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         [ComVisible(true)]
  38         [Obsolete ("Please use StringComparer instead.")]
  39 #if INSIDE_CORLIB
  40         public
  41 #else
  42         internal
  43 #endif
  44         class CaseInsensitiveHashCodeProvider : IHashCodeProvider
  45         {
  46                 static readonly CaseInsensitiveHashCodeProvider singletonInvariant = new CaseInsensitiveHashCodeProvider (
  47                         CultureInfo.InvariantCulture);
  48                 static CaseInsensitiveHashCodeProvider singleton;
  49                 static readonly object sync = new object ();
  50
  51                 TextInfo m_text; // must match MS name for serialization
  52
  53                 // Public instance constructor
  54                 public CaseInsensitiveHashCodeProvider ()
  55                 {
  56                         CultureInfo culture = CultureInfo.CurrentCulture;
  57                         if (!AreEqual (culture, CultureInfo.InvariantCulture))
  58                                 m_text = CultureInfo.CurrentCulture.TextInfo;
  59                 }
  60
  61                 public CaseInsensitiveHashCodeProvider (CultureInfo culture)
  62                 {
  63                         if (culture == null)
  64                                 throw new ArgumentNullException ("culture");
  65                         if (!AreEqual (culture, CultureInfo.InvariantCulture))
  66                                 m_text = culture.TextInfo;
  67                 }
  68
  69                 //
  70                 // Public static properties
  71                 //
  72
  73                 public static CaseInsensitiveHashCodeProvider Default {
  74                         get {
  75                                 // MS actually constructs a new instance on each call, for
  76                                 // performance reasons we're only constructing a new instance
  77                                 // if the CurrentCulture changes
  78                                 lock (sync) {
  79                                         if (singleton == null) {
  80                                                 singleton = new CaseInsensitiveHashCodeProvider ();
  81                                         } else if (singleton.m_text == null) {
  82                                                 if (!AreEqual (CultureInfo.CurrentCulture, CultureInfo.InvariantCulture))
  83                                                         singleton = new CaseInsensitiveHashCodeProvider ();
  84                                         } else if (!AreEqual (singleton.m_text, CultureInfo.CurrentCulture)) {
  85                                                 singleton = new CaseInsensitiveHashCodeProvider ();
  86                                         }
  87                                         return singleton;
  88                                 }
  89                         }
  90                 }
  91
  92                 static bool AreEqual (CultureInfo a, CultureInfo b)
  93                 {
  94 #if !NET_2_1
  95                         return a.LCID == b.LCID;
  96 #else
  97                         return a.Name == b.Name;
  98 #endif
  99                 }
 100
 101                 static bool AreEqual (TextInfo info, CultureInfo culture)
 102                 {
 103 #if !NET_2_1
 104                         return info.LCID == culture.LCID;
 105 #else
 106                         return info.CultureName == culture.Name;
 107 #endif
 108                 }
 109
 110                 public
 111                 static CaseInsensitiveHashCodeProvider DefaultInvariant {
 112                         get {
 113                                 return singletonInvariant;
 114                         }
 115                 }
 116
 117                 //
 118                 // IHashCodeProvider
 119                 //
 120
 121                 public int GetHashCode (object obj)
 122                 {
 123                         if (obj == null)
 124                                 throw new ArgumentNullException ("obj");
 125
 126                         string str = obj as string;
 127
 128                         if (str == null)
 129                                 return obj.GetHashCode ();
 130
 131                         int h = 0;
 132                         char c;
 133
 134                         if ((m_text != null) && !AreEqual (m_text, CultureInfo.InvariantCulture)) {
 135                                 str = m_text.ToLower (str);
 136                                 for (int i = 0; i < str.Length; i++) {
 137                                         c = str [i];
 138                                         h = h * 31 + c;
 139                                 }
 140                         } else {
 141                                 for (int i = 0; i < str.Length; i++) {
 142                                         c = Char.ToLower (str [i], CultureInfo.InvariantCulture);
 143                                         h = h * 31 + c;
 144                                 }
 145                         }
 146                         return h;
 147                 }
 148         }
 149 }