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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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// 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();

}