mcs/class/corlib/System/CharEnumerator.cs

   1 //
   2 // System.CharEnumerator.cs
   3 //
   4 // Author:
   5 //   Duncan Mak (duncan@ximian.com)
   6 //
   7 // (C) Ximian, Inc.
   8 //
   9
  10 //
  11 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32
  33 using System.Collections;
  34
  35 namespace System
  36 {
  37         [Serializable]
  38         public sealed class CharEnumerator : IEnumerator, ICloneable
  39         {
  40                 private string str;
  41                 private int index;
  42                 private int length;
  43                 // Representation invariant:
  44                 // length == str.Length
  45                 // -1 <= index <= length
  46
  47                 // Constructor
  48                 internal CharEnumerator (string s)
  49                 {
  50                         str = s;
  51                         index = -1;
  52                         length = s.Length;
  53                 }
  54
  55                 // Properties
  56                 public char Current {
  57                         get {
  58                                 if (index == -1 || index >= length)
  59                                         throw new InvalidOperationException (Locale.GetText ("The position is not valid."));
  60                                 return str [index];
  61                         }
  62                 }
  63
  64                 object IEnumerator.Current {
  65                         get {
  66                                 return Current;
  67                         }
  68                 }
  69
  70                 // Methods
  71                 public object Clone ()
  72                 {
  73                         CharEnumerator x = new CharEnumerator (str);
  74                         x.index = index;
  75                         return x;
  76                 }
  77
  78                 public bool MoveNext ()
  79                 {
  80                         // Representation invariant holds: -1 <= index <= length
  81
  82                         index ++;
  83
  84                         // Now: 0 <= index <= length+1;
  85                         //   <=>
  86                         // 0 <= index < length (OK) ||
  87                         // length <= index <= length+1 (Out of bounds)
  88
  89                         if (index >= length) {
  90                                 index = length;
  91                                 // Invariant restored:
  92                                 // length == index
  93                                 //   =>
  94                                 // -1 <= index <= length
  95                                 return false;
  96                         }
  97                         else
  98                                 return true;
  99                 }
 100
 101                 public void Reset ()
 102                 {
 103                         index = -1;
 104                 }
 105         }
 106 }