/*----------------------------------------------------------------------------*/
/*                                                                            */
/* Copyright (c) 1995, 2004 IBM Corporation. All rights reserved.             */
/* Copyright (c) 2005-2014 Rexx Language Association. All rights reserved.    */
/*                                                                            */
/* This program and the accompanying materials are made available under       */
/* the terms of the Common Public License v1.0 which accompanies this         */
/* distribution. A copy is also available at the following address:           */
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/* the documentation and/or other materials provided with the distribution.   */
/*                                                                            */
/* Neither the name of Rexx Language Association nor the names                */
/* of its contributors may be used to endorse or promote products             */
/* derived from this software without specific prior written permission.      */
/*                                                                            */
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/*                                                                            */
/*----------------------------------------------------------------------------*/
/******************************************************************************/
/* REXX Memory access                                                         */
/*                                                                            */
/* Implementation of a weak reference model                                   */
/*                                                                            */
/******************************************************************************/

#ifndef Included_WeakReference
#define Included_WeakReference

#include "RexxCore.h"


// A weak reference handler.  When the object referenced by a weak reference
// goes out of scope, the reference field is nulled, and the WeakReference object
// is enqueued to notify the owning object that a state change has occurred.
class WeakReference : public RexxObject
{
    friend class MemoryObject;
public:
    inline WeakReference(RESTORETYPE restoreType) { ; };
    WeakReference();
    WeakReference(RexxInternalObject *referent);

           void *operator new(size_t);

    void live(size_t) override;
    void liveGeneral(MarkReason) override;
    void flatten(Envelope *) override;
    RexxInternalObject *unflatten(Envelope *) override;
    RexxInternalObject *copy() override;

    RexxInternalObject *value();
    inline RexxInternalObject *get() { return referentObject; }
    inline bool hasReferent() { return referentObject != OREF_NULL; }
    void   clear();

    RexxObject *newRexx(RexxObject **args, size_t argc);

    static void createInstance();

    static RexxClass *classInstance;   // singleton class instance

protected:

    RexxInternalObject *referentObject;      // the object we refer to
    WeakReference *nextReferenceList;        // used by memory management to keep track of reference objects
};

#endif