DifferenceIterator.cs

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using System.ComponentModel;
using System.Xml.XPath;
 
namespace System.Xml.Xsl.Runtime;
 
[EditorBrowsable(EditorBrowsableState.Never)]
public struct DifferenceIterator
{
    private enum IteratorState
    {
        InitLeft,
        NeedLeft,
        NeedRight,
        NeedLeftAndRight,
        HaveCurrent
    }
 
    private XmlQueryRuntime _runtime;
 
    private XPathNavigator _navLeft;
 
    private XPathNavigator _navRight;
 
    private IteratorState _state;
 
    public XPathNavigator Current => _navLeft;
 
    public void Create(XmlQueryRuntime runtime)
    {
        _runtime = runtime;
        _state = IteratorState.InitLeft;
    }
 
    public SetIteratorResult MoveNext(XPathNavigator nestedNavigator)
    {
        switch (_state)
        {
        case IteratorState.InitLeft:
            _navLeft = nestedNavigator;
            _state = IteratorState.NeedRight;
            return SetIteratorResult.InitRightIterator;
        case IteratorState.NeedLeft:
            _navLeft = nestedNavigator;
            break;
        case IteratorState.NeedRight:
            _navRight = nestedNavigator;
            break;
        case IteratorState.NeedLeftAndRight:
            _navLeft = nestedNavigator;
            _state = IteratorState.NeedRight;
            return SetIteratorResult.NeedRightNode;
        case IteratorState.HaveCurrent:
            _state = IteratorState.NeedLeft;
            return SetIteratorResult.NeedLeftNode;
        }
        if (_navLeft == null)
        {
            return SetIteratorResult.NoMoreNodes;
        }
        if (_navRight != null)
        {
            int num = _runtime.ComparePosition(_navLeft, _navRight);
            if (num == 0)
            {
                _state = IteratorState.NeedLeftAndRight;
                return SetIteratorResult.NeedLeftNode;
            }
            if (num > 0)
            {
                _state = IteratorState.NeedRight;
                return SetIteratorResult.NeedRightNode;
            }
        }
        _state = IteratorState.HaveCurrent;
        return SetIteratorResult.HaveCurrentNode;
    }
}