#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 <boost/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; #ifndef BOOST_NO_EXCEPTIONS try { #endif pthread::pthread_mutex_scoped_unlock relocker(&detail::once_epoch_mutex); f(); #ifndef BOOST_NO_EXCEPTIONS } catch(...) { flag.epoch=uninitialized_flag; BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv)); throw; } #endif 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