/*

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

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 *

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 * 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_OCCUPANCYMAP_HPP

#define SHARE_MEMORY_METASPACE_OCCUPANCYMAP_HPP

#include "memory/allocation.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

namespace metaspace {

class Metachunk;

// Helper for Occupancy Bitmap. A type trait to give an all-bits-are-one-unsigned constant.

template <typename T> struct all_ones  { static const T value; };

template <> struct all_ones <uint64_t> { static const uint64_t value = 0xFFFFFFFFFFFFFFFFULL; };

template <> struct all_ones <uint32_t> { static const uint32_t value = 0xFFFFFFFF; };

// The OccupancyMap is a bitmap which, for a given VirtualSpaceNode,

// keeps information about

// - where a chunk starts

// - whether a chunk is in-use or free

// A bit in this bitmap represents one range of memory in the smallest

// chunk size (SpecializedChunk or ClassSpecializedChunk).

class OccupancyMap : public CHeapObj<mtInternal> {

  // The address range this map covers.

  const MetaWord* const _reference_address;

  const size_t _word_size;

  // The word size of a specialized chunk, aka the number of words one

  // bit in this map represents.

  const size_t _smallest_chunk_word_size;

  // map data

  // Data are organized in two bit layers:

  // The first layer is the chunk-start-map. Here, a bit is set to mark

  // the corresponding region as the head of a chunk.

  // The second layer is the in-use-map. Here, a set bit indicates that

  // the corresponding belongs to a chunk which is in use.

  uint8_t* _map[2];

  enum { layer_chunk_start_map = 0, layer_in_use_map = 1 };

  // length, in bytes, of bitmap data

  size_t _map_size;

  // Returns true if bit at position pos at bit-layer layer is set.

  bool get_bit_at_position(unsigned pos, unsigned layer) const {

    assert(layer == 0 || layer == 1, "Invalid layer %d", layer);

    const unsigned byteoffset = pos / 8;

    assert(byteoffset < _map_size,

           "invalid byte offset (%u), map size is " SIZE_FORMAT ".", byteoffset, _map_size);

    const unsigned mask = 1 << (pos % 8);

    return (_map[layer][byteoffset] & mask) > 0;

  }

  // Changes bit at position pos at bit-layer layer to value v.

  void set_bit_at_position(unsigned pos, unsigned layer, bool v) {

    assert(layer == 0 || layer == 1, "Invalid layer %d", layer);

    const unsigned byteoffset = pos / 8;

    assert(byteoffset < _map_size,

           "invalid byte offset (%u), map size is " SIZE_FORMAT ".", byteoffset, _map_size);

    const unsigned mask = 1 << (pos % 8);

    if (v) {

      _map[layer][byteoffset] |= mask;

    } else {

      _map[layer][byteoffset] &= ~mask;

    }

  }

  // Optimized case of is_any_bit_set_in_region for 32/64bit aligned access:

  // pos is 32/64 aligned and num_bits is 32/64.

  // This is the typical case when coalescing to medium chunks, whose size is

  // 32 or 64 times the specialized chunk size (depending on class or non class

  // case), so they occupy 64 bits which should be 64bit aligned, because

  // chunks are chunk-size aligned.

  template <typename T>

  bool is_any_bit_set_in_region_3264(unsigned pos, unsigned num_bits, unsigned layer) const {

    assert(_map_size > 0, "not initialized");

    assert(layer == 0 || layer == 1, "Invalid layer %d.", layer);

    assert(pos % (sizeof(T) * 8) == 0, "Bit position must be aligned (%u).", pos);

    assert(num_bits == (sizeof(T) * 8), "Number of bits incorrect (%u).", num_bits);

    const size_t byteoffset = pos / 8;

    assert(byteoffset <= (_map_size - sizeof(T)),

           "Invalid byte offset (" SIZE_FORMAT "), map size is " SIZE_FORMAT ".", byteoffset, _map_size);

    const T w = *(T*)(_map[layer] + byteoffset);

    return w > 0 ? true : false;

  }

  // Returns true if any bit in region [pos1, pos1 + num_bits) is set in bit-layer layer.

  bool is_any_bit_set_in_region(unsigned pos, unsigned num_bits, unsigned layer) const {

    if (pos % 32 == 0 && num_bits == 32) {

      return is_any_bit_set_in_region_3264<uint32_t>(pos, num_bits, layer);

    } else if (pos % 64 == 0 && num_bits == 64) {

      return is_any_bit_set_in_region_3264<uint64_t>(pos, num_bits, layer);

    } else {

      for (unsigned n = 0; n < num_bits; n ++) {

        if (get_bit_at_position(pos + n, layer)) {

          return true;

        }

      }

    }

    return false;

  }

  // Returns true if any bit in region [p, p+word_size) is set in bit-layer layer.

  bool is_any_bit_set_in_region(MetaWord* p, size_t word_size, unsigned layer) const {

    assert(word_size % _smallest_chunk_word_size == 0,

        "Region size " SIZE_FORMAT " not a multiple of smallest chunk size.", word_size);

    const unsigned pos = get_bitpos_for_address(p);

    const unsigned num_bits = (unsigned) (word_size / _smallest_chunk_word_size);

    return is_any_bit_set_in_region(pos, num_bits, layer);

  }

  // Optimized case of set_bits_of_region for 32/64bit aligned access:

  // pos is 32/64 aligned and num_bits is 32/64.

