Java example source code file (modRefBarrierSet.hpp)

This example Java source code file (modRefBarrierSet.hpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

barrierset, barrierset::modref, generation, modrefbarrierset, oopclosure, share_vm_memory_modrefbarrierset_hpp

The modRefBarrierSet.hpp Java example source code

/*
 * Copyright (c) 2000, 2012, 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_VM_MEMORY_MODREFBARRIERSET_HPP
#define SHARE_VM_MEMORY_MODREFBARRIERSET_HPP

#include "memory/barrierSet.hpp"

// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
// enumerate ref fields that have been modified (since the last
// enumeration), using a card table.

class OopClosure;
class Generation;

class ModRefBarrierSet: public BarrierSet {
public:

  ModRefBarrierSet() { _kind = BarrierSet::ModRef; }

  bool is_a(BarrierSet::Name bsn) {
    return bsn == BarrierSet::ModRef;
  }

  // Barriers only on ref writes.
  bool has_read_ref_barrier() { return false; }
  bool has_read_prim_barrier() { return false; }
  bool has_write_ref_barrier() { return true; }
  bool has_write_prim_barrier() { return false; }

  bool read_ref_needs_barrier(void* field) { return false; }
  bool read_prim_needs_barrier(HeapWord* field, size_t bytes) { return false; }
  bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
                                juint val1, juint val2) { return false; }

  void write_prim_field(oop obj, size_t offset, size_t bytes,
                        juint val1, juint val2) {}

  void read_ref_field(void* field) {}
  void read_prim_field(HeapWord* field, size_t bytes) {}
protected:
  virtual void write_ref_field_work(void* field, oop new_val) = 0;
public:
  void write_prim_field(HeapWord* field, size_t bytes,
                        juint val1, juint val2) {}

  bool has_read_ref_array_opt() { return false; }
  bool has_read_prim_array_opt() { return false; }
  bool has_write_prim_array_opt() { return false; }

  bool has_read_region_opt() { return false; }


  // These operations should assert false unless the correponding operation
  // above returns true.
  void read_ref_array(MemRegion mr) {
    assert(false, "can't call");
  }
  void read_prim_array(MemRegion mr) {
    assert(false, "can't call");
  }
  void write_prim_array(MemRegion mr) {
    assert(false, "can't call");
  }
  void read_region(MemRegion mr) {
    assert(false, "can't call");
  }

  // Causes all refs in "mr" to be assumed to be modified.  If "whole_heap"
  // is true, the caller asserts that the entire heap is being invalidated,
  // which may admit an optimized implementation for some barriers.
  virtual void invalidate(MemRegion mr, bool whole_heap = false) = 0;

  // The caller guarantees that "mr" contains no references.  (Perhaps it's
  // objects have been moved elsewhere.)
  virtual void clear(MemRegion mr) = 0;

  // Pass along the argument to the superclass.
  ModRefBarrierSet(int max_covered_regions) :
    BarrierSet(max_covered_regions) {}
};

#endif // SHARE_VM_MEMORY_MODREFBARRIERSET_HPP