1/*
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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
43class MemRegion {
44 friend class VMStructs;
45private:
46 HeapWord* _start;
47 size_t _word_size;
48
49public:
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
103class MemRegionClosure : public StackObj {
104public:
105 virtual void do_MemRegion(MemRegion mr) = 0;
106};
107
108// A ResourceObj version of MemRegionClosure
109
110class MemRegionClosureRO: public MemRegionClosure {
111public:
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
126