static intset *intsetResize(intset *is, uint32_t len) {
    uint64_t size = (uint64_t)len*intrev32ifbe(is->encoding);
    assert(size <= SIZE_MAX - sizeof(intset));
    is = zrealloc(is,sizeof(intset)+size);
    return is;
}
static intset *intsetResize(intset *is, uint32_t len) {
    uint64_t size = (uint64_t)len*intrev32ifbe(is->encoding);
    assert(size <= SIZE_MAX - sizeof(intset));
    is = zrealloc(is,sizeof(intset)+size);
    return is;
}