libbase/ref_counted.h

   1 //
   2 //   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
   3 //   Foundation, Inc
   4 //
   5 // This program is free software; you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation; either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // This program is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with this program; if not, write to the Free Software
  17 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18
  19 #ifndef GNASH_REF_COUNTED_H
  20 #define GNASH_REF_COUNTED_H
  21
  22 #include "dsodefs.h" // for DSOEXPORT
  23
  24 #include <cassert>
  25 #include <boost/detail/atomic_count.hpp>
  26
  27 namespace gnash {
  28
  29 /// \brief
  30 /// For stuff that's tricky to keep track of w/r/t ownership & cleanup.
  31 /// The only use for this class seems to be for putting derived
  32 /// classes in smart_ptr
  33 ///
  34 class DSOEXPORT ref_counted
  35 {
  36
  37 private:
  38
  39         // We use an atomic counter to make ref-counting
  40         // thread-safe. The drop_ref() method must be
  41         // carefully designed for this to be effective
  42         // (decrement & check in a single statement)
  43         //
  44         typedef boost::detail::atomic_count Counter;
  45
  46         mutable Counter m_ref_count;
  47
  48 protected:
  49
  50         // A ref-counted object only deletes self,
  51         // must never be explicitly deleted !
  52         virtual ~ref_counted()
  53         {
  54                 assert(m_ref_count == 0);
  55         }
  56
  57 public:
  58         ref_counted()
  59                 :
  60                 m_ref_count(0)
  61         {
  62         }
  63
  64         ref_counted(const ref_counted&)
  65                 :
  66                 m_ref_count(0)
  67         {
  68         }
  69
  70         void add_ref() const {
  71                 assert(m_ref_count >= 0);
  72                 ++m_ref_count;
  73         }
  74
  75         void drop_ref() const {
  76
  77                 assert(m_ref_count > 0);
  78                 if (!--m_ref_count) {
  79                         // Delete me!
  80                         delete this;
  81                 }
  82         }
  83
  84         long get_ref_count() const { return m_ref_count; }
  85 };
  86
  87 } // namespace gnash
  88
  89 #endif // GNASH_REF_COUNTED_H