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 /*

  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

  * 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.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP

 #include "utilities/debug.hpp"

 #include "memory/allocation.inline.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) {

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

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

     return NEW_C_HEAP_ARRAY(u_char, length * elem_size, mtGC);

   }

   // 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 %zd, 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, 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, end));

     size_t num_target_elems = (end - bottom) / (mapping_granularity_in_bytes / HeapWordSize);

     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