public bool VisitAndTryRemove(T val, out T removeVal)
{
LRULInkedListNode <T> valNode = null;
removeVal = default(T);
bool isCacheContaionVal = cache.TryGetValue(val, out valNode);
bool ret = false;
if (isCacheContaionVal)
{
MoveNodeToTheFront(valNode);
}
else
{
LRULInkedListNode <T> node = PopNode();
node.val = val;
cache.Add(val, node);
LinkAtTheFront(node);
if (capacity < cache.Count)
{
removeVal = tail.prev.val;
cache.Remove(tail.prev.val);
RemoveTheLastNode();
ret = true;
}
}
return(ret);
}
private void LinkAtTheFront(LRULInkedListNode <T> node)
{
LRULInkedListNode <T> headNext = head.Next;
head.Next = node;
node.prev = head;
node.Next = headNext;
headNext.prev = node;
}
private void MoveNodeToTheFront(LRULInkedListNode <T> node)
{
LRULInkedListNode <T> prevNode = node.prev;
LRULInkedListNode <T> nextNode = node.Next;
prevNode.Next = nextNode;
nextNode.prev = prevNode;
LinkAtTheFront(node);
}
private void GeneratePool()
{
int cap = this.pool.Capacity;
for (int i = 0; i < cap; i++)
{
LRULInkedListNode <T> node = new LRULInkedListNode <T>();
pool.Add(node);
}
}
private void RemoveTheLastNode()
{
LRULInkedListNode <T> tailPrev = tail.prev;
LRULInkedListNode <T> tailPrevPrev = tail.prev.prev;
tailPrevPrev.Next = tail;
tailPrev.prev = tailPrevPrev;
RecycleNode(tailPrev);
tailPrev = null;
}
public LRUCache(int capacity)
{
this.capacity = capacity;
this.cache = new Dictionary <T, LRULInkedListNode <T> >(this.capacity);
this.pool = new List <LRULInkedListNode <T> >(this.capacity + POOL_EXTRA_SIZE);
GeneratePool();
this.head = new LRULInkedListNode <T>();
this.tail = new LRULInkedListNode <T>();
Clear();
}
private LRULInkedListNode <T> PopNode()
{
LRULInkedListNode <T> node;
if (pool.Count > 0)
{
int last = pool.Count - 1;
node = pool[last];
pool.RemoveAt(last);
}
else
{
node = new LRULInkedListNode <T>();
}
return(node);
}
private void RecycleNode(LRULInkedListNode <T> node)
{
pool.Add(node);
}
