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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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145
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7 public abstract class AbstractEvent<THandler> : ICancellationToken, ICancellable {
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144
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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 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 MTQueue<THandler> m_extraHandlers;
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27 int m_handlerPointer = -1;
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28 int m_handlersCommited;
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29
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30 int m_cancelRequest;
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31 Exception m_cancelationReason;
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32 MTQueue<Action<Exception>> m_cancelationHandlers;
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33
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34
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35 #region state managment
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36 bool BeginTransit() {
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37 return UNRESOLVED_SATE == Interlocked.CompareExchange(ref m_state, TRANSITIONAL_STATE, UNRESOLVED_SATE);
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38 }
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39
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40 void CompleteTransit(int state) {
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41 if (TRANSITIONAL_STATE != Interlocked.CompareExchange(ref m_state, state, TRANSITIONAL_STATE))
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42 throw new InvalidOperationException("Can't complete transition when the object isn't in the transitional state");
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43 }
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44
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45 void WaitTransition() {
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46 while (m_state == TRANSITIONAL_STATE) {
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47 Thread.MemoryBarrier();
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48 }
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49 }
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50
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51 protected bool BeginSetResult() {
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52 if (!BeginTransit()) {
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53 WaitTransition();
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54 if (m_state != CANCELLED_STATE)
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55 throw new InvalidOperationException("The promise is already resolved");
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56 return false;
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57 }
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58 return true;
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59 }
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60
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61 protected void EndSetResult() {
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62 CompleteTransit(SUCCEEDED_STATE);
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63 OnSuccess();
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64 }
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65
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66
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67
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68 /// <summary>
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69 /// Выполняет обещание, сообщая об ошибке
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70 /// </summary>
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71 /// <remarks>
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72 /// Поскольку обещание должно работать в многопточной среде, при его выполнении сразу несколько потоков
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73 /// могу вернуть ошибку, при этом только первая будет использована в качестве результата, остальные
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74 /// будут проигнорированы.
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75 /// </remarks>
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76 /// <param name="error">Исключение возникшее при выполнении операции</param>
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77 /// <exception cref="InvalidOperationException">Данное обещание уже выполнено</exception>
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78 protected void SetError(Exception error) {
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79 if (BeginTransit()) {
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80 if (error is OperationCanceledException) {
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81 CompleteTransit(CANCELLED_STATE);
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82 m_error = error.InnerException;
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83 OnCancelled();
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84 } else {
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85 m_error = error is PromiseTransientException ? error.InnerException : error;
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86 CompleteTransit(REJECTED_STATE);
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87 OnError();
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88 }
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89 } else {
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90 WaitTransition();
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91 if (m_state == SUCCEEDED_STATE)
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92 throw new InvalidOperationException("The promise is already resolved");
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93 }
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94 }
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95
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96 /// <summary>
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97 /// Отменяет операцию, если это возможно.
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98 /// </summary>
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99 /// <remarks>Для определения была ли операция отменена следует использовать свойство <see cref="IsCancelled"/>.</remarks>
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100 protected void SetCancelled(Exception reason) {
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101 if (BeginTransit()) {
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102 m_error = reason;
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103 CompleteTransit(CANCELLED_STATE);
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104 OnCancelled();
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105 }
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106 }
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107
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108 protected abstract void SignalSuccess(THandler handler);
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109
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110 protected abstract void SignalError(THandler handler, Exception error);
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111
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112 protected abstract void SignalCancelled(THandler handler, Exception reason);
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113
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114 void OnSuccess() {
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115 var hp = m_handlerPointer;
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116 var slot = hp +1 ;
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117 while (slot < m_handlersCommited) {
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118 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) == hp) {
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119 SignalSuccess(m_handlers[slot]);
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120 }
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121 hp = m_handlerPointer;
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122 slot = hp +1 ;
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123 }
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124
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125
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126 if (m_extraHandlers != null) {
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127 THandler handler;
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128 while (m_extraHandlers.TryDequeue(out handler))
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129 SignalSuccess(handler);
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130 }
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131 }
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132
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133 void OnError() {
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134 var hp = m_handlerPointer;
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135 var slot = hp +1 ;
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136 while (slot < m_handlersCommited) {
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137 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) == hp) {
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138 SignalError(m_handlers[slot],m_error);
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139 }
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140 hp = m_handlerPointer;
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141 slot = hp +1 ;
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142 }
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143
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144 if (m_extraHandlers != null) {
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145 THandler handler;
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146 while (m_extraHandlers.TryDequeue(out handler))
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147 SignalError(handler, m_error);
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148 }
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149 }
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150
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151 void OnCancelled() {
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152 var hp = m_handlerPointer;
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153 var slot = hp +1 ;
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154 while (slot < m_handlersCommited) {
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155 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) == hp) {
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156 SignalCancelled(m_handlers[slot], m_error);
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157 }
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158 hp = m_handlerPointer;
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159 slot = hp +1 ;
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160 }
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161
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162 if (m_extraHandlers != null) {
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163 THandler handler;
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164 while (m_extraHandlers.TryDequeue(out handler))
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165 SignalCancelled(handler, m_error);
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166 }
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167 }
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168
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169 #endregion
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170
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171 protected abstract Signal GetResolveSignal();
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172
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173 #region synchronization traits
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174 protected void WaitResult(int timeout) {
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175 if (!IsResolved)
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176 GetResolveSignal().Wait(timeout);
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177
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178 switch (m_state) {
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179 case SUCCEEDED_STATE:
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180 return;
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181 case CANCELLED_STATE:
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182 throw new OperationCanceledException();
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183 case REJECTED_STATE:
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184 throw new TargetInvocationException(m_error);
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185 default:
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186 throw new ApplicationException(String.Format("Invalid promise state {0}", m_state));
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187 }
