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

   1 #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
   2 #define BOOST_SMART_PTR_DETAIL_SPINLOCK_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 //
  11 //  Copyright (c) 2014 Peter Dimov
  12 //
  13 //  Distributed under the Boost Software License, Version 1.0.
  14 //  See accompanying file LICENSE_1_0.txt or copy at
  15 //  http://www.boost.org/LICENSE_1_0.txt)
  16 //
  17
  18 #include <boost/smart_ptr/detail/yield_k.hpp>
  19 #include <boost/config.hpp>
  20 #include <atomic>
  21
  22 namespace boost
  23 {
  24
  25 namespace detail
  26 {
  27
  28 class spinlock
  29 {
  30 public:
  31
  32     std::atomic_flag v_;
  33
  34 public:
  35
  36     bool try_lock() BOOST_NOEXCEPT
  37     {
  38         return !v_.test_and_set( std::memory_order_acquire );
  39     }
  40
  41     void lock() BOOST_NOEXCEPT
  42     {
  43         for( unsigned k = 0; !try_lock(); ++k )
  44         {
  45             boost::detail::yield( k );
  46         }
  47     }
  48
  49     void unlock() BOOST_NOEXCEPT
  50     {
  51         v_ .clear( std::memory_order_release );
  52     }
  53
  54 public:
  55
  56     class scoped_lock
  57     {
  58     private:
  59
  60         spinlock & sp_;
  61
  62         scoped_lock( scoped_lock const & );
  63         scoped_lock & operator=( scoped_lock const & );
  64
  65     public:
  66
  67         explicit scoped_lock( spinlock & sp ) BOOST_NOEXCEPT: sp_( sp )
  68         {
  69             sp.lock();
  70         }
  71
  72         ~scoped_lock() /*BOOST_NOEXCEPT*/
  73         {
  74             sp_.unlock();
  75         }
  76     };
  77 };
  78
  79 } // namespace detail
  80 } // namespace boost
  81
  82 #define BOOST_DETAIL_SPINLOCK_INIT { ATOMIC_FLAG_INIT }
  83
  84 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED