private void lru_insert(head_t h)
{
// insert to last position
h.next = lru_head;
h.prev = lru_head.prev;
h.prev.next = h;
h.next.prev = h;
}
Cache(int l_, int size_)
{
l = l_;
size = size_;
head = new head_t[l];
for(int i=0;i<l;i++) head[i] = new head_t();
size /= 4;
size -= l * (16/4); // sizeof(head_t) == 16
lru_head = new head_t();
lru_head.next = lru_head.prev = lru_head;
}