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 /*

  * Copyright (c) 1997, 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

  * questions.

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  */

 #ifndef SHARE_VM_MEMORY_HEAP_HPP

 #define SHARE_VM_MEMORY_HEAP_HPP

 #include "memory/allocation.hpp"

 #include "runtime/virtualspace.hpp"

 // Blocks

 class HeapBlock VALUE_OBJ_CLASS_SPEC {

   friend class VMStructs;

  public:

   struct Header {

     size_t  _length;                             // the length in segments

     bool    _used;                               // Used bit

   };

  protected:

   union {

     Header _header;

     int64_t _padding[ (sizeof(Header) + sizeof(int64_t)-1) / sizeof(int64_t) ];

                         // pad to 0 mod 8

   };

  public:

   // Initialization

   void initialize(size_t length)                 { _header._length = length; set_used(); }

   // Accessors

   void* allocated_space() const                  { return (void*)(this + 1); }

   size_t length() const                          { return _header._length; }

   // Used/free

   void set_used()                                { _header._used = true; }

   void set_free()                                { _header._used = false; }

   bool free()                                    { return !_header._used; }

 };

 class FreeBlock: public HeapBlock {

   friend class VMStructs;

  protected:

   FreeBlock* _link;

  public:

   // Initialization

   void initialize(size_t length)             { HeapBlock::initialize(length); _link= NULL; }

   // Merging

   void set_length(size_t l)                  { _header._length = l; }

   // Accessors

   FreeBlock* link() const                    { return _link; }

   void set_link(FreeBlock* link)             { _link = link; }

 };

 class CodeHeap : public CHeapObj<mtCode> {

   friend class VMStructs;

  private:

   VirtualSpace _memory;                          // the memory holding the blocks

   VirtualSpace _segmap;                          // the memory holding the segment map

   size_t       _number_of_committed_segments;

   size_t       _number_of_reserved_segments;

   size_t       _segment_size;

   int          _log2_segment_size;

   size_t       _next_segment;

   FreeBlock*   _freelist;

   size_t       _freelist_segments;               // No. of segments in freelist

   // Helper functions

   size_t   size_to_segments(size_t size) const { return (size + _segment_size - 1) >> _log2_segment_size; }

   size_t   segments_to_size(size_t number_of_segments) const { return number_of_segments << _log2_segment_size; }

   size_t   segment_for(void* p) const            { return ((char*)p - _memory.low()) >> _log2_segment_size; }

   HeapBlock* block_at(size_t i) const            { return (HeapBlock*)(_memory.low() + (i << _log2_segment_size)); }

   void  mark_segmap_as_free(size_t beg, size_t end);

   void  mark_segmap_as_used(size_t beg, size_t end);

   // Freelist management helpers

   FreeBlock* following_block(FreeBlock *b);

   void insert_after(FreeBlock* a, FreeBlock* b);

   void merge_right (FreeBlock* a);

   // Toplevel freelist management

   void add_to_freelist(HeapBlock *b);

   FreeBlock* search_freelist(size_t length, bool is_critical);

   // Iteration helpers

   void*      next_free(HeapBlock* b) const;

   HeapBlock* first_block() const;

   HeapBlock* next_block(HeapBlock* b) const;

   HeapBlock* block_start(void* p) const;

   // to perform additional actions on creation of executable code

   void on_code_mapping(char* base, size_t size);

  public:

   CodeHeap();

   // Heap extents

   bool  reserve(size_t reserved_size, size_t committed_size, size_t segment_size);

   void  release();                               // releases all allocated memory

   bool  expand_by(size_t size);                  // expands commited memory by size

   void  shrink_by(size_t size);                  // shrinks commited memory by size

   void  clear();                                 // clears all heap contents

   // Memory allocation

   void* allocate  (size_t size, bool is_critical);  // allocates a block of size or returns NULL

   void  deallocate(void* p);                     // deallocates a block

   // Attributes

   char* low_boundary() const                     { return _memory.low_boundary (); }

   char* high() const                             { return _memory.high(); }

   char* high_boundary() const                    { return _memory.high_boundary(); }

   bool  contains(const void* p) const            { return low_boundary() <= p && p < high(); }

   void* find_start(void* p) const;              // returns the block containing p or NULL

   size_t alignment_unit() const;                // alignment of any block

   size_t alignment_offset() const;              // offset of first byte of any block, within the enclosing alignment unit

   static size_t header_size();                  // returns the header size for each heap block

   // Iteration

   // returns the first block or NULL

   void* first() const       { return next_free(first_block()); }

   // returns the next block given a block p or NULL

   void* next(void* p) const { return next_free(next_block(block_start(p))); }

   // Statistics

   size_t capacity() const;

   size_t max_capacity() const;

   size_t allocated_capacity() const;

   size_t unallocated_capacity() const            { return max_capacity() - allocated_capacity(); }

 private:

   size_t heap_unallocated_capacity() const;

 public:

   // Debugging

   void verify();

   void print()  PRODUCT_RETURN;

 };

 #endif // SHARE_VM_MEMORY_HEAP_HPP