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 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 }