/// <summary>
/// Retrieves the value for key requested. If the key does not exist
/// in the cache then the Fetch method is used to retrieve the value
/// from another source.
/// </summary>
/// <param name="key">Key for the item required</param>
/// <param name="loader">Loader to fetch the item from if not in the cache</param>
/// <returns>An instance of the value associated with the key</returns>
public V this[K key, IValueLoader <K, V> loader]
{
get
{
bool added = false;
Interlocked.Increment(ref _requests);
CachedItem node, newNode = null;
if (_dictionary.TryGetValue(key, out node) == false)
{
// Get the item fresh from the loader before trying
// to write the item to the cache.
Interlocked.Increment(ref _misses);
newNode = new CachedItem(
GetRandomLinkedList(),
key,
loader.Load(key));
// If the node has already been added to the dictionary
// then get it, otherwise add the one just fetched.
node = _dictionary.GetOrAdd(key, newNode);
// If the node got from the dictionary is the new one
// just fetched then it needs to be added to the linked
// list.
if (node == newNode)
{
// Set the node as the first item in the list.
newNode.List.AddNew(newNode);
added = true;
}
}
// The item is in the dictionary. Check it's still in the list
// and if so them move it to the head of the linked list.
if (added == false)
{
node.List.MoveFirst(node);
}
return(node.Value);
}
}
public ValueHolder(IValueLoader <T> loader)
{
Loader = loader;
}
/// <summary>
/// Set the value loader that will be used to load items on a cache miss
/// </summary>
/// <param name="loader"></param>
public void SetValueLoader(IValueLoader <K, V> loader)
{
_loader = loader;
}
/// <summary>
/// Constructs a new instance of the cache.
/// </summary>
/// <param name="cacheSize">The number of items to store in the cache</param>
/// <param name="loader">Loader used to fetch items not in the cache</param>
/// <param name="concurrency">
/// The expected number of concurrent requests to the cache
/// </param>
internal LruCache(int cacheSize, IValueLoader <K, V> loader, int concurrency)
: this(cacheSize, concurrency)
{
SetValueLoader(loader);
}
/// <summary>
/// Constructs a new instance of the cache.
/// </summary>
/// <param name="cacheSize">The number of items to store in the cache</param>
/// <param name="loader">Loader used to fetch items not in the cache</param>
internal LruCache(int cacheSize, IValueLoader <K, V> loader)
: this(cacheSize, loader, Environment.ProcessorCount)
{
}
private void AddValueLoader(IValueLoader loader)
{
m_valueLoaders.Add(loader.AppliesTo, loader);
loader.GameLoader = this;
}
public ValueHolder(IValueLoader <T> loader) => _loader = loader;
private void AddValueLoader(IValueLoader loader)
{
m_valueLoaders.Add(loader.AppliesTo, loader);
loader.GameLoader = this;
}