memRegion.cpp revision 1472:c18cbe5936b8 
1/*
2 * Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25// A very simple data structure representing a contigous word-aligned
26// region of address space.
27
28#include "incls/_precompiled.incl"
29#include "incls/_memRegion.cpp.incl"
30
31MemRegion MemRegion::intersection(const MemRegion mr2) const {
32  MemRegion res;
33  HeapWord* res_start = MAX2(start(), mr2.start());
34  HeapWord* res_end   = MIN2(end(),   mr2.end());
35  if (res_start < res_end) {
36    res.set_start(res_start);
37    res.set_end(res_end);
38  }
39  return res;
40}
41
42MemRegion MemRegion::_union(const MemRegion mr2) const {
43  // If one region is empty, return the other
44  if (is_empty()) return mr2;
45  if (mr2.is_empty()) return MemRegion(start(), end());
46
47  // Otherwise, regions must overlap or be adjacent
48  assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||
49         ((mr2.start() <= start()) && (mr2.end() >= start())),
50             "non-adjacent or overlapping regions");
51  MemRegion res;
52  HeapWord* res_start = MIN2(start(), mr2.start());
53  HeapWord* res_end   = MAX2(end(),   mr2.end());
54  res.set_start(res_start);
55  res.set_end(res_end);
56  return res;
57}
58
59MemRegion MemRegion::minus(const MemRegion mr2) const {
60  // There seem to be 6 cases:
61  //                  |this MemRegion|
62  // |strictly below|
63  //   |overlap beginning|
64  //                    |interior|
65  //                        |overlap ending|
66  //                                   |strictly above|
67  //              |completely overlapping|
68  // We can't deal with an interior case because it would
69  // produce two disjoint regions as a result.
70  // We aren't trying to be optimal in the number of tests below,
71  // but the order is important to distinguish the strictly cases
72  // from the overlapping cases.
73  if (mr2.end() <= start()) {
74    // strictly below
75    return MemRegion(start(), end());
76  }
77  if (mr2.start() <= start() && mr2.end() <= end()) {
78    // overlap beginning
79    return MemRegion(mr2.end(), end());
80  }
81  if (mr2.start() >= end()) {
82    // strictly above
83    return MemRegion(start(), end());
84  }
85  if (mr2.start() >= start() && mr2.end() >= end()) {
86    // overlap ending
87    return MemRegion(start(), mr2.start());
88  }
89  if (mr2.start() <= start() && mr2.end() >= end()) {
90    // completely overlapping
91    return MemRegion();
92  }
93  if (mr2.start() > start() && mr2.end() < end()) {
94    // interior
95    guarantee(false, "MemRegion::minus, but interior");
96    return MemRegion();
97  }
98  ShouldNotReachHere();
99  return MemRegion();
100}
101