/// <summary>Create item enumerator</summary>
public IEnumerator <Node> GetEnumerator()
{
lock (this)
{
for (int bagNumber = _current; bagNumber >= _oldest; --bagNumber)
{
AgeBag bag = _bags[bagNumber];
// if bag.first == null then bag is empty or being cleaned up, so skip it!
for (Node node = bag.First; node != null && bag.First != null; node = node.Next)
{
if (node.Value != null)
{
yield return(node);
}
}
}
}
}
/// <summary>remove old items or items beyond capacity from LifespanMgr allowing them to be garbage collected</summary>
/// <remarks>since we do not physically move items when touched we must check items in bag to determine if they should be deleted
/// or moved. Also items that were removed by setting value to null get removed now. Rremoving an item from LifespanMgr allows
/// it to be garbage collected. If removed item is retrieved by index prior to GC then it will be readded to LifespanMgr.</remarks>
public void CleanUp(DateTime now)
{
lock (this) {
//calculate how many items should be removed
DateTime maxAge = now.Subtract(_maxAge);
DateTime minAge = now.Subtract(_minAge);
int itemsToRemove = _owner._curCount - _owner._capacity;
AgeBag bag = _bags[_oldest % _size];
while (_current != _oldest &&
(_current - _oldest > _size - 5 || bag.startTime < maxAge ||
(itemsToRemove > 0 && bag.stopTime > minAge)))
{
// cache is still too big / old so remove oldest bag
Node node = bag.first;
bag.first = null;
while (node != null)
{
Node next = node.next;
node.next = null;
if (node.Value != null && node.ageBag != null)
{
if (node.ageBag == bag)
{
// item has not been touched since bag was closed, so remove it from LifespanMgr
++itemsToRemove;
node.ageBag = null;
Interlocked.Decrement(ref _owner._curCount);
}
else
{
// item has been touched and should be moved to correct age bag now
node.next = node.ageBag.first;
node.ageBag.first = node;
}
}
node = next;
}
// increment oldest bag
bag = _bags[(++_oldest) % _size];
}
OpenCurrentBag(now, ++_current);
CheckIndexValid();
}
}
/// <summary>ready a new current AgeBag for use and close the previous one</summary>
private void OpenCurrentBag(DateTime now, int bagNumber)
{
lock (this)
{
// close last age bag
if (_currentBag != null)
{
_currentBag.stopTime = now;
}
// open new age bag for next time slice
AgeBag currentBag = _bags[(_current = bagNumber) % _size];
currentBag.startTime = now;
currentBag.first = null;
_currentBag = currentBag;
// reset counters for CheckValid()
_nextValidCheck = now.Add(_timeSlice);
_currentSize = 0;
}
}
/// <summary>Updates the status of the node to prevent it from being dropped from cache</summary>
public void Touch()
{
if (Value != null && ageBag != _mgr._currentBag)
{
if (ageBag == null)
{
lock (_mgr)
if (ageBag == null)
{
// if node.AgeBag==null then the object is not currently managed by LifespanMgr so add it
next = _mgr._currentBag.first;
_mgr._currentBag.first = this;
Interlocked.Increment(ref _mgr._owner._curCount);
}
}
ageBag = _mgr._currentBag;
Interlocked.Increment(ref _mgr._currentSize);
}
_mgr.CheckValid();
}
