3rdparty/boost/boost/smart_ptr/detail/sp_counted_base_std_atomic.hpp

   1 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_ATOMIC_HPP_INCLUDED
   2 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_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 //  detail/sp_counted_base_std_atomic.hpp - C++11 std::atomic
  11 //
  12 //  Copyright (c) 2007, 2013 Peter Dimov
  13 //
  14 //  Distributed under the Boost Software License, Version 1.0.
  15 //  See accompanying file LICENSE_1_0.txt or copy at
  16 //  http://www.boost.org/LICENSE_1_0.txt
  17
  18 #include <boost/smart_ptr/detail/sp_typeinfo_.hpp>
  19 #include <boost/smart_ptr/detail/sp_noexcept.hpp>
  20 #include <boost/config.hpp>
  21 #include <atomic>
  22 #include <cstdint>
  23
  24 namespace boost
  25 {
  26
  27 namespace detail
  28 {
  29
  30 inline void atomic_increment( std::atomic_int_least32_t * pw ) BOOST_SP_NOEXCEPT
  31 {
  32     pw->fetch_add( 1, std::memory_order_relaxed );
  33 }
  34
  35 inline std::int_least32_t atomic_decrement( std::atomic_int_least32_t * pw ) BOOST_SP_NOEXCEPT
  36 {
  37     return pw->fetch_sub( 1, std::memory_order_acq_rel );
  38 }
  39
  40 inline std::int_least32_t atomic_conditional_increment( std::atomic_int_least32_t * pw ) BOOST_SP_NOEXCEPT
  41 {
  42     // long r = *pw;
  43     // if( r != 0 ) ++*pw;
  44     // return r;
  45
  46     std::int_least32_t r = pw->load( std::memory_order_relaxed );
  47
  48     for( ;; )
  49     {
  50         if( r == 0 )
  51         {
  52             return r;
  53         }
  54
  55         if( pw->compare_exchange_weak( r, r + 1, std::memory_order_relaxed, std::memory_order_relaxed ) )
  56         {
  57             return r;
  58         }
  59     }
  60 }
  61
  62 class BOOST_SYMBOL_VISIBLE sp_counted_base
  63 {
  64 private:
  65
  66     sp_counted_base( sp_counted_base const & );
  67     sp_counted_base & operator= ( sp_counted_base const & );
  68
  69     std::atomic_int_least32_t use_count_;   // #shared
  70     std::atomic_int_least32_t weak_count_;  // #weak + (#shared != 0)
  71
  72 public:
  73
  74     sp_counted_base() BOOST_SP_NOEXCEPT: use_count_( 1 ), weak_count_( 1 )
  75     {
  76     }
  77
  78     virtual ~sp_counted_base() /*BOOST_SP_NOEXCEPT*/
  79     {
  80     }
  81
  82     // dispose() is called when use_count_ drops to zero, to release
  83     // the resources managed by *this.
  84
  85     virtual void dispose() BOOST_SP_NOEXCEPT = 0;
  86
  87     // destroy() is called when weak_count_ drops to zero.
  88
  89     virtual void destroy() BOOST_SP_NOEXCEPT
  90     {
  91         delete this;
  92     }
  93
  94     virtual void * get_deleter( sp_typeinfo_ const & ti ) BOOST_SP_NOEXCEPT = 0;
  95     virtual void * get_local_deleter( sp_typeinfo_ const & ti ) BOOST_SP_NOEXCEPT = 0;
  96     virtual void * get_untyped_deleter() BOOST_SP_NOEXCEPT = 0;
  97
  98     void add_ref_copy() BOOST_SP_NOEXCEPT
  99     {
 100         atomic_increment( &use_count_ );
 101     }
 102
 103     bool add_ref_lock() BOOST_SP_NOEXCEPT // true on success
 104     {
 105         return atomic_conditional_increment( &use_count_ ) != 0;
 106     }
 107
 108     void release() BOOST_SP_NOEXCEPT
 109     {
 110         if( atomic_decrement( &use_count_ ) == 1 )
 111         {
 112             dispose();
 113             weak_release();
 114         }
 115     }
 116
 117     void weak_add_ref() BOOST_SP_NOEXCEPT
 118     {
 119         atomic_increment( &weak_count_ );
 120     }
 121
 122     void weak_release() BOOST_SP_NOEXCEPT
 123     {
 124         if( atomic_decrement( &weak_count_ ) == 1 )
 125         {
 126             destroy();
 127         }
 128     }
 129
 130     long use_count() const BOOST_SP_NOEXCEPT
 131     {
 132         return use_count_.load( std::memory_order_acquire );
 133     }
 134 };
 135
 136 } // namespace detail
 137
 138 } // namespace boost
 139
 140 #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_STD_ATOMIC_HPP_INCLUDED