memRegion.hpp revision 1879:f95d63e2154a 
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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.
38
39class MemRegion VALUE_OBJ_CLASS_SPEC {
40  friend class VMStructs;
41private:
42  HeapWord* _start;
43  size_t    _word_size;
44
45public:
46  MemRegion() : _start(NULL), _word_size(0) {};
47  MemRegion(HeapWord* start, size_t word_size) :
48    _start(start), _word_size(word_size) {};
49  MemRegion(HeapWord* start, HeapWord* end) :
50    _start(start), _word_size(pointer_delta(end, start)) {
51    assert(end >= start, "incorrect constructor arguments");
52  }
53
54  MemRegion(const MemRegion& mr): _start(mr._start), _word_size(mr._word_size) {}
55
56  MemRegion intersection(const MemRegion mr2) const;
57  // regions must overlap or be adjacent
58  MemRegion _union(const MemRegion mr2) const;
59  // minus will fail a guarantee if mr2 is interior to this,
60  // since there's no way to return 2 disjoint regions.
61  MemRegion minus(const MemRegion mr2) const;
62
63  HeapWord* start() const { return _start; }
64  HeapWord* end() const   { return _start + _word_size; }
65  HeapWord* last() const  { return _start + _word_size - 1; }
66
67  void set_start(HeapWord* start) { _start = start; }
68  void set_end(HeapWord* end)     { _word_size = pointer_delta(end, _start); }
69  void set_word_size(size_t word_size) {
70    _word_size = word_size;
71  }
72
73  bool contains(const MemRegion mr2) const {
74    return _start <= mr2._start && end() >= mr2.end();
75  }
76  bool contains(const void* addr) const {
77    return addr >= (void*)_start && addr < (void*)end();
78  }
79  bool equals(const MemRegion mr2) const {
80    // first disjunct since we do not have a canonical empty set
81    return ((is_empty() && mr2.is_empty()) ||
82            (start() == mr2.start() && end() == mr2.end()));
83  }
84
85  size_t byte_size() const { return _word_size * sizeof(HeapWord); }
86  size_t word_size() const { return _word_size; }
87
88  bool is_empty() const { return word_size() == 0; }
89};
90
91// For iteration over MemRegion's.
92
93class MemRegionClosure : public StackObj {
94public:
95  virtual void do_MemRegion(MemRegion mr) = 0;
96};
97
98// A ResourceObj version of MemRegionClosure
99
100class MemRegionClosureRO: public MemRegionClosure {
101public:
102  void* operator new(size_t size, ResourceObj::allocation_type type) {
103        return ResourceObj::operator new(size, type);
104  }
105  void* operator new(size_t size, Arena *arena) {
106        return ResourceObj::operator new(size, arena);
107  }
108  void* operator new(size_t size) {
109        return ResourceObj::operator new(size);
110  }
111
112  void  operator delete(void* p) {} // nothing to do
113};
114
115#endif // SHARE_VM_MEMORY_MEMREGION_HPP
116