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#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
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