DocumentXPathNodeIterator_ElemDescendants.cs

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using System.Xml.XPath;
 
namespace System.Xml;
 
internal abstract class DocumentXPathNodeIterator_ElemDescendants : XPathNodeIterator
{
    private readonly DocumentXPathNavigator _nav;
 
    private int _level;
 
    private int _position;
 
    public override XPathNavigator Current => _nav;
 
    public override int CurrentPosition => _position;
 
    internal DocumentXPathNodeIterator_ElemDescendants(DocumentXPathNavigator nav)
    {
        _nav = (DocumentXPathNavigator)nav.Clone();
        _level = 0;
        _position = 0;
    }
 
    internal DocumentXPathNodeIterator_ElemDescendants(DocumentXPathNodeIterator_ElemDescendants other)
    {
        _nav = (DocumentXPathNavigator)other._nav.Clone();
        _level = other._level;
        _position = other._position;
    }
 
    protected abstract bool Match(XmlNode node);
 
    protected void SetPosition(int pos)
    {
        _position = pos;
    }
 
    public override bool MoveNext()
    {
        XmlNode xmlNode;
        do
        {
            if (_nav.MoveToFirstChild())
            {
                _level++;
            }
            else
            {
                if (_level == 0)
                {
                    return false;
                }
                while (!_nav.MoveToNext())
                {
                    _level--;
                    if (_level == 0)
                    {
                        return false;
                    }
                    if (!_nav.MoveToParent())
                    {
                        return false;
                    }
                }
            }
            xmlNode = (XmlNode)_nav.UnderlyingObject;
        }
        while (xmlNode.NodeType != XmlNodeType.Element || !Match(xmlNode));
        _position++;
        return true;
    }
}