boost/smart_ptr/detail/spinlock_w32.hpp

#ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_W32_HPP_INCLUDED
#define BOOST_SMART_PTR_DETAIL_SPINLOCK_W32_HPP_INCLUDED
// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
//
//  Copyright (c) 2008 Peter Dimov
//
//  Distributed under the Boost Software License, Version 1.0.
//  See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
#include <boost/smart_ptr/detail/sp_interlocked.hpp>
#include <boost/smart_ptr/detail/yield_k.hpp>
// BOOST_COMPILER_FENCE
#if defined(__INTEL_COMPILER)
#define BOOST_COMPILER_FENCE __memory_barrier();
#elif defined( _MSC_VER ) && _MSC_VER >= 1310
extern "C" void _ReadWriteBarrier();
#pragma intrinsic( _ReadWriteBarrier )
#define BOOST_COMPILER_FENCE _ReadWriteBarrier();
#elif defined(__GNUC__)
#define BOOST_COMPILER_FENCE __asm__ __volatile__( "" : : : "memory" );
#else
#define BOOST_COMPILER_FENCE
#endif
//
namespace boost
{
namespace detail
{
class spinlock
{
public:
    long v_;
public:
    bool try_lock()
    {
        long r = BOOST_SP_INTERLOCKED_EXCHANGE( &v_, 1 );
        BOOST_COMPILER_FENCE
        return r == 0;
    }
    void lock()
    {
        for( unsigned k = 0; !try_lock(); ++k )
        {
            boost::detail::yield( k );
        }
    }
    void unlock()
    {
        BOOST_COMPILER_FENCE
        *const_cast< long volatile* >( &v_ ) = 0;
    }
public:
    class scoped_lock
    {
    private:
        spinlock & sp_;
        scoped_lock( scoped_lock const & );
        scoped_lock & operator=( scoped_lock const & );
    public:
        explicit scoped_lock( spinlock & sp ): sp_( sp )
        {
            sp.lock();
        }
        ~scoped_lock()
        {
            sp_.unlock();
        }
    };
};
} // namespace detail
} // namespace boost
#define BOOST_DETAIL_SPINLOCK_INIT {0}
#endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_W32_HPP_INCLUDED