Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.Entity/System/Data/Common/FieldNameLookup.cs

@@ -0,0 +1,125 @@
+//------------------------------------------------------------------------------
+// <copyright file="FieldNameLookup.cs" company="Microsoft">
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="false" primary="false">[....]</owner>
+//------------------------------------------------------------------------------
+
+
+namespace System.Data 
+{
+    using System;
+    using System.Collections;
+    using System.ComponentModel;
+    using System.Data;
+    using System.Data.Common;
+    using System.Diagnostics;
+    using System.Globalization;
+    using System.Text;
+    
+    internal sealed class FieldNameLookup { // V1.2.3300, MDAC 69015, 71470
+
+        // hashtable stores the index into the _fieldNames, match via case-sensitive
+        private Hashtable _fieldNameLookup;
+
+        // original names for linear searches when exact matches fail
+        private string[] _fieldNames;
+
+        // if _defaultLocaleID is -1 then _compareInfo is initialized with InvariantCulture CompareInfo
+        // otherwise it is specified by the server? for the correct compare info
+        private CompareInfo _compareInfo;
+        private int _defaultLocaleID;
+
+        public FieldNameLookup(System.Collections.ObjectModel.ReadOnlyCollection<string> columnNames, int defaultLocaleID) {
+
+            int length = columnNames.Count;
+            string[] fieldNames = new string[length];
+            for (int i = 0; i < length; ++i) {
+                fieldNames[i] = columnNames[i];
+                Debug.Assert(null != fieldNames[i], "MDAC 66681");
+            }
+            _fieldNames = fieldNames;
+            _defaultLocaleID = defaultLocaleID;
+            GenerateLookup();
+        }
+
+        public FieldNameLookup(IDataRecord reader, int defaultLocaleID) { // V1.2.3300
+
+            int length = reader.FieldCount;
+            string[] fieldNames = new string[length];
+            for (int i = 0; i < length; ++i) {
+                fieldNames[i] = reader.GetName(i);
+                Debug.Assert(null != fieldNames[i], "MDAC 66681");
+            }
+            _fieldNames = fieldNames;
+            _defaultLocaleID = defaultLocaleID;
+        }
+
+        public int GetOrdinal(string fieldName) { // V1.2.3300
+            if (null == fieldName) {
+                throw EntityUtil.ArgumentNull("fieldName");
+            }
+            int index = IndexOf(fieldName);
+            if (-1 == index) {
+                throw EntityUtil.IndexOutOfRange(fieldName);
+            }
+            return index;
+        }
+
+        public int IndexOf(string fieldName) { // V1.2.3300
+            if (null == _fieldNameLookup) {
+                GenerateLookup();
+            }
+            int index;
+            object value = _fieldNameLookup[fieldName];
+            if (null != value) {
+                // via case sensitive search, first match with lowest ordinal matches
+                index = (int) value;
+            }
+            else {
+                // via case insensitive search, first match with lowest ordinal matches
+                index = LinearIndexOf(fieldName, CompareOptions.IgnoreCase);
+                if (-1 == index) {
+                    // do the slow search now (kana, width insensitive comparison)
+                    index = LinearIndexOf(fieldName, EntityUtil.StringCompareOptions);
+                }
+            }
+            return index;
+        }
+
+        private int LinearIndexOf(string fieldName, CompareOptions compareOptions) {
+            CompareInfo compareInfo = _compareInfo;
+            if (null == compareInfo) {
+                if (-1 != _defaultLocaleID) {
+                    compareInfo = CompareInfo.GetCompareInfo(_defaultLocaleID);
+                }
+                if (null == compareInfo) {
+                    compareInfo = CultureInfo.InvariantCulture.CompareInfo;
+                }
+                _compareInfo = compareInfo;
+            }
+            int length = _fieldNames.Length;
+            for (int i = 0; i < length; ++i) {
+                if (0 == compareInfo.Compare(fieldName, _fieldNames[i], compareOptions)) {
+                    _fieldNameLookup[fieldName] = i; // add an exact match for the future
+                    return i;
+                }
+            }
+            return -1;
+        }
+
+        // RTM common code for generating Hashtable from array of column names
+        private void GenerateLookup() {
+            int length = _fieldNames.Length;
+            Hashtable hash = new Hashtable(length);
+
+            // via case sensitive search, first match with lowest ordinal matches
+            for (int i = length-1; 0 <= i; --i) {
+                string fieldName = _fieldNames[i];
+                hash[fieldName] = i;
+            }
+            _fieldNameLookup = hash;
+        }
+    }
+}