1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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   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  *
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  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
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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 passed by value, not by reference.
  36 // The intent is that they remain very small and contain no
  37 // objects. These 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_MEMORY_MEMREGION_HPP