Method GetPacketBuffer

library/cpp/netliba/v12/udp_host.cpp:851–871

Tries to get packet buffer in non-blocking way for given transfer returns std::pair if _current_ transfer was removed during FlushPackets() or buffer ovrflow for _any_ transfers

    // Tries to get packet buffer in non-blocking way for given transfer
    // returns std::pair<nullptr, err> if _current_ transfer was removed during FlushPackets() or buffer ovrflow for _any_ transfers
    std::pair<char*, ui8> TUdpHost::GetPacketBuffer(const size_t bufSize, const TConnection* connection, const ui64 id) {
        Y_ASSERT(connection);
        ui8 err = TUdpHost::EFlashPacketResult::FPR_OK;
        // if small packet optimization is enabled then there could be thousands of packets added before we reach max udp packets in queue
        if (++NewPacketsAfterLastFlush > UDP_MAX_NEW_PACKETS_BEFORE_FORCED_FLUSH) {
            //printf("TUdpHost::GetPacketBuffer: too many small packets added, flushing\n");
            err = FlushPacketsAndCheck(connection, id);
            if (err)
                return std::make_pair(nullptr, err);
        }

        char* msgBuf = S.NewPacketBuffer(bufSize);
        if (!msgBuf) {
            err = FlushPacketsAndCheck(connection, id);
            if (err)
                return std::make_pair(nullptr, err);

            msgBuf = S.NewPacketBuffer(bufSize);
        }
        return std::make_pair(msgBuf, err);
    }

    // ui8 - error bitmap
    // FPR_OVERFLOW - there were non-sent packets because of udp/kernel buffer overflow.