95 lines
2.9 KiB
C++
95 lines
2.9 KiB
C++
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#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 <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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