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