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comparison src/share/vm/memory/memRegion.cpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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1 /*
2 * Copyright 2000-2004 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any 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
31 MemRegion 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
42 MemRegion 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
59 MemRegion 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 }