DodSequenceMerge.cs

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using System.Collections.Generic;
using System.ComponentModel;
using System.Xml.XPath;
 
namespace System.Xml.Xsl.Runtime;
 
[EditorBrowsable(EditorBrowsableState.Never)]
public struct DodSequenceMerge
{
    private IList<XPathNavigator> _firstSequence;
 
    private List<IEnumerator<XPathNavigator>> _sequencesToMerge;
 
    private int _nodeCount;
 
    private XmlQueryRuntime _runtime;
 
    public void Create(XmlQueryRuntime runtime)
    {
        _firstSequence = null;
        _sequencesToMerge = null;
        _nodeCount = 0;
        _runtime = runtime;
    }
 
    public void AddSequence(IList<XPathNavigator> sequence)
    {
        if (sequence.Count == 0)
        {
            return;
        }
        if (_firstSequence == null)
        {
            _firstSequence = sequence;
            return;
        }
        if (_sequencesToMerge == null)
        {
            _sequencesToMerge = new List<IEnumerator<XPathNavigator>>();
            MoveAndInsertSequence(_firstSequence.GetEnumerator());
            _nodeCount = _firstSequence.Count;
        }
        MoveAndInsertSequence(sequence.GetEnumerator());
        _nodeCount += sequence.Count;
    }
 
    public IList<XPathNavigator> MergeSequences()
    {
        if (_firstSequence == null)
        {
            return XmlQueryNodeSequence.Empty;
        }
        if (_sequencesToMerge == null || _sequencesToMerge.Count <= 1)
        {
            return _firstSequence;
        }
        XmlQueryNodeSequence xmlQueryNodeSequence = new XmlQueryNodeSequence(_nodeCount);
        while (_sequencesToMerge.Count != 1)
        {
            IEnumerator<XPathNavigator> enumerator = _sequencesToMerge[_sequencesToMerge.Count - 1];
            _sequencesToMerge.RemoveAt(_sequencesToMerge.Count - 1);
            xmlQueryNodeSequence.Add(enumerator.Current);
            MoveAndInsertSequence(enumerator);
        }
        do
        {
            xmlQueryNodeSequence.Add(_sequencesToMerge[0].Current);
        }
        while (_sequencesToMerge[0].MoveNext());
        return xmlQueryNodeSequence;
    }
 
    private void MoveAndInsertSequence(IEnumerator<XPathNavigator> sequence)
    {
        if (sequence.MoveNext())
        {
            InsertSequence(sequence);
        }
    }
 
    private void InsertSequence(IEnumerator<XPathNavigator> sequence)
    {
        for (int num = _sequencesToMerge.Count - 1; num >= 0; num--)
        {
            switch (_runtime.ComparePosition(sequence.Current, _sequencesToMerge[num].Current))
            {
            case -1:
                _sequencesToMerge.Insert(num + 1, sequence);
                return;
            case 0:
                if (!sequence.MoveNext())
                {
                    return;
                }
                break;
            }
        }
        _sequencesToMerge.Insert(0, sequence);
    }
}