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1 using System;
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2 using Implab.Parallels;
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3 using System.Threading;
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4 using System.Reflection;
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5
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6 namespace Implab {
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7 public abstract class AbstractPromise<THandler> {
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8
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9 const int UNRESOLVED_SATE = 0;
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10 const int TRANSITIONAL_STATE = 1;
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11 const int SUCCEEDED_STATE = 2;
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12 const int REJECTED_STATE = 3;
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13 const int CANCELLED_STATE = 4;
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14
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15 int m_state;
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16 Exception m_error;
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17
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18 readonly AsyncQueue<THandler> m_handlers = new AsyncQueue<THandler>();
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19
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20 #region state managment
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21 bool BeginTransit() {
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22 return UNRESOLVED_SATE == Interlocked.CompareExchange(ref m_state, TRANSITIONAL_STATE, UNRESOLVED_SATE);
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23 }
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24
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25 void CompleteTransit(int state) {
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26 if (TRANSITIONAL_STATE != Interlocked.CompareExchange(ref m_state, state, TRANSITIONAL_STATE))
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27 throw new InvalidOperationException("Can't complete transition when the object isn't in the transitional state");
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28 }
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29
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30 void WaitTransition() {
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31 while (m_state == TRANSITIONAL_STATE) {
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32 Thread.MemoryBarrier();
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33 }
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34 }
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35
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36 protected void BeginSetResult() {
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37 if (!BeginTransit()) {
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38 WaitTransition();
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39 if (m_state != CANCELLED_STATE)
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40 throw new InvalidOperationException("The promise is already resolved");
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41 }
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42 }
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43
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44 protected void EndSetResult() {
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45 CompleteTransit(SUCCEEDED_STATE);
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46 OnSuccess();
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47 }
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48
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49
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50
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51 /// <summary>
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52 /// Выполняет обещание, сообщая об ошибке
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53 /// </summary>
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54 /// <remarks>
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55 /// Поскольку обещание должно работать в многопточной среде, при его выполнении сразу несколько потоков
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56 /// могу вернуть ошибку, при этом только первая будет использована в качестве результата, остальные
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57 /// будут проигнорированы.
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58 /// </remarks>
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59 /// <param name="error">Исключение возникшее при выполнении операции</param>
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60 /// <exception cref="InvalidOperationException">Данное обещание уже выполнено</exception>
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61 protected void SetError(Exception error) {
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62 if (BeginTransit()) {
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63 m_error = error is PromiseTransientException ? error.InnerException : error;
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64 CompleteTransit(REJECTED_STATE);
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65 OnError();
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66 } else {
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67 WaitTransition();
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68 if (m_state == SUCCEEDED_STATE)
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69 throw new InvalidOperationException("The promise is already resolved");
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70 }
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71 }
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72
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73 /// <summary>
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74 /// Отменяет операцию, если это возможно.
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75 /// </summary>
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76 /// <remarks>Для определения была ли операция отменена следует использовать свойство <see cref="IsCancelled"/>.</remarks>
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77 protected void SetCancelled() {
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78 if (BeginTransit()) {
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79 CompleteTransit(CANCELLED_STATE);
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80 OnCancelled();
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81 }
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82 }
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83
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84 protected abstract void SignalSuccess(THandler handler);
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85
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86 protected abstract void SignalError(THandler handler, Exception error);
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87
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88 protected abstract void SignalCancelled(THandler handler);
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89
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90 void OnSuccess() {
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91 THandler handler;
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92 while (m_handlers.TryDequeue(out handler))
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93 SignalSuccess(handler);
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94 }
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95
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96 void OnError() {
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97 THandler handler;
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98 while (m_handlers.TryDequeue(out handler))
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99 SignalError(handler,m_error);
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100 }
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101
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102 void OnCancelled() {
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103 THandler handler;
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104 while (m_handlers.TryDequeue(out handler))
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105 SignalCancelled(handler);
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106 }
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107
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108 #endregion
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109
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110 protected abstract void Listen(PromiseEventType events, Action handler);
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111
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112 #region synchronization traits
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113 protected void WaitResult(int timeout) {
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114 if (!IsResolved) {
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115 var lk = new object();
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116
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117 Listen(PromiseEventType.All, () => {
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118 lock(lk) {
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119 Monitor.Pulse(lk);
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120 }
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121 });
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122
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123 lock (lk) {
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124 while(!IsResolved) {
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125 if(!Monitor.Wait(lk,timeout))
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126 throw new TimeoutException();
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127 }
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128 }
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129
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130 }
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131 switch (m_state) {
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132 case SUCCEEDED_STATE:
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133 return;
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134 case CANCELLED_STATE:
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135 throw new OperationCanceledException();
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136 case REJECTED_STATE:
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137 throw new TargetInvocationException(m_error);
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138 default:
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139 throw new ApplicationException(String.Format("Invalid promise state {0}", m_state));
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140 }
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141 }
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142 #endregion
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143
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144 #region handlers managment
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145
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146 protected void AddHandler(THandler handler) {
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147
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148 if (IsResolved) {
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149 InvokeHandler(handler);
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150
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151 } else {
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152 // the promise is in the resolved state, just invoke the handler
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153 m_handlers.Enqueue(handler);
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154
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155
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156 if (IsResolved && m_handlers.TryDequeue(out handler))
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157 // if the promise have been resolved while we was adding the handler to the queue
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158 // we can't guarantee that someone is still processing it
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159 // therefore we need to fetch a handler from the queue and execute it
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160 // note that fetched handler may be not the one that we have added
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161 // even we can fetch no handlers at all :)
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162 InvokeHandler(handler);
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163 }
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164 }
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165
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166 protected void InvokeHandler(THandler handler) {
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167 switch (m_state) {
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168 case SUCCEEDED_STATE:
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169 SignalSuccess(handler);
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170 break;
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171 case CANCELLED_STATE:
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172 SignalCancelled(handler);
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173 break;
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174 case REJECTED_STATE:
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175 SignalError(handler, m_error);
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176 break;
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177 default:
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178 throw new Exception(String.Format("Invalid promise state {0}", m_state));
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179 }
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180 }
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181
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182 #endregion
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183
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184 #region IPromise implementation
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185
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186 public void Join(int timeout) {
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187 WaitResult(timeout);
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188 }
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189
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190 public void Join() {
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191 WaitResult(-1);
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192 }
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193
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194 public bool IsResolved {
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195 get {
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196 Thread.MemoryBarrier();
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197 return m_state > 1;
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198 }
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199 }
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200
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201 public bool IsCancelled {
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202 get {
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203 Thread.MemoryBarrier();
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204 return m_state == CANCELLED_STATE;
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205 }
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206 }
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207
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208 #endregion
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209
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210 #region ICancellable implementation
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211
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212 public void Cancel() {
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213 SetCancelled();
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214 }
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215
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216 #endregion
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217 }
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218 }
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219
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