/*

 * 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

 * questions.

 *

 */

#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