#ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED

#define BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED

// MS compatible compilers support #pragma once

#if defined(_MSC_VER) && (_MSC_VER >= 1020)

# pragma once

#endif

//

//  yield_k.hpp

//

//  Copyright (c) 2008 Peter Dimov

//

//  void yield( unsigned k );

//

//  Typical use:

//

//  for( unsigned k = 0; !try_lock(); ++k ) yield( k );

//

//  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/config.hpp>

// BOOST_SMT_PAUSE

#if defined(_MSC_VER) && _MSC_VER >= 1310 && ( defined(_M_IX86) || defined(_M_X64) )

extern "C" void _mm_pause();

#pragma intrinsic( _mm_pause )

#define BOOST_SMT_PAUSE _mm_pause();

#elif defined(__GNUC__) && ( defined(__i386__) || defined(__x86_64__) )

#define BOOST_SMT_PAUSE __asm__ __volatile__( "rep; nop" : : : "memory" );

#endif

//

#if defined( WIN32 ) || defined( _WIN32 ) || defined( __WIN32__ ) || defined( __CYGWIN__ )

#if defined( BOOST_USE_WINDOWS_H )

# include <windows.h>

#endif

namespace boost

{

namespace detail

{

#if !defined( BOOST_USE_WINDOWS_H )

  extern "C" void __stdcall Sleep( unsigned ms );

#endif

inline void yield( unsigned k )

{

    if( k < 4 )

    {

    }

#if defined( BOOST_SMT_PAUSE )

    else if( k < 16 )

    {

        BOOST_SMT_PAUSE

    }

#endif

    else if( k < 32 )

    {

        Sleep( 0 );

    }

    else

    {

        Sleep( 1 );

    }

}

} // namespace detail

} // namespace boost

#elif defined( BOOST_HAS_PTHREADS )

#include <sched.h>

#include <time.h>

namespace boost

{

namespace detail

{

inline void yield( unsigned k )

{

    if( k < 4 )

    {

    }

#if defined( BOOST_SMT_PAUSE )

    else if( k < 16 )

    {

        BOOST_SMT_PAUSE

    }

#endif

    else if( k < 32 || k & 1 )

    {

        sched_yield();

    }

    else

    {

        // g++ -Wextra warns on {} or {0}

        struct timespec rqtp = { 0, 0 };

        // POSIX says that timespec has tv_sec and tv_nsec

        // But it doesn't guarantee order or placement

        rqtp.tv_sec = 0;

        rqtp.tv_nsec = 1000;

        nanosleep( &rqtp, 0 );

    }

}

} // namespace detail

} // namespace boost

#else

namespace boost

{

namespace detail

{

inline void yield( unsigned )

{

}

} // namespace detail

} // namespace boost

#endif

#endif // #ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED