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 * 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.

 *

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#ifndef SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP

#define SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP

#include "gc/shared/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:

  // 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:

  ModRefBarrierSet(const BarrierSet::FakeRtti& fake_rtti)

    : BarrierSet(fake_rtti.add_tag(BarrierSet::ModRef)) { }

  ~ModRefBarrierSet() { }

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 corresponding 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;

};

template<>

struct BarrierSet::GetName<ModRefBarrierSet> {

  static const BarrierSet::Name value = BarrierSet::ModRef;

};

#endif // SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP