rev 58060 : [mq]: 8238999-iklam-review

   1 /*
   2  * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   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.
   8  *
   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  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  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
  21  * questions.
  22  *
  23  */
  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:
  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 
 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:
 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
--- EOF ---