#ifndef BOOST_THREAD_PTHREAD_ONCE_HPP

#define BOOST_THREAD_PTHREAD_ONCE_HPP

//  once.hpp

//

//  (C) Copyright 2007-8 Anthony Williams 

//

//  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/thread/detail/config.hpp>

#include <pthread.h>

#include <boost/assert.hpp>

#include "pthread_mutex_scoped_lock.hpp"

#include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp>

#include <boost/cstdint.hpp>

#include <boost/config/abi_prefix.hpp>

namespace boost

{

    struct once_flag

    {

        boost::uintmax_t epoch;

    };

    namespace detail

    {

        BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch();

        BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch;

        BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex;

        BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv;

    }

#define BOOST_ONCE_INITIAL_FLAG_VALUE 0

#define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE}

    // Based on Mike Burrows fast_pthread_once algorithm as described in

    // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html

    template<typename Function>

    void call_once(once_flag& flag,Function f)

    {

        static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE;

        static boost::uintmax_t const being_initialized=uninitialized_flag+1;

        boost::uintmax_t const epoch=flag.epoch;

        boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch();

        if(epoch<this_thread_epoch)

        {

            pthread::pthread_mutex_scoped_lock lk(&detail::once_epoch_mutex);

            while(flag.epoch<=being_initialized)

            {

                if(flag.epoch==uninitialized_flag)

                {

                    flag.epoch=being_initialized;

                    try

                    {

                        pthread::pthread_mutex_scoped_unlock relocker(&detail::once_epoch_mutex);

                        f();

                    }

                    catch(...)

                    {

                        flag.epoch=uninitialized_flag;

                        BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv));

                        throw;

                    }

                    flag.epoch=--detail::once_global_epoch;

                    BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv));

                }

                else

                {

                    while(flag.epoch==being_initialized)

                    {

                        BOOST_VERIFY(!pthread_cond_wait(&detail::once_epoch_cv,&detail::once_epoch_mutex));

                    }

                }

            }

            this_thread_epoch=detail::once_global_epoch;

        }

    }

}

#include <boost/config/abi_suffix.hpp>

#endif