/usr/include/boost/thread/pthread/once.hpp is in libboost1.46-dev 1.46.1-7ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 | #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
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