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1 /*
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2 * Copyright 2000-2004 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // A very simple data structure representing a contigous word-aligned
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26 // region of address space.
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27
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28 #include "incls/_precompiled.incl"
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29 #include "incls/_memRegion.cpp.incl"
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30
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31 MemRegion MemRegion::intersection(const MemRegion mr2) const {
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32 MemRegion res;
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33 HeapWord* res_start = MAX2(start(), mr2.start());
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34 HeapWord* res_end = MIN2(end(), mr2.end());
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35 if (res_start < res_end) {
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36 res.set_start(res_start);
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37 res.set_end(res_end);
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38 }
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39 return res;
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40 }
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41
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42 MemRegion MemRegion::_union(const MemRegion mr2) const {
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43 // If one region is empty, return the other
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44 if (is_empty()) return mr2;
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45 if (mr2.is_empty()) return MemRegion(start(), end());
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46
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47 // Otherwise, regions must overlap or be adjacent
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48 assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||
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49 ((mr2.start() <= start()) && (mr2.end() >= start())),
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50 "non-adjacent or overlapping regions");
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51 MemRegion res;
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52 HeapWord* res_start = MIN2(start(), mr2.start());
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53 HeapWord* res_end = MAX2(end(), mr2.end());
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54 res.set_start(res_start);
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55 res.set_end(res_end);
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56 return res;
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57 }
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58
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59 MemRegion MemRegion::minus(const MemRegion mr2) const {
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60 // There seem to be 6 cases:
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61 // |this MemRegion|
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62 // |strictly below|
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63 // |overlap beginning|
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64 // |interior|
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65 // |overlap ending|
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66 // |strictly above|
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67 // |completely overlapping|
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68 // We can't deal with an interior case because it would
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69 // produce two disjoint regions as a result.
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70 // We aren't trying to be optimal in the number of tests below,
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71 // but the order is important to distinguish the strictly cases
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72 // from the overlapping cases.
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73 if (mr2.end() <= start()) {
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74 // strictly below
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75 return MemRegion(start(), end());
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76 }
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77 if (mr2.start() <= start() && mr2.end() <= end()) {
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78 // overlap beginning
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79 return MemRegion(mr2.end(), end());
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80 }
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81 if (mr2.start() >= end()) {
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82 // strictly above
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83 return MemRegion(start(), end());
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84 }
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85 if (mr2.start() >= start() && mr2.end() >= end()) {
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86 // overlap ending
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87 return MemRegion(start(), mr2.start());
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88 }
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89 if (mr2.start() <= start() && mr2.end() >= end()) {
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90 // completely overlapping
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91 return MemRegion();
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92 }
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93 if (mr2.start() > start() && mr2.end() < end()) {
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94 // interior
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95 guarantee(false, "MemRegion::minus, but interior");
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96 return MemRegion();
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97 }
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98 ShouldNotReachHere();
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99 return MemRegion();
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100 }
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