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#ifndef BOOST_THREAD_WIN32_ONCE_HPP
#define BOOST_THREAD_WIN32_ONCE_HPP
// once.hpp
//
// (C) Copyright 2005-7 Anthony Williams
// (C) Copyright 2005 John Maddock
//
// 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 <cstring>
#include <cstddef>
#include <boost/assert.hpp>
#include <boost/static_assert.hpp>
#include <boost/detail/interlocked.hpp>
#include <boost/thread/win32/thread_primitives.hpp>
#include <boost/thread/win32/interlocked_read.hpp>
#include <boost/config/abi_prefix.hpp>
#ifdef BOOST_NO_STDC_NAMESPACE
namespace std
{
using ::memcpy;
using ::ptrdiff_t;
}
#endif
namespace boost
{
struct once_flag
{
long status;
long count;
long throw_count;
void* event_handle;
~once_flag()
{
if(count)
{
BOOST_ASSERT(count==throw_count);
}
void* const old_event=BOOST_INTERLOCKED_EXCHANGE_POINTER(&event_handle,0);
if(old_event)
{
::boost::detail::win32::CloseHandle(old_event);
}
}
};
#define BOOST_ONCE_INIT {0,0,0,0}
namespace detail
{
inline void* allocate_event_handle(void*& handle)
{
void* const new_handle=::boost::detail::win32::create_anonymous_event(
::boost::detail::win32::manual_reset_event,
::boost::detail::win32::event_initially_reset);
void* event_handle=BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(&handle,
new_handle,0);
if(event_handle)
{
::boost::detail::win32::CloseHandle(new_handle);
return event_handle;
}
return new_handle;
}
}
template<typename Function>
void call_once(once_flag& flag,Function f)
{
// Try for a quick win: if the procedure has already been called
// just skip through:
long const function_complete_flag_value=0xc15730e2;
long const running_value=0x7f0725e3;
long status;
bool counted=false;
void* event_handle=0;
long throw_count=0;
while((status=::boost::detail::interlocked_read_acquire(&flag.status))
!=function_complete_flag_value)
{
status=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&flag.status,running_value,0);
if(!status)
{
try
{
if(!event_handle)
{
event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
}
if(event_handle)
{
::boost::detail::win32::ResetEvent(event_handle);
}
f();
if(!counted)
{
BOOST_INTERLOCKED_INCREMENT(&flag.count);
counted=true;
}
BOOST_INTERLOCKED_EXCHANGE(&flag.status,function_complete_flag_value);
if(!event_handle &&
(::boost::detail::interlocked_read_acquire(&flag.count)>1))
{
event_handle=::boost::detail::allocate_event_handle(flag.event_handle);
}
if(event_handle)
{
::boost::detail::win32::SetEvent(event_handle);
}
throw_count=::boost::detail::interlocked_read_acquire(&flag.throw_count);
break;
}
catch(...)
{
if(counted)
{
BOOST_INTERLOCKED_INCREMENT(&flag.throw_count);
}
BOOST