EnumEqualityComparer.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
 
namespace System.Collections.Generic;
 
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public sealed class EnumEqualityComparer<T> : EqualityComparer<T>, ISerializable where T : struct, Enum
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override bool Equals(T x, T y)
    {
        return RuntimeHelpers.EnumEquals(x, y);
    }
 
    internal override int IndexOf(T[] array, T value, int startIndex, int count)
    {
        int num = startIndex + count;
        for (int i = startIndex; i < num; i++)
        {
            if (RuntimeHelpers.EnumEquals(array[i], value))
            {
                return i;
            }
        }
        return -1;
    }
 
    internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
    {
        int num = startIndex - count + 1;
        for (int num2 = startIndex; num2 >= num; num2--)
        {
            if (RuntimeHelpers.EnumEquals(array[num2], value))
            {
                return num2;
            }
        }
        return -1;
    }
 
    public EnumEqualityComparer()
    {
    }
 
    private EnumEqualityComparer(SerializationInfo information, StreamingContext context)
    {
    }
 
    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (Type.GetTypeCode(Enum.GetUnderlyingType(typeof(T))) != TypeCode.Int32)
        {
            info.SetType(typeof(ObjectEqualityComparer<T>));
        }
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override int GetHashCode(T obj)
    {
        return obj.GetHashCode();
    }
 
    public override bool Equals([NotNullWhen(true)] object? obj)
    {
        if (obj != null)
        {
            return GetType() == obj.GetType();
        }
        return false;
    }
 
    public override int GetHashCode()
    {
        return GetType().GetHashCode();
    }
}