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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_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP

#define SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP

#include "memory/allocation.hpp"

#include "utilities/debug.hpp"

// Implements the common base functionality for arrays that contain provisions

// for accessing its elements using a biased index.

// The element type is defined by the instantiating the template.

class G1BiasedMappedArrayBase VALUE_OBJ_CLASS_SPEC {

  friend class VMStructs;

public:

  typedef size_t idx_t;

protected:

  address _base;          // the real base address

  size_t _length;         // the length of the array

  address _biased_base;   // base address biased by "bias" elements

  size_t _bias;           // the bias, i.e. the offset biased_base is located to the right in elements

  uint _shift_by;         // the amount of bits to shift right when mapping to an index of the array.

protected:

  G1BiasedMappedArrayBase() : _base(NULL), _length(0), _biased_base(NULL),

    _bias(0), _shift_by(0) { }

  // Allocate a new array, generic version.

  static address create_new_base_array(size_t length, size_t elem_size);

  // Initialize the members of this class. The biased start address of this array

  // is the bias (in elements) multiplied by the element size.

  void initialize_base(address base, size_t length, size_t bias, size_t elem_size, uint shift_by) {

    assert(base != NULL, "just checking");

    assert(length > 0, "just checking");

    assert(shift_by < sizeof(uintptr_t) * 8, err_msg("Shifting by %u, larger than word size?", shift_by));

    _base = base;

    _length = length;

    _biased_base = base - (bias * elem_size);

    _bias = bias;

    _shift_by = shift_by;

  }

  // Allocate and initialize this array to cover the heap addresses in the range

  // of [bottom, end).

  void initialize(HeapWord* bottom, HeapWord* end, size_t target_elem_size_in_bytes, size_t mapping_granularity_in_bytes) {

    assert(mapping_granularity_in_bytes > 0, "just checking");

    assert(is_power_of_2(mapping_granularity_in_bytes),

      err_msg("mapping granularity must be power of 2, is %zd", mapping_granularity_in_bytes));

    assert((uintptr_t)bottom % mapping_granularity_in_bytes == 0,

      err_msg("bottom mapping area address must be a multiple of mapping granularity %zd, is "PTR_FORMAT,

        mapping_granularity_in_bytes, p2i(bottom)));

    assert((uintptr_t)end % mapping_granularity_in_bytes == 0,

      err_msg("end mapping area address must be a multiple of mapping granularity %zd, is "PTR_FORMAT,

        mapping_granularity_in_bytes, p2i(end)));

    size_t num_target_elems = pointer_delta(end, bottom, mapping_granularity_in_bytes);

    idx_t bias = (uintptr_t)bottom / mapping_granularity_in_bytes;

    address base = create_new_base_array(num_target_elems, target_elem_size_in_bytes);

    initialize_base(base, num_target_elems, bias, target_elem_size_in_bytes, log2_intptr(mapping_granularity_in_bytes));

  }

  size_t bias() const { return _bias; }

  uint shift_by() const { return _shift_by; }

  void verify_index(idx_t index) const PRODUCT_RETURN;

  void verify_biased_index(idx_t biased_index) const PRODUCT_RETURN;

  void verify_biased_index_inclusive_end(idx_t biased_index) const PRODUCT_RETURN;

public:

   // Return the length of the array in elements.

   size_t length() const { return _length; }

};

// Array that provides biased access and mapping from (valid) addresses in the

// heap into this array.

template<class T>

class G1BiasedMappedArray : public G1BiasedMappedArrayBase {

public:

  typedef G1BiasedMappedArrayBase::idx_t idx_t;

  T* base() const { return (T*)G1BiasedMappedArrayBase::_base; }

  // Return the element of the given array at the given index. Assume

  // the index is valid. This is a convenience method that does sanity

  // checking on the index.

  T get_by_index(idx_t index) const {

    verify_index(index);

    return this->base()[index];

  }

  // Set the element of the given array at the given index to the

  // given value. Assume the index is valid. This is a convenience

  // method that does sanity checking on the index.

  void set_by_index(idx_t index, T value) {

    verify_index(index);

    this->base()[index] = value;

  }

  // The raw biased base pointer.

  T* biased_base() const { return (T*)G1BiasedMappedArrayBase::_biased_base; }

  // Return the element of the given array that covers the given word in the

  // heap. Assumes the index is valid.

  T get_by_address(HeapWord* value) const {

    idx_t biased_index = ((uintptr_t)value) >> this->shift_by();

    this->verify_biased_index(biased_index);

    return biased_base()[biased_index];

  }

  // Set the value of the array entry that corresponds to the given array.

  void set_by_address(HeapWord * address, T value) {

    idx_t biased_index = ((uintptr_t)address) >> this->shift_by();

    this->verify_biased_index(biased_index);

    biased_base()[biased_index] = value;

  }

protected:

  // Returns the address of the element the given address maps to

  T* address_mapped_to(HeapWord* address) {

    idx_t biased_index = ((uintptr_t)address) >> this->shift_by();

    this->verify_biased_index_inclusive_end(biased_index);

    return biased_base() + biased_index;

  }

public:

  // Return the smallest address (inclusive) in the heap that this array covers.

  HeapWord* bottom_address_mapped() const {

    return (HeapWord*) ((uintptr_t)this->bias() << this->shift_by());

  }

  // Return the highest address (exclusive) in the heap that this array covers.

  HeapWord* end_address_mapped() const {

    return (HeapWord*) ((uintptr_t)(this->bias() + this->length()) << this->shift_by());

  }

protected:

  virtual T default_value() const = 0;

  // Set all elements of the given array to the given value.

  void clear() {

    T value = default_value();

    for (idx_t i = 0; i < length(); i++) {

      set_by_index(i, value);

    }

  }

public:

  G1BiasedMappedArray() {}

  // Allocate and initialize this array to cover the heap addresses in the range

  // of [bottom, end).

  void initialize(HeapWord* bottom, HeapWord* end, size_t mapping_granularity) {

    G1BiasedMappedArrayBase::initialize(bottom, end, sizeof(T), mapping_granularity);

    this->clear();

  }

};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP