FollSiblingQuery.cs

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using System.Collections.Generic;
using System.Xml.XPath;
 
namespace MS.Internal.Xml.XPath;
 
internal sealed class FollSiblingQuery : BaseAxisQuery
{
    private readonly ClonableStack<XPathNavigator> _elementStk;
 
    private readonly List<XPathNavigator> _parentStk;
 
    private XPathNavigator _nextInput;
 
    public FollSiblingQuery(Query qyInput, string name, string prefix, XPathNodeType type)
        : base(qyInput, name, prefix, type)
    {
        _elementStk = new ClonableStack<XPathNavigator>();
        _parentStk = new List<XPathNavigator>();
    }
 
    private FollSiblingQuery(FollSiblingQuery other)
        : base(other)
    {
        _elementStk = other._elementStk.Clone();
        _parentStk = new List<XPathNavigator>(other._parentStk);
        _nextInput = Query.Clone(other._nextInput);
    }
 
    public override void Reset()
    {
        _elementStk.Clear();
        _parentStk.Clear();
        _nextInput = null;
        base.Reset();
    }
 
    private bool Visited(XPathNavigator nav)
    {
        XPathNavigator xPathNavigator = nav.Clone();
        xPathNavigator.MoveToParent();
        for (int i = 0; i < _parentStk.Count; i++)
        {
            if (xPathNavigator.IsSamePosition(_parentStk[i]))
            {
                return true;
            }
        }
        _parentStk.Add(xPathNavigator);
        return false;
    }
 
    private XPathNavigator FetchInput()
    {
        XPathNavigator xPathNavigator;
        do
        {
            xPathNavigator = qyInput.Advance();
            if (xPathNavigator == null)
            {
                return null;
            }
        }
        while (Visited(xPathNavigator));
        return xPathNavigator.Clone();
    }
 
    public override XPathNavigator Advance()
    {
        while (true)
        {
            if (currentNode == null)
            {
                if (_nextInput == null)
                {
                    _nextInput = FetchInput();
                }
                if (_elementStk.Count == 0)
                {
                    if (_nextInput == null)
                    {
                        break;
                    }
                    currentNode = _nextInput;
                    _nextInput = FetchInput();
                }
                else
                {
                    currentNode = _elementStk.Pop();
                }
            }
            while (currentNode.IsDescendant(_nextInput))
            {
                _elementStk.Push(currentNode);
                currentNode = _nextInput;
                _nextInput = qyInput.Advance();
                if (_nextInput != null)
                {
                    _nextInput = _nextInput.Clone();
                }
            }
            while (currentNode.MoveToNext())
            {
                if (matches(currentNode))
                {
                    position++;
                    return currentNode;
                }
            }
            currentNode = null;
        }
        return null;
    }
 
    public override XPathNodeIterator Clone()
    {
        return new FollSiblingQuery(this);
    }
}