annotate Implab/AbstractEvent.cs @ 196:40d7fed4a09e

fixed promise chaining behavior, the error handler doesn't handle result or cancellation handlers exceptions these exceptions are propagated to the next handlers.
author cin
date Mon, 29 Aug 2016 23:15:51 +0300
parents 75103928da09
children d6fe09f5592c
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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 AbstractEvent<THandler> : ICancellationToken, ICancellable {
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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 protected const int SUCCEEDED_STATE = 2;
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12 protected const int REJECTED_STATE = 3;
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13 protected const int CANCELLED_STATE = 4;
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14
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15 const int CANCEL_NOT_REQUESTED = 0;
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16 const int CANCEL_REQUESTING = 1;
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17 const int CANCEL_REQUESTED = 2;
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18
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19 const int RESERVED_HANDLERS_COUNT = 4;
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20
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21 int m_state;
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22 Exception m_error;
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23 int m_handlersCount;
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24
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25 //readonly THandler[] m_handlers = new THandler[RESERVED_HANDLERS_COUNT];
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26 THandler[] m_handlers;
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27 MTQueue<THandler> m_extraHandlers;
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28 int m_handlerPointer = -1;
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29 int m_handlersCommited;
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30
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31 int m_cancelRequest;
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32 Exception m_cancelationReason;
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33 MTQueue<Action<Exception>> m_cancelationHandlers;
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34
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35
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36 #region state managment
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37 bool BeginTransit() {
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38 return UNRESOLVED_SATE == Interlocked.CompareExchange(ref m_state, TRANSITIONAL_STATE, UNRESOLVED_SATE);
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39 }
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40
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41 void CompleteTransit(int state) {
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42 if (TRANSITIONAL_STATE != Interlocked.CompareExchange(ref m_state, state, TRANSITIONAL_STATE))
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43 throw new InvalidOperationException("Can't complete transition when the object isn't in the transitional state");
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44 }
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45
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46 void WaitTransition() {
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47 while (m_state == TRANSITIONAL_STATE) {
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48 Thread.MemoryBarrier();
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49 }
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50 }
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51
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52 protected bool BeginSetResult() {
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53 if (!BeginTransit()) {
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54 WaitTransition();
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55 if (m_state != CANCELLED_STATE)
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56 throw new InvalidOperationException("The promise is already resolved");
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57 return false;
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58 }
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59 return true;
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60 }
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61
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62 protected void EndSetResult() {
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63 CompleteTransit(SUCCEEDED_STATE);
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64 Signal();
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65 }
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66
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67
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68
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69 /// <summary>
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70 /// Выполняет обещание, сообщая об ошибке
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71 /// </summary>
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72 /// <remarks>
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73 /// Поскольку обещание должно работать в многопточной среде, при его выполнении сразу несколько потоков
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74 /// могу вернуть ошибку, при этом только первая будет использована в качестве результата, остальные
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75 /// будут проигнорированы.
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76 /// </remarks>
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77 /// <param name="error">Исключение возникшее при выполнении операции</param>
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78 /// <exception cref="InvalidOperationException">Данное обещание уже выполнено</exception>
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79 protected void SetError(Exception error) {
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80 if (BeginTransit()) {
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81 m_error = error;
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82 CompleteTransit(REJECTED_STATE);
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83
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84 Signal();
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85 } else {
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86 WaitTransition();
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87 if (m_state == SUCCEEDED_STATE)
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88 throw new InvalidOperationException("The promise is already resolved");
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89 }
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90 }
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91
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92 /// <summary>
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93 /// Отменяет операцию, если это возможно.
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94 /// </summary>
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95 /// <remarks>Для определения была ли операция отменена следует использовать свойство <see cref="IsCancelled"/>.</remarks>
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96 protected void SetCancelled(Exception reason) {
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97 if (BeginTransit()) {
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98 m_error = reason;
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99 CompleteTransit(CANCELLED_STATE);
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100 Signal();
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101 }
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102 }
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103
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104 protected abstract void SignalHandler(THandler handler, int signal);
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105
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106 void Signal() {
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107 var hp = m_handlerPointer;
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108 var slot = hp +1 ;
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109 while (slot < m_handlersCommited) {
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110 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) == hp) {
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111 SignalHandler(m_handlers[slot], m_state);
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112 }
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113 hp = m_handlerPointer;
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114 slot = hp +1 ;
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115 }
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116
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117
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118 if (m_extraHandlers != null) {
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119 THandler handler;
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120 while (m_extraHandlers.TryDequeue(out handler))
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121 SignalHandler(handler, m_state);
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122 }
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123 }
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124
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125 #endregion
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126
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127 protected abstract Signal GetResolveSignal();
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128
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129 #region synchronization traits
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130 protected void WaitResult(int timeout) {
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131 if (!(IsResolved || GetResolveSignal().Wait(timeout)))
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132 throw new TimeoutException();
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133
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134 switch (m_state) {
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135 case SUCCEEDED_STATE:
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136 return;
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137 case CANCELLED_STATE:
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138 throw new OperationCanceledException("The operation has been cancelled", m_error);
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139 case REJECTED_STATE:
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140 throw new TargetInvocationException(m_error);
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141 default:
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142 throw new ApplicationException(String.Format("The promise state {0} is invalid", m_state));
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143 }
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144 }
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145 #endregion
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146
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147 #region handlers managment
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148
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149 protected void AddHandler(THandler handler) {
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150
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151 if (m_state > 1) {
