/// <summary>
/// Makes the specified node the most recently accessed one by moving it to the front of the LRU list.
/// </summary>
/// <param name="node">The node that was most recently accessed.</param>
private void MostRecent(ILruCacheEntry <WeakReference <T>, R> node)
{
//
// NB: We opted for a linked list approach for the LRU cache to have constant overhead for memoized function
// invocation, with a minor increment upon cache pruning. Alternatively, we could sort entries by their
// last access time, having less overhead during a lookup (just store the new access time) but at the
// expensive of having to sort the entries in the Trim procedure. That'd cause a hiccup in lookup times.
//
// NB: If a ranking based eviction is desirable, resulting in higher lookup speeds but lower pruning speeds,
// one can use the CreateEvictedBy* methods on WeakMemoizationCacheFactory.
//
_lock.EnterWriteLock();
try
{
while (_lruList.Last != null && !_lruList.Last.Key.TryGetTarget(out _))
{
LruLinkedList.RemoveLast(ref _lruList);
Interlocked.Decrement(ref _count);
}
LruLinkedList.MoveFirst(ref _lruList, node);
}
finally
{
_lock.ExitWriteLock();
}
}
/// <summary>
/// Trims the LRU cache if needed.
/// </summary>
private void Trim()
{
//
// NB: We can have temporary oversubscription during concurrent accesses because we avoid to enter the write lock
// until absolutely necessary, so _cache.Count can be a dirty read.
//
if (_count >= _maxCapacity)
{
_lock.EnterWriteLock();
try
{
do
{
var entry = _lruList.Last;
if (entry.Key.TryGetTarget(out T key))
{
_cache.Remove(key);
}
LruLinkedList.RemoveLast(ref _lruList);
Interlocked.Decrement(ref _count);
#if DEBUG
_lastEvicted = entry;
_evictionCount++;
#endif
} while (_count >= _maxCapacity);
}
finally
{
_lock.ExitWriteLock();
}
}
}
/// <summary>
/// Trims the LRU cache if needed.
/// </summary>
private void Trim()
{
while (_cache.Count >= _maxCapacity)
{
var entry = _lruList.Last;
_cache.Remove(entry.Key);
LruLinkedList.RemoveLast(ref _lruList);
#if DEBUG
_lastEvicted = entry;
_evictionCount++;
#endif
}
}