133 lines
5.0 KiB
C#
133 lines
5.0 KiB
C#
// ==++==
|
|
//
|
|
// Copyright (c) Microsoft Corporation. All rights reserved.
|
|
//
|
|
// ==--==
|
|
/*============================================================
|
|
**
|
|
** Class: WeakReference
|
|
**
|
|
** Purpose: A wrapper for establishing a WeakReference to an Object.
|
|
**
|
|
===========================================================*/
|
|
namespace System {
|
|
|
|
using System;
|
|
using System.Runtime.Serialization;
|
|
using System.Security;
|
|
using System.Security.Permissions;
|
|
using System.Runtime.CompilerServices;
|
|
using System.Runtime.Versioning;
|
|
using System.Diagnostics.Contracts;
|
|
[System.Runtime.InteropServices.ComVisible(true)]
|
|
#if !FEATURE_CORECLR
|
|
[SecurityPermissionAttribute(SecurityAction.InheritanceDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] // Don't call Object::MemberwiseClone.
|
|
#endif
|
|
[Serializable]
|
|
public class WeakReference : ISerializable {
|
|
// If you fix bugs here, please fix them in WeakReference<T> at the same time.
|
|
|
|
// This field is not a regular GC handle. It can have a special values that are used to prevent ----s between setting the target and finalization.
|
|
internal IntPtr m_handle;
|
|
|
|
#if FEATURE_CORECLR
|
|
// Migrating InheritanceDemands requires this default ctor, so we can mark it SafeCritical
|
|
[SecuritySafeCritical]
|
|
protected WeakReference() {
|
|
Contract.Assert(false, "WeakReference's protected default ctor should never be used!");
|
|
throw new NotImplementedException();
|
|
}
|
|
#endif
|
|
|
|
// Creates a new WeakReference that keeps track of target.
|
|
// Assumes a Short Weak Reference (ie TrackResurrection is false.)
|
|
//
|
|
public WeakReference(Object target)
|
|
: this(target, false) {
|
|
}
|
|
|
|
//Creates a new WeakReference that keeps track of target.
|
|
//
|
|
public WeakReference(Object target, bool trackResurrection) {
|
|
Create(target, trackResurrection);
|
|
}
|
|
|
|
protected WeakReference(SerializationInfo info, StreamingContext context) {
|
|
if (info==null) {
|
|
throw new ArgumentNullException("info");
|
|
}
|
|
Contract.EndContractBlock();
|
|
|
|
Object target = info.GetValue("TrackedObject",typeof(Object));
|
|
bool trackResurrection = info.GetBoolean("TrackResurrection");
|
|
|
|
Create(target, trackResurrection);
|
|
}
|
|
|
|
//Determines whether or not this instance of WeakReference still refers to an object
|
|
//that has not been collected.
|
|
//
|
|
public extern virtual bool IsAlive {
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
get;
|
|
}
|
|
|
|
//Returns a boolean indicating whether or not we're tracking objects until they're collected (true)
|
|
//or just until they're finalized (false).
|
|
//
|
|
public virtual bool TrackResurrection {
|
|
// We need to call IsTrackResurrection non-virtually in GetObjectData, and so the virtual property cannot be FCall directly
|
|
get { return IsTrackResurrection(); }
|
|
}
|
|
|
|
//Gets the Object stored in the handle if it's accessible.
|
|
// Or sets it.
|
|
//
|
|
public extern virtual Object Target {
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
get;
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
set;
|
|
}
|
|
|
|
// Free all system resources associated with this reference.
|
|
//
|
|
// Note: The WeakReference finalizer is not actually run, but
|
|
// treated specially in gc.cpp's ScanForFinalization
|
|
// This is needed for subclasses deriving from WeakReference, however.
|
|
// Additionally, there may be some cases during shutdown when we run this finalizer.
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
extern ~WeakReference();
|
|
|
|
[SecurityCritical]
|
|
public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
|
|
{
|
|
if (info==null) {
|
|
throw new ArgumentNullException("info");
|
|
}
|
|
Contract.EndContractBlock();
|
|
info.AddValue("TrackedObject", Target, typeof(Object));
|
|
info.AddValue("TrackResurrection", IsTrackResurrection());
|
|
}
|
|
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
private extern void Create(Object target, bool trackResurrection);
|
|
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
private extern bool IsTrackResurrection();
|
|
}
|
|
|
|
}
|