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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Apache License, Version 2.0. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Apache License, Version 2.0, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Apache License, Version 2.0.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Linq.Expressions;
using System.Dynamic;
namespace Microsoft.Scripting.Utils {
public sealed class ReferenceEqualityComparer<T> : IEqualityComparer<T> where T : class {
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]
public static readonly ReferenceEqualityComparer<T> Instance = new ReferenceEqualityComparer<T>();
private ReferenceEqualityComparer() { }
public bool Equals(T x, T y) {
return object.ReferenceEquals(x, y);
}
#if WIN8
private static Expression NullConst = Expression.Constant(null);
private static int H = 536870912 ^ NullConst.GetHashCode();
#endif
public int GetHashCode(T obj) {
#if WP75 // CF RH.GetHashCode throws NullReferenceException if the argument is null
return obj != null ? RuntimeHelpers.GetHashCode(obj) : 0;
#elif WIN8
// TODO: HACK!
return BindingRestrictions.GetInstanceRestriction(NullConst, obj).GetHashCode() ^ H;
#else
return RuntimeHelpers.GetHashCode(obj);
#endif
}
}
}
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