ReverseIterator.cs

   1 using System;
   2 using System.Collections;
   3
   4 namespace Eithne
   5 {
   6         public class ReverseIterator : IEnumerable
   7         {
   8                 IEnumerable _enumerable;
   9
  10                 public ReverseIterator(IEnumerable enumerable)
  11                 {
  12                         _enumerable = enumerable;
  13                 }
  14
  15                 public IEnumerator GetEnumerator()
  16                 {
  17                         return new ReverseIteratorEnumerator(_enumerable.GetEnumerator());
  18                 }
  19
  20                 internal class ReverseIteratorEnumerator : IEnumerator
  21                 {
  22                         private ArrayList _list;
  23                         private int       _index;
  24
  25                         internal ReverseIteratorEnumerator( IEnumerator enumerator )
  26                         {
  27                                 _list = new ArrayList();
  28
  29                                 while(enumerator.MoveNext())
  30                                 {
  31                                         _list.Add( enumerator.Current );
  32                                 }
  33
  34                                 _index = _list.Count;
  35                         }
  36
  37                         public void Reset()
  38                         {
  39                                 _index = _list.Count;
  40                         }
  41
  42                         public object Current
  43                         {
  44                                 get
  45                                 {
  46                                         if((_index < 0) || (_index == _list.Count))
  47                                                 throw new InvalidOperationException();
  48                                         return _list[_index];
  49                                 }
  50                         }
  51
  52                         public bool MoveNext()
  53                         {
  54                                 if(_index >= 0)
  55                                         --_index;
  56
  57                                 return _index >= 0;
  58                         }
  59                 }
  60         }
  61 }