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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
 * 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_MEMORY_METASPACE_COMMITMASK_HPP
#define SHARE_MEMORY_METASPACE_COMMITMASK_HPP

#include "memory/metaspace/constants.hpp"
#include "utilities/debug.hpp"
#include "utilities/bitMap.hpp"
#include "utilities/globalDefinitions.hpp"

namespace metaspace {

// A bitmap covering a range of metaspace; each bit in this mask corresponds to
//
class CommitMask : public CHeapBitMap {

  const MetaWord* const _base;
  const size_t _word_size;

  // Given an offset, in words, into the area, return the number of the bit
  // covering it.
  static idx_t bitno_for_word_offset(size_t offset) {
    return offset / constants::commit_granule_words;
  }

  idx_t bitno_for_address(const MetaWord* p) const {
    assert(p >= _base && p < _base + _word_size, "Invalid address");
    const size_t off = p - _base;
    return bitno_for_word_offset(off);
  }

  static idx_t mask_size(size_t word_size) {
    assert(is_aligned(word_size, constants::commit_granule_words), "size not aligned correctly.");
    return bitno_for_word_offset(word_size) + 1;
  }

  struct BitCounterClosure : public BitMapClosure {
    idx_t cnt;
    bool do_bit(BitMap::idx_t offset) { cnt ++; return true; }
  };

  // Missing from BitMap.
  // Count 1 bits in range [start, end).
  idx_t count_one_bits_in_range(idx_t start, idx_t end) const {
    if (start == end) {
      return at(start) ? 1 : 0;
    }
    // TODO: This can be done more efficiently.
    BitCounterClosure bcc;
    bcc.cnt = 0;
    iterate(&bcc, start, end + 1);
    return bcc.cnt;
  }

#ifdef ASSERT
  // Given a pointer, check if it points into the range this bitmap covers.
  bool is_pointer_valid(const MetaWord* p) const {
    return p >= _base && p < _base + _word_size;
  }
  // Given a pointer, check if it points into the range this bitmap covers,
  // and if it is aligned to commit granule border.
  bool is_pointer_valid_and_aligned(const MetaWord* p) const {
    return is_pointer_valid(p) && is_aligned(p, constants::commit_granule_bytes);
  }
  // Given a pointer, check if it points into the range this bitmap covers.
  void check_pointer(const MetaWord* p) const {
    assert(is_pointer_valid(p),
           "Pointer " PTR_FORMAT " not in range of this bitmap [" PTR_FORMAT ", " PTR_FORMAT ").",
           p2i(p), p2i(_base), p2i(_base + _word_size));
  }
  // Given a pointer, check if it points into the range this bitmap covers,
  // and if it is aligned to commit granule border.
  void check_pointer_aligned(const MetaWord* p) const {
    check_pointer(p);
    assert(is_aligned(p, constants::commit_granule_bytes),
           "Pointer " PTR_FORMAT " should be aligned to commit granule size " SIZE_FORMAT ".", p2i(p), constants::commit_granule_bytes);
  }
  // Given a range, check if it points into the range this bitmap covers,
  // and if its borders are aligned to commit granule border.
  void check_range(const MetaWord* start, size_t word_size) const {
    check_pointer_aligned(start);
    check_pointer_aligned(start + word_size);
  }
#endif

  // Marks a single commit granule as committed or uncomitted and returns
  // its prior state.
  bool mark_granule(idx_t bitno, bool value) {
    bool b = at(bitno);
    at_put(bitno, value);
    return b;
  }

public:

  CommitMask(const MetaWord* start, size_t word_size)
    : CHeapBitMap(mask_size(word_size))
    , _base(start)
    , _word_size(word_size)
  {}

  // Given an address, returns true if the address is committed, false if not.
  bool is_committed_address(const MetaWord* p) const {
    DEBUG_ONLY(check_pointer(p));
    const idx_t bitno = bitno_for_address(p);
    return at(bitno);
  }

  // Given an address range [start, end), returns true if area is fully committed through.
  bool is_fully_committed_range(const MetaWord* start, size_t word_size) const {
    DEBUG_ONLY(check_range(start, word_size));
    const idx_t b1 = bitno_for_address(start);
    const idx_t b2 = bitno_for_address(start + word_size);
    return get_next_zero_offset(b1, b2) == b2;
  }

  // Given an address range, return size, in number of words, of committed area within that range.
  size_t get_committed_size_in_range(const MetaWord* start, size_t word_size) const {
    DEBUG_ONLY(check_range(start, word_size));
    const idx_t b1 = bitno_for_address(start);
    const idx_t b2 = bitno_for_address(start + word_size);
    const idx_t num_bits = count_one_bits_in_range(b1, b2);
    return num_bits * constants::commit_granule_words;
  }

  // Return total committed size, in number of words.
  size_t get_committed_size() const {
    return count_one_bits() * constants::commit_granule_words;
  }

  // Mark a whole address range [start, end) as committed.
  // Return the number of words which had already been committed before this operation.
  size_t mark_range_as_committed(const MetaWord* start, size_t word_size) {
    DEBUG_ONLY(check_range(start, word_size));
    const idx_t b1 = bitno_for_address(start);
    const idx_t b2 = bitno_for_address(start + word_size);
    if (b1 == b2) { // Simple case, 1 granule
      return mark_granule(b1, true) ? constants::commit_granule_words : 0;
    }
    const idx_t bits_set_before = count_one_bits_in_range(bitno_for_address(start), word_size);
    set_range(b1, b2);
    return bits_set_before * constants::commit_granule_words;
  }

  // Mark a whole address range [start, end) as uncommitted.
  // Return the number of words which had already been uncommitted before this operation.
  size_t mark_range_as_uncommitted(const MetaWord* start, size_t word_size) {
    DEBUG_ONLY(check_range(start, word_size));
    const idx_t b1 = bitno_for_address(start);
    const idx_t b2 = bitno_for_address(start + word_size);
    if (b1 == b2) { // Simple case, 1 granule
      return mark_granule(b1, true) ? constants::commit_granule_words : 0;
    }
    const idx_t bits_set_before = count_one_bits_in_range(bitno_for_address(start), word_size);
    clear_range(b1, b2);
    return ((b2 - b1) - bits_set_before) * constants::commit_granule_words;
  }


  //// Debug stuff ////
  DEBUG_ONLY(void verify(bool slow) const;)

};

} // namespace metaspace

#endif // SHARE_MEMORY_METASPACE_COMMITMASK_HPP