mcs/class/System.Core/System.Linq.Parallel.QueryNodes/QueryDefaultEmptyNode.cs

   1 //
   2 // QueryDefaultEmptyNode.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2010 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0
  28 using System;
  29 using System.Threading;
  30 using System.Collections;
  31 using System.Collections.Generic;
  32
  33 namespace System.Linq.Parallel.QueryNodes
  34 {
  35         internal class QueryDefaultEmptyNode<TSource> : QueryStreamNode<TSource, TSource>
  36         {
  37                 TSource defaultValue;
  38
  39                 internal QueryDefaultEmptyNode (QueryBaseNode<TSource> parent, TSource defaultValue)
  40                         : base (parent, false)
  41                 {
  42                         this.defaultValue = defaultValue;
  43                 }
  44
  45                 internal override IEnumerable<TSource> GetSequential ()
  46                 {
  47                         return Parent.GetSequential ().DefaultIfEmpty (defaultValue);
  48                 }
  49
  50                 internal override IList<IEnumerable<TSource>> GetEnumerables (QueryOptions options)
  51                 {
  52                         IList<IEnumerable<TSource>> enumerables = Parent.GetEnumerables (options);
  53                         CountdownEvent evt = new CountdownEvent (enumerables.Count);
  54
  55                         return enumerables
  56                                 .Select ((e) => GetEnumerableInternal<TSource> (e,
  57                                                                                 evt,
  58                                                                                 (s) => s))
  59                                 .ToList ();
  60                 }
  61
  62                 internal override IList<IEnumerable<KeyValuePair<long, TSource>>> GetOrderedEnumerables (QueryOptions options)
  63                 {
  64                         IList<IEnumerable<KeyValuePair<long, TSource>>> enumerables = Parent.GetOrderedEnumerables (options);
  65                         CountdownEvent evt = new CountdownEvent (enumerables.Count);
  66
  67                         return enumerables
  68                                 .Select ((e) => GetEnumerableInternal<KeyValuePair<long, TSource>> (e,
  69                                                                                                     evt,
  70                                                                                                     (s) => new KeyValuePair<long, TSource> (0, s)))
  71                                 .ToList ();
  72                 }
  73
  74                 IEnumerable<TSecond> GetEnumerableInternal<TSecond> (IEnumerable<TSecond> source,
  75                                                                      CountdownEvent evt,
  76                                                                      Func<TSource, TSecond> converter)
  77                 {
  78                         bool processed = false;
  79
  80                         foreach (TSecond second in source) {
  81                                 processed = true;
  82                                 yield return second;
  83                         }
  84
  85                         if (!processed && evt.Signal ())
  86                                 yield return converter (defaultValue);
  87                 }
  88         }
  89 }
  90
  91 #endif