mcs/class/System.Data/System.Data.Common/ComparerFactory.cs

   1
   2 //
   3 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining
   6 // a copy of this software and associated documentation files (the
   7 // "Software"), to deal in the Software without restriction, including
   8 // without limitation the rights to use, copy, modify, merge, publish,
   9 // distribute, sublicense, and/or sell copies of the Software, and to
  10 // permit persons to whom the Software is furnished to do so, subject to
  11 // the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be
  14 // included in all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  19 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  20 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  21 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  22 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23 //
  24 using System;
  25 using System.Collections;
  26
  27 namespace System.Data.Common
  28 {
  29         /// <summary>
  30         /// Summary description for ComparerFactory.
  31         /// </summary>
  32         internal class DBComparerFactory
  33         {
  34                 private static IComparer comparableComparer = new ComparebleComparer();
  35                 private static IComparer ignoreCaseComparer = new IgnoreCaseComparer();
  36                 private static IComparer caseComparer = new CaseComparer();
  37                 private static IComparer byteArrayComparer = new ByteArrayComparer();
  38                 private static Type icomparerType = typeof (IComparable);
  39
  40                 public static IComparer GetComparer (Type type, bool ignoreCase)
  41                 {
  42                         if (type == typeof (string)) {
  43                                 if (ignoreCase)
  44                                         return ignoreCaseComparer;
  45                                 return caseComparer;
  46                         }
  47                         if (icomparerType.IsAssignableFrom(type))
  48                                 return comparableComparer;
  49                         if (type == typeof (byte[]))
  50                                 return byteArrayComparer;
  51                         return null;
  52                 }
  53
  54                 class ComparebleComparer :IComparer
  55                 {
  56                         #region IComparer Members
  57
  58                         public int Compare(object x, object y)
  59                         {
  60                                 if (x == DBNull.Value) {
  61                                         if (y == DBNull.Value)
  62                                                 return 0;
  63
  64                                         return -1;
  65                                 }
  66
  67                                 if (y == DBNull.Value)
  68                                         return 1;
  69
  70                                 return ((IComparable)x).CompareTo (y);
  71                         }
  72
  73                         #endregion
  74                 }
  75
  76                 class CaseComparer : IComparer
  77                 {
  78                         #region IComparer Members
  79
  80                         public int Compare(object x, object y)
  81                         {
  82                                 if (x == DBNull.Value) {
  83                                         if (y == DBNull.Value)
  84                                                 return 0;
  85
  86                                         return -1;
  87                                 }
  88
  89                                 if (y == DBNull.Value)
  90                                         return 1;
  91
  92                                 return String.Compare ((string)x, (string)y, false);
  93                         }
  94
  95                         #endregion
  96                 }
  97
  98                 class IgnoreCaseComparer : IComparer
  99                 {
 100                         #region IComparer Members
 101
 102                         public int Compare(object x, object y)
 103                         {
 104                                 if (x == DBNull.Value) {
 105                                         if (y == DBNull.Value)
 106                                                 return 0;
 107
 108                                         return -1;
 109                                 }
 110
 111                                 if (y == DBNull.Value)
 112                                         return 1;
 113
 114                                 return String.Compare ((string)x, (string)y, true);
 115                         }
 116
 117                         #endregion
 118                 }
 119
 120                 class ByteArrayComparer : IComparer
 121                 {
 122                         #region IComparer Members
 123
 124                         public int Compare(object x, object y)
 125                         {
 126                                 if (x == DBNull.Value) {
 127                                         if (y == DBNull.Value)
 128                                                 return 0;
 129
 130                                         return -1;
 131                                 }
 132
 133                                 if (y == DBNull.Value)
 134                                         return 1;
 135
 136                                 byte[] o1 = (byte[])x;
 137                                 byte[] o2 = (byte[])y;
 138                                 int len  = o1.Length;
 139                                 int lenb = o2.Length;
 140
 141                                 for (int i = 0; ; i++) {
 142                                         int a = 0;
 143                                         int b = 0;
 144
 145                                         if (i < len) {
 146                                                 a = o1[i];
 147                                         }
 148                                         else if (i >= lenb) {
 149                                                 return 0;
 150                                         }
 151
 152                                         if (i < lenb) {
 153                                                 b = o2[i];
 154                                         }
 155
 156                                         if (a > b) {
 157                                                 return 1;
 158                                         }
 159
 160                                         if (b > a) {
 161                                                 return -1;
 162                                         }
 163                                 }
 164                         }
 165
 166                         #endregion
 167                 }
 168         }
 169 }