// Grab a Perl function object as a Perl object.%typemap(in) void *perl_cb {  SV *obj = $input;  if (SvROK(obj)) {        obj = SvRV($input);  }  if (SvTYPE(obj) != SVt_PVCV) {          SWIG_Error(SWIG_TypeError, "Parameter is not a function");           return;  }  $1 = obj;}%{#include <arpa/inet.h>#include <linux/netfilter.h>#include <linux/ip.h>#include "nfq_utils.h"int  swig_nfq_callback(struct nfq_q_handle *qh, struct nfgenmsg *nfmsg,                       struct nfq_data *nfad, void *data){        int id = 0;        struct nfqnl_msg_packet_hdr *ph;        int ret;        char *payload_data;        int payload_len;        struct timeval tv1, tv2, diff;        if (data == NULL) {                fprintf(stderr,"No callback set !\n");                return -1;        }        ph = nfq_get_msg_packet_hdr(nfad);        if (ph){                id = ntohl(ph->packet_id);        }        ret = nfq_get_payload(nfad, &payload_data);        payload_len = ret;        gettimeofday(&tv1, NULL);        /*printf("callback called\n");        printf("callback argument: %p\n",data);*/        {                SV *func = (SV*)data;                struct payload *p;                SV * payload_obj;                dSP ;                ENTER ;                SAVETMPS ;                PUSHMARK(SP) ;                XPUSHs(sv_2mortal(newSViv(42)));                p = malloc(sizeof(struct payload));                p->data = payload_data;                p->len = payload_len;                p->id = id;                p->qh = qh;                p->nfad = nfad;                payload_obj = sv_newmortal();                SWIG_MakePtr(payload_obj, (void*) p, SWIGTYPE_p_payload, 0);                XPUSHs(payload_obj);                PUTBACK;                call_sv(func, G_DISCARD);                free(p);                FREETMPS ;                LEAVE ;        }        gettimeofday(&tv2, NULL);        timeval_subtract(&diff, &tv2, &tv1);        printf("perl callback call: %d sec %d usec\n",                (int)diff.tv_sec,                (int)diff.tv_usec);        return nfq_set_verdict(qh, id, NF_ACCEPT, 0, NULL);}void raise_swig_error(const char *errstr){        fprintf(stderr,"ERROR %s\n",errstr);        SWIG_Error(SWIG_RuntimeError, errstr); }%}%extend queue {int set_callback(void *perl_cb){        self->_cb = (void*)perl_cb;        return 0;}};%typemap (out) const char* get_data {        $result = sv_2mortal(newSVpvn($1,arg1->len)); // blah        argvi++;}%extend payload {const char* get_data(void) {        return self->data;}};