/*

 * Copyright (c) 2000, 2010, 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.

 *

 */

#include "precompiled.hpp"

#include "memory/memRegion.hpp"

#include "runtime/globals.hpp"

// A very simple data structure representing a contigous word-aligned

// region of address space.

MemRegion MemRegion::intersection(const MemRegion mr2) const {

  MemRegion res;

  HeapWord* res_start = MAX2(start(), mr2.start());

  HeapWord* res_end   = MIN2(end(),   mr2.end());

  if (res_start < res_end) {

    res.set_start(res_start);

    res.set_end(res_end);

  }

  return res;

}

MemRegion MemRegion::_union(const MemRegion mr2) const {

  // If one region is empty, return the other

  if (is_empty()) return mr2;

  if (mr2.is_empty()) return MemRegion(start(), end());

  // Otherwise, regions must overlap or be adjacent

  assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||

         ((mr2.start() <= start()) && (mr2.end() >= start())),

             "non-adjacent or overlapping regions");

  MemRegion res;

  HeapWord* res_start = MIN2(start(), mr2.start());

  HeapWord* res_end   = MAX2(end(),   mr2.end());

  res.set_start(res_start);

  res.set_end(res_end);

  return res;

}

MemRegion MemRegion::minus(const MemRegion mr2) const {

  // There seem to be 6 cases:

  //                  |this MemRegion|

  // |strictly below|

  //   |overlap beginning|

  //                    |interior|

  //                        |overlap ending|

  //                                   |strictly above|

  //              |completely overlapping|

  // We can't deal with an interior case because it would

  // produce two disjoint regions as a result.

  // We aren't trying to be optimal in the number of tests below,

  // but the order is important to distinguish the strictly cases

  // from the overlapping cases.

  if (mr2.end() <= start()) {

    // strictly below

    return MemRegion(start(), end());

  }

  if (mr2.start() <= start() && mr2.end() <= end()) {

    // overlap beginning

    return MemRegion(mr2.end(), end());

  }

  if (mr2.start() >= end()) {

    // strictly above

    return MemRegion(start(), end());

  }

  if (mr2.start() >= start() && mr2.end() >= end()) {

    // overlap ending

    return MemRegion(start(), mr2.start());

  }

  if (mr2.start() <= start() && mr2.end() >= end()) {

    // completely overlapping

    return MemRegion();

  }

  if (mr2.start() > start() && mr2.end() < end()) {

    // interior

    guarantee(false, "MemRegion::minus, but interior");

    return MemRegion();

  }

  ShouldNotReachHere();

  return MemRegion();

}