Optimize FIFOSet

src/neo/IO/Caching/FIFOSet.cs

@@ -1,16 +1,23 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Collections.Specialized;
-using System.Linq;
+using System.Collections.ObjectModel;
 
 namespace Neo.IO.Caching
 {
  internal class FIFOSet<T> : IReadOnlyCollection<T> where T : IEquatable<T>
  {
+ private class Collection : KeyedCollection<T, T>
+ {
+ protected override T GetKeyForItem(T item)
+ {
+ return item;
+ }
+ }
+
  private readonly int maxCapacity;
  private readonly int removeCount;
- private readonly OrderedDictionary dictionary;
+ private readonly Collection dictionary;
 
  public int Count => dictionary.Count;
 
@@ -21,7 +28,7 @@ public FIFOSet(int maxCapacity, decimal batchSize = 0.1m)
 
  this.maxCapacity = maxCapacity;
  this.removeCount = Math.Max((int)(maxCapacity * batchSize), 1);
- this.dictionary = new OrderedDictionary(maxCapacity);
+ this.dictionary = new Collection();
  }
 
  public bool Add(T item)
@@ -39,7 +46,7 @@ public bool Add(T item)
  dictionary.RemoveAt(0);
  }
  }
- dictionary.Add(item, null);
+ dictionary.Add(item);
  return true;
  }
 
@@ -58,8 +65,7 @@ public void ExceptWith(IEnumerable<T> entries)
 
  public IEnumerator<T> GetEnumerator()
  {
- var entries = dictionary.Keys.Cast<T>().ToArray();
- foreach (var entry in entries) yield return entry;
+ return dictionary.GetEnumerator();
  }
 
  IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();