/// <inheritdoc />
public void AddOrUpdate(TKey key, TValue value)
{
SpinLock sLock = new SpinLock();
bool lockTaken = false;
try
{
sLock.Enter(ref lockTaken);
//Support updating the cache (find by key and update the value)
_cache.TryGetValue(key, out var valueToUpdate);
if (valueToUpdate != null)
{
valueToUpdate.Value = value;
_mostRecentlyUsed = valueToUpdate;
//Eviction policy shouldn't be required when just performing an update.
return;
}
// Insert the new node at the right-most end of the linked-list (recently used)
Node <TKey, TValue> myNode = new Node <TKey, TValue>(_mostRecentlyUsed, null, key, value);
//Support Adding to the cache
_mostRecentlyUsed.Next = myNode;
_cache.Add(key, myNode);
_mostRecentlyUsed = myNode;
//When an item is added to the cache, a check should be run to see if the cache size exceeds the maximum number of elements permitted.
// Delete the left-most entry and update the least recently used pointer
if (_evictionPolicy.MemberRequiresEviction())
{
//If this is the case, then the least recently added/updated/retrieved item should be evicted from the cache.
_cache.Remove(_leastRecentlyUsed.Key);
_leastRecentlyUsed = _leastRecentlyUsed.Next;
_leastRecentlyUsed.Previous = null;
}
//Update cache size
else
{
// If this is the only node in the list, also set it as the least recently used.
if (_evictionPolicy.CacheSize == 0)
{
_leastRecentlyUsed = myNode;
}
_evictionPolicy.CacheSize++;
}
}
finally
{
if (lockTaken)
{
sLock.Exit(false);
}
}
}
