/*

 * 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_METABLOCK_HPP

#define SHARE_VM_MEMORY_METABLOCK_HPP

// Metablock are the unit of allocation from a Chunk.  It is initialized

// with the size of the requested allocation.  That size is overwritten

// once the allocation returns.

//

// 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 VALUE_OBJ_CLASS_SPEC {

  friend class VMStructs;

 private:

  // Used to align the allocation (see below).

  union block_t {

    void* _data[3];

    struct header_t {

      size_t _word_size;

      Metablock* _next;

      Metablock* _prev;

    } _header;

  } _block;

  static size_t _min_block_byte_size;

  static size_t _overhead;

  typedef union block_t Block;

  typedef struct header_t Header;

  const Block* block() const { return &_block; }

  const Block::header_t* header() const { return &(block()->_header); }

 public:

  static Metablock* initialize(MetaWord* p, size_t word_size);

  // This places the body of the block at a 2 word boundary

  // because every block starts on a 2 word boundary.  Work out

  // how to make the body on a 2 word boundary if the block

  // starts on a arbitrary boundary.  JJJ

  size_t word_size() const  { return header()->_word_size; }

  void set_word_size(size_t v) { _block._header._word_size = v; }

  size_t size() const volatile { return _block._header._word_size; }

  void set_size(size_t v) { _block._header._word_size = v; }

  Metablock* next() const { return header()->_next; }

  void set_next(Metablock* v) { _block._header._next = v; }

  Metablock* prev() const { return header()->_prev; }

  void set_prev(Metablock* v) { _block._header._prev = v; }

  static size_t min_block_byte_size() { return _min_block_byte_size; }

  static size_t overhead() { return _overhead; }

  bool is_free()                 { return header()->_word_size != 0; }

  void clear_next()              { set_next(NULL); }

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

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

  bool cantCoalesce() const     { return false; }

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

  void link_after(Metablock* ptr){

    link_next(ptr);

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

  }

  // Should not be needed in a free list of Metablocks

  void markNotFree()            { ShouldNotReachHere(); }

  // Debug support

#ifdef ASSERT

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

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

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

#endif

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

  bool verify_par_locked() { return true; }

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

};

#endif // SHARE_VM_MEMORY_METABLOCK_HPP