smart_ptr/detail/sp_counted_base_std_atomic.hpp

0001 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_ATOMIC_HPP_INCLUDED
0002 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_ATOMIC_HPP_INCLUDED
0003
0004 // MS compatible compilers support #pragma once
0005
0006 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
0007 # pragma once
0008 #endif
0009
0010 //  detail/sp_counted_base_std_atomic.hpp - C++11 std::atomic
0011 //
0012 //  Copyright (c) 2007, 2013 Peter Dimov
0013 //
0014 //  Distributed under the Boost Software License, Version 1.0.
0015 //  See accompanying file LICENSE_1_0.txt or copy at
0016 //  http://www.boost.org/LICENSE_1_0.txt
0017
0018 #include <boost/smart_ptr/detail/sp_typeinfo_.hpp>
0019 #include <boost/config.hpp>
0020 #include <atomic>
0021 #include <cstdint>
0022
0023 #if defined(BOOST_SP_REPORT_IMPLEMENTATION)
0024
0025 #include <boost/config/pragma_message.hpp>
0026 BOOST_PRAGMA_MESSAGE("Using std::atomic sp_counted_base")
0027
0028 #endif
0029
0030 namespace boost
0031 {
0032
0033 namespace detail
0034 {
0035
0036 inline void atomic_increment( std::atomic_int_least32_t * pw ) noexcept
0037 {
0038     pw->fetch_add( 1, std::memory_order_relaxed );
0039 }
0040
0041 inline std::int_least32_t atomic_decrement( std::atomic_int_least32_t * pw ) noexcept
0042 {
0043     return pw->fetch_sub( 1, std::memory_order_acq_rel );
0044 }
0045
0046 inline std::int_least32_t atomic_conditional_increment( std::atomic_int_least32_t * pw ) noexcept
0047 {
0048     // long r = *pw;
0049     // if( r != 0 ) ++*pw;
0050     // return r;
0051
0052     std::int_least32_t r = pw->load( std::memory_order_relaxed );
0053
0054     for( ;; )
0055     {
0056         if( r == 0 )
0057         {
0058             return r;
0059         }
0060
0061         if( pw->compare_exchange_weak( r, r + 1, std::memory_order_relaxed, std::memory_order_relaxed ) )
0062         {
0063             return r;
0064         }
0065     }
0066 }
0067
0068 class BOOST_SYMBOL_VISIBLE sp_counted_base
0069 {
0070 private:
0071
0072     sp_counted_base( sp_counted_base const & );
0073     sp_counted_base & operator= ( sp_counted_base const & );
0074
0075     std::atomic_int_least32_t use_count_;   // #shared
0076     std::atomic_int_least32_t weak_count_;  // #weak + (#shared != 0)
0077
0078 public:
0079
0080     sp_counted_base() noexcept: use_count_( 1 ), weak_count_( 1 )
0081     {
0082     }
0083
0084     virtual ~sp_counted_base() /*noexcept*/
0085     {
0086     }
0087
0088     // dispose() is called when use_count_ drops to zero, to release
0089     // the resources managed by *this.
0090
0091     virtual void dispose() noexcept = 0;
0092
0093     // destroy() is called when weak_count_ drops to zero.
0094
0095     virtual void destroy() noexcept
0096     {
0097         delete this;
0098     }
0099
0100     virtual void * get_deleter( sp_typeinfo_ const & ti ) noexcept = 0;
0101     virtual void * get_local_deleter( sp_typeinfo_ const & ti ) noexcept = 0;
0102     virtual void * get_untyped_deleter() noexcept = 0;
0103
0104     void add_ref_copy() noexcept
0105     {
0106         atomic_increment( &use_count_ );
0107     }
0108
0109     bool add_ref_lock() noexcept // true on success
0110     {
0111         return atomic_conditional_increment( &use_count_ ) != 0;
0112     }
0113
0114     void release() noexcept
0115     {
0116         if( atomic_decrement( &use_count_ ) == 1 )
0117         {
0118             dispose();
0119             weak_release();
0120         }
0121     }
0122
0123     void weak_add_ref() noexcept
0124     {
0125         atomic_increment( &weak_count_ );
0126     }
0127
0128     void weak_release() noexcept
0129     {
0130         if( atomic_decrement( &weak_count_ ) == 1 )
0131         {
0132             destroy();
0133         }
0134     }
0135
0136     long use_count() const noexcept
0137     {
0138         return use_count_.load( std::memory_order_acquire );
0139     }
0140 };
0141
0142 } // namespace detail
0143
0144 } // namespace boost
0145
0146 #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_ATOMIC_HPP_INCLUDED