NamespaceResolver.cs

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namespace System.Xml.Linq;
 
internal struct NamespaceResolver
{
    private sealed class NamespaceDeclaration
    {
        public string prefix;
 
        public XNamespace ns;
 
        public int scope;
 
        public NamespaceDeclaration prev;
    }
 
    private int _scope;
 
    private NamespaceDeclaration _declaration;
 
    private NamespaceDeclaration _rover;
 
    public void PushScope()
    {
        _scope++;
    }
 
    public void PopScope()
    {
        NamespaceDeclaration namespaceDeclaration = _declaration;
        if (namespaceDeclaration != null)
        {
            do
            {
                namespaceDeclaration = namespaceDeclaration.prev;
                if (namespaceDeclaration.scope != _scope)
                {
                    break;
                }
                if (namespaceDeclaration == _declaration)
                {
                    _declaration = null;
                }
                else
                {
                    _declaration.prev = namespaceDeclaration.prev;
                }
                _rover = null;
            }
            while (namespaceDeclaration != _declaration && _declaration != null);
        }
        _scope--;
    }
 
    public void Add(string prefix, XNamespace ns)
    {
        NamespaceDeclaration namespaceDeclaration = new NamespaceDeclaration();
        namespaceDeclaration.prefix = prefix;
        namespaceDeclaration.ns = ns;
        namespaceDeclaration.scope = _scope;
        if (_declaration == null)
        {
            _declaration = namespaceDeclaration;
        }
        else
        {
            namespaceDeclaration.prev = _declaration.prev;
        }
        _declaration.prev = namespaceDeclaration;
        _rover = null;
    }
 
    public void AddFirst(string prefix, XNamespace ns)
    {
        NamespaceDeclaration namespaceDeclaration = new NamespaceDeclaration();
        namespaceDeclaration.prefix = prefix;
        namespaceDeclaration.ns = ns;
        namespaceDeclaration.scope = _scope;
        if (_declaration == null)
        {
            namespaceDeclaration.prev = namespaceDeclaration;
        }
        else
        {
            namespaceDeclaration.prev = _declaration.prev;
            _declaration.prev = namespaceDeclaration;
        }
        _declaration = namespaceDeclaration;
        _rover = null;
    }
 
    public string GetPrefixOfNamespace(XNamespace ns, bool allowDefaultNamespace)
    {
        if (_rover != null && _rover.ns == ns && (allowDefaultNamespace || _rover.prefix.Length > 0))
        {
            return _rover.prefix;
        }
        NamespaceDeclaration namespaceDeclaration = _declaration;
        if (namespaceDeclaration != null)
        {
            do
            {
                namespaceDeclaration = namespaceDeclaration.prev;
                if (!(namespaceDeclaration.ns == ns))
                {
                    continue;
                }
                NamespaceDeclaration prev = _declaration.prev;
                while (prev != namespaceDeclaration && prev.prefix != namespaceDeclaration.prefix)
                {
                    prev = prev.prev;
                }
                if (prev == namespaceDeclaration)
                {
                    if (allowDefaultNamespace)
                    {
                        _rover = namespaceDeclaration;
                        return namespaceDeclaration.prefix;
                    }
                    if (namespaceDeclaration.prefix.Length > 0)
                    {
                        return namespaceDeclaration.prefix;
                    }
                }
            }
            while (namespaceDeclaration != _declaration);
        }
        return null;
    }
}