src/Boo.Lang.Compiler/TypeSystem/ArrayEqualityComparer.cs

   1 #region license
   2 // Copyright (c) 2003, 2004, 2005 Rodrigo B. de Oliveira (rbo@acm.org)
   3 // All rights reserved.
   4 //
   5 // Redistribution and use in source and binary forms, with or without modification,
   6 // are permitted provided that the following conditions are met:
   7 //
   8 //     * Redistributions of source code must retain the above copyright notice,
   9 //     this list of conditions and the following disclaimer.
  10 //     * Redistributions in binary form must reproduce the above copyright notice,
  11 //     this list of conditions and the following disclaimer in the documentation
  12 //     and/or other materials provided with the distribution.
  13 //     * Neither the name of Rodrigo B. de Oliveira nor the names of its
  14 //     contributors may be used to endorse or promote products derived from this
  15 //     software without specific prior written permission.
  16 //
  17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  18 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
  21 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  23 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  24 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  25 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27 #endregion
  28
  29 namespace Boo.Lang.Compiler.TypeSystem
  30 {
  31         using System;
  32         using System.Collections.Generic;
  33
  34         /// <summary>
  35         /// Compares arrays based on their items.
  36         /// </summary>
  37         internal class ArrayEqualityComparer<T>: IEqualityComparer<T[]>
  38         {
  39                 private static ArrayEqualityComparer<T> _default = null;
  40
  41                 private ArrayEqualityComparer()
  42                 {
  43                 }
  44
  45                 public static ArrayEqualityComparer<T> Default
  46                 {
  47                         get { return _default ?? (_default = new ArrayEqualityComparer<T>()); }
  48                 }
  49
  50                 public bool Equals(T[] x, T[] y)
  51                 {
  52                         // Null equals null, and nothing else
  53                         if (x == null && y == null) return true;
  54                         if (x == null || y == null) return false;
  55
  56                         // Compare arrays' lengths
  57                         if (x.Length != y.Length) return false;
  58
  59                         // Compare arrays' contents
  60                         for (int i = 0; i < x.Length; i++)
  61                         {
  62                                 if ((x[i] == null && y[i] != null) || (!x[i].Equals(y[i])))
  63                                 {
  64                                         return false;
  65                                 }
  66                         }
  67
  68                         return true;
  69                 }
  70
  71                 public int GetHashCode(T[] args)
  72                 {
  73                         // Make a simple hash code from the hash codes of the items
  74                         int hash = 0;
  75                         for (int i = 0; i < args.Length; i++)
  76                         {
  77                                 hash ^= i ^ args[i].GetHashCode();
  78                         }
  79
  80                         return hash;
  81                 }
  82         }
  83 }