/*

 * Copyright (c) 2012, 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

//  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     |

//            |              |            |          |

//            |              |            |          | capacity

//            |              |            |          |

//            |              | <- top   --+          |

//            |              |           ---+        |

//            |              |              | used   |

//            |              |              |        |

//            |              |              |        |

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

class Metachunk VALUE_OBJ_CLASS_SPEC {

  // link to support lists of chunks

  Metachunk* _next;

  Metachunk* _prev;

  MetaWord* _bottom;

  MetaWord* _end;

  MetaWord* _top;

  size_t _word_size;

  // Used in a guarantee() so included in the Product builds

  // even through it is only for debugging.

  bool _is_free;

  // 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.

  static size_t _overhead;

  void set_bottom(MetaWord* v) { _bottom = v; }

  void set_end(MetaWord* v) { _end = v; }

  void set_top(MetaWord* v) { _top = v; }

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

 public:

#ifdef ASSERT

  Metachunk() : _bottom(NULL), _end(NULL), _top(NULL), _is_free(false),

    _next(NULL), _prev(NULL) {}

#else

  Metachunk() : _bottom(NULL), _end(NULL), _top(NULL),

    _next(NULL), _prev(NULL) {}

#endif

  // Used to add a Metachunk to a list of Metachunks

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

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

  MetaWord* allocate(size_t word_size);

  static Metachunk* initialize(MetaWord* ptr, size_t word_size);

  // Accessors

  Metachunk* next() const { return _next; }

  Metachunk* prev() const { return _prev; }

  MetaWord* bottom() const { return _bottom; }

  MetaWord* end() const { return _end; }

  MetaWord* top() const { return _top; }

  size_t word_size() const { return _word_size; }

  size_t size() const volatile { return _word_size; }

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

  bool is_free() { return _is_free; }

  void set_is_free(bool v) { _is_free = v; }

  static size_t overhead() { return _overhead; }

  void clear_next()              { set_next(NULL); }

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

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

  bool cantCoalesce() const     { return false; }

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

  void link_after(Metachunk* ptr){

    link_next(ptr);

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

  }

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

  void reset_empty() { _top = (_bottom + _overhead); _next = NULL; _prev = NULL; }

  bool is_empty() { return _top == (_bottom + _overhead); }

  // used (has been allocated)

  // free (available for future allocations)

  // capacity (total size of chunk)

  size_t used_word_size() const;

  size_t free_word_size() const;

  size_t capacity_word_size()const;

  // 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(Metachunk* tc) const { return true; }

  bool verify_par_locked() { return true; }

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

  NOT_PRODUCT(void mangle();)

  void print_on(outputStream* st) const;

  void verify();

};

#endif  // SHARE_VM_MEMORY_METACHUNK_HPP