1 /* 2 * Copyright (c) 2000, 2019, 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 #ifndef SHARE_MEMORY_MEMREGION_HPP 26 #define SHARE_MEMORY_MEMREGION_HPP 27 28 #include "memory/allocation.hpp" 29 #include "utilities/debug.hpp" 30 #include "utilities/globalDefinitions.hpp" 31 32 // A very simple data structure representing a contigous region 33 // region of address space. 34 35 // Note that MemRegions are typically passed by value, not by reference. 36 // The intent is that they remain very small and contain no 37 // objects. The copy constructor and destructor must be trivial, 38 // to support optimization for pass-by-value. 39 // These should almost never be allocated in heap but we do 40 // create MemRegions (in CardTable and G1CMRootMemRegions) on the heap so operator 41 // new and operator new [] were added for these special cases. 42 43 class MemRegion { 44 friend class VMStructs; 45 private: 46 HeapWord* _start; 47 size_t _word_size; 48 49 public: 50 MemRegion() : _start(NULL), _word_size(0) {}; 51 MemRegion(HeapWord* start, size_t word_size) : 52 _start(start), _word_size(word_size) {}; 53 MemRegion(HeapWord* start, HeapWord* end) : 54 _start(start), _word_size(pointer_delta(end, start)) { 55 assert(end >= start, "incorrect constructor arguments"); 56 } 57 MemRegion(MetaWord* start, MetaWord* end) : 58 _start((HeapWord*)start), _word_size(pointer_delta(end, start)) { 59 assert(end >= start, "incorrect constructor arguments"); 60 } 61 62 MemRegion intersection(const MemRegion mr2) const; 63 // regions must overlap or be adjacent 64 MemRegion _union(const MemRegion mr2) const; 65 // minus will fail a guarantee if mr2 is interior to this, 66 // since there's no way to return 2 disjoint regions. 67 MemRegion minus(const MemRegion mr2) const; 68 69 HeapWord* start() const { return _start; } 70 HeapWord* end() const { return _start + _word_size; } 71 HeapWord* last() const { return _start + _word_size - 1; } 72 73 void set_start(HeapWord* start) { _start = start; } 74 void set_end(HeapWord* end) { _word_size = pointer_delta(end, _start); } 75 void set_word_size(size_t word_size) { 76 _word_size = word_size; 77 } 78 79 bool contains(const MemRegion mr2) const { 80 return _start <= mr2._start && end() >= mr2.end(); 81 } 82 bool contains(const void* addr) const { 83 return addr >= (void*)_start && addr < (void*)end(); 84 } 85 bool equals(const MemRegion mr2) const { 86 // first disjunct since we do not have a canonical empty set 87 return ((is_empty() && mr2.is_empty()) || 88 (start() == mr2.start() && end() == mr2.end())); 89 } 90 91 size_t byte_size() const { return _word_size * sizeof(HeapWord); } 92 size_t word_size() const { return _word_size; } 93 94 bool is_empty() const { return word_size() == 0; } 95 void* operator new(size_t size) throw(); 96 void* operator new [](size_t size) throw(); 97 void operator delete(void* p); 98 void operator delete [](void* p); 99 }; 100 101 // For iteration over MemRegion's. 102 103 class MemRegionClosure : public StackObj { 104 public: 105 virtual void do_MemRegion(MemRegion mr) = 0; 106 }; 107 108 // A ResourceObj version of MemRegionClosure 109 110 class MemRegionClosureRO: public MemRegionClosure { 111 public: 112 void* operator new(size_t size, ResourceObj::allocation_type type, MEMFLAGS flags) throw() { 113 return ResourceObj::operator new(size, type, flags); 114 } 115 void* operator new(size_t size, Arena *arena) throw() { 116 return ResourceObj::operator new(size, arena); 117 } 118 void* operator new(size_t size) throw() { 119 return ResourceObj::operator new(size); 120 } 121 122 void operator delete(void* p) {} // nothing to do 123 }; 124 125 #endif // SHARE_MEMORY_MEMREGION_HPP