2 // TaskCompletionQueue.cs
5 // Jérémie Laval <jeremie dot laval at xamarin dot com>
7 // Copyright 2011 Xamarin Inc (http://www.xamarin.com).
9 // Permission is hereby granted, free of charge, to any person obtaining a copy
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13 // copies of the Software, and to permit persons to whom the Software is
14 // furnished to do so, subject to the following conditions:
16 // The above copyright notice and this permission notice shall be included in
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19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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32 using System.Threading;
33 using System.Collections.Generic;
34 using System.Collections.Concurrent;
36 namespace System.Threading.Tasks
38 internal struct TaskCompletionQueue<TCompletion> where TCompletion : class
41 ConcurrentOrderedList<TCompletion> completed;
43 public void Add (TCompletion continuation)
45 if (single == null && Interlocked.CompareExchange (ref single, continuation, null) == null)
47 if (completed == null)
48 Interlocked.CompareExchange (ref completed, new ConcurrentOrderedList<TCompletion> (), null);
49 completed.TryAdd (continuation);
52 public bool Remove (TCompletion continuation)
54 TCompletion temp = single;
55 if (temp != null && temp == continuation && Interlocked.CompareExchange (ref single, null, continuation) == continuation)
57 if (completed != null)
58 return completed.TryRemove (continuation);
62 public bool HasElements {
64 Thread.MemoryBarrier ();
65 return single != null || (completed != null && completed.Count != 0);
69 public bool TryGetNextCompletion (out TCompletion continuation)
73 if (single != null && (continuation = Interlocked.Exchange (ref single, null)) != null)
76 return completed != null && completed.TryPop (out continuation);