Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data/System/NewXml/TreeIterator.cs

@@ -0,0 +1,77 @@
+//------------------------------------------------------------------------------
+// <copyright file="TreeIterator.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="true" primary="false">[....]</owner>
+//------------------------------------------------------------------------------
+#pragma warning disable 618 // ignore obsolete warning about XmlDataDocument
+namespace System.Xml {
+    using System.Diagnostics;
+
+    // Iterates over non-attribute nodes
+    internal sealed class TreeIterator : BaseTreeIterator {
+        private XmlNode         nodeTop;
+        private XmlNode         currentNode;
+
+        internal TreeIterator( XmlNode nodeTop ) : base( ((XmlDataDocument)(nodeTop.OwnerDocument)).Mapper ) {
+            Debug.Assert( nodeTop != null );
+            this.nodeTop     = nodeTop;
+            this.currentNode = nodeTop;
+        }
+
+        internal override void Reset() {
+            currentNode = nodeTop;
+        }
+
+        internal override XmlNode CurrentNode {
+            get {
+                return currentNode;
+            }
+        }
+
+        internal override bool Next() {
+            XmlNode nextNode;
+
+            // Try to move to the first child
+            nextNode = currentNode.FirstChild;
+
+            // No children, try next sibling
+            if ( nextNode != null ) {
+                currentNode = nextNode;
+                return true;
+            }
+            return NextRight();
+        }
+
+        internal override bool NextRight() {
+            // Make sure we do not get past the nodeTop if we call NextRight on a just initialized iterator and nodeTop has no children
+            if ( currentNode == nodeTop ) {
+                currentNode = null;
+                return false;
+            }
+
+            XmlNode nextNode = currentNode.NextSibling;
+
+            if ( nextNode != null ) {
+                currentNode = nextNode;
+                return true;
+            }
+
+            // No next sibling, try the first sibling of from the parent chain
+            nextNode = currentNode;
+            while ( nextNode != nodeTop && nextNode.NextSibling == null )
+                nextNode = nextNode.ParentNode;
+
+            if ( nextNode == nodeTop ) {
+                currentNode = null;
+                return false;
+            }
+
+            currentNode = nextNode.NextSibling;
+            Debug.Assert( currentNode != null );
+            return true;
+        }
+    }
+}
+