Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.SqlXml/System/Xml/Xsl/Runtime/XmlILIndex.cs

@@ -0,0 +1,64 @@
+//------------------------------------------------------------------------------
+// <copyright file="XmlILIndex.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Xml.XPath;
+
+namespace System.Xml.Xsl.Runtime {
+
+    /// <summary>
+    /// This class manages nodes from one input document, indexed by key value(s).
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public sealed class XmlILIndex {
+        private Dictionary<string, XmlQueryNodeSequence> table;
+
+        /// <summary>
+        /// This constructor is internal so that external users cannot construct it (and therefore we do not have to test it separately).
+        /// </summary>
+        internal XmlILIndex() {
+            this.table = new Dictionary<string, XmlQueryNodeSequence>();
+        }
+
+        /// <summary>
+        /// Add a node indexed by the specified key value.
+        /// </summary>
+        public void Add(string key, XPathNavigator navigator) {
+            XmlQueryNodeSequence seq;
+
+            if (!this.table.TryGetValue(key, out seq)) {
+                // Create a new sequence and add it to the index
+                seq = new XmlQueryNodeSequence();
+                seq.AddClone(navigator);
+                this.table.Add(key, seq);
+            }
+            else {
+                // The nodes are guaranteed to be added in document order with possible duplicates.
+                // Add node to the existing sequence if it differs from the last one.
+                Debug.Assert(navigator.ComparePosition(seq[seq.Count - 1]) >= 0, "Index nodes must be added in document order");
+                if (!navigator.IsSamePosition(seq[seq.Count - 1])) {
+                    seq.AddClone(navigator);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Lookup a sequence of nodes that are indexed by the specified key value.
+        /// Return a non-null empty sequence, if there are no nodes associated with the key.
+        /// </summary>
+        public XmlQueryNodeSequence Lookup(string key) {
+            XmlQueryNodeSequence seq;
+
+            if (!this.table.TryGetValue(key, out seq))
+                seq = new XmlQueryNodeSequence();
+
+            return seq;
+        }
+    }
+}