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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. The copy constructor and destructor must be trivial,
38 // to support optimization for pass-by-value.
39 // These should never be allocated in heap but we do
40 // create MemRegions (in CardTableBarrierSet) in heap so operator
41 // new and operator new [] added for this special case.
42 
43 class MetaWord;
44 
45 class MemRegion {
46   friend class VMStructs;
47 private:
48   HeapWord* _start;
49   size_t    _word_size;
50 
51 public:
MemRegion()52   MemRegion() : _start(NULL), _word_size(0) {};
MemRegion(HeapWord * start,size_t word_size)53   MemRegion(HeapWord* start, size_t word_size) :
54     _start(start), _word_size(word_size) {};
MemRegion(HeapWord * start,HeapWord * end)55   MemRegion(HeapWord* start, HeapWord* end) :
56     _start(start), _word_size(pointer_delta(end, start)) {
57     assert(end >= start, "incorrect constructor arguments");
58   }
MemRegion(MetaWord * start,MetaWord * end)59   MemRegion(MetaWord* start, MetaWord* end) :
60     _start((HeapWord*)start), _word_size(pointer_delta(end, start)) {
61     assert(end >= start, "incorrect constructor arguments");
62   }
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 
start() const71   HeapWord* start() const { return _start; }
end() const72   HeapWord* end() const   { return _start + _word_size; }
last() const73   HeapWord* last() const  { return _start + _word_size - 1; }
74 
set_start(HeapWord * start)75   void set_start(HeapWord* start) { _start = start; }
set_end(HeapWord * end)76   void set_end(HeapWord* end)     { _word_size = pointer_delta(end, _start); }
set_word_size(size_t word_size)77   void set_word_size(size_t word_size) {
78     _word_size = word_size;
79   }
80 
contains(const MemRegion mr2) const81   bool contains(const MemRegion mr2) const {
82     return _start <= mr2._start && end() >= mr2.end();
83   }
contains(const void * addr) const84   bool contains(const void* addr) const {
85     return addr >= (void*)_start && addr < (void*)end();
86   }
equals(const MemRegion mr2) const87   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 
byte_size() const93   size_t byte_size() const { return _word_size * sizeof(HeapWord); }
word_size() const94   size_t word_size() const { return _word_size; }
95 
is_empty() const96   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:
operator new(size_t size,ResourceObj::allocation_type type,MEMFLAGS flags)114   void* operator new(size_t size, ResourceObj::allocation_type type, MEMFLAGS flags) throw() {
115         return ResourceObj::operator new(size, type, flags);
116   }
operator new(size_t size,Arena * arena)117   void* operator new(size_t size, Arena *arena) throw() {
118         return ResourceObj::operator new(size, arena);
119   }
operator new(size_t size)120   void* operator new(size_t size) throw() {
121         return ResourceObj::operator new(size);
122   }
123 
operator delete(void * p)124   void  operator delete(void* p) {} // nothing to do
125 };
126 
127 #endif // SHARE_VM_MEMORY_MEMREGION_HPP
128