public async void AddOrUpdate(string key, object value)
{
SemaphoreSlim item_lock = _locks.GetOrAdd(key, k => new SemaphoreSlim(1, 1));
await item_lock.WaitAsync();
try
{
var cacheItemNode = new CacheItemNode(key, value);
if (_memoryCache.Contains(key))
{
CacheItemNode source = (CacheItemNode)_memoryCache.Get(key);
_lRUQueue.Remove(source);
_lRUQueue.MoveToFront(cacheItemNode);
_memoryCache.Remove(key);
_memoryCache.Set(key, cacheItemNode, _policy);
OnUpdate(source, cacheItemNode);
}
else
{
OnAdd(key);
_memoryCache.Set(key, cacheItemNode, _policy);
_lRUQueue.MoveToFront(cacheItemNode);
// For DEBUG purpose
Console.WriteLine($"LRU queue state = {_lRUQueue.QueueState()}");
Console.WriteLine($"Cache size = {Count}");
}
}
finally
{
item_lock.Release();
}
}
public LRUQueue()
{
Head = new CacheItemNode(default(String), null);
Tail = new CacheItemNode(default(String), null);
Head.Next = Tail;
Tail.Previous = Head;
}
public CacheItemNode RemoveLast()
{
CacheItemNode node = Tail.Previous;
Tail.Previous = node.Previous;
node.Previous.Next = Tail;
node.Next = null;
node.Previous = null;
return(node);
}
public CacheItemNode Remove(CacheItemNode node)
{
if (node.Next != null && node.Previous != null)
{
node.Previous.Next = node.Next;
node.Next.Previous = node.Previous;
}
node.Next = null;
node.Previous = null;
return(node);
}
public void MoveToFront(CacheItemNode node)
{
if (node.Next != null && node.Previous != null)
{
node.Previous.Next = node.Next;
node.Next.Previous = node.Previous;
}
node.Next = Head.Next;
Head.Next.Previous = node;
node.Previous = Head;
Head.Next = node;
}
public string QueueState()
{
StringBuilder strb = new StringBuilder();
CacheItemNode node = Head.Next;
while (node.Next != null)
{
if (node != null)
{
strb.Append($"{node.Key}:{node.Value.ToString()}, ");
}
node = node.Next;
}
return(strb.ToString());
}
public static void OnAdd(string key)
{
if (Count >= _capacity)
{
CacheItemNode cin = _lRUQueue.RemoveLast();
_memoryCache.Remove(cin.Key);
// To ensure that we keep consistency between items in Cache
// and in _locks dictionary, we remove the entry for the evited
// key in _locks.
if (!cin.Key.Equals(key))
{
SemaphoreSlim semaphore;
_locks.TryRemove(key, out semaphore);
}
}
}
public bool TryGet(string key, out object result)
{
CacheItemNode cacheItemNode = null;
if (_memoryCache.Contains(key))
{
cacheItemNode = (CacheItemNode)_memoryCache[key];
_lRUQueue.MoveToFront(cacheItemNode);
result = cacheItemNode.Value;
return(true);
}
else
{
result = null;
return(false);
}
}
public static void OnUpdate(CacheItemNode source, CacheItemNode updated)
{
Console.WriteLine($"Key Updated: {source.Key}, Item: (Original: {source.Value}, Updated: {updated.Value})");
}
public CacheItemNode(string key, object value) : base(key, value)
{
Previous = null;
Next = null;
}