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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 
43 class MemRegion {
44   friend class VMStructs;
45 private:
46   HeapWord* _start;
47   size_t    _word_size;
48 
49 public:
MemRegion()50   MemRegion() : _start(NULL), _word_size(0) {};
MemRegion(HeapWord * start,size_t word_size)51   MemRegion(HeapWord* start, size_t word_size) :
52     _start(start), _word_size(word_size) {};
MemRegion(HeapWord * start,HeapWord * end)53   MemRegion(HeapWord* start, HeapWord* end) :
54     _start(start), _word_size(pointer_delta(end, start)) {
55     assert(end >= start, "incorrect constructor arguments");
56   }
MemRegion(MetaWord * start,MetaWord * end)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 
start() const69   HeapWord* start() const { return _start; }
end() const70   HeapWord* end() const   { return _start + _word_size; }
last() const71   HeapWord* last() const  { return _start + _word_size - 1; }
72 
set_start(HeapWord * start)73   void set_start(HeapWord* start) { _start = start; }
set_end(HeapWord * end)74   void set_end(HeapWord* end)     { _word_size = pointer_delta(end, _start); }
set_word_size(size_t word_size)75   void set_word_size(size_t word_size) {
76     _word_size = word_size;
77   }
78 
contains(const MemRegion mr2) const79   bool contains(const MemRegion mr2) const {
80     return _start <= mr2._start && end() >= mr2.end();
81   }
contains(const void * addr) const82   bool contains(const void* addr) const {
83     return addr >= (void*)_start && addr < (void*)end();
84   }
equals(const MemRegion mr2) const85   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 
byte_size() const91   size_t byte_size() const { return _word_size * sizeof(HeapWord); }
word_size() const92   size_t word_size() const { return _word_size; }
93 
is_empty() const94   bool is_empty() const { return word_size() == 0; }
95 
96   // Creates and initializes an array of MemRegions of the given length.
97   static MemRegion* create_array(size_t length, MEMFLAGS flags);
98   static void destroy_array(MemRegion* array, size_t length);
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:
operator new(size_t size,ResourceObj::allocation_type type,MEMFLAGS flags)112   void* operator new(size_t size, ResourceObj::allocation_type type, MEMFLAGS flags) throw() {
113         return ResourceObj::operator new(size, type, flags);
114   }
operator new(size_t size,Arena * arena)115   void* operator new(size_t size, Arena *arena) throw() {
116         return ResourceObj::operator new(size, arena);
117   }
operator new(size_t size)118   void* operator new(size_t size) throw() {
119         return ResourceObj::operator new(size);
120   }
121 
operator delete(void * p)122   void  operator delete(void* p) {} // nothing to do
123 };
124 
125 #endif // SHARE_MEMORY_MEMREGION_HPP
126