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 using System.Collections.Generic;
  35 using System.Runtime.InteropServices;
  36
  37 namespace System
  38 {
  39         [Serializable]
  40         [ComVisible (true)]
  41         public sealed class CharEnumerator : IEnumerator, ICloneable, IEnumerator<char>
  42         {
  43                 private string str;
  44                 private int index;
  45                 private int length;
  46                 // Representation invariant:
  47                 // length == str.Length
  48                 // -1 <= index <= length
  49
  50                 // Constructor
  51                 internal CharEnumerator (string s)
  52                 {
  53                         str = s;
  54                         index = -1;
  55                         length = s.Length;
  56                 }
  57
  58                 // Properties
  59                 public char Current {
  60                         get {
  61                                 if (index == -1 || index >= length)
  62                                         throw new InvalidOperationException (Locale.GetText ("The position is not valid."));
  63                                 return str [index];
  64                         }
  65                 }
  66
  67                 object IEnumerator.Current {
  68                         get {
  69                                 return Current;
  70                         }
  71                 }
  72
  73                 public void Dispose ()
  74                 {
  75                         // nop
  76                 }
  77
  78                 // Methods
  79                 public object Clone ()
  80                 {
  81                         CharEnumerator x = new CharEnumerator (str);
  82                         x.index = index;
  83                         return x;
  84                 }
  85
  86                 public bool MoveNext ()
  87                 {
  88                         // Representation invariant holds: -1 <= index <= length
  89
  90                         index ++;
  91
  92                         // Now: 0 <= index <= length+1;
  93                         //   <=>
  94                         // 0 <= index < length (OK) ||
  95                         // length <= index <= length+1 (Out of bounds)
  96
  97                         if (index >= length) {
  98                                 index = length;
  99                                 // Invariant restored:
 100                                 // length == index
 101                                 //   =>
 102                                 // -1 <= index <= length
 103                                 return false;
 104                         }
 105                         else
 106                                 return true;
 107                 }
 108
 109                 public void Reset ()
 110                 {
 111                         index = -1;
 112                 }
 113         }
 114 }