opensim-development – Blame information for rev 1
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1 | eva | 1 | /* |
2 | * Copyright (c) 2009, openmetaverse.org |
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3 | * All rights reserved. |
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4 | * |
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5 | * - Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions are met: |
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7 | * |
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8 | * - Redistributions of source code must retain the above copyright notice, this |
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9 | * list of conditions and the following disclaimer. |
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10 | * - Neither the name of the openmetaverse.org nor the names |
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11 | * of its contributors may be used to endorse or promote products derived from |
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12 | * this software without specific prior written permission. |
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13 | * |
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14 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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15 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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16 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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17 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
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18 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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19 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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20 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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21 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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22 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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23 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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24 | * POSSIBILITY OF SUCH DAMAGE. |
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25 | */ |
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26 | |||
27 | using System; |
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28 | using System.Threading; |
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29 | |||
30 | namespace OpenSim.Framework |
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31 | { |
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32 | public sealed class LocklessQueue<T> |
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33 | { |
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34 | private sealed class SingleLinkNode |
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35 | { |
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36 | public SingleLinkNode Next; |
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37 | public T Item; |
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38 | } |
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39 | |||
40 | SingleLinkNode head; |
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41 | SingleLinkNode tail; |
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42 | int count; |
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43 | |||
44 | public int Count { get { return count; } } |
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45 | |||
46 | public LocklessQueue() |
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47 | { |
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48 | Init(); |
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49 | } |
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50 | |||
51 | public void Enqueue(T item) |
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52 | { |
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53 | SingleLinkNode oldTail = null; |
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54 | SingleLinkNode oldTailNext; |
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55 | |||
56 | SingleLinkNode newNode = new SingleLinkNode(); |
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57 | newNode.Item = item; |
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58 | |||
59 | bool newNodeWasAdded = false; |
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60 | |||
61 | while (!newNodeWasAdded) |
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62 | { |
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63 | oldTail = tail; |
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64 | oldTailNext = oldTail.Next; |
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65 | |||
66 | if (tail == oldTail) |
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67 | { |
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68 | if (oldTailNext == null) |
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69 | newNodeWasAdded = CAS(ref tail.Next, null, newNode); |
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70 | else |
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71 | CAS(ref tail, oldTail, oldTailNext); |
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72 | } |
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73 | } |
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74 | |||
75 | CAS(ref tail, oldTail, newNode); |
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76 | Interlocked.Increment(ref count); |
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77 | } |
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78 | |||
79 | public bool Dequeue(out T item) |
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80 | { |
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81 | item = default(T); |
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82 | SingleLinkNode oldHead = null; |
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83 | bool haveAdvancedHead = false; |
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84 | |||
85 | while (!haveAdvancedHead) |
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86 | { |
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87 | oldHead = head; |
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88 | SingleLinkNode oldTail = tail; |
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89 | SingleLinkNode oldHeadNext = oldHead.Next; |
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90 | |||
91 | if (oldHead == head) |
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92 | { |
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93 | if (oldHead == oldTail) |
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94 | { |
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95 | if (oldHeadNext == null) |
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96 | return false; |
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97 | |||
98 | CAS(ref tail, oldTail, oldHeadNext); |
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99 | } |
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100 | else |
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101 | { |
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102 | item = oldHeadNext.Item; |
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103 | haveAdvancedHead = CAS(ref head, oldHead, oldHeadNext); |
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104 | if (haveAdvancedHead) |
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105 | { |
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106 | oldHeadNext.Item = default(T); |
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107 | oldHead.Next = null; |
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108 | } |
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109 | } |
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110 | } |
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111 | } |
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112 | |||
113 | Interlocked.Decrement(ref count); |
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114 | return true; |
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115 | } |
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116 | |||
117 | public void Clear() |
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118 | { |
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119 | // ugly |
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120 | T item; |
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121 | while(count > 0) |
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122 | Dequeue(out item); |
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123 | Init(); |
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124 | } |
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125 | |||
126 | private void Init() |
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127 | { |
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128 | count = 0; |
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129 | head = tail = new SingleLinkNode(); |
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130 | } |
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131 | |||
132 | private static bool CAS(ref SingleLinkNode location, SingleLinkNode comparand, SingleLinkNode newValue) |
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133 | { |
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134 | return |
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135 | (object)comparand == |
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136 | (object)Interlocked.CompareExchange<SingleLinkNode>(ref location, newValue, comparand); |
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137 | } |
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138 | } |
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139 | } |