Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/XPath/Internal/FollowingSibling.cs

@@ -0,0 +1,99 @@
+//------------------------------------------------------------------------------
+// <copyright file="followingsibling.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace MS.Internal.Xml.XPath {
+    using System;
+    using System.Xml;
+    using System.Xml.XPath;
+    using System.Diagnostics;
+    using System.Collections.Generic;
+    using StackNav = ClonableStack<System.Xml.XPath.XPathNavigator>;
+
+    internal sealed class FollSiblingQuery : BaseAxisQuery {
+        StackNav              elementStk;
+        List<XPathNavigator>  parentStk;
+        XPathNavigator        nextInput;
+		
+        public FollSiblingQuery(Query qyInput, string name, string prefix, XPathNodeType type) : base (qyInput, name, prefix, type) {
+            this.elementStk = new StackNav();
+            this.parentStk  = new List<XPathNavigator>();
+        }
+        private FollSiblingQuery(FollSiblingQuery other) : base(other) {
+            this.elementStk = other.elementStk.Clone();
+            this.parentStk = new List<XPathNavigator>(other.parentStk);
+            this.nextInput = Clone(other.nextInput);
+        }
+
+        public override void Reset() {
+            elementStk.Clear();
+            parentStk.Clear();
+            nextInput = null;
+            base.Reset();
+        }
+
+        private bool Visited(XPathNavigator nav) {
+            XPathNavigator parent = nav.Clone();
+            parent.MoveToParent();
+            for (int i = 0; i < parentStk.Count; i++) {
+                if (parent.IsSamePosition(parentStk[i])) {
+                    return true;
+                }
+            }
+            parentStk.Add(parent);
+            return false;
+        }
+
+        private XPathNavigator FetchInput() {
+            XPathNavigator input;
+            do {
+                input = qyInput.Advance();
+                if (input == null) {
+                    return null;
+                }
+            } while (Visited(input));
+            return input.Clone();
+        }
+
+        public override XPathNavigator Advance() {
+        	while (true) {
+                if (currentNode == null) {
+                    if (nextInput == null) {
+                        nextInput = FetchInput(); // This can happen at the begining and at the end 
+                    }
+                    if (elementStk.Count == 0) {
+                        if (nextInput == null) {
+                            return null;
+                        }
+                        currentNode = nextInput;
+                        nextInput = FetchInput();
+                    } else {
+                        currentNode = elementStk.Pop();
+                    }
+                }
+
+                while (currentNode.IsDescendant(nextInput)) {
+                    elementStk.Push(currentNode);
+                    currentNode = nextInput;
+                    nextInput = qyInput.Advance();
+                    if (nextInput != null) {
+                        nextInput = nextInput.Clone();
+                    }
+                }
+
+				while (currentNode.MoveToNext()) {
+				    if (matches(currentNode)) {
+				        position++;
+    				    return currentNode;
+			        }
+			    }
+		        currentNode = null;
+			}
+        } // Advance
+                
+        public override XPathNodeIterator Clone() { return new FollSiblingQuery(this); }
+    }
+}