/// <summary>
/// Gets a dynamic view of the underlying cache based on the parameters given.
/// </summary>
/// <param name="mode">View mode.</param>
/// <param name="startKey">Start key of view.</param>
/// <param name="endKey">End key of view.</param>
/// <param name="tailCount">Number of items to include in view.</param>
/// <param name="tailRange">Tail duration function. Takes last item's key and returns a new startKey.</param>
/// <returns>An instance of <see cref="ObservableKeyedView"/>.</returns>
/// <exception cref="ArgumentException"><paramref name="startKey"/> must be less than or equal to <paramref name="endKey"/>.</exception>
public ObservableKeyedView GetView(ObservableKeyedView.ViewMode mode, TKey startKey, TKey endKey, uint tailCount, Func <TKey, TKey> tailRange)
{
if (this.keyComparer.Compare(startKey, endKey) > 0)
{
throw new ArgumentException($"startKey ({startKey}) must be less than or equal to endKey ({endKey}).");
}
var viewKey = Tuple.Create(startKey, endKey, tailCount, tailRange);
WeakReference <ObservableKeyedView> weakView = null;
ObservableKeyedView view = null;
if (this.views.TryGetValue(viewKey, out weakView))
{
if (weakView.TryGetTarget(out view))
{
return(view);
}
else
{
view = new ObservableKeyedView(this, mode, startKey, endKey, tailCount, tailRange);
weakView.SetTarget(view);
}
}
else
{
view = new ObservableKeyedView(this, mode, startKey, endKey, tailCount, tailRange);
weakView = new WeakReference <ObservableKeyedView>(view);
this.views.Add(viewKey, weakView);
}
return(view);
}
/// <summary>
/// Gets a dynamic view of the underlying cache based on the parameters given.
/// </summary>
/// <param name="mode">View mode.</param>
/// <param name="startKey">Start key of view.</param>
/// <param name="endKey">End key of view.</param>
/// <param name="tailCount">Number of items to include in view.</param>
/// <param name="tailRange">Tail duration function. Takes last item's key and returns a new startKey.</param>
/// <returns>An instance of <see cref="ObservableKeyedView"/>.</returns>
/// <exception cref="ArgumentException"><paramref name="startKey"/> must be less than or equal to <paramref name="endKey"/>.</exception>
public ObservableKeyedView GetView(ObservableKeyedView.ViewMode mode, TKey startKey, TKey endKey, uint tailCount, Func <TKey, TKey> tailRange)
{
if (this.keyComparer.Compare(startKey, endKey) > 0)
{
throw new ArgumentException($"startKey ({startKey}) must be less than or equal to endKey ({endKey}).");
}
var viewKey = Tuple.Create(startKey, endKey, tailCount, tailRange);
WeakReference <ObservableKeyedView> weakView = null;
ObservableKeyedView view = null;
if (this.views.TryGetValue(viewKey, out weakView))
{
if (weakView.TryGetTarget(out view))
{
return(view);
}
else
{
view = new ObservableKeyedView(this, mode, startKey, endKey, tailCount, tailRange);
weakView.SetTarget(view);
// Sometimes the weak view gets deleted between when we grab it to check
// if it has a hard reference and when we actually set the new hard reference
// that we just created. If that happens, then the following code makes sure
// the weak view gets put back into the collection.
this.views[viewKey] = weakView;
}
}
else
{
view = new ObservableKeyedView(this, mode, startKey, endKey, tailCount, tailRange);
weakView = new WeakReference <ObservableKeyedView>(view);
this.views.Add(viewKey, weakView);
}
return(view);
}
public Enumerator(ObservableKeyedView view)
{
this.view = view;
this.index = 0;
this.value = default(TItem);
}
/// <summary>
/// Walks views and prunes out dead (GC'd) views and the resulting unreferenced data.
/// </summary>
private void PruneCache()
{
// More than one call to PruneCache can be queued. Only process the first one.
if (!this.needsPruning)
{
return;
}
this.needsPruning = false;
// track whether we did any pruning to adjust our threshold
bool didPrune = false;
// find dead views
ObservableKeyedView view = null;
var deadViews = this.views.Where(v => !v.Value.TryGetTarget(out view));
// remove dead views from views collection
foreach (var deadView in deadViews.ToList())
{
this.views.Remove(deadView.Key);
}
// remove cached items that are no longer referenced by a view
var liveViews = this.views.OrderBy(lv => lv.Key.Item1, this.keyComparer).ThenBy(lv => lv.Key.Item2, this.keyComparer);
int startIndex = 0;
foreach (var liveView in liveViews)
{
// find exclusive endIndex of range to be removed
int endIndex = startIndex;
while (this.Count > endIndex && this.keyComparer.Compare(this.getKeyForItem(this[endIndex]), liveView.Key.Item1) < 0)
{
endIndex++;
}
// remove items preceding current live view
if (endIndex > startIndex)
{
this.RemoveRange(startIndex, endIndex - startIndex);
didPrune = true;
}
// advance startIndex to end of current live view
while (this.Count > startIndex && this.keyComparer.Compare(this.getKeyForItem(this[startIndex]), liveView.Key.Item2) < 0)
{
startIndex++;
}
}
// remove items after last live view
if (startIndex == 0)
{
// no live view that contains any data - clear all
this.Clear();
didPrune = true;
}
else
{
// at least one live view that contains data - remove to the end
if (this.Count > startIndex)
{
this.RemoveRange(startIndex, this.Count - startIndex);
didPrune = true;
}
}
// adjust pruning threshold
this.pruneThreshold = didPrune ?
Math.Max(this.pruneThreshold >> 1, ObservableSortedCollection <TItem> .DefaultCapacity >> 2) :
Math.Min(this.pruneThreshold << 1, ObservableSortedCollection <TItem> .DefaultCapacity << 2);
}
