XmlDictionaryString.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.Serialization;
using System.Text;
 
namespace System.Xml;
 
public class XmlDictionaryString
{
    private sealed class EmptyStringDictionary : IXmlDictionary
    {
        private readonly XmlDictionaryString _empty;
 
        public XmlDictionaryString EmptyString => _empty;
 
        public EmptyStringDictionary()
        {
            _empty = new XmlDictionaryString(this, string.Empty, 0);
        }
 
        public bool TryLookup(string value, [NotNullWhen(true)] out XmlDictionaryString result)
        {
            if (value == null)
            {
                throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("value");
            }
            if (value.Length == 0)
            {
                result = _empty;
                return true;
            }
            result = null;
            return false;
        }
 
        public bool TryLookup(int key, [NotNullWhen(true)] out XmlDictionaryString result)
        {
            if (key == 0)
            {
                result = _empty;
                return true;
            }
            result = null;
            return false;
        }
 
        public 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;
        }
    }
 
    internal const int MinKey = 0;
 
    internal const int MaxKey = 536870911;
 
    private readonly IXmlDictionary _dictionary;
 
    private readonly string _value;
 
    private readonly int _key;
 
    private byte[] _buffer;
 
    private static readonly EmptyStringDictionary s_emptyStringDictionary = new EmptyStringDictionary();
 
    public static XmlDictionaryString Empty => s_emptyStringDictionary.EmptyString;
 
    public IXmlDictionary Dictionary => _dictionary;
 
    public int Key => _key;
 
    public string Value => _value;
 
    public XmlDictionaryString(IXmlDictionary dictionary, string value, int key)
    {
        if (dictionary == null)
        {
            throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentNullException("dictionary"));
        }
        if (value == null)
        {
            throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentNullException("value"));
        }
        if (key < 0 || key > 536870911)
        {
            throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentOutOfRangeException("key", System.SR.Format(System.SR.ValueMustBeInRange, 0, 536870911)));
        }
        _dictionary = dictionary;
        _value = value;
        _key = key;
    }
 
    [return: NotNullIfNotNull("s")]
    internal static string GetString(XmlDictionaryString s)
    {
        return s?.Value;
    }
 
    internal byte[] ToUTF8()
    {
        if (_buffer == null)
        {
            _buffer = Encoding.UTF8.GetBytes(_value);
        }
        return _buffer;
    }
 
    public override string ToString()
    {
        return _value;
    }
}