initialize_copy

static VALUE
random_copy(VALUE obj, VALUE orig)
{
    rb_random_t *rnd1 = get_rnd(obj);
    rb_random_t *rnd2 = get_rnd(orig);
    struct MT *mt = &rnd1->mt;

    *rnd1 = *rnd2;
    mt->next = mt->state + numberof(mt->state) - mt->left + 1;
    return obj;
}