statechart/detail/counted_base.hpp

0001 #ifndef BOOST_STATECHART_DETAIL_COUNTED_BASE_HPP_INCLUDED
0002 #define BOOST_STATECHART_DETAIL_COUNTED_BASE_HPP_INCLUDED
0003 //////////////////////////////////////////////////////////////////////////////
0004 // Copyright 2002-2006 Andreas Huber Doenni
0005 // Distributed under the Boost Software License, Version 1.0. (See accompany-
0006 // ing file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 //////////////////////////////////////////////////////////////////////////////
0008
0009
0010
0011 #include <boost/detail/atomic_count.hpp>
0012 #include <boost/config.hpp> // BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP
0013
0014
0015
0016 namespace boost
0017 {
0018 namespace statechart
0019 {
0020 namespace detail
0021 {
0022
0023
0024
0025 template< bool NeedsLocking >
0026 struct count_base
0027 {
0028   count_base() : count_( 0 ) {}
0029   mutable boost::detail::atomic_count count_;
0030 };
0031
0032 template<>
0033 struct count_base< false >
0034 {
0035   count_base() : count_( 0 ) {}
0036   mutable long count_;
0037 };
0038
0039 //////////////////////////////////////////////////////////////////////////////
0040 template< bool NeedsLocking = true >
0041 class counted_base : private count_base< NeedsLocking >
0042 {
0043   typedef count_base< NeedsLocking > base_type;
0044   public:
0045     //////////////////////////////////////////////////////////////////////////
0046     bool ref_counted() const
0047     {
0048       return base_type::count_ != 0;
0049     }
0050
0051     long ref_count() const
0052     {
0053       return base_type::count_;
0054     }
0055
0056   protected:
0057     //////////////////////////////////////////////////////////////////////////
0058     counted_base() {}
0059     ~counted_base() {}
0060
0061     // do nothing copy implementation is intentional (the number of
0062     // referencing pointers of the source and the destination is not changed
0063     // through the copy operation)
0064     counted_base( const counted_base & ) : base_type() {}
0065     counted_base & operator=( const counted_base & ) { return *this; }
0066
0067   public:
0068     //////////////////////////////////////////////////////////////////////////
0069     // The following declarations should be private.
0070     // They are only public because many compilers lack template friends.
0071     //////////////////////////////////////////////////////////////////////////
0072     void add_ref() const
0073     {
0074       ++base_type::count_;
0075     }
0076
0077     bool release() const
0078     {
0079       BOOST_ASSERT( base_type::count_ > 0 );
0080       return --base_type::count_ == 0;
0081     }
0082 };
0083
0084
0085
0086 } // namespace detail
0087 } // namespace statechart
0088 } // namespace boost
0089
0090
0091
0092 #endif