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 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * 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_MARKBITMAP_HPP

#define SHARE_VM_GC_SHARED_MARKBITMAP_HPP

#include "memory/memRegion.hpp"

#include "oops/oopsHierarchy.hpp"

#include "utilities/bitMap.hpp"

// A generic mark bitmap for concurrent marking.  This is essentially a wrapper

// around the BitMap class that is based on HeapWords, with one bit per (1 << _shifter) HeapWords.

class MarkBitMap {

protected:

  MemRegion _covered;    // The heap area covered by this bitmap.

  const int _shifter;    // Shift amount from heap index to bit index in the bitmap.

  BitMapView _bm;        // The actual bitmap.

  virtual void check_mark(HeapWord* addr) NOT_DEBUG_RETURN;

  // Convert from bit offset to address.

  HeapWord* offset_to_addr(size_t offset) const {

    return _covered.start() + (offset << _shifter);

  }

  // Convert from address to bit offset.

  size_t addr_to_offset(const HeapWord* addr) const {

    return pointer_delta(addr, _covered.start()) >> _shifter;

  }

public:

  static size_t compute_size(size_t heap_size);

  // Returns the amount of bytes on the heap between two marks in the bitmap.

  static size_t mark_distance();

  // Returns how many bytes (or bits) of the heap a single byte (or bit) of the

  // mark bitmap corresponds to. This is the same as the mark distance above.

  static size_t heap_map_factor() {

    return mark_distance();

  }

  MarkBitMap() : _covered(), _shifter(LogMinObjAlignment), _bm() {}

  // Initializes the underlying BitMap to cover the given area.

  void initialize(MemRegion heap, MemRegion storage);

  // Read marks

  bool is_marked(oop obj) const;

  bool is_marked(HeapWord* addr) const {

    assert(_covered.contains(addr),

           "Address " PTR_FORMAT " is outside underlying space from " PTR_FORMAT " to " PTR_FORMAT,

           p2i(addr), p2i(_covered.start()), p2i(_covered.end()));

    return _bm.at(addr_to_offset(addr));

  }

  // Return the address corresponding to the next marked bit at or after

  // "addr", and before "limit", if "limit" is non-NULL.  If there is no

  // such bit, returns "limit" if that is non-NULL, or else "endWord()".

  inline HeapWord* get_next_marked_addr(const HeapWord* addr,

                                        const HeapWord* limit) const;

  void print_on_error(outputStream* st, const char* prefix) const;

  // Write marks.

  inline void mark(HeapWord* addr);

  inline void clear(HeapWord* addr);

  inline void clear(oop obj);

  inline bool par_mark(HeapWord* addr);

  inline bool par_mark(oop obj);

  void clear_range(MemRegion mr);

};

#endif // SHARE_VM_GC_SHARED_MARKBITMAP_HPP