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 //
   8
   9 using System.Globalization;
  10
  11 namespace System.Collections
  12 {
  13         [Serializable]
  14         public class CaseInsensitiveHashCodeProvider : IHashCodeProvider
  15         {
  16                 static readonly CaseInsensitiveHashCodeProvider singleton = new CaseInsensitiveHashCodeProvider ();
  17                 static readonly CaseInsensitiveHashCodeProvider singletonInvariant = new CaseInsensitiveHashCodeProvider (true);
  18
  19                 CultureInfo culture;
  20
  21                 // Public instance constructor
  22                 public CaseInsensitiveHashCodeProvider ()
  23                 {
  24                         culture = CultureInfo.CurrentCulture;
  25                 }
  26
  27                 private CaseInsensitiveHashCodeProvider (bool invariant)
  28                 {
  29                         // leave culture == null
  30                 }
  31
  32                 public CaseInsensitiveHashCodeProvider (CultureInfo culture)
  33                 {
  34                         if (culture == null)
  35                                 throw new ArgumentNullException ("culture");
  36                         if (culture.LCID != CultureInfo.InvariantCulture.LCID)
  37                                 this.culture = culture;
  38                         // else leave culture == null
  39                 }
  40
  41                 //
  42                 // Public static properties
  43                 //
  44
  45                 public static CaseInsensitiveHashCodeProvider Default {
  46                         get {
  47                                 return singleton;
  48                         }
  49                 }
  50
  51 #if NET_1_1
  52                 public
  53 #else
  54                 internal
  55 #endif
  56                 static CaseInsensitiveHashCodeProvider DefaultInvariant {
  57                         get {
  58                                 return singletonInvariant;
  59                         }
  60                 }
  61
  62                 //
  63                 // IHashCodeProvider
  64                 //
  65
  66                 public int GetHashCode (object obj)
  67                 {
  68                         if (obj == null)
  69                                 throw new ArgumentNullException ("obj");
  70
  71                         string str = obj as string;
  72
  73                         if (str == null)
  74                                 return obj.GetHashCode ();
  75
  76                         int h = 0;
  77                         char c;
  78
  79                         if (culture != null) {
  80                                 for (int i = 0; i < str.Length; i++) {
  81                                         c = Char.ToLower (str [i], culture);
  82                                         h = h * 31 + c;
  83                                 }
  84                         }
  85                         else {
  86                                 for (int i = 0; i < str.Length; i++) {
  87                                         c = Char.ToLowerInvariant (str [i]);
  88                                         h = h * 31 + c;
  89                                 }
  90                         }
  91                         return h;
  92                 }
  93         }
  94 }