tools/test/p4src/p4-14/include/parser.p4

#ifndef __PARSER_P4__
#define __PARSER_P4__
#include "defines.p4"
#include "headers.p4"

header packet_in_t packet_in_hdr;
header packet_out_t packet_out_hdr;
header ethernet_t ethernet;
header ipv4_t ipv4;
header tcp_t tcp;
header udp_t udp;

parser start {
    // FIXME: Cheat the compiler to generate the deparser of packet in
    // This is just a hack, we assume first 8 bit of etherType won't be 0
    return select( current(96, 8) ) {
        NULL_ETH_TYPE : parse_pkt_in;
        default       : default_parser;
    }
}

parser parse_pkt_in {
    extract(packet_in_hdr);
    return parse_ethernet;
}

parser default_parser {
    return select(IGR_PORT_FIELD) {
        CPU_PORT : parse_pkt_out;
        default  : parse_ethernet;
    }
}

parser parse_pkt_out {
    extract(packet_out_hdr);
    return parse_ethernet;
}

parser parse_ethernet {
    extract(ethernet);
    return select(latest.etherType) {
        ETHERTYPE_IPV4 : parse_ipv4;
        default : ingress;
    }
}

parser parse_ipv4 {
    extract(ipv4);
    return select(latest.fragOffset, latest.protocol) {
        IP_PROTOCOLS_TCP : parse_tcp;
        IP_PROTOCOLS_UDP : parse_udp;
        default: ingress;
    }
}

parser parse_tcp {
    extract(tcp);
    return ingress;
}

parser parse_udp {
    extract(udp);
    return ingress;
}

#endif