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1 using System;
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2 using System.Threading;
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3 using System.Threading.Tasks;
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4
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5 namespace Implab.Components {
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6 public abstract class PollingComponent : RunnableComponent {
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7
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8 readonly Timer m_timer;
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9
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10 readonly CancellationTokenSource m_cancellation = new CancellationTokenSource();
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11
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12 Task m_pending;
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13 Task m_poll;
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14
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15 /// <summary>
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16 /// Poll interval in milliseconds.
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17 /// </summary>
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18 /// <returns></returns>
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19 public int Interval { get; set; }
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20
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21 /// <summary>
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22 /// Delay to the first poll after start in milliseconds
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23 /// </summary>
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24 /// <returns></returns>
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25 public int Delay { get; set; }
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26
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27 /// <summary>
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28 /// Indicates how to handle unhandled exceptions in <see cref="Poll()"/> method.
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29 /// </summary>
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30 /// <returns></returns>
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31 public bool FailOnError { get; set; }
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32
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33 /// <summary>
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34 /// Event for the unhandled exceptions in <see cref="Poll()"/> method.
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35 /// </summary>
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36 public event EventHandler<UnhandledExceptionEventArgs> UnhandledException;
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37
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38 protected PollingComponent(bool initialized) : base(initialized) {
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39 m_timer = new Timer(OnTimer);
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40 }
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41
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42 protected override void RunInternal() {
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43 ScheduleNextPoll(Delay);
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44 }
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45
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46
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47 protected override async Task StopInternalAsync(CancellationToken ct) {
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48 // component in Stopping state, no new polls will be scheduled
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49 m_cancellation.Cancel();
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50 try {
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51 // await for pending poll
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52 await m_poll;
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53 } catch (OperationCanceledException) {
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54 // OK
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55 }
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56 }
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258
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57
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58 protected abstract Task Poll(CancellationToken ct);
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59
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60 void ScheduleNextPoll(int timeout) {
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61 lock (SynchronizationObject) {
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62 if (State == ExecutionState.Running) {
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63 m_pending = Safe.CreateTask(m_cancellation.Token);
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64 m_poll = m_pending.Then(() => Poll(m_cancellation.Token));
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65 m_timer.Change(timeout, Timeout.Infinite);
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66 }
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67 }
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68 }
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69
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259
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70 async void OnTimer(object state) {
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71 try {
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72 m_pending.Start();
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73 await m_poll;
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74 ScheduleNextPoll(Interval);
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75 } catch (Exception e) {
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76 UnhandledException.DispatchEvent(this, new UnhandledExceptionEventArgs(e, false));
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260
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77
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78 if (FailOnError)
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79 Fail(e);
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80 else
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81 ScheduleNextPoll(Interval);
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82 }
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83
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84 }
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85
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86 protected override void Dispose(bool disposing) {
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87 if (disposing)
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88 Safe.Dispose(m_timer, m_cancellation);
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89 base.Dispose(disposing);
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90 }
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91
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92 }
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93 } |
