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
22namespace boost
23{
24
25namespace detail
26{
27
28class spinlock
29{
30public:
31
32 std::atomic_flag v_;
33
34public:
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
54public:
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
85