mcs/class/corlib/System.Collections/CaseInsensitiveHashCodeProvider.cs

   1 //
   2 // System.Collections.CaseInsensitiveHashCodeProvider.cs
   3 //
   4 // Authors:
   5 //   Sergey Chaban (serge@wildwestsoftware.com)
   6 //   Andreas Nahr (ClassDevelopment@A-SoftTech.com)
   7 //   Sebastien Pouliot  <sebastien@ximian.com>
   8 //
   9 // Copyright (C) 2004-2005 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 using System.Globalization;
  32 using System.Runtime.InteropServices;
  33
  34 namespace System.Collections
  35 {
  36         [Serializable]
  37 #if NET_2_0
  38         [ComVisible(true)]
  39         [Obsolete ("Please use StringComparer instead.")]
  40 #endif
  41 #if INSIDE_CORLIB
  42         public
  43 #else
  44         internal
  45 #endif
  46         class CaseInsensitiveHashCodeProvider : IHashCodeProvider
  47         {
  48                 static readonly CaseInsensitiveHashCodeProvider singletonInvariant = new CaseInsensitiveHashCodeProvider (
  49                         CultureInfo.InvariantCulture);
  50                 static CaseInsensitiveHashCodeProvider singleton;
  51                 static readonly object sync = new object ();
  52
  53                 TextInfo m_text; // must match MS name for serialization
  54
  55                 // Public instance constructor
  56                 public CaseInsensitiveHashCodeProvider ()
  57                 {
  58                         CultureInfo culture = CultureInfo.CurrentCulture;
  59                         if (culture.LCID != CultureInfo.InvariantCulture.LCID)
  60                                 m_text = CultureInfo.CurrentCulture.TextInfo;
  61                 }
  62
  63                 public CaseInsensitiveHashCodeProvider (CultureInfo culture)
  64                 {
  65                         if (culture == null)
  66                                 throw new ArgumentNullException ("culture");
  67                         if (culture.LCID != CultureInfo.InvariantCulture.LCID)
  68                                 m_text = culture.TextInfo;
  69                 }
  70
  71                 //
  72                 // Public static properties
  73                 //
  74
  75                 public static CaseInsensitiveHashCodeProvider Default {
  76                         get {
  77                                 // MS actually constructs a new instance on each call, for
  78                                 // performance reasons we're only constructing a new instance
  79                                 // if the CurrentCulture changes
  80                                 lock (sync) {
  81                                         if (singleton == null) {
  82                                                 singleton = new CaseInsensitiveHashCodeProvider ();
  83                                         } else if (singleton.m_text == null) {
  84                                                 if (CultureInfo.CurrentCulture.LCID != CultureInfo.InvariantCulture.LCID)
  85                                                         singleton = new CaseInsensitiveHashCodeProvider ();
  86                                         } else if (singleton.m_text.LCID != CultureInfo.CurrentCulture.LCID) {
  87                                                 singleton = new CaseInsensitiveHashCodeProvider ();
  88                                         }
  89                                         return singleton;
  90                                 }
  91                         }
  92                 }
  93
  94 #if NET_1_1
  95                 public
  96 #else
  97                 internal
  98 #endif
  99                 static CaseInsensitiveHashCodeProvider DefaultInvariant {
 100                         get {
 101                                 return singletonInvariant;
 102                         }
 103                 }
 104
 105                 //
 106                 // IHashCodeProvider
 107                 //
 108
 109                 public int GetHashCode (object obj)
 110                 {
 111                         if (obj == null)
 112                                 throw new ArgumentNullException ("obj");
 113
 114                         string str = obj as string;
 115
 116                         if (str == null)
 117                                 return obj.GetHashCode ();
 118
 119                         int h = 0;
 120                         char c;
 121
 122                         if ((m_text != null) && (m_text.LCID != CultureInfo.InvariantCulture.LCID)) {
 123                                 str = m_text.ToLower (str);
 124                                 for (int i = 0; i < str.Length; i++) {
 125                                         c = str [i];
 126                                         h = h * 31 + c;
 127                                 }
 128                         } else {
 129                                 for (int i = 0; i < str.Length; i++) {
 130                                         c = Char.ToLowerInvariant (str [i]);
 131                                         h = h * 31 + c;
 132                                 }
 133                         }
 134                         return h;
 135                 }
 136         }
 137 }