mcs/class/referencesource/System.Core/System/Linq/Parallel/QueryOperators/QueryOperatorEnumerator.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   7 //
   8 // QueryOperatorEnumerator.cs
   9 //
  10 // <OWNER>Microsoft</OWNER>
  11 //
  12 // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
  13
  14 using System.Collections;
  15 using System.Collections.Generic;
  16 using System.Diagnostics.Contracts;
  17 #if SILVERLIGHT
  18 using System.Core; // for System.Core.SR
  19 #endif
  20
  21 namespace System.Linq.Parallel
  22 {
  23     /// <summary>
  24     /// A common enumerator type that unifies all query operator enumerators.
  25     /// </summary>
  26     /// <typeparam name="TElement"></typeparam>
  27     /// <typeparam name="TKey"></typeparam>
  28     internal abstract class QueryOperatorEnumerator<TElement, TKey>
  29     {
  30         // Moves the position of the enumerator forward by one, and simultaneously returns
  31         // the (new) current element and key. If empty, false is returned.
  32         internal abstract bool MoveNext(ref TElement currentElement, ref TKey currentKey);
  33
  34         // Standard implementation of the disposable pattern.
  35         public void Dispose()
  36         {
  37             Dispose(true);
  38         }
  39
  40         protected virtual void Dispose(bool disposing)
  41         {
  42             // This is a no-op by default.  Subclasses can override.
  43         }
  44
  45         internal virtual void Reset()
  46         {
  47             // This is a no-op by default.  Subclasses can override.
  48         }
  49
  50         //-----------------------------------------------------------------------------------
  51         // A simple way to turn a query operator enumerator into a "classic" one.
  52         //
  53
  54         internal IEnumerator<TElement> AsClassicEnumerator()
  55         {
  56             return new QueryOperatorClassicEnumerator(this);
  57         }
  58
  59         class QueryOperatorClassicEnumerator : IEnumerator<TElement>
  60         {
  61             private QueryOperatorEnumerator<TElement, TKey> m_operatorEnumerator;
  62             private TElement m_current;
  63
  64             internal QueryOperatorClassicEnumerator(QueryOperatorEnumerator<TElement, TKey> operatorEnumerator)
  65             {
  66                 Contract.Assert(operatorEnumerator != null);
  67                 m_operatorEnumerator = operatorEnumerator;
  68             }
  69
  70             public bool MoveNext()
  71             {
  72                 TKey keyUnused = default(TKey);
  73                 return m_operatorEnumerator.MoveNext(ref m_current, ref keyUnused);
  74             }
  75
  76             public TElement Current
  77             {
  78                 get { return m_current; }
  79             }
  80
  81             object IEnumerator.Current
  82             {
  83                 get { return m_current; }
  84             }
  85
  86             public void Dispose()
  87             {
  88                 m_operatorEnumerator.Dispose();
  89                 m_operatorEnumerator = null;
  90             }
  91
  92             public void Reset()
  93             {
  94                 m_operatorEnumerator.Reset();
  95             }
  96         }
  97     }
  98 }