DiagLinkedList.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Diagnostics;
 
internal sealed class DiagLinkedList<T> : IEnumerable<T>, IEnumerable
{
    private DiagNode<T> _first;
 
    private DiagNode<T> _last;
 
    public DiagNode<T> First => _first;
 
    public DiagLinkedList()
    {
    }
 
    public DiagLinkedList(T firstValue)
    {
        _last = (_first = new DiagNode<T>(firstValue));
    }
 
    public DiagLinkedList(IEnumerator<T> e)
    {
        _last = (_first = new DiagNode<T>(e.Current));
        while (e.MoveNext())
        {
            _last.Next = new DiagNode<T>(e.Current);
            _last = _last.Next;
        }
    }
 
    public void Clear()
    {
        lock (this)
        {
            _first = (_last = null);
        }
    }
 
    private void UnsafeAdd(DiagNode<T> newNode)
    {
        if (_first == null)
        {
            _first = (_last = newNode);
            return;
        }
        _last.Next = newNode;
        _last = newNode;
    }
 
    public void Add(T value)
    {
        DiagNode<T> newNode = new DiagNode<T>(value);
        lock (this)
        {
            UnsafeAdd(newNode);
        }
    }
 
    public bool AddIfNotExist(T value, Func<T, T, bool> compare)
    {
        lock (this)
        {
            for (DiagNode<T> diagNode = _first; diagNode != null; diagNode = diagNode.Next)
            {
                if (compare(value, diagNode.Value))
                {
                    return false;
                }
            }
            DiagNode<T> newNode = new DiagNode<T>(value);
            UnsafeAdd(newNode);
            return true;
        }
    }
 
    public T Remove(T value, Func<T, T, bool> compare)
    {
        lock (this)
        {
            DiagNode<T> diagNode = _first;
            if (diagNode == null)
            {
                return default(T);
            }
            if (compare(diagNode.Value, value))
            {
                _first = diagNode.Next;
                if (_first == null)
                {
                    _last = null;
                }
                return diagNode.Value;
            }
            for (DiagNode<T> next = diagNode.Next; next != null; next = next.Next)
            {
                if (compare(next.Value, value))
                {
                    diagNode.Next = next.Next;
                    if (_last == next)
                    {
                        _last = diagNode;
                    }
                    return next.Value;
                }
                diagNode = next;
            }
            return default(T);
        }
    }
 
    public Enumerator<T> GetEnumerator()
    {
        return new Enumerator<T>(_first);
    }
 
    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}