boost/interprocess/smart_ptr/detail/sp_counted_base_atomic.hpp

   1 #ifndef BOOST_INTERPROCESS_DETAIL_SP_COUNTED_BASE_ATOMIC_HPP_INCLUDED
   2 #define BOOST_INTERPROCESS_DETAIL_SP_COUNTED_BASE_ATOMIC_HPP_INCLUDED
   3
   4 // MS compatible compilers support #pragma once
   5
   6 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
   7 # pragma once
   8 #endif
   9
  10 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
  11 //  Copyright 2004-2005 Peter Dimov
  12 //  Copyright 2007-2008 Ion Gaztanaga
  13 //
  14 // Distributed under the Boost Software License, Version 1.0. (See
  15 // accompanying file LICENSE_1_0.txt or copy at
  16 // http://www.boost.org/LICENSE_1_0.txt)
  17 //
  18 //
  19 //  Lock-free algorithm by Alexander Terekhov
  20 //
  21 //  Thanks to Ben Hitchings for the #weak + (#shared != 0)
  22 //  formulation
  23 //
  24
  25 #include <boost/interprocess/detail/config_begin.hpp>
  26 #include <boost/interprocess/detail/workaround.hpp>
  27
  28 #include <boost/interprocess/detail/atomic.hpp>
  29 #include <typeinfo>
  30
  31 namespace boost {
  32
  33 namespace interprocess {
  34
  35 namespace detail {
  36
  37 class sp_counted_base
  38 {
  39 private:
  40
  41     sp_counted_base( sp_counted_base const & );
  42     sp_counted_base & operator= ( sp_counted_base const & );
  43
  44     boost::uint32_t use_count_;        // #shared
  45     boost::uint32_t weak_count_;       // #weak + (#shared != 0)
  46
  47 public:
  48
  49     sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
  50     {}
  51
  52     ~sp_counted_base() // nothrow
  53     {}
  54
  55     void add_ref_copy()
  56     {
  57         detail::atomic_inc32( &use_count_ );
  58     }
  59
  60     bool add_ref_lock() // true on success
  61     {
  62         for( ;; )
  63         {
  64             boost::uint32_t tmp = static_cast< boost::uint32_t const volatile& >( use_count_ );
  65             if( tmp == 0 ) return false;
  66             if( detail::atomic_cas32( &use_count_, tmp + 1, tmp ) == tmp )
  67                return true;
  68         }
  69     }
  70
  71    bool ref_release() // nothrow
  72    { return 1 == detail::atomic_dec32( &use_count_ );  }
  73
  74    void weak_add_ref() // nothrow
  75    { detail::atomic_inc32( &weak_count_ ); }
  76
  77    bool weak_release() // nothrow
  78    { return 1 == detail::atomic_dec32( &weak_count_ ); }
  79
  80    long use_count() const // nothrow
  81    { return (long)static_cast<boost::uint32_t const volatile &>( use_count_ ); }
  82 };
  83
  84 } // namespace detail
  85
  86 } // namespace interprocess
  87
  88 } // namespace boost
  89
  90 #include <boost/interprocess/detail/config_end.hpp>
  91
  92 #endif  // #ifndef BOOST_INTERPROCESS_DETAIL_SP_COUNTED_BASE_ATOMIC_HPP_INCLUDED