Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

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

@@ -0,0 +1,60 @@
+//------------------------------------------------------------------------------
+// <copyright file="CacheAxisQuery.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;
+
+    internal abstract class CacheAxisQuery : BaseAxisQuery {
+        // int count; -- we reusing it here
+        protected List<XPathNavigator> outputBuffer;
+
+        public CacheAxisQuery(Query qyInput, string name, string prefix, XPathNodeType typeTest) : base(qyInput, name, prefix, typeTest)  {
+            this.outputBuffer = new List<XPathNavigator>();
+            this.count = 0;
+        }
+        protected CacheAxisQuery(CacheAxisQuery other) : base(other) { 
+            this.outputBuffer = new List<XPathNavigator>(other.outputBuffer);
+            this.count = other.count;
+        }
+
+        public override void Reset() {
+            this.count = 0;
+        }
+
+        public override object Evaluate(XPathNodeIterator context) {
+            base.Evaluate(context);
+            outputBuffer.Clear();
+            return this;
+        }
+
+        public override XPathNavigator Advance() {
+            Debug.Assert(0 <= count && count <= outputBuffer.Count);
+            if (count < outputBuffer.Count) {
+                return outputBuffer[count++];
+            }
+            return null;
+        }
+        
+        public override XPathNavigator Current { 
+            get {
+                Debug.Assert(0 <= count && count <= outputBuffer.Count);
+                if (count == 0) {
+                    return null;
+                }
+                return outputBuffer[count - 1];
+            } 
+        }
+
+        public override int CurrentPosition   { get { return count; } }
+        public override int Count             { get { return outputBuffer.Count; } }
+        public override QueryProps Properties { get { return QueryProps.Merge | QueryProps.Cached | QueryProps.Position | QueryProps.Count; } }
+    }
+}