Extensions.cs

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using System.Collections.Generic;
 
namespace System.Xml.Linq;
 
public static class Extensions
{
    public static IEnumerable<XAttribute> Attributes(this IEnumerable<XElement?> source)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetAttributes(source, null);
    }
 
    public static IEnumerable<XAttribute> Attributes(this IEnumerable<XElement?> source, XName? name)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XAttribute.EmptySequence;
        }
        return GetAttributes(source, name);
    }
 
    public static IEnumerable<XElement> Ancestors<T>(this IEnumerable<T?> source) where T : XNode
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetAncestors(source, null, self: false);
    }
 
    public static IEnumerable<XElement> Ancestors<T>(this IEnumerable<T?> source, XName? name) where T : XNode
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XElement.EmptySequence;
        }
        return GetAncestors(source, name, self: false);
    }
 
    public static IEnumerable<XElement> AncestorsAndSelf(this IEnumerable<XElement?> source)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetAncestors(source, null, self: true);
    }
 
    public static IEnumerable<XElement> AncestorsAndSelf(this IEnumerable<XElement?> source, XName? name)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XElement.EmptySequence;
        }
        return GetAncestors(source, name, self: true);
    }
 
    public static IEnumerable<XNode> Nodes<T>(this IEnumerable<T?> source) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return NodesIterator(source);
    }
 
    private static IEnumerable<XNode> NodesIterator<T>(IEnumerable<T> source) where T : XContainer
    {
        foreach (T root in source)
        {
            if (root == null)
            {
                continue;
            }
            XNode i = root.LastNode;
            if (i != null)
            {
                do
                {
                    i = i.next;
                    yield return i;
                }
                while (i.parent == root && i != root.content);
            }
        }
    }
 
    public static IEnumerable<XNode> DescendantNodes<T>(this IEnumerable<T?> source) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetDescendantNodes(source, self: false);
    }
 
    public static IEnumerable<XElement> Descendants<T>(this IEnumerable<T?> source) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetDescendants(source, null, self: false);
    }
 
    public static IEnumerable<XElement> Descendants<T>(this IEnumerable<T?> source, XName? name) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XElement.EmptySequence;
        }
        return GetDescendants(source, name, self: false);
    }
 
    public static IEnumerable<XNode> DescendantNodesAndSelf(this IEnumerable<XElement?> source)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetDescendantNodes(source, self: true);
    }
 
    public static IEnumerable<XElement> DescendantsAndSelf(this IEnumerable<XElement?> source)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetDescendants(source, null, self: true);
    }
 
    public static IEnumerable<XElement> DescendantsAndSelf(this IEnumerable<XElement?> source, XName? name)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XElement.EmptySequence;
        }
        return GetDescendants(source, name, self: true);
    }
 
    public static IEnumerable<XElement> Elements<T>(this IEnumerable<T?> source) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return GetElements(source, null);
    }
 
    public static IEnumerable<XElement> Elements<T>(this IEnumerable<T?> source, XName? name) where T : XContainer
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        if (!(name != null))
        {
            return XElement.EmptySequence;
        }
        return GetElements(source, name);
    }
 
    public static IEnumerable<T> InDocumentOrder<T>(this IEnumerable<T> source) where T : XNode?
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        return DocumentOrderIterator(source);
    }
 
    private static IEnumerable<T> DocumentOrderIterator<T>(IEnumerable<T> source) where T : XNode
    {
        int count;
        T[] items = System.Collections.Generic.EnumerableHelpers.ToArray(source, out count);
        if (count > 0)
        {
            Array.Sort(items, 0, count, XNode.DocumentOrderComparer);
            int i = 0;
            while (i != count)
            {
                yield return items[i];
                int num = i + 1;
                i = num;
            }
        }
    }
 
    public static void Remove(this IEnumerable<XAttribute?> source)
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        int length;
        XAttribute[] array = System.Collections.Generic.EnumerableHelpers.ToArray(source, out length);
        for (int i = 0; i < length; i++)
        {
            array[i]?.Remove();
        }
    }
 
    public static void Remove<T>(this IEnumerable<T?> source) where T : XNode
    {
        if (source == null)
        {
            throw new ArgumentNullException("source");
        }
        int length;
        T[] array = System.Collections.Generic.EnumerableHelpers.ToArray(source, out length);
        for (int i = 0; i < length; i++)
        {
            array[i]?.Remove();
        }
    }
 
    private static IEnumerable<XAttribute> GetAttributes(IEnumerable<XElement> source, XName name)
    {
        foreach (XElement e in source)
        {
            if (e == null)
            {
                continue;
            }
            XAttribute a = e.lastAttr;
            if (a == null)
            {
                continue;
            }
            do
            {
                a = a.next;
                if (name == null || a.name == name)
                {
                    yield return a;
                }
            }
            while (a.parent == e && a != e.lastAttr);
        }
    }
 
    private static IEnumerable<XElement> GetAncestors<T>(IEnumerable<T> source, XName name, bool self) where T : XNode
    {
        foreach (T item in source)
        {
            if (item == null)
            {
                continue;
            }
            for (XElement e = (self ? ((XNode)item) : ((XNode)item.parent)) as XElement; e != null; e = e.parent as XElement)
            {
                if (name == null || e.name == name)
                {
                    yield return e;
                }
            }
        }
    }
 
    private static IEnumerable<XNode> GetDescendantNodes<T>(IEnumerable<T> source, bool self) where T : XContainer
    {
        foreach (T root in source)
        {
            if (root == null)
            {
                continue;
            }
            if (self)
            {
                yield return root;
            }
            XNode i = root;
            while (true)
            {
                XNode firstNode;
                if (i is XContainer xContainer && (firstNode = xContainer.FirstNode) != null)
                {
                    i = firstNode;
                }
                else
                {
                    while (i != null && i != root && i == i.parent.content)
                    {
                        i = i.parent;
                    }
                    if (i == null || i == root)
                    {
                        break;
                    }
                    i = i.next;
                }
                yield return i;
            }
        }
    }
 
    private static IEnumerable<XElement> GetDescendants<T>(IEnumerable<T> source, XName name, bool self) where T : XContainer
    {
        foreach (T root in source)
        {
            if (root == null)
            {
                continue;
            }
            if (self)
            {
                XElement xElement = (XElement)(object)root;
                if (name == null || xElement.name == name)
                {
                    yield return xElement;
                }
            }
            XNode i = root;
            XContainer xContainer = root;
            while (true)
            {
                if (xContainer != null && xContainer.content is XNode)
                {
                    i = ((XNode)xContainer.content).next;
                }
                else
                {
                    while (i != null && i != root && i == i.parent.content)
                    {
                        i = i.parent;
                    }
                    if (i == null || i == root)
                    {
                        break;
                    }
                    i = i.next;
                }
                XElement e = i as XElement;
                if (e != null && (name == null || e.name == name))
                {
                    yield return e;
                }
                xContainer = e;
            }
        }
    }
 
    private static IEnumerable<XElement> GetElements<T>(IEnumerable<T> source, XName name) where T : XContainer
    {
        foreach (T root in source)
        {
            if (root == null)
            {
                continue;
            }
            XNode i = root.content as XNode;
            if (i == null)
            {
                continue;
            }
            do
            {
                i = i.next;
                if (i is XElement xElement && (name == null || xElement.name == name))
                {
                    yield return xElement;
                }
            }
            while (i.parent == root && i != root.content);
        }
    }
}