/*

 * Copyright (c) 2000, 2018, 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

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 */

#ifndef SHARE_VM_GC_SHARED_REFERENCEPOLICY_HPP

#define SHARE_VM_GC_SHARED_REFERENCEPOLICY_HPP

#include "oops/oopsHierarchy.hpp"

// referencePolicy is used to determine when soft reference objects

// should be cleared.

class ReferencePolicy : public CHeapObj<mtGC> {

 public:

  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {

    ShouldNotReachHere();

    return true;

  }

  // Capture state (of-the-VM) information needed to evaluate the policy

  virtual void setup() { /* do nothing */ }

};

class NeverClearPolicy : public ReferencePolicy {

 public:

  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {

    return false;

  }

};

class AlwaysClearPolicy : public ReferencePolicy {

 public:

  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {

    return true;

  }

};

class LRUCurrentHeapPolicy : public ReferencePolicy {

 private:

  jlong _max_interval;

 public:

  LRUCurrentHeapPolicy();

  // Capture state (of-the-VM) information needed to evaluate the policy

  void setup();

  virtual bool should_clear_reference(oop p, jlong timestamp_clock);

};

class LRUMaxHeapPolicy : public ReferencePolicy {

 private:

  jlong _max_interval;

 public:

  LRUMaxHeapPolicy();

  // Capture state (of-the-VM) information needed to evaluate the policy

  void setup();

  virtual bool should_clear_reference(oop p, jlong timestamp_clock);

};

#endif // SHARE_VM_GC_SHARED_REFERENCEPOLICY_HPP