CompatibleComparer.cs

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namespace System.Collections;
 
internal sealed class CompatibleComparer : IEqualityComparer
{
    private readonly IHashCodeProvider _hcp;
 
    private readonly IComparer _comparer;
 
    internal IHashCodeProvider HashCodeProvider => _hcp;
 
    internal IComparer Comparer => _comparer;
 
    internal CompatibleComparer(IHashCodeProvider hashCodeProvider, IComparer comparer)
    {
        _hcp = hashCodeProvider;
        _comparer = comparer;
    }
 
    public new bool Equals(object a, object b)
    {
        return Compare(a, b) == 0;
    }
 
    public int Compare(object a, object b)
    {
        if (a == b)
        {
            return 0;
        }
        if (a == null)
        {
            return -1;
        }
        if (b == null)
        {
            return 1;
        }
        if (_comparer != null)
        {
            return _comparer.Compare(a, b);
        }
        if (a is IComparable comparable)
        {
            return comparable.CompareTo(b);
        }
        throw new ArgumentException(SR.Argument_ImplementIComparable);
    }
 
    public int GetHashCode(object obj)
    {
        if (obj == null)
        {
            throw new ArgumentNullException("obj");
        }
        if (_hcp == null)
        {
            return obj.GetHashCode();
        }
        return _hcp.GetHashCode(obj);
    }
}