1 /*
  2  * Copyright (c) 2000, 2018, 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_VM_MEMORY_MEMREGION_HPP
 26 #define SHARE_VM_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 passed by value, not by reference.
 36 // The intent is that they remain very small and contain no
 37 // objects. _ValueObj should never be allocated in heap but we do
 38 // create MemRegions (in CardTableBarrierSet) in heap so operator
 39 // new and operator new [] added for this special case.
 40 
 41 class MetaWord;
 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(const MemRegion& mr): _start(mr._start), _word_size(mr._word_size) {}
 63 
 64   MemRegion intersection(const MemRegion mr2) const;
 65   // regions must overlap or be adjacent
 66   MemRegion _union(const MemRegion mr2) const;
 67   // minus will fail a guarantee if mr2 is interior to this,
 68   // since there's no way to return 2 disjoint regions.
 69   MemRegion minus(const MemRegion mr2) const;
 70 
 71   HeapWord* start() const { return _start; }
 72   HeapWord* end() const   { return _start + _word_size; }
 73   HeapWord* last() const  { return _start + _word_size - 1; }
 74 
 75   void set_start(HeapWord* start) { _start = start; }
 76   void set_end(HeapWord* end)     { _word_size = pointer_delta(end, _start); }
 77   void set_word_size(size_t word_size) {
 78     _word_size = word_size;
 79   }
 80 
 81   bool contains(const MemRegion mr2) const {
 82     return _start <= mr2._start && end() >= mr2.end();
 83   }
 84   bool contains(const void* addr) const {
 85     return addr >= (void*)_start && addr < (void*)end();
 86   }
 87   bool equals(const MemRegion mr2) const {
 88     // first disjunct since we do not have a canonical empty set
 89     return ((is_empty() && mr2.is_empty()) ||
 90             (start() == mr2.start() && end() == mr2.end()));
 91   }
 92 
 93   size_t byte_size() const { return _word_size * sizeof(HeapWord); }
 94   size_t word_size() const { return _word_size; }
 95 
 96   bool is_empty() const { return word_size() == 0; }
 97   void* operator new(size_t size) throw();
 98   void* operator new [](size_t size) throw();
 99   void  operator delete(void* p);
100   void  operator delete [](void* p);
101 };
102 
103 // For iteration over MemRegion's.
104 
105 class MemRegionClosure : public StackObj {
106 public:
107   virtual void do_MemRegion(MemRegion mr) = 0;
108 };
109 
110 // A ResourceObj version of MemRegionClosure
111 
112 class MemRegionClosureRO: public MemRegionClosure {
113 public:
114   void* operator new(size_t size, ResourceObj::allocation_type type, MEMFLAGS flags) throw() {
115         return ResourceObj::operator new(size, type, flags);
116   }
117   void* operator new(size_t size, Arena *arena) throw() {
118         return ResourceObj::operator new(size, arena);
119   }
120   void* operator new(size_t size) throw() {
121         return ResourceObj::operator new(size);
122   }
123 
124   void  operator delete(void* p) {} // nothing to do
125 };
126 
127 #endif // SHARE_VM_MEMORY_MEMREGION_HPP