shared source/vb/language/shared/iconstiterator.h

   1 //-------------------------------------------------------------------------------------------------
   2 //
   3 //  Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 //-------------------------------------------------------------------------------------------------
   6
   7 #pragma once
   8
   9 template <class T>
  10 class IConstIterator
  11 {
  12 public:
  13     virtual
  14     ~IConstIterator()
  15     {
  16     }
  17
  18     virtual
  19     bool MoveNext() = 0;
  20
  21     virtual
  22     T Current() = 0;
  23 };
  24
  25 template <class T>
  26 class ConstIterator : public virtual IConstIterator<T>
  27 {
  28 public:
  29     ConstIterator()
  30     {
  31     }
  32
  33     explicit ConstIterator(RefCountedPtr<IConstIterator<T> > spIterator)
  34         : m_spIterator(spIterator)
  35     {
  36
  37     }
  38
  39     template <class U>
  40     ConstIterator(const U& it)
  41     {
  42         m_spIterator.Attach(new (zeromemory) U(it));
  43     }
  44
  45     virtual __override
  46     bool MoveNext()
  47     {
  48         if ( m_spIterator)
  49         {
  50             return m_spIterator->MoveNext();
  51         }
  52         else
  53         {
  54             // NULL is used to represent an empty iterator
  55             return false;
  56         }
  57     }
  58
  59     virtual __override
  60     T Current()
  61     {
  62         ThrowIfFalse2(m_spIterator, "Calling current on a NULL iterator");
  63         return m_spIterator->Current();
  64     }
  65
  66 private:
  67
  68     // Allow default copy constructor and assignment operators to
  69     // be generated because RefCountedPtr is copy safe
  70     RefCountedPtr<IConstIterator<T> > m_spIterator;
  71 };
  72
  73