Revert FIFOSet

neo/IO/Caching/FIFOSet.cs

@@ -1,30 +1,16 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Linq;
 
 namespace Neo.IO.Caching
 {
  internal class FIFOSet<T> : IEnumerable<T> where T : IEquatable<T>
  {
- class Entry
- {
- public readonly T Value;
- public Entry Next;
-
- public Entry(T current)
- {
- Value = current;
- }
- }
-
  private readonly int maxCapacity;
  private readonly int removeCount;
-
- private int _count = 0;
- private Entry _firstEntry = null;
- private Entry _lastEntry = null;
-
- public int Count => _count;
+ private readonly OrderedDictionary dictionary;
 
  public FIFOSet(int maxCapacity, decimal batchSize = 0.1m)
  {
@@ -33,113 +19,45 @@ public FIFOSet(int maxCapacity, decimal batchSize = 0.1m)
 
  this.maxCapacity = maxCapacity;
  this.removeCount = Math.Max((int)(maxCapacity * batchSize), 1);
+ this.dictionary = new OrderedDictionary(maxCapacity);
  }
 
  public bool Add(T item)
  {
- if (Contains(item)) return false;
- if (Count >= maxCapacity)
+ if (dictionary.Contains(item)) return false;
+ if (dictionary.Count >= maxCapacity)
  {
  if (removeCount == maxCapacity)
  {
- _lastEntry = _firstEntry = null;
- _count = 0;
+ dictionary.Clear();
  }
  else
  {
  for (int i = 0; i < removeCount; i++)
- {
- RemoveFirst();
- }
+ dictionary.RemoveAt(0);
  }
  }
-
- if (_lastEntry == null)
- {
- _firstEntry = _lastEntry = new Entry(item);
- }
- else
- {
- _lastEntry = _lastEntry.Next = new Entry(item);
- }
-
- _count++;
+ dictionary.Add(item, null);
  return true;
  }
 
- private void RemoveFirst()
- {
- if (_firstEntry != null)
- {
- _firstEntry = _firstEntry.Next;
- _count--;
- }
- }
-
  public bool Contains(T item)
  {
- var current = _firstEntry;
-
- while (current != null)
- {
- if (current.Value.Equals(item)) return true;
- current = current.Next;
- }
-
- return false;
- }
-
- private void Remove(T item)
- {
- var prev = _firstEntry;
- var current = _firstEntry;
-
- while (current != null)
- {
- if (current.Value.Equals(item))
- {
- if (prev == null)
- {
- // First entry
- _firstEntry = current.Next;
- }
- else
- {
- if (current == _firstEntry)
- {
- _firstEntry = prev.Next;
- }
- else
- {
- prev.Next = current.Next;
- }
- }
- _count--;
- return;
- }
-
- prev = current;
- current = current.Next;
- }
+ return dictionary.Contains(item);
  }
 
  public void ExceptWith(IEnumerable<T> entries)
  {
  foreach (var entry in entries)
  {
- Remove(entry);
+ dictionary.Remove(entry);
  }
  }
 
  public IEnumerator<T> GetEnumerator()
  {
- var current = _firstEntry;
-
- while (current != null)
- {
- yield return current.Value;
- current = current.Next;
- }
+ var entries = dictionary.Keys.Cast<T>().ToArray();
+ foreach (var entry in entries) yield return entry;
  }
 
  IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();