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