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1 using System;
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2 using System.Threading;
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3 using Implab.Diagnostics;
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4
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5 namespace Implab.Components {
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6 public class PollingRunnableComponent : RunnableComponent {
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7 readonly Timer m_timer;
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8 readonly Func<Func<IPromise>, IPromise> m_dispatcher;
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9 readonly TimeSpan m_interval;
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10
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11 int m_processing;
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12 Promise m_pending;
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13
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14 protected PollingRunnableComponent(TimeSpan interval, Func<Func<IPromise>, IPromise> dispatcher, bool initialized) : base(initialized) {
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15 m_timer = new Timer(OnInternalTick);
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16
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17 m_interval = interval;
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18 m_dispatcher = dispatcher;
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19 }
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20
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21 protected override IPromise OnStart() {
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22 m_timer.Change(TimeSpan.Zero, m_interval);
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23
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24 return base.OnStart();
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25 }
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26
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27 void OnInternalTick(object state) {
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28 if (StartTick()) {
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29 try {
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30 AwaitTick(m_dispatcher != null ? m_dispatcher(OnTick) : OnTick());
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31 } catch (Exception error) {
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32 HandleTickError(error);
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33 }
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34 }
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35 }
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36
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37 /// <summary>
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38 /// Starts the tick handler.
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39 /// </summary>
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40 /// <returns>boolean value, true - the new tick handler may be invoked, false - a tick handler is already running or a component isn't running.</returns>
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41 /// <remarks>
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42 /// If the component is stopping no new handlers can be run. Every successful call to this method must be completed with either AwaitTick or HandleTickError handlers.
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43 /// </remarks>
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44 protected virtual bool StartTick() {
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45 if (State == ExecutionState.Running && Interlocked.CompareExchange(ref m_processing, 1, 0) == 0) {
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46 m_pending = new Promise();
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47 m_pending
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48 .On(() => m_processing = 0, PromiseEventType.All)
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49 .On(null, LogTickError);
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50 return true;
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51 }
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52 return false;
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53 }
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54
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55 protected virtual void AwaitTick(IPromise tick) {
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56 if (tick == null) {
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57 m_pending.Resolve();
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58 } else {
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59 tick.On(
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60 m_pending.Resolve,
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61 m_pending.Reject,
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62 m_pending.CancelOperation
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63 );
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64 m_pending.CancellationRequested(tick.Cancel);
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65 }
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66 }
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67
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68 protected virtual void HandleTickError(Exception error) {
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69 m_pending.Reject(error);
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70 }
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71
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72 protected virtual void LogTickError(Exception error) {
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73 }
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74
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75 protected virtual IPromise OnTick() {
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76 return Promise.SUCCESS;
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77 }
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78
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79 protected override IPromise OnStop() {
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80 m_timer.Change(-1, -1);
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81
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82 if (m_pending != null) {
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83 m_pending.Cancel();
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84 return m_pending.Then(base.OnStop);
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85 }
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86
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87 return base.OnStop();
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88 }
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89
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90 protected override void Dispose(bool disposing, Exception lastError) {
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91 if (disposing)
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92 Safe.Dispose(m_timer);
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93
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94 base.Dispose(disposing, lastError);
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95 }
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96 }
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97 }
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98
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