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152 // the promise is in the resolved state, just invoke the handler
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153 SignalHandler(handler, m_state);
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154 } else {
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155 var slot = Interlocked.Increment(ref m_handlersCount) - 1;
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156
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157 if (slot < RESERVED_HANDLERS_COUNT) {
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158
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159 if (slot == 0) {
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160 m_handlers = new THandler[RESERVED_HANDLERS_COUNT];
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161 } else {
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162 while (m_handlers == null)
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163 Thread.MemoryBarrier();
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164 }
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165
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166 m_handlers[slot] = handler;
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167
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168 while (slot != Interlocked.CompareExchange(ref m_handlersCommited, slot + 1, slot)) {
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169 }
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170
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171 if (m_state > 1) {
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172 do {
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173 var hp = m_handlerPointer;
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174 slot = hp + 1;
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175 if (slot < m_handlersCommited) {
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176 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) != hp)
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177 continue;
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178 SignalHandler(m_handlers[slot], m_state);
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179 }
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180 break;
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181 } while(true);
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182 }
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183 } else {
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184 if (slot == RESERVED_HANDLERS_COUNT) {
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185 m_extraHandlers = new MTQueue<THandler>();
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186 } else {
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187 while (m_extraHandlers == null)
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188 Thread.MemoryBarrier();
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189 }
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190
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191 m_extraHandlers.Enqueue(handler);
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192
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193 if (m_state > 1 && m_extraHandlers.TryDequeue(out handler))
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194 // if the promise have been resolved while we was adding the handler to the queue
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195 // we can't guarantee that someone is still processing it
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196 // therefore we need to fetch a handler from the queue and execute it
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197 // note that fetched handler may be not the one that we have added
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198 // even we can fetch no handlers at all :)
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199 SignalHandler(handler, m_state);
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200 }
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201 }
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202 }
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203
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204 #endregion
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205
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206 #region IPromise implementation
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207
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208 public bool IsResolved {
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209 get {
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210 Thread.MemoryBarrier();
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211 return m_state > 1;
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212 }
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213 }
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214
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215 public bool IsCancelled {
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216 get {
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217 Thread.MemoryBarrier();
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218 return m_state == CANCELLED_STATE;
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219 }
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220 }
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221
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222 #endregion
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223
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224 public Exception Error {
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225 get {
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226 return m_error;
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227 }
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228 }
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229
145
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230 public bool CancelOperationIfRequested() {
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231 if (IsCancellationRequested) {
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232 CancelOperation(CancellationReason);
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233 return true;
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234 }
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235 return false;
144
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236 }
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237
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238 public virtual void CancelOperation(Exception reason) {
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239 SetCancelled(reason);
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240 }
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241
145
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242 public void CancellationRequested(Action<Exception> handler) {
144
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243 Safe.ArgumentNotNull(handler, "handler");
145
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244 if (IsCancellationRequested)
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245 handler(CancellationReason);
144
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246
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247 if (m_cancelationHandlers == null)
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248 Interlocked.CompareExchange(ref m_cancelationHandlers, new MTQueue<Action<Exception>>(), null);
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249
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250 m_cancelationHandlers.Enqueue(handler);
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251
145
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252 if (IsCancellationRequested && m_cancelationHandlers.TryDequeue(out handler))
144
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253 // TryDeque implies MemoryBarrier()
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254 handler(m_cancelationReason);
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255 }
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256
145
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257 public bool IsCancellationRequested {
144
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258 get {
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259 do {
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260 if (m_cancelRequest == CANCEL_NOT_REQUESTED)
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261 return false;
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262 if (m_cancelRequest == CANCEL_REQUESTED)
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263 return true;
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264 Thread.MemoryBarrier();
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265 } while(true);
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266 }
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267 }
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268
145
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269 public Exception CancellationReason {
144
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270 get {
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271 do {
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272 Thread.MemoryBarrier();
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273 } while(m_cancelRequest == CANCEL_REQUESTING);
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274
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275 return m_cancelationReason;
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276 }
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277 }
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278
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279 #region ICancellable implementation
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280
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281 public void Cancel() {
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282 Cancel(null);
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283 }
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284
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285 public void Cancel(Exception reason) {
145
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diff changeset
286 if (CANCEL_NOT_REQUESTED == Interlocked.CompareExchange(ref m_cancelRequest, CANCEL_REQUESTING, CANCEL_NOT_REQUESTED)) {
144
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287 m_cancelationReason = reason;
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288 m_cancelRequest = CANCEL_REQUESTED;
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289 if (m_cancelationHandlers != null) {
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290 Action<Exception> handler;
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291 while (m_cancelationHandlers.TryDequeue(out handler))
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292 handler(m_cancelationReason);
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parents:
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293 }
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294 }
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295 }
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parents:
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296
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297 #endregion
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parents:
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298 }
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parents:
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299 }
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parents:
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300