StringConcat.cs

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using System.Collections.Generic;
using System.ComponentModel;
 
namespace System.Xml.Xsl.Runtime;
 
[EditorBrowsable(EditorBrowsableState.Never)]
public struct StringConcat
{
    private string _s1;
 
    private string _s2;
 
    private string _s3;
 
    private string _s4;
 
    private string _delimiter;
 
    private List<string> _strList;
 
    private int _idxStr;
 
    public string? Delimiter
    {
        get
        {
            return _delimiter;
        }
        set
        {
            _delimiter = value;
        }
    }
 
    internal int Count => _idxStr;
 
    public void Clear()
    {
        _idxStr = 0;
        _delimiter = null;
    }
 
    public void Concat(string value)
    {
        if (_delimiter != null && _idxStr != 0)
        {
            ConcatNoDelimiter(_delimiter);
        }
        ConcatNoDelimiter(value);
    }
 
    public string GetResult()
    {
        return _idxStr switch
        {
            0 => string.Empty, 
            1 => _s1 ?? string.Empty, 
            2 => _s1 + _s2, 
            3 => _s1 + _s2 + _s3, 
            4 => _s1 + _s2 + _s3 + _s4, 
            _ => string.Concat(_strList.ToArray()), 
        };
    }
 
    internal void ConcatNoDelimiter(string s)
    {
        switch (_idxStr)
        {
        case 0:
            _s1 = s;
            break;
        case 1:
            _s2 = s;
            break;
        case 2:
            _s3 = s;
            break;
        case 3:
            _s4 = s;
            break;
        case 4:
        {
            int capacity = ((_strList == null) ? 8 : _strList.Count);
            List<string> list = (_strList = new List<string>(capacity));
            list.Add(_s1);
            list.Add(_s2);
            list.Add(_s3);
            list.Add(_s4);
            goto default;
        }
        default:
            _strList.Add(s);
            break;
        }
        _idxStr++;
    }
}