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188 }
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189 #endregion
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190
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191 #region handlers managment
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192
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193 protected void AddHandler(THandler handler) {
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194
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195 if (m_state > 1) {
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196 // the promise is in the resolved state, just invoke the handler
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197 InvokeHandler(handler);
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198 } else {
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199 var slot = Interlocked.Increment(ref m_handlersCount) - 1;
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200
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201 if (slot < RESERVED_HANDLERS_COUNT) {
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202
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203 m_handlers[slot] = handler;
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204
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205 while (slot != Interlocked.CompareExchange(ref m_handlersCommited, slot + 1, slot)) {
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206 }
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207
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208 if (m_state > 1) {
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209 do {
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210 var hp = m_handlerPointer;
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211 slot = hp + 1;
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212 if (slot < m_handlersCommited) {
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213 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) != hp)
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214 continue;
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215 InvokeHandler(m_handlers[slot]);
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216 }
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217 break;
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218 } while(true);
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219 }
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220 } else {
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221 if (slot == RESERVED_HANDLERS_COUNT) {
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222 m_extraHandlers = new MTQueue<THandler>();
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223 } else {
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224 while (m_extraHandlers == null)
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225 Thread.MemoryBarrier();
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226 }
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227
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228 m_extraHandlers.Enqueue(handler);
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229
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230 if (m_state > 1 && m_extraHandlers.TryDequeue(out handler))
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231 // if the promise have been resolved while we was adding the handler to the queue
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232 // we can't guarantee that someone is still processing it
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233 // therefore we need to fetch a handler from the queue and execute it
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234 // note that fetched handler may be not the one that we have added
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235 // even we can fetch no handlers at all :)
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236 InvokeHandler(handler);
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237 }
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238 }
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239 }
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240
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241 protected void InvokeHandler(THandler handler) {
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242 switch (m_state) {
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243 case SUCCEEDED_STATE:
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244 SignalSuccess(handler);
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245 break;
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246 case CANCELLED_STATE:
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247 SignalCancelled(handler, m_error);
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248 break;
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249 case REJECTED_STATE:
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250 SignalError(handler, m_error);
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251 break;
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252 default:
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253 throw new Exception(String.Format("Invalid promise state {0}", m_state));
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254 }
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255 }
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256
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257 #endregion
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258
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259 #region IPromise implementation
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260
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261 public bool IsResolved {
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262 get {
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263 Thread.MemoryBarrier();
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264 return m_state > 1;
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265 }
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266 }
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267
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268 public bool IsCancelled {
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269 get {
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270 Thread.MemoryBarrier();
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271 return m_state == CANCELLED_STATE;
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272 }
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273 }
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274
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275 #endregion
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276
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277 public Exception Error {
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278 get {
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279 return m_error;
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280 }
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281 }
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282
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145
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283 public bool CancelOperationIfRequested() {
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284 if (IsCancellationRequested) {
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285 CancelOperation(CancellationReason);
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286 return true;
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287 }
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288 return false;
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144
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289 }
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290
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291 public virtual void CancelOperation(Exception reason) {
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292 SetCancelled(reason);
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293 }
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294
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145
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295 public void CancellationRequested(Action<Exception> handler) {
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144
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296 Safe.ArgumentNotNull(handler, "handler");
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145
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297 if (IsCancellationRequested)
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298 handler(CancellationReason);
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144
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299
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300 if (m_cancelationHandlers == null)
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301 Interlocked.CompareExchange(ref m_cancelationHandlers, new MTQueue<Action<Exception>>(), null);
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302
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303 m_cancelationHandlers.Enqueue(handler);
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304
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145
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305 if (IsCancellationRequested && m_cancelationHandlers.TryDequeue(out handler))
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144
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306 // TryDeque implies MemoryBarrier()
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307 handler(m_cancelationReason);
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308 }
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309
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145
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310 public bool IsCancellationRequested {
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144
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311 get {
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312 do {
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313 if (m_cancelRequest == CANCEL_NOT_REQUESTED)
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314 return false;
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315 if (m_cancelRequest == CANCEL_REQUESTED)
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316 return true;
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317 Thread.MemoryBarrier();
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318 } while(true);
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319 }
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320 }
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321
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145
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322 public Exception CancellationReason {
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144
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323 get {
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324 do {
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325 Thread.MemoryBarrier();
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326 } while(m_cancelRequest == CANCEL_REQUESTING);
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327
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328 return m_cancelationReason;
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329 }
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330 }
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331
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332 #region ICancellable implementation
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333
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334 public void Cancel() {
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335 Cancel(null);
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336 }
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337
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338 public void Cancel(Exception reason) {
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145
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339 if (CANCEL_NOT_REQUESTED == Interlocked.CompareExchange(ref m_cancelRequest, CANCEL_REQUESTING, CANCEL_NOT_REQUESTED)) {
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144
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340 m_cancelationReason = reason;
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341 m_cancelRequest = CANCEL_REQUESTED;
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342 if (m_cancelationHandlers != null) {
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343 Action<Exception> handler;
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344 while (m_cancelationHandlers.TryDequeue(out handler))
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345 handler(m_cancelationReason);
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346 }
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347 }
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348 }
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349
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350 #endregion
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351 }
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352 }
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353
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