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145
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1 using System;
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2 using System.Threading;
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3
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4 namespace Implab {
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5 public class FuncChainTaskBase<TResult> : AbstractPromise<TResult> {
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6 readonly Func<Exception, IPromise<TResult>> m_error;
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7 readonly Func<Exception, IPromise<TResult>> m_cancel;
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8
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9 int m_cancelationLock;
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10
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11 protected FuncChainTaskBase( Func<Exception, IPromise<TResult>> error, Func<Exception, IPromise<TResult>> cancel) {
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12 m_error = error;
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13 m_cancel = cancel;
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14 }
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15
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16 public void Reject(Exception error) {
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17 if (LockCancelation())
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18 HandleErrorInternal(error);
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19 }
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20
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21 public override void CancelOperation(Exception reason) {
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22 if (m_cancel != null && LockCancelation()) {
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23 try {
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24 Observe(m_cancel(reason));
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25 } catch(Exception err) {
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26 HandleErrorInternal(err);
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27 }
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28 }
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29
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30 }
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31
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32 protected void HandleErrorInternal(Exception error) {
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33 if (m_error != null) {
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34 try {
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35 Observe(m_error(error));
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36 } catch(Exception err) {
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37 SetError(err);
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38 }
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39 } else {
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40 SetError(error);
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41 }
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42 }
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43
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44 protected void Observe(IPromise<TResult> operation) {
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45 if (operation == null)
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46 throw new NullReferenceException("The task returned null promise");
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47
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48 // pass operation results to the current promise
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49 operation.On(SetResult, SetError, SetCancelled);
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50
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51 // pass the cancelation request
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52 CancellationRequested(operation.Cancel);
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53 }
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54
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55 protected bool LockCancelation() {
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56 return 0 == Interlocked.CompareExchange(ref m_cancelationLock, 1, 0);
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57 }
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58 }
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59 }
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60
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