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/*
* Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_OOPS_WEAKHANDLE_HPP
#define SHARE_OOPS_WEAKHANDLE_HPP
#include "oops/oop.hpp"
#include "runtime/handles.hpp"
class outputStream;
class OopStorage;
// A WeakHandle is a pointer to an oop that is stored in an OopStorage that is
// processed weakly by GC. The runtime structures that point to the oop must
// either peek or resolve the oop, the latter will keep the oop alive for
// the GC cycle. The runtime structures that reference the oop must test
// if the value is NULL. If it is NULL, it has been cleaned out by GC.
// This is the vm version of jweak but has different GC lifetimes and policies,
// depending on the type.
class WeakHandle {
public:
private:
oop* _obj;
WeakHandle(oop* w) : _obj(w) {}
public:
WeakHandle() : _obj(NULL) {} // needed for init
WeakHandle(OopStorage* storage, Handle obj);
WeakHandle(OopStorage* storage, oop obj);
inline oop resolve() const;
inline oop peek() const;
void release(OopStorage* storage) const;
bool is_null() const { return _obj == NULL; }
void replace(oop with_obj);
void print() const;
void print_on(outputStream* st) const;
bool is_empty() const { return _obj == NULL; }
oop* ptr_raw() const { return _obj; }
};
#endif // SHARE_OOPS_WEAKHANDLE_HPP
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