/// <summary>
/// Invalidates <see cref="Entry{TKey,Tvalue}"/> by provided key and deletes it from the set.
/// </summary>
/// <param name="key">Cache entry key to invalidate.</param>
/// <param name="source">Value indicating the source of invalidation request.</param>
/// <returns>Returns true if cache entry invalidation is successful,
/// false if key is missing in cache set.</returns>
internal bool InvalidateAndDelete(TKey key, InvalidationSource source)
{
lock (thisLock)
{
if (!cacheDictionary.ContainsKey(key))
{
return(false);
}
cacheDictionary.Remove(key);
EntryCount--;
EvictionListener?.Invoke(
this,
new InvalidationEventArgs
{
Source = source
});
return(true);
}
}
/// <summary>
/// Insert key/value pair into cache set.
/// </summary>
/// <param name="key">Cache entry key.</param>
/// <param name="value">Cache entry value.</param>
internal void InsertEntry(TKey key, TValue value)
{
// we are locking the object to provide thread-safety.
lock (thisLock)
{
// if key already exists in the cache set - replace the value.
if (cacheDictionary.ContainsKey(key))
{
EvictionListener?.Invoke(
this,
new InvalidationEventArgs
{
Source = InvalidationSource.Replacement
});
cacheDictionary[key] = new Entry <TKey, TValue>(key, value);
return;
}
// if cache set has more entries than n-Way parameter
// we call the eviction algorithm
if (EntryCount >= nWay)
{
// selected entry is invalidated and the entry deletion procedure is being called.
if (!InvalidateAndDelete(
evictionAlgorithm.Evict(cacheDictionary.Values.ToList()).Key,
InvalidationSource.Eviction))
{
throw new ArgumentException("Eviction algorithm didn't provide valid entry to evict!");
}
}
// a new entry is then created and inserted into dictionary
cacheDictionary.Add(key, new Entry <TKey, TValue>(key, value));
EntryCount++;
}
}