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

   1 //------------------------------------------------------------------------------
   2 // <copyright file="FieldNameLookup.cs" company="Microsoft">
   3 //      Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 // <owner current="true" primary="true">Microsoft</owner>
   6 // <owner current="false" primary="false">Microsoft</owner>
   7 //------------------------------------------------------------------------------
   8
   9
  10 namespace System.Data
  11 {
  12     using System;
  13     using System.Collections;
  14     using System.ComponentModel;
  15     using System.Data;
  16     using System.Data.Common;
  17     using System.Diagnostics;
  18     using System.Globalization;
  19     using System.Text;
  20
  21     internal sealed class FieldNameLookup { // V1.2.3300, MDAC 69015, 71470
  22
  23         // hashtable stores the index into the _fieldNames, match via case-sensitive
  24         private Hashtable _fieldNameLookup;
  25
  26         // original names for linear searches when exact matches fail
  27         private string[] _fieldNames;
  28
  29         // if _defaultLocaleID is -1 then _compareInfo is initialized with InvariantCulture CompareInfo
  30         // otherwise it is specified by the server? for the correct compare info
  31         private CompareInfo _compareInfo;
  32         private int _defaultLocaleID;
  33
  34         public FieldNameLookup(System.Collections.ObjectModel.ReadOnlyCollection<string> columnNames, int defaultLocaleID) {
  35
  36             int length = columnNames.Count;
  37             string[] fieldNames = new string[length];
  38             for (int i = 0; i < length; ++i) {
  39                 fieldNames[i] = columnNames[i];
  40                 Debug.Assert(null != fieldNames[i], "MDAC 66681");
  41             }
  42             _fieldNames = fieldNames;
  43             _defaultLocaleID = defaultLocaleID;
  44             GenerateLookup();
  45         }
  46
  47         public FieldNameLookup(IDataRecord reader, int defaultLocaleID) { // V1.2.3300
  48
  49             int length = reader.FieldCount;
  50             string[] fieldNames = new string[length];
  51             for (int i = 0; i < length; ++i) {
  52                 fieldNames[i] = reader.GetName(i);
  53                 Debug.Assert(null != fieldNames[i], "MDAC 66681");
  54             }
  55             _fieldNames = fieldNames;
  56             _defaultLocaleID = defaultLocaleID;
  57         }
  58
  59         public int GetOrdinal(string fieldName) { // V1.2.3300
  60             if (null == fieldName) {
  61                 throw EntityUtil.ArgumentNull("fieldName");
  62             }
  63             int index = IndexOf(fieldName);
  64             if (-1 == index) {
  65                 throw EntityUtil.IndexOutOfRange(fieldName);
  66             }
  67             return index;
  68         }
  69
  70         public int IndexOf(string fieldName) { // V1.2.3300
  71             if (null == _fieldNameLookup) {
  72                 GenerateLookup();
  73             }
  74             int index;
  75             object value = _fieldNameLookup[fieldName];
  76             if (null != value) {
  77                 // via case sensitive search, first match with lowest ordinal matches
  78                 index = (int) value;
  79             }
  80             else {
  81                 // via case insensitive search, first match with lowest ordinal matches
  82                 index = LinearIndexOf(fieldName, CompareOptions.IgnoreCase);
  83                 if (-1 == index) {
  84                     // do the slow search now (kana, width insensitive comparison)
  85                     index = LinearIndexOf(fieldName, EntityUtil.StringCompareOptions);
  86                 }
  87             }
  88             return index;
  89         }
  90
  91         private int LinearIndexOf(string fieldName, CompareOptions compareOptions) {
  92             CompareInfo compareInfo = _compareInfo;
  93             if (null == compareInfo) {
  94                 if (-1 != _defaultLocaleID) {
  95                     compareInfo = CompareInfo.GetCompareInfo(_defaultLocaleID);
  96                 }
  97                 if (null == compareInfo) {
  98                     compareInfo = CultureInfo.InvariantCulture.CompareInfo;
  99                 }
 100                 _compareInfo = compareInfo;
 101             }
 102             int length = _fieldNames.Length;
 103             for (int i = 0; i < length; ++i) {
 104                 if (0 == compareInfo.Compare(fieldName, _fieldNames[i], compareOptions)) {
 105                     _fieldNameLookup[fieldName] = i; // add an exact match for the future
 106                     return i;
 107                 }
 108             }
 109             return -1;
 110         }
 111
 112         // RTM common code for generating Hashtable from array of column names
 113         private void GenerateLookup() {
 114             int length = _fieldNames.Length;
 115             Hashtable hash = new Hashtable(length);
 116
 117             // via case sensitive search, first match with lowest ordinal matches
 118             for (int i = length-1; 0 <= i; --i) {
 119                 string fieldName = _fieldNames[i];
 120                 hash[fieldName] = i;
 121             }
 122             _fieldNameLookup = hash;
 123         }
 124     }
 125 }