XmlDictionary.cs

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using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.Serialization;
 
namespace System.Xml;
 
public class XmlDictionary : IXmlDictionary
{
    private sealed class EmptyDictionary : IXmlDictionary
    {
        public bool TryLookup(string value, [NotNullWhen(true)] out XmlDictionaryString result)
        {
            result = null;
            return false;
        }
 
        public bool TryLookup(int key, [NotNullWhen(true)] out XmlDictionaryString result)
        {
            result = null;
            return false;
        }
 
        public bool TryLookup(XmlDictionaryString value, [NotNullWhen(true)] out XmlDictionaryString result)
        {
            result = null;
            return false;
        }
    }
 
    private static IXmlDictionary s_empty;
 
    private readonly Dictionary<string, XmlDictionaryString> _lookup;
 
    private XmlDictionaryString[] _strings;
 
    private int _nextId;
 
    public static IXmlDictionary Empty
    {
        get
        {
            if (s_empty == null)
            {
                s_empty = new EmptyDictionary();
            }
            return s_empty;
        }
    }
 
    public XmlDictionary()
    {
        _lookup = new Dictionary<string, XmlDictionaryString>();
        _strings = null;
        _nextId = 0;
    }
 
    public XmlDictionary(int capacity)
    {
        _lookup = new Dictionary<string, XmlDictionaryString>(capacity);
        _strings = new XmlDictionaryString[capacity];
        _nextId = 0;
    }
 
    public virtual XmlDictionaryString Add(string value)
    {
        if (!_lookup.TryGetValue(value, out var value2))
        {
            if (_strings == null)
            {
                _strings = new XmlDictionaryString[4];
            }
            else if (_nextId == _strings.Length)
            {
                int num = _nextId * 2;
                if (num == 0)
                {
                    num = 4;
                }
                Array.Resize(ref _strings, num);
            }
            value2 = new XmlDictionaryString(this, value, _nextId);
            _strings[_nextId] = value2;
            _lookup.Add(value, value2);
            _nextId++;
        }
        return value2;
    }
 
    public virtual bool TryLookup(string value, [NotNullWhen(true)] out XmlDictionaryString? result)
    {
        return _lookup.TryGetValue(value, out result);
    }
 
    public virtual bool TryLookup(int key, [NotNullWhen(true)] out XmlDictionaryString? result)
    {
        if (key < 0 || key >= _nextId)
        {
            result = null;
            return false;
        }
        result = _strings[key];
        return true;
    }
 
    public virtual bool TryLookup(XmlDictionaryString value, [NotNullWhen(true)] out XmlDictionaryString? result)
    {
        if (value == null)
        {
            throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentNullException("value"));
        }
        if (value.Dictionary != this)
        {
            result = null;
            return false;
        }
        result = value;
        return true;
    }
}