ObjectReferenceStack.cs

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using System.Collections.Generic;
 
namespace System.Runtime.Serialization;
 
internal struct ObjectReferenceStack
{
    private const int MaximumArraySize = 16;
 
    private const int InitialArraySize = 4;
 
    private int _count;
 
    private object[] _objectArray;
 
    private bool[] _isReferenceArray;
 
    private Dictionary<object, object> _objectDictionary;
 
    internal void Push(object obj)
    {
        if (_objectArray == null)
        {
            _objectArray = new object[4];
            _objectArray[_count++] = obj;
            return;
        }
        if (_count < 16)
        {
            if (_count == _objectArray.Length)
            {
                Array.Resize(ref _objectArray, _objectArray.Length * 2);
            }
            _objectArray[_count++] = obj;
            return;
        }
        if (_objectDictionary == null)
        {
            _objectDictionary = new Dictionary<object, object>();
        }
        _objectDictionary.Add(obj, null);
        _count++;
    }
 
    internal void EnsureSetAsIsReference(object obj)
    {
        if (_count == 0)
        {
            return;
        }
        if (_count > 16)
        {
            _ = _objectDictionary;
            _objectDictionary.Remove(obj);
        }
        else if (_objectArray != null && _objectArray[_count - 1] == obj)
        {
            if (_isReferenceArray == null)
            {
                _isReferenceArray = new bool[_objectArray.Length];
            }
            else if (_count >= _isReferenceArray.Length)
            {
                Array.Resize(ref _isReferenceArray, _objectArray.Length);
            }
            _isReferenceArray[_count - 1] = true;
        }
    }
 
    internal void Pop(object obj)
    {
        if (_count > 16)
        {
            _ = _objectDictionary;
            _objectDictionary.Remove(obj);
        }
        _count--;
    }
 
    internal bool Contains(object obj)
    {
        int num = _count;
        if (num > 16)
        {
            if (_objectDictionary != null && _objectDictionary.ContainsKey(obj))
            {
                return true;
            }
            num = 16;
        }
        for (int num2 = num - 1; num2 >= 0; num2--)
        {
            if (obj == _objectArray[num2] && _isReferenceArray != null && !_isReferenceArray[num2])
            {
                return true;
            }
        }
        return false;
    }
}