annotate Implab/Components/DisposablePool.cs @ 176:0c3c69fe225b ref20160224

rewritten the text scanner
author cin
date Tue, 22 Mar 2016 18:58:40 +0300
parents b933ec88446e
children c52691faaf21
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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.Diagnostics;
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5 using System.Diagnostics.CodeAnalysis;
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6
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7 namespace Implab.Components {
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8 /// <summary>
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9 /// The base class for implementing pools of disposable objects.
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10 /// </summary>
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11 /// <remarks>
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12 /// <para>This class maintains a set of pre-created objects and which are frequently allocated and released
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13 /// by clients. The pool maintains maximum number of unsued object, any object above this limit is disposed,
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14 /// if the pool is empty it will create new objects on demand.</para>
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15 /// <para>Instances of this class are thread-safe.</para>
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16 /// </remarks>
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17 public abstract class DisposablePool<T> : IDisposable {
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18 readonly int m_size;
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19 readonly AsyncQueue<T> m_queue = new AsyncQueue<T>();
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20
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21 [SuppressMessage("Microsoft.Design", "CA1000:DoNotDeclareStaticMembersOnGenericTypes")]
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22 static readonly bool _isValueType = typeof(T).IsValueType;
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23
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24 bool m_disposed;
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25
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26 int m_count;
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27
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28 protected DisposablePool(int size) {
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29 m_size = size;
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30 }
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31
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32 protected DisposablePool() : this(Environment.ProcessorCount+1) {
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33 }
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34
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35 public T Allocate() {
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36 if (m_disposed)
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37 throw new ObjectDisposedException(ToString());
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38
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39 T instance;
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40 if (m_queue.TryDequeue(out instance)) {
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41 Interlocked.Decrement(ref m_count);
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42 } else {
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43 instance = CreateInstance();
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44 Debug.Assert(!Object.Equals(instance, default(T)) || _isValueType);
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45 }
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46 return instance;
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47 }
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48
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49 protected abstract T CreateInstance();
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50
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51 protected virtual void CleanupInstance(T instance) {
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52 }
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53
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54 public void Release(T instance) {
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55 if ( Object.Equals(instance,default(T)) && !_isValueType)
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56 return;
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57
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58 Thread.MemoryBarrier();
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59 if (m_count < m_size && !m_disposed) {
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60 Interlocked.Increment(ref m_count);
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61
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62 CleanupInstance(instance);
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63
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64 m_queue.Enqueue(instance);
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65
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66 // пока элемент возвращался в кеш, была начата операция освобождения всего кеша
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67 // и возможно уже законцена, в таком случае следует извлечь элемент обратно и
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68 // освободить его. Если операция освобождения кеша еще не заврешилась, то будет
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69 // изъят и освобожден произвольный элемен, что не повлияет на ход всего процесса.
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70 if (m_disposed && m_queue.TryDequeue(out instance) && instance is IDisposable)
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71 ((IDisposable)instance).Dispose() ;
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72
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73 } else {
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74 var disposable = instance as IDisposable;
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75 if (disposable != null)
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76 disposable.Dispose();
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77 }
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78 }
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79
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80 protected virtual void Dispose(bool disposing) {
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81 if (disposing) {
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82 m_disposed = true;
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83 T instance;
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84 while (m_queue.TryDequeue(out instance)) {
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85 var disposable = instance as IDisposable;
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86 if (disposable != null)
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87 disposable.Dispose();
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88 }
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89 }
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90 }
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91
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92 #region IDisposable implementation
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93
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94 public void Dispose() {
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95 Dispose(true);
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96 GC.SuppressFinalize(this);
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97 }
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98
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99 #endregion
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100 }
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101 }
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102