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 /*

  * Copyright (c) 2012, 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_MEMORY_METACHUNK_HPP

 #define SHARE_VM_MEMORY_METACHUNK_HPP

 #include "memory/allocation.hpp"

 #include "utilities/debug.hpp"

 #include "utilities/globalDefinitions.hpp"

 class VirtualSpaceNode;

 // Super class of Metablock and Metachunk to allow them to

 // be put on the FreeList and in the BinaryTreeDictionary.

 template <class T>

 class Metabase VALUE_OBJ_CLASS_SPEC {

   size_t _word_size;

   T*     _next;

   T*     _prev;

  protected:

   Metabase(size_t word_size) : _word_size(word_size), _next(NULL), _prev(NULL) {}

  public:

   T* next() const         { return _next; }

   T* prev() const         { return _prev; }

   void set_next(T* v)     { _next = v; assert(v != this, "Boom");}

   void set_prev(T* v)     { _prev = v; assert(v != this, "Boom");}

   void clear_next()       { set_next(NULL); }

   void clear_prev()       { set_prev(NULL); }

   size_t size() const volatile { return _word_size; }

   void set_size(size_t v) { _word_size = v; }

   void link_next(T* ptr)  { set_next(ptr); }

   void link_prev(T* ptr)  { set_prev(ptr); }

   void link_after(T* ptr) {

     link_next(ptr);

     if (ptr != NULL) ptr->link_prev((T*)this);

   }

   uintptr_t* end() const        { return ((uintptr_t*) this) + size(); }

   bool cantCoalesce() const     { return false; }

   // Debug support

 #ifdef ASSERT

   void* prev_addr() const { return (void*)&_prev; }

   void* next_addr() const { return (void*)&_next; }

   void* size_addr() const { return (void*)&_word_size; }

 #endif

   bool verify_chunk_in_free_list(T* tc) const { return true; }

   bool verify_par_locked() { return true; }

   void assert_is_mangled() const {/* Don't check "\*/}

   bool is_free()                 { return true; }

 };

 //  Metachunk - Quantum of allocation from a Virtualspace

 //    Metachunks are reused (when freed are put on a global freelist) and

 //    have no permanent association to a SpaceManager.

 //            +--------------+ <- end    --+       --+

 //            |              |             |         |

 //            |              |             | free    |

 //            |              |             |         |

 //            |              |             |         | size | capacity

 //            |              |             |         |

 //            |              | <- top   -- +         |

 //            |              |             |         |

 //            |              |             | used    |

 //            |              |             |         |

 //            |              |             |         |

 //            +--------------+ <- bottom --+       --+

 class Metachunk : public Metabase<Metachunk> {

   friend class TestMetachunk;

   // The VirtualSpaceNode containing this chunk.

   VirtualSpaceNode* _container;

   // Current allocation top.

   MetaWord* _top;

   DEBUG_ONLY(bool _is_tagged_free;)

   MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }

   MetaWord* top() const         { return _top; }

  public:

   // Metachunks are allocated out of a MetadataVirtualSpace and

   // and use some of its space to describe itself (plus alignment

   // considerations).  Metadata is allocated in the rest of the chunk.

   // This size is the overhead of maintaining the Metachunk within

   // the space.

   // Alignment of each allocation in the chunks.

   static size_t object_alignment();

   // Size of the Metachunk header, including alignment.

   static size_t overhead();

   Metachunk(size_t word_size , VirtualSpaceNode* container);

   MetaWord* allocate(size_t word_size);

   VirtualSpaceNode* container() const { return _container; }

   MetaWord* bottom() const { return (MetaWord*) this; }

   // Reset top to bottom so chunk can be reused.

   void reset_empty() { _top = initial_top(); clear_next(); clear_prev(); }

   bool is_empty() { return _top == initial_top(); }

   // used (has been allocated)

   // free (available for future allocations)

   size_t word_size() const { return size(); }

   size_t used_word_size() const;

   size_t free_word_size() const;

 #ifdef ASSERT

   bool is_tagged_free() { return _is_tagged_free; }

   void set_is_tagged_free(bool v) { _is_tagged_free = v; }

 #endif

   bool contains(const void* ptr) { return bottom() <= ptr && ptr < _top; }

   NOT_PRODUCT(void mangle();)

   void print_on(outputStream* st) const;

   void verify();

 };

 // Metablock is the unit of allocation from a Chunk.

 //

 // A Metablock may be reused by its SpaceManager but are never moved between

 // SpaceManagers.  There is no explicit link to the Metachunk

 // from which it was allocated.  Metablock may be deallocated and

 // put on a freelist but the space is never freed, rather

 // the Metachunk it is a part of will be deallocated when it's

 // associated class loader is collected.

 class Metablock : public Metabase<Metablock> {

   friend class VMStructs;

  public:

   Metablock(size_t word_size) : Metabase<Metablock>(word_size) {}

 };

 #endif  // SHARE_VM_MEMORY_METACHUNK_HPP