FME_HDR_PORT_OFST
port_offset = readq(fme_hdr + FME_HDR_PORT_OFST(i));
v = readq(base + FME_HDR_PORT_OFST(i));
v = readq(base + FME_HDR_PORT_OFST(port_id));
writeq(v, base + FME_HDR_PORT_OFST(port_id));