  // This is the typical case when coalescing to medium chunks, whose size

  // is 32 or 64 times the specialized chunk size (depending on class or non

  // class case), so they occupy 64 bits which should be 64bit aligned,

  // because chunks are chunk-size aligned.

  template <typename T>

  void set_bits_of_region_T(unsigned pos, unsigned num_bits, unsigned layer, bool v) {

    assert(pos % (sizeof(T) * 8) == 0, "Bit position must be aligned to %u (%u).",

           (unsigned)(sizeof(T) * 8), pos);

    assert(num_bits == (sizeof(T) * 8), "Number of bits incorrect (%u), expected %u.",

           num_bits, (unsigned)(sizeof(T) * 8));

    const size_t byteoffset = pos / 8;

    assert(byteoffset <= (_map_size - sizeof(T)),

           "invalid byte offset (" SIZE_FORMAT "), map size is " SIZE_FORMAT ".", byteoffset, _map_size);

    T* const pw = (T*)(_map[layer] + byteoffset);

    *pw = v ? all_ones<T>::value : (T) 0;

  }

  // Set all bits in a region starting at pos to a value.

  void set_bits_of_region(unsigned pos, unsigned num_bits, unsigned layer, bool v) {

    assert(_map_size > 0, "not initialized");

    assert(layer == 0 || layer == 1, "Invalid layer %d.", layer);

    if (pos % 32 == 0 && num_bits == 32) {

      set_bits_of_region_T<uint32_t>(pos, num_bits, layer, v);

    } else if (pos % 64 == 0 && num_bits == 64) {

      set_bits_of_region_T<uint64_t>(pos, num_bits, layer, v);

    } else {

      for (unsigned n = 0; n < num_bits; n ++) {

        set_bit_at_position(pos + n, layer, v);

      }

    }

  }

  // Helper: sets all bits in a region [p, p+word_size).

  void set_bits_of_region(MetaWord* p, size_t word_size, unsigned layer, bool v) {

    assert(word_size % _smallest_chunk_word_size == 0,

        "Region size " SIZE_FORMAT " not a multiple of smallest chunk size.", word_size);

    const unsigned pos = get_bitpos_for_address(p);

    const unsigned num_bits = (unsigned) (word_size / _smallest_chunk_word_size);

    set_bits_of_region(pos, num_bits, layer, v);

  }

  // Helper: given an address, return the bit position representing that address.

  unsigned get_bitpos_for_address(const MetaWord* p) const {

    assert(_reference_address != NULL, "not initialized");

    assert(p >= _reference_address && p < _reference_address + _word_size,

           "Address %p out of range for occupancy map [%p..%p).",

            p, _reference_address, _reference_address + _word_size);

    assert(is_aligned(p, _smallest_chunk_word_size * sizeof(MetaWord)),

           "Address not aligned (%p).", p);

    const ptrdiff_t d = (p - _reference_address) / _smallest_chunk_word_size;

    assert(d >= 0 && (size_t)d < _map_size * 8, "Sanity.");

    return (unsigned) d;

  }

 public:

  OccupancyMap(const MetaWord* reference_address, size_t word_size, size_t smallest_chunk_word_size);

  ~OccupancyMap();

  // Returns true if at address x a chunk is starting.

  bool chunk_starts_at_address(MetaWord* p) const {

    const unsigned pos = get_bitpos_for_address(p);

    return get_bit_at_position(pos, layer_chunk_start_map);

  }

  void set_chunk_starts_at_address(MetaWord* p, bool v) {

    const unsigned pos = get_bitpos_for_address(p);

    set_bit_at_position(pos, layer_chunk_start_map, v);

  }

  // Removes all chunk-start-bits inside a region, typically as a

  // result of a chunk merge.

  void wipe_chunk_start_bits_in_region(MetaWord* p, size_t word_size) {

    set_bits_of_region(p, word_size, layer_chunk_start_map, false);

  }

  // Returns true if there are life (in use) chunks in the region limited

  // by [p, p+word_size).

  bool is_region_in_use(MetaWord* p, size_t word_size) const {

    return is_any_bit_set_in_region(p, word_size, layer_in_use_map);

  }

  // Marks the region starting at p with the size word_size as in use

  // or free, depending on v.

  void set_region_in_use(MetaWord* p, size_t word_size, bool v) {

    set_bits_of_region(p, word_size, layer_in_use_map, v);

  }

  // Verify occupancy map for the address range [from, to).

  // We need to tell it the address range, because the memory the

  // occupancy map is covering may not be fully comitted yet.

  DEBUG_ONLY(void verify(MetaWord* from, MetaWord* to);)

  // Verify that a given chunk is correctly accounted for in the bitmap.

  DEBUG_ONLY(void verify_for_chunk(Metachunk* chunk);)

};

} // namespace metaspace