NonRandomizedStringEqualityComparer.cs

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using System.Runtime.Serialization;
 
namespace System.Collections.Generic;
 
[Serializable]
public class NonRandomizedStringEqualityComparer : IEqualityComparer<string?>, IInternalStringEqualityComparer, ISerializable
{
    private sealed class OrdinalComparer : NonRandomizedStringEqualityComparer
    {
        internal OrdinalComparer(IEqualityComparer<string> wrappedComparer)
            : base(wrappedComparer)
        {
        }
 
        public override bool Equals(string x, string y)
        {
            return string.Equals(x, y);
        }
 
        public override int GetHashCode(string obj)
        {
            return obj.GetNonRandomizedHashCode();
        }
    }
 
    private sealed class OrdinalIgnoreCaseComparer : NonRandomizedStringEqualityComparer
    {
        internal OrdinalIgnoreCaseComparer(IEqualityComparer<string> wrappedComparer)
            : base(wrappedComparer)
        {
        }
 
        public override bool Equals(string x, string y)
        {
            return string.EqualsOrdinalIgnoreCase(x, y);
        }
 
        public override int GetHashCode(string obj)
        {
            return obj.GetNonRandomizedHashCodeOrdinalIgnoreCase();
        }
 
        internal override RandomizedStringEqualityComparer GetRandomizedEqualityComparer()
        {
            return RandomizedStringEqualityComparer.Create(_underlyingComparer, ignoreCase: true);
        }
    }
 
    private static readonly NonRandomizedStringEqualityComparer WrappedAroundDefaultComparer = new OrdinalComparer(EqualityComparer<string>.Default);
 
    private static readonly NonRandomizedStringEqualityComparer WrappedAroundStringComparerOrdinal = new OrdinalComparer(StringComparer.Ordinal);
 
    private static readonly NonRandomizedStringEqualityComparer WrappedAroundStringComparerOrdinalIgnoreCase = new OrdinalIgnoreCaseComparer(StringComparer.OrdinalIgnoreCase);
 
    private readonly IEqualityComparer<string> _underlyingComparer;
 
    private NonRandomizedStringEqualityComparer(IEqualityComparer<string> underlyingComparer)
    {
        _underlyingComparer = underlyingComparer;
    }
 
    protected NonRandomizedStringEqualityComparer(SerializationInfo information, StreamingContext context)
        : this(EqualityComparer<string>.Default)
    {
    }
 
    public virtual bool Equals(string? x, string? y)
    {
        return string.Equals(x, y);
    }
 
    public virtual int GetHashCode(string? obj)
    {
        return obj?.GetNonRandomizedHashCode() ?? 0;
    }
 
    internal virtual RandomizedStringEqualityComparer GetRandomizedEqualityComparer()
    {
        return RandomizedStringEqualityComparer.Create(_underlyingComparer, ignoreCase: false);
    }
 
    public virtual IEqualityComparer<string?> GetUnderlyingEqualityComparer()
    {
        return _underlyingComparer;
    }
 
    void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
    {
        info.SetType(typeof(GenericEqualityComparer<string>));
    }
 
    public static IEqualityComparer<string>? GetStringComparer(object? comparer)
    {
        if (comparer == null)
        {
            return WrappedAroundDefaultComparer;
        }
        if (comparer == StringComparer.Ordinal)
        {
            return WrappedAroundStringComparerOrdinal;
        }
        if (comparer == StringComparer.OrdinalIgnoreCase)
        {
            return WrappedAroundStringComparerOrdinalIgnoreCase;
        }
        return null;
    }
}