#lang ivy1.7

# a fake deserializer for quic

object quic_deser = {}

<<< member

    class `quic_deser`;

>>>

<<< impl

    class `quic_deser` : public ivy_binary_deser {
        enum {quic_s_init,
              quic_s_type,
              quic_s_cid,
              quic_s_version,
              quic_s_pkt_num,
              quic_s_payload,
              quic_s_done} state;
        bool long_format;
        char hdr_type;

    public:
        quic_deser(const std::vector<char> &inp) : ivy_binary_deser(inp),state(quic_s_init) {
            pos = 42; // skip 42 bytes of IP and UDP header
        }
        virtual void  get(long long &res) {
            if (state == quic_s_init) {
                getn(res,1);
                long_format = (res & 0x80) ? true : false;
                hdr_type = res & 0x7f;
                res = long_format;
                state = quic_s_type;
            } else if (state == quic_s_type) {
                res = hdr_type;
                state = quic_s_cid;
            } else if (state == quic_s_cid) { 
                ivy_binary_deser::get(res);
                state = quic_s_version;
            } else if (state == quic_s_version) {
                if (long_format)
                    ivy_binary_deser::getn(res,4);
                else
                    res = 0;
                state = quic_s_pkt_num;
            } else if (state == quic_s_pkt_num) {
                ivy_binary_deser::getn(res,(long_format || (hdr_type & 0x1f) == 0x1d) ? 4 : (hdr_type & 0x1f) == 0x1e ? 2 : 1);
                state = quic_s_done;
            }
            else throw deser_err();
        }
        ~quic_deser(){}
    };

>>>