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

   1 using System;
   2 using System.Collections;
   3
   4 namespace System.Data.Common
   5 {
   6         /// <summary>
   7         /// Summary description for ComparerFactory.
   8         /// </summary>
   9         internal class DBComparerFactory
  10         {
  11                 private static IComparer comparableComparer = new ComparebleComparer();
  12                 private static IComparer ignoreCaseComparer = new IgnoreCaseComparer();
  13                 private static IComparer caseComparer = new CaseComparer();
  14                 private static IComparer byteArrayComparer = new ByteArrayComparer();
  15                 private static Type icomparerType = typeof (IComparable);
  16
  17                 public static IComparer GetComparer (Type type, bool ignoreCase)
  18                 {
  19                         if (type == typeof (string)) {
  20                                 if (ignoreCase)
  21                                         return ignoreCaseComparer;
  22                                 return caseComparer;
  23                         }
  24                         if (icomparerType.IsAssignableFrom(type))
  25                                 return comparableComparer;
  26                         if (type == typeof (byte[]))
  27                                 return byteArrayComparer;
  28                         return null;
  29                 }
  30
  31                 class ComparebleComparer :IComparer
  32                 {
  33                         #region IComparer Members
  34
  35                         public int Compare(object x, object y)
  36                         {
  37                                 if (x == DBNull.Value) {
  38                                         if (y == DBNull.Value)
  39                                                 return 0;
  40
  41                                         return -1;
  42                                 }
  43
  44                                 if (y == DBNull.Value)
  45                                         return 1;
  46
  47                                 return ((IComparable)x).CompareTo (y);
  48                         }
  49
  50                         #endregion
  51                 }
  52
  53                 class CaseComparer : IComparer
  54                 {
  55                         #region IComparer Members
  56
  57                         public int Compare(object x, object y)
  58                         {
  59                                 if (x == DBNull.Value) {
  60                                         if (y == DBNull.Value)
  61                                                 return 0;
  62
  63                                         return -1;
  64                                 }
  65
  66                                 if (y == DBNull.Value)
  67                                         return 1;
  68
  69                                 return String.Compare ((string)x, (string)y, false);
  70                         }
  71
  72                         #endregion
  73                 }
  74
  75                 class IgnoreCaseComparer : IComparer
  76                 {
  77                         #region IComparer Members
  78
  79                         public int Compare(object x, object y)
  80                         {
  81                                 if (x == DBNull.Value) {
  82                                         if (y == DBNull.Value)
  83                                                 return 0;
  84
  85                                         return -1;
  86                                 }
  87
  88                                 if (y == DBNull.Value)
  89                                         return 1;
  90
  91                                 return String.Compare ((string)x, (string)y, true);
  92                         }
  93
  94                         #endregion
  95                 }
  96
  97                 class ByteArrayComparer : IComparer
  98                 {
  99                         #region IComparer Members
 100
 101                         public int Compare(object x, object y)
 102                         {
 103                                 if (x == DBNull.Value) {
 104                                         if (y == DBNull.Value)
 105                                                 return 0;
 106
 107                                         return -1;
 108                                 }
 109
 110                                 if (y == DBNull.Value)
 111                                         return 1;
 112
 113                                 byte[] o1 = (byte[])x;
 114                                 byte[] o2 = (byte[])y;
 115                                 int len  = o1.Length;
 116                                 int lenb = o2.Length;
 117
 118                                 for (int i = 0; ; i++) {
 119                                         int a = 0;
 120                                         int b = 0;
 121
 122                                         if (i < len) {
 123                                                 a = o1[i];
 124                                         }
 125                                         else if (i >= lenb) {
 126                                                 return 0;
 127                                         }
 128
 129                                         if (i < lenb) {
 130                                                 b = o2[i];
 131                                         }
 132
 133                                         if (a > b) {
 134                                                 return 1;
 135                                         }
 136
 137                                         if (b > a) {
 138                                                 return -1;
 139                                         }
 140                                 }
 141                         }
 142
 143                         #endregion
 144                 }
 145         }
 146 }