using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
 
namespace PostSharp.Samples.WeakEvent
{
  internal static class DelegateReferenceKeeper
  {
    private static readonly object staticObj = new object();
 
    private static readonly ConditionalWeakTable<object, List<Delegate>> table =
      new ConditionalWeakTable<object, List<Delegate>>();
 
    public static void AddReference(Delegate handler)
    {
      var list = table.GetOrCreateValue(handler.Target ?? staticObj);
      lock (list)
      {
        list.Add(handler);
      }
    }
 
    public static void RemoveReference(Delegate handler)
    {
      List<Delegate> list;
      if (table.TryGetValue(handler.Target ?? staticObj, out list))
      {
        lock (list)
        {
          list.Remove(handler);
        }
      }
    }
  }
}