1 /*
   2  * Copyright (c) 2018, 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_METASPACE_COUNTER_HPP
  26 #define SHARE_MEMORY_METASPACE_COUNTER_HPP
  27 
  28 #include "runtime/atomic.hpp"
  29 #include "utilities/debug.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 
  33 namespace metaspace {
  34 
  35 // A very simple helper class which counts something, offers decrement/increment
  36 // methods and checks for overflow/underflow on increment/decrement.
  37 //
  38 // (since we seem to do that alot....)
  39 
  40 template <class T>
  41 class AbstractCounter {
  42 
  43   T _c;
  44 
  45 public:
  46 
  47   AbstractCounter() : _c(0) {}
  48 
  49   T get() const           { return _c; }
  50 
  51   void increment()            { assert(_c + 1 > _c, "overflow"); _c ++; }
  52   void increment_by(T v)      { assert(_c + v >= _c, "overflow"); _c += v; }
  53   void decrement()            { assert(_c - 1 < _c, "underflow"); _c --; }
  54   void decrement_by(T v)      { assert(_c - v <= _c, "underflow"); _c -= v; }
  55 
  56 #ifdef ASSERT
  57   void check(T expected) const {
  58     assert(_c == expected, "Counter mismatch: %d, expected: %d.",
  59            (int)_c, (int)expected);
  60     }
  61 #endif
  62 
  63 };
  64 
  65 typedef AbstractCounter<size_t>   SizeCounter;
  66 typedef AbstractCounter<int>      IntCounter;
  67 
  68 
  69 template <class T>
  70 class AbstractAtomicCounter {
  71 
  72   volatile T _c;
  73 
  74 public:
  75 
  76   AbstractAtomicCounter() : _c(0) {}
  77 
  78   T get() const               { return _c; }
  79 
  80   void increment()            { assert(_c + 1 > _c, "overflow"); Atomic::inc(&_c); }
  81   void increment_by(T v)      { assert(_c + v >= _c, "overflow"); Atomic::add(&_c, v); }
  82   void decrement()            { assert(_c - 1 < _c, "underflow"); Atomic::dec(&_c); }
  83   void decrement_by(T v)      { assert(_c - v <= _c, "underflow"); Atomic::sub(&_c, v); }
  84 
  85 #ifdef ASSERT
  86   void check(T expected) const {
  87     assert(_c == expected, "Counter mismatch: %d, expected: %d.",
  88            (int)_c, (int)expected);
  89     }
  90 #endif
  91 
  92 };
  93 
  94 typedef AbstractAtomicCounter<size_t> SizeAtomicCounter;
  95 
  96 
  97 
  98 } // namespace metaspace
  99 
 100 #endif // SHARE_MEMORY_METASPACE_WORDSIZECOUNTER_HPP
 101