/*
 * Copyright 2003 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 */


// Contains two generations that both use an AdjoiningVirtualSpaces.
// The two generations are adjacent in the reserved space for the
// heap.  Each generation has a virtual space and shrinking and
// expanding of the generations can still be down with that
// virtual space as was previously done.  If expanding of reserved
// size of a generation is required, the adjacent generation
// must be shrunk.  Adjusting the boundary between the generations
// is called for in this class.

class AdjoiningGenerations : public CHeapObj {
  friend class VMStructs;
 private:
  // The young generation and old generation, respectively
  PSYoungGen* _young_gen;
  PSOldGen* _old_gen;

  // The spaces used by the two generations.
  AdjoiningVirtualSpaces _virtual_spaces;

  // Move boundary up to expand old gen.  Checks are made to
  // determine if the move can be done with specified limits.
  void request_old_gen_expansion(size_t desired_change_in_bytes);
  // Move boundary down to expand young gen.
  bool request_young_gen_expansion(size_t desired_change_in_bytes);

 public:
  AdjoiningGenerations(ReservedSpace rs,
                       size_t init_low_byte_size,
                       size_t min_low_byte_size,
                       size_t max_low_byte_size,
                       size_t init_high_byte_size,
                       size_t min_high_byte_size,
                       size_t max_high_bytes_size,
                       size_t alignment);

  // Accessors
  PSYoungGen* young_gen() { return _young_gen; }
  PSOldGen* old_gen() { return _old_gen; }

  AdjoiningVirtualSpaces* virtual_spaces() { return &_virtual_spaces; }

  // Additional space is needed in the old generation.  Check
  // the available space and attempt to move the boundary if more space
  // is needed.  The growth is not guaranteed to occur.
  void adjust_boundary_for_old_gen_needs(size_t desired_change_in_bytes);
  // Similary for a growth of the young generation.
  void adjust_boundary_for_young_gen_needs(size_t eden_size, size_t survivor_size);

  // Return the total byte size of the reserved space
  // for the adjoining generations.
  size_t reserved_byte_size();
};