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comparison Implab/Parallels/SimpleAsyncQueue.cs @ 233:d6fe09f5592c v2

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Improved AsyncQueue Removed ImplabFx
author cin
date Wed, 04 Oct 2017 15:44:47 +0300
parents
children cbe10ac0731e
comparison
equal deleted inserted replaced
229:5f7a3e1d32b9 233:d6fe09f5592c
1 using System.Threading;
2 using System.Collections.Generic;
3 using System;
4 using System.Collections;
5
6 namespace Implab.Parallels {
7 public class SimpleAsyncQueue<T> : IEnumerable<T> {
8 class Node {
9 public Node(T value) {
10 this.value = value;
11 }
12 public readonly T value;
13 public volatile Node next;
14 }
15
16 // the reader and the writer are mainteined completely independent,
17 // the reader can read next item when m_first.next is not null
18 // the writer creates the a new node, moves m_last to this node and
19 // only after that restores the reference from the previous node
20 // making available the reader to read the new node.
21
22 Node m_first; // position on the node which is already read
23 Node m_last; // position on the node which is already written
24
25 public SimpleAsyncQueue() {
26 m_first = m_last = new Node(default(T));
27 }
28
29 public void Enqueue(T value) {
30 var next = new Node(value);
31
32 // Interlocaked.CompareExchange implies Thread.MemoryBarrier();
33 // to ensure that the next node is completely constructed
34 var last = Interlocked.Exchange(ref m_last, next);
35
36 // release-fence
37 last.next = next;
38
39 }
40
41 public bool TryDequeue(out T value) {
42 Node first;
43 Node next;
44
45 Thread.MemoryBarrier(); // ensure m_first is fresh
46 SpinWait spin = new SpinWait();
47 do {
48 first = m_first;
49 // aquire-fence
50 next = first.next;
51 if (next == null) {
52 value = default(T);
53 return false;
54 }
55
56 if (first == Interlocked.CompareExchange(ref m_first, next, first))
57 // head succesfully updated
58 break;
59 spin.SpinOnce();
60 } while (true);
61
62 value = next.value;
63 return true;
64 }
65
66 #region IEnumerable implementation
67
68 class Enumerator : IEnumerator<T> {
69 Node m_current;
70 Node m_first;
71
72 public Enumerator(Node first) {
73 m_first = first;
74 }
75
76 #region IEnumerator implementation
77
78 public bool MoveNext() {
79 m_current = m_current == null ? m_first : m_current.next;
80 return m_current != null;
81 }
82
83 public void Reset() {
84 m_current = null;
85 }
86
87 object IEnumerator.Current {
88 get {
89 if (m_current == null)
90 throw new InvalidOperationException();
91 return m_current.value;
92 }
93 }
94
95 #endregion
96
97 #region IDisposable implementation
98
99 public void Dispose() {
100 }
101
102 #endregion
103
104 #region IEnumerator implementation
105
106 public T Current {
107 get {
108 if (m_current == null)
109 throw new InvalidOperationException();
110 return m_current.value;
111 }
112 }
113
114 #endregion
115 }
116
117 public IEnumerator<T> GetEnumerator() {
118 return new Enumerator(m_first);
119 }
120
121 #endregion
122
123 #region IEnumerable implementation
124
125 IEnumerator IEnumerable.GetEnumerator() {
126 return GetEnumerator();
127 }
128
129 #endregion
130 }
131 }