Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Util/GCUtil.cs

@@ -0,0 +1,39 @@
+//------------------------------------------------------------------------------
+// <copyright file="GCUtil.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.Web.Util {
+    using System;
+    using System.Runtime.InteropServices;
+    using System.Security.Permissions;
+
+    // Provides helper methods for wrapping managed objects so that they can be passed to and from unmanaged code.
+    // Unmanaged code can't actually inspect these objects at all since they're just GCHandles. And these handles
+    // cannot be reused (they're single-shot).
+
+    [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
+    internal static class GCUtil {
+
+        public static IntPtr RootObject(object obj) {
+            return (obj != null)
+                ? (IntPtr)GCHandle.Alloc(obj)
+                : IntPtr.Zero;
+        }
+
+        public static object UnrootObject(IntPtr pointer) {
+            if (pointer != IntPtr.Zero) {
+                GCHandle gcHandle = (GCHandle)pointer;
+                if (gcHandle.IsAllocated) {
+                    object target = gcHandle.Target;
+                    gcHandle.Free();
+                    return target;
+                }
+            }
+
+            return null;
+        }
+
+    }
+}