/IronPython_Main/Runtime/Microsoft.Dynamic/Utils/WeakHandle.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, please send an email to 

 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 

 * by the terms of the Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

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 * ***************************************************************************/



using System;

using System.Runtime.InteropServices;



namespace Microsoft.Scripting.Utils {



#if SILVERLIGHT

    // TODO: finalizers in user types aren't supported in Silverlight

    // we need to come up with another solution for Python's _weakref library

    public struct WeakHandle {

        private WeakReference _weakRef;



        public WeakHandle(object target, bool trackResurrection) {

            _weakRef = new WeakReference(target, trackResurrection);

            GC.SuppressFinalize(this._weakRef);

        }



        public bool IsAlive { get { return _weakRef != null && _weakRef.IsAlive; } }

        public object Target { get { return _weakRef != null ? _weakRef.Target : null; } }



        public void Free() {

            if (_weakRef != null) {

                GC.ReRegisterForFinalize(_weakRef);

                _weakRef.Target = null;

                _weakRef = null;

            }

        }

    }

#else

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1815:OverrideEqualsAndOperatorEqualsOnValueTypes")] // TODO: fix

    public struct WeakHandle {



        private GCHandle weakRef;



        public WeakHandle(object target, bool trackResurrection) {

            this.weakRef = GCHandle.Alloc(target, trackResurrection ? GCHandleType.WeakTrackResurrection : GCHandleType.Weak);

        }



        public bool IsAlive { get { return weakRef.IsAllocated; } }

        public object Target { get { return weakRef.Target; } }

        public void Free() { weakRef.Free(); }

    }

#endif

}