1 /*
   2  * Copyright (c) 2000, 2004, 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 // A very simple data structure representing a contigous region
  26 // region of address space.
  27 
  28 // Note that MemRegions are passed by value, not by reference.
  29 // The intent is that they remain very small and contain no
  30 // objects.
  31 
  32 class MemRegion VALUE_OBJ_CLASS_SPEC {
  33   friend class VMStructs;
  34 private:
  35   HeapWord* _start;
  36   size_t    _word_size;
  37 
  38 public:
  39   MemRegion() : _start(NULL), _word_size(0) {};
  40   MemRegion(HeapWord* start, size_t word_size) :
  41     _start(start), _word_size(word_size) {};
  42   MemRegion(HeapWord* start, HeapWord* end) :
  43     _start(start), _word_size(pointer_delta(end, start)) {
  44     assert(end >= start, "incorrect constructor arguments");
  45   }
  46 
  47   MemRegion(const MemRegion& mr): _start(mr._start), _word_size(mr._word_size) {}
  48 
  49   MemRegion intersection(const MemRegion mr2) const;
  50   // regions must overlap or be adjacent
  51   MemRegion _union(const MemRegion mr2) const;
  52   // minus will fail a guarantee if mr2 is interior to this,
  53   // since there's no way to return 2 disjoint regions.
  54   MemRegion minus(const MemRegion mr2) const;
  55 
  56   HeapWord* start() const { return _start; }
  57   HeapWord* end() const   { return _start + _word_size; }
  58   HeapWord* last() const  { return _start + _word_size - 1; }
  59 
  60   void set_start(HeapWord* start) { _start = start; }
  61   void set_end(HeapWord* end)     { _word_size = pointer_delta(end, _start); }
  62   void set_word_size(size_t word_size) {
  63     _word_size = word_size;
  64   }
  65 
  66   bool contains(const MemRegion mr2) const {
  67     return _start <= mr2._start && end() >= mr2.end();
  68   }
  69   bool contains(const void* addr) const {
  70     return addr >= (void*)_start && addr < (void*)end();
  71   }
  72   bool equals(const MemRegion mr2) const {
  73     // first disjunct since we do not have a canonical empty set
  74     return ((is_empty() && mr2.is_empty()) ||
  75             (start() == mr2.start() && end() == mr2.end()));
  76   }
  77 
  78   size_t byte_size() const { return _word_size * sizeof(HeapWord); }
  79   size_t word_size() const { return _word_size; }
  80 
  81   bool is_empty() const { return word_size() == 0; }
  82 };
  83 
  84 // For iteration over MemRegion's.
  85 
  86 class MemRegionClosure : public StackObj {
  87 public:
  88   virtual void do_MemRegion(MemRegion mr) = 0;
  89 };
  90 
  91 // A ResourceObj version of MemRegionClosure
  92 
  93 class MemRegionClosureRO: public MemRegionClosure {
  94 public:
  95   void* operator new(size_t size, ResourceObj::allocation_type type) {
  96         return ResourceObj::operator new(size, type);
  97   }
  98   void* operator new(size_t size, Arena *arena) {
  99         return ResourceObj::operator new(size, arena);
 100   }
 101   void* operator new(size_t size) {
 102         return ResourceObj::operator new(size);
 103   }
 104 
 105   void  operator delete(void* p) {} // nothing to do
 106 };