class/System.Core/System.Linq/SortSequenceContext.cs

   1 //
   2 // SortSequenceContext.cs
   3 //
   4 // Author:
   5 //   Jb Evain (jbevain@novell.com)
   6 //
   7 // (C) 2008 Novell, Inc. (http://www.novell.com)
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining
  10 // a copy of this software and associated documentation files (the
  11 // "Software"), to deal in the Software without restriction, including
  12 // without limitation the rights to use, copy, modify, merge, publish,
  13 // distribute, sublicense, and/or sell copies of the Software, and to
  14 // permit persons to whom the Software is furnished to do so, subject to
  15 // the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be
  18 // included in all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27 //
  28
  29 using System;
  30 using System.Collections.Generic;
  31
  32 namespace System.Linq {
  33
  34         class SortSequenceContext<TElement, TKey> : SortContext<TElement> {
  35
  36                 Func<TElement, TKey> selector;
  37                 IComparer<TKey> comparer;
  38
  39                 TKey [] keys;
  40
  41                 public SortSequenceContext (Func<TElement, TKey> selector, IComparer<TKey> comparer, SortDirection direction, SortContext<TElement> child_context)
  42                         : base (direction, child_context)
  43                 {
  44                         this.selector = selector;
  45                         this.comparer = comparer;
  46                 }
  47
  48                 public override void Initialize (TElement [] elements)
  49                 {
  50                         if (child_context != null)
  51                                 child_context.Initialize (elements);
  52
  53                         keys = new TKey [elements.Length];
  54                         for (int i = 0; i < keys.Length; i++)
  55                                 keys [i] = selector (elements [i]);
  56                 }
  57
  58                 public override int Compare (int first_index, int second_index)
  59                 {
  60                         int comparison = comparer.Compare (keys [first_index], keys [second_index]);
  61
  62                         if (comparison == 0) {
  63                                 if (child_context != null)
  64                                         return child_context.Compare (first_index, second_index);
  65
  66                                 comparison = direction == SortDirection.Descending
  67                                         ? second_index - first_index
  68                                         : first_index - second_index;
  69                         }
  70
  71                         return direction == SortDirection.Descending ? -comparison : comparison;
  72                 }
  73         }
  74 }