MAXCDNAME> exchange{};