mcs/class/referencesource/mscorlib/system/collections/structuralcomparisons.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // <OWNER>Microsoft</OWNER>
   7 //
   8
   9 using System;
  10
  11 namespace System.Collections {
  12     public static class StructuralComparisons {
  13
  14         private static volatile IComparer s_StructuralComparer;
  15         private static volatile IEqualityComparer s_StructuralEqualityComparer;
  16
  17         public static IComparer StructuralComparer {
  18             get {
  19                 IComparer comparer = s_StructuralComparer;
  20                 if (comparer == null) {
  21                     comparer = new StructuralComparer();
  22                     s_StructuralComparer = comparer;
  23                 }
  24                 return comparer;
  25             }
  26         }
  27
  28         public static IEqualityComparer StructuralEqualityComparer {
  29             get {
  30                 IEqualityComparer comparer = s_StructuralEqualityComparer;
  31                 if (comparer == null) {
  32                     comparer = new StructuralEqualityComparer();
  33                     s_StructuralEqualityComparer = comparer;
  34                 }
  35                 return comparer;
  36             }
  37         }
  38     }
  39
  40     [Serializable]
  41     internal class StructuralEqualityComparer : IEqualityComparer {
  42         public new bool Equals(Object x, Object y) {
  43             if (x != null) {
  44
  45                 IStructuralEquatable seObj = x as IStructuralEquatable;
  46
  47                 if (seObj != null){
  48                     return seObj.Equals(y, this);
  49                 }
  50
  51                 if (y != null) {
  52                     return x.Equals(y);
  53                 } else {
  54                     return false;
  55                 }
  56             }
  57             if (y != null) return false;
  58             return true;
  59         }
  60
  61         public int GetHashCode(Object obj) {
  62             if (obj == null) return 0;
  63
  64             IStructuralEquatable seObj = obj as IStructuralEquatable;
  65
  66             if (seObj != null) {
  67                 return seObj.GetHashCode(this);
  68             }
  69
  70             return obj.GetHashCode();
  71         }
  72     }
  73
  74     [Serializable]
  75     internal class StructuralComparer : IComparer {
  76         public int Compare(Object x, Object y) {
  77
  78             if (x == null) return y == null ? 0 : -1;
  79             if (y == null) return 1;
  80
  81             IStructuralComparable scX = x as IStructuralComparable;
  82
  83             if (scX != null) {
  84                 return scX.CompareTo(y, this);
  85             }
  86
  87             return Comparer.Default.Compare(x, y);
  88         }
  89     }
  90
  91 }