class/corlib/System.Text/DecoderReplacementFallbackBuffer.cs

   1 //
   2 // DecoderReplacementFallbackBuffer.cs
   3 //
   4 // Author:
   5 //      Atsushi Enomoto <atsushi@ximian.com>
   6 //
   7
   8 //
   9 // Copyright (C) 2005 Novell, Inc (http://www.novell.com)
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31
  32 namespace System.Text
  33 {
  34         // This DecoderFallbackBuffer is simple. It ignores the input buffers.
  35         // DecoderFallbackBuffer users could implement their own complex
  36         // fallback buffers.
  37
  38         public sealed class DecoderReplacementFallbackBuffer
  39                 : DecoderFallbackBuffer
  40         {
  41                 bool fallback_assigned;
  42                 int current;
  43                 string replacement;
  44
  45                 public DecoderReplacementFallbackBuffer (
  46                         DecoderReplacementFallback fallback)
  47                 {
  48                         if (fallback == null)
  49                                 throw new ArgumentNullException ("fallback");
  50                         replacement = fallback.DefaultString;
  51                         current = 0;
  52                 }
  53
  54                 public override int Remaining {
  55                         get { return fallback_assigned ? replacement.Length - current : 0; }
  56                 }
  57
  58                 public override bool Fallback (byte [] bytesUnknown, int index)
  59                 {
  60                         if (bytesUnknown == null)
  61                                 throw new ArgumentNullException ("bytesUnknown");
  62                         if (fallback_assigned && Remaining != 0)
  63                                 throw new ArgumentException ("Reentrant Fallback method invocation occured. It might be because either this FallbackBuffer is incorrectly shared by multiple threads, invoked inside Encoding recursively, or Reset invocation is forgotten.");
  64                         if (index < 0 || bytesUnknown.Length < index)
  65                                 throw new ArgumentOutOfRangeException ("index");
  66                         fallback_assigned = true;
  67                         current = 0;
  68
  69                         return replacement.Length > 0;
  70                 }
  71
  72                 public override char GetNextChar ()
  73                 {
  74                         if (!fallback_assigned)
  75                                 return '\0';
  76                         if (current >= replacement.Length)
  77                                 return char.MinValue;
  78                         return replacement [current++];
  79                 }
  80
  81                 public override bool MovePrevious ()
  82                 {
  83                         if (current == 0)
  84                                 return false;
  85                         current--;
  86                         return true;
  87                 }
  88
  89                 public override void Reset ()
  90                 {
  91                         fallback_assigned = false;
  92                         current = 0;
  93                 }
  94         }
  95 }