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95 lines
2.9 KiB
95 lines
2.9 KiB
#ifndef BOOST_THREAD_PTHREAD_ONCE_HPP |
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#define BOOST_THREAD_PTHREAD_ONCE_HPP |
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// once.hpp |
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// |
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// (C) Copyright 2007-8 Anthony Williams |
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// |
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// Distributed under the Boost Software License, Version 1.0. (See |
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// accompanying file LICENSE_1_0.txt or copy at |
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// http://www.boost.org/LICENSE_1_0.txt) |
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#include <boost/thread/detail/config.hpp> |
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#include <boost/config.hpp> |
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#include <pthread.h> |
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#include <boost/assert.hpp> |
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#include "pthread_mutex_scoped_lock.hpp" |
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#include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp> |
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#include <boost/cstdint.hpp> |
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#include <boost/config/abi_prefix.hpp> |
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namespace boost |
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{ |
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struct once_flag |
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{ |
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boost::uintmax_t epoch; |
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}; |
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namespace detail |
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{ |
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BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); |
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BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; |
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BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; |
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BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; |
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} |
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#define BOOST_ONCE_INITIAL_FLAG_VALUE 0 |
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#define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} |
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// Based on Mike Burrows fast_pthread_once algorithm as described in |
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// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html |
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template<typename Function> |
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void call_once(once_flag& flag,Function f) |
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{ |
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static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; |
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static boost::uintmax_t const being_initialized=uninitialized_flag+1; |
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boost::uintmax_t const epoch=flag.epoch; |
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boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); |
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if(epoch<this_thread_epoch) |
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{ |
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pthread::pthread_mutex_scoped_lock lk(&detail::once_epoch_mutex); |
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while(flag.epoch<=being_initialized) |
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{ |
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if(flag.epoch==uninitialized_flag) |
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{ |
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flag.epoch=being_initialized; |
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#ifndef BOOST_NO_EXCEPTIONS |
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try |
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{ |
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#endif |
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pthread::pthread_mutex_scoped_unlock relocker(&detail::once_epoch_mutex); |
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f(); |
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#ifndef BOOST_NO_EXCEPTIONS |
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} |
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catch(...) |
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{ |
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flag.epoch=uninitialized_flag; |
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BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv)); |
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throw; |
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} |
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#endif |
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flag.epoch=--detail::once_global_epoch; |
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BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv)); |
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} |
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else |
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{ |
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while(flag.epoch==being_initialized) |
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{ |
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BOOST_VERIFY(!pthread_cond_wait(&detail::once_epoch_cv,&detail::once_epoch_mutex)); |
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} |
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} |
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} |
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this_thread_epoch=detail::once_global_epoch; |
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} |
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} |
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} |
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#include <boost/config/abi_suffix.hpp> |
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#endif
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