mcs/class/corlib/System/WeakReference_T.cs

   1 //
   2 // WeakReference_T.cs
   3 //
   4 // Author:
   5 //       Martin Baulig <martin.baulig@xamarin.com>
   6 //
   7 // Copyright (c) 2013 Xamarin Inc. (http://www.xamarin.com)
   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_5
  28 using System.Runtime.Serialization;
  29 using System.Runtime.InteropServices;
  30
  31 namespace System {
  32         [SerializableAttribute]
  33         public sealed class WeakReference<T> : ISerializable
  34                 where T : class
  35         {
  36                 GCHandle handle;
  37                 bool trackResurrection;
  38
  39                 public WeakReference (T target)
  40                         : this (target, false)
  41                 {
  42                 }
  43
  44                 public WeakReference (T target, bool trackResurrection)
  45                 {
  46                         this.trackResurrection = trackResurrection;
  47                         var handleType = trackResurrection ? GCHandleType.WeakTrackResurrection : GCHandleType.Weak;
  48                         handle = GCHandle.Alloc (target, handleType);
  49                 }
  50
  51                 WeakReference (SerializationInfo info, StreamingContext context)
  52                 {
  53                         if (info == null)
  54                                 throw new ArgumentNullException ("info");
  55
  56                         trackResurrection = info.GetBoolean ("TrackResurrection");
  57                         var target = info.GetValue ("TrackedObject", typeof (T));
  58
  59                         var handleType = trackResurrection ? GCHandleType.WeakTrackResurrection : GCHandleType.Weak;
  60                         handle = GCHandle.Alloc (target, handleType);
  61                 }
  62
  63                 public void GetObjectData (SerializationInfo info, StreamingContext context)
  64                 {
  65                         if (info == null)
  66                                 throw new ArgumentNullException ("info");
  67
  68                         info.AddValue ("TrackResurrection", trackResurrection);
  69
  70                         if (handle.IsAllocated)
  71                                 info.AddValue ("TrackedObject", handle.Target);
  72                         else
  73                                 info.AddValue ("TrackedObject", null);
  74                 }
  75
  76                 public void SetTarget (T target)
  77                 {
  78                         handle.Target = target;
  79                 }
  80
  81                 public bool TryGetTarget (out T target)
  82                 {
  83                         if (!handle.IsAllocated) {
  84                                 target = null;
  85                                 return false;
  86                         }
  87
  88                         target = (T)handle.Target;
  89                         return true;
  90                 }
  91
  92                 //Methods
  93                 ~WeakReference ()
  94                 {
  95                         handle.Free ();
  96                 }
  97         }
  98 }
  99 #endif