mcs/class/System.Data.DataSetExtensions/System.Data/OrderedEnumerableRowCollection.cs

   1 //
   2 // OrderedEnumerableRowCollection.cs
   3 //
   4 // Author:
   5 //   Atsushi Enomoto  <atsushi@ximian.com>
   6 //
   7 // Copyright (C) 2008 Novell, Inc. http://www.novell.com
   8 //
   9
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31 using System;
  32 using System.Collections;
  33 using System.Collections.Generic;
  34
  35 namespace System.Data
  36 {
  37         public sealed class OrderedEnumerableRowCollection<TRow>
  38                 : EnumerableRowCollection<TRow>
  39         {
  40                 internal static OrderedEnumerableRowCollection<TRow> Create<TRow, TKey> (IEnumerable<TRow> source, Func<TRow, TKey> keySelector, IComparer<TKey> comparer, bool descending)
  41                 {
  42                         var sorter = new SortComparer<TRow> ();
  43                         sorter.AddSort<TKey> (keySelector, comparer, descending);
  44                         return new OrderedEnumerableRowCollection<TRow> (new SortedEnumerable <TRow> (source, sorter));
  45                 }
  46
  47                 internal static OrderedEnumerableRowCollection<TRow> AddSort<TRow, TKey> (OrderedEnumerableRowCollection<TRow> source, Func<TRow, TKey> keySelector, IComparer<TKey> comparer, bool descending)
  48                 {
  49                         source.source.Sorter.AddSort<TKey> (keySelector, comparer, descending);
  50                         return source;
  51                 }
  52
  53                 OrderedEnumerableRowCollection (SortedEnumerable<TRow> source)
  54                         : base (source)
  55                 {
  56                         this.source = source;
  57                 }
  58
  59                 SortedEnumerable<TRow> source;
  60         }
  61
  62         class SortComparer<TRow> : IComparer<TRow>
  63         {
  64                 public SortComparer ()
  65                 {
  66                 }
  67
  68                 List<Comparison<TRow>> comparers = new List<Comparison<TRow>> ();
  69
  70                 public void AddSort (Comparison<TRow> comparer)
  71                 {
  72                         comparers.Add (comparer);
  73                 }
  74
  75                 public void AddSort<TKey> (Func<TRow, TKey> keySelector, IComparer<TKey> comparer, bool descending)
  76                 {
  77                         if (keySelector == null)
  78                                 throw new ArgumentNullException ("keySelector");
  79                         if (comparer == null)
  80                                 comparer = Comparer<TKey>.Default;
  81                         comparers.Add (delegate (TRow r1, TRow r2) {
  82                                 int ret = comparer.Compare (keySelector (r1), keySelector (r2));
  83                                 return descending ? -ret : ret;
  84                                 });
  85                 }
  86
  87                 public int Compare (TRow r1, TRow r2)
  88                 {
  89                         foreach (var c in comparers) {
  90                                 int ret = c (r1, r2);
  91                                 if (ret != 0)
  92                                         return ret;
  93                         }
  94                         return 0;
  95                 }
  96         }
  97
  98         class SortedEnumerable<TRow> : IEnumerable<TRow>
  99         {
 100                 IEnumerable<TRow> source;
 101                 SortComparer<TRow> sorter;
 102
 103                 public SortedEnumerable (IEnumerable<TRow> source, SortComparer<TRow> sorter)
 104                 {
 105                         this.source = source;
 106                         this.sorter = sorter;
 107                 }
 108
 109                 public SortComparer<TRow> Sorter {
 110                         get { return sorter; }
 111                 }
 112
 113                 public IEnumerator<TRow> GetEnumerator ()
 114                 {
 115                         var list = new List<TRow> ();
 116                         foreach (TRow row in source)
 117                                 list.Add (row);
 118                         list.Sort (sorter);
 119                         for (int i = 0, c = list.Count; i < c; i++)
 120                                 yield return list [i];
 121                 }
 122
 123                 IEnumerator IEnumerable.GetEnumerator ()
 124                 {
 125                         return GetEnumerator ();
 126                 }
 127         }
 128 }