class/corlib/System.Collections/StructuralComparisons.cs

   1 //
   2 // StructuralComparisons.cs
   3 //
   4 // Authors:
   5 //      Marek Safar (marek.safar@gmail.com)
   6 //
   7 // Copyright (C) 2009 Novell, Inc (http://www.novell.com)
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining
  10 // a copy of this software and associated documentation files (the
  11 // "Software"), to deal in the Software without restriction, including
  12 // without limitation the rights to use, copy, modify, merge, publish,
  13 // distribute, sublicense, and/or sell copies of the Software, and to
  14 // permit persons to whom the Software is furnished to do so, subject to
  15 // the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be
  18 // included in all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27 //
  28
  29 #if NET_4_0
  30
  31 namespace System.Collections
  32 {
  33         public static class StructuralComparisons
  34         {
  35                 sealed class ComparerImpl : IComparer, IEqualityComparer
  36                 {
  37                         int IComparer.Compare (object x, object y)
  38                         {
  39                                 var comparer = x as IStructuralComparable;
  40                                 if (comparer != null)
  41                                         return comparer.CompareTo (y, this);
  42
  43                                 return Comparer.Default.Compare (x, y);
  44                         }
  45
  46                         int IEqualityComparer.GetHashCode (object obj)
  47                         {
  48                                 var comparer = obj as IEqualityComparer;
  49                                 if (comparer != null)
  50                                         return comparer.GetHashCode (this);
  51
  52                                 return Generic.EqualityComparer<object>.Default.GetHashCode (obj);
  53                         }
  54
  55                         bool IEqualityComparer.Equals (object x, object y)
  56                         {
  57                                 var comparer = x as IEqualityComparer;
  58                                 if (comparer != null)
  59                                         return comparer.Equals (y, this);
  60
  61                                 return Generic.EqualityComparer<object>.Default.Equals (x, y);
  62                         }
  63                 }
  64
  65                 static readonly ComparerImpl comparer = new ComparerImpl ();
  66
  67                 public static IComparer StructuralComparer {
  68                         get {
  69                                 return comparer;
  70                         }
  71                 }
  72
  73                 public static IEqualityComparer StructuralEqualityComparer {
  74                         get {
  75                                 return comparer;
  76                         }
  77                 }
  78         }
  79 }
  80
  81 #endif