class/System.Core/System.Linq/OrderedEnumerable.cs

   1 //
   2 // OrderedEnumerable.cs
   3 //
   4 // Authors:
   5 //      Marek Safar  <marek.safar@gmail.com>
   6 //      Jb Evain  <jbevain@novell.com>
   7 //
   8 // Copyright (C) 2007 - 2008 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System;
  31 using System.Collections;
  32 using System.Collections.Generic;
  33
  34 namespace System.Linq {
  35
  36         abstract class OrderedEnumerable<TElement> : IOrderedEnumerable<TElement> {
  37
  38                 IEnumerable<TElement> source;
  39
  40                 protected OrderedEnumerable (IEnumerable<TElement> source)
  41                 {
  42                         this.source = source;
  43                 }
  44
  45                 IEnumerator IEnumerable.GetEnumerator ()
  46                 {
  47                         return GetEnumerator ();
  48                 }
  49
  50                 public IEnumerator<TElement> GetEnumerator ()
  51                 {
  52                         return Sort (source).GetEnumerator ();
  53                 }
  54
  55                 public abstract SortContext<TElement> CreateContext (SortContext<TElement> current);
  56
  57                 protected abstract IEnumerable<TElement> Sort (IEnumerable<TElement> source);
  58
  59                 public IOrderedEnumerable<TElement> CreateOrderedEnumerable<TKey> (
  60                         Func<TElement, TKey> selector, IComparer<TKey> comparer, bool descending)
  61                 {
  62                         return new OrderedSequence<TElement, TKey> (this, source, selector, comparer,
  63                                 descending ? SortDirection.Descending : SortDirection.Ascending);
  64                 }
  65         }
  66 }