An XS constructor taking either a hash or hash ref

test.xs

SV * some_constructor_new(SV *class, ...)
    CODE:
{
    int iStack;
    SV *temp;
    SV **val;
    HV *params;
    PERL_UNUSED_VAR(class);

    if (items < 2) {
        /* Nothing was provided, construct an empty hash for parameters */
        params = (HV *)sv_2mortal((SV *)newHV());
    }
    if (items == 2) {
        /* only one item was supplied, let's see if it was a hash ref */
        temp = newSVsv(ST(1));
        if (SvROK(temp) && SvTYPE(SvRV(temp)) == SVt_PVHV) {
            params = (HV *)SvRV(temp);
        }
        else {
            croak("Expected a hash reference or a hash of parameters to new");
        }
    }
    else if (items > 2 && (items-1) % 2 == 0) {
        /* we have many things, but an even number of them, let's assume key, value pairs */
        params = (HV *)sv_2mortal((SV *)newHV());
        for (iStack = 1; iStack < items; iStack += 2) {
            hv_store_ent(params, ST(iStack), newSVsv(ST(iStack+1)), 0);
        }
    }
    else {
        /* we have no idea what the user gave us. DIE */
        croak("Expected a hash reference or a hash of parameters to new");
    }
    
    /* dump the hash params to ensure we have what we thought we should */
    sv_dump((SV *)params);
    
    /* check if a hash param exists! */    
    if (hv_exists(params, "int_val", 4)) {
        /* get the value if it does exist */
        val = hv_fetchs(params, "int_val", NULL);
        /* do something with that value */
    }
    
    /* return our hash ref to Perl to see what we should do with it there. */
    /* we'd normally make our object from the data in the hash ref here and return that */
    /* but this is just for my own memory of how to do all of the above */
    RETVAL = newRV_inc((SV*)params);
}
    OUTPUT:
    RETVAL