1 /* ****************************************************************************
3 * Copyright (c) Microsoft Corporation.
5 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A
6 * copy of the license can be found in the License.html file at the root of this distribution. If
7 * you cannot locate the Apache License, Version 2.0, please send an email to
8 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
9 * by the terms of the Apache License, Version 2.0.
11 * You must not remove this notice, or any other, from this software.
14 * ***************************************************************************/
16 using System.Collections.Generic;
17 using System.Runtime.CompilerServices;
18 using System.Linq.Expressions;
21 namespace Microsoft.Scripting.Utils {
22 public sealed class ReferenceEqualityComparer<T> : IEqualityComparer<T> where T : class {
23 [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]
24 public static readonly ReferenceEqualityComparer<T> Instance = new ReferenceEqualityComparer<T>();
26 private ReferenceEqualityComparer() { }
28 public bool Equals(T x, T y) {
29 return object.ReferenceEquals(x, y);
33 private static Expression NullConst = Expression.Constant(null);
34 private static int H = 536870912 ^ NullConst.GetHashCode();
37 public int GetHashCode(T obj) {
38 #if WP75 // CF RH.GetHashCode throws NullReferenceException if the argument is null
39 return obj != null ? RuntimeHelpers.GetHashCode(obj) : 0;
42 return BindingRestrictions.GetInstanceRestriction(NullConst, obj).GetHashCode() ^ H;
44 return RuntimeHelpers.GetHashCode(obj);