Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.SqlXml/System/Xml/Xsl/XsltOld/Avt.cs

@@ -0,0 +1,65 @@
+//------------------------------------------------------------------------------
+// <copyright file="Avt.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace System.Xml.Xsl.XsltOld {
+    using Res = System.Xml.Utils.Res;
+    using System;
+    using System.Diagnostics;
+    using System.Collections;
+    using System.Xml;
+    using System.Xml.XPath;
+    using System.Text;
+
+    internal sealed class Avt {
+        private string      constAvt;
+        private TextEvent[] events;
+
+        private Avt(string constAvt) {
+            Debug.Assert(constAvt != null);
+            this.constAvt = constAvt;
+        }
+
+        private Avt(ArrayList eventList) {
+            Debug.Assert(eventList != null);
+            this.events = new TextEvent[eventList.Count];
+            for(int i = 0; i < eventList.Count; i ++) {
+                this.events[i] = (TextEvent) eventList[i];
+            }
+        }
+
+        public bool IsConstant {
+            get {return this.events == null;}
+        }
+
+        internal string Evaluate(Processor processor, ActionFrame frame) {
+            if (IsConstant) {
+                Debug.Assert(constAvt != null);
+                return constAvt;
+            }
+            else {
+                Debug.Assert(processor != null && frame != null);
+
+                StringBuilder builder = processor.GetSharedStringBuilder();
+
+                for(int i = 0; i < events.Length; i ++) {
+                    builder.Append(events[i].Evaluate(processor, frame));
+                }
+                processor.ReleaseSharedStringBuilder();
+                return builder.ToString();
+            }
+        }
+
+        internal static Avt CompileAvt(Compiler compiler, string avtText) {
+            Debug.Assert(compiler != null);
+            Debug.Assert(avtText != null);
+
+            bool constant;
+            ArrayList list = compiler.CompileAvt(avtText, out constant);
+            return constant ? new Avt(avtText) : new Avt(list);
+        }
+    }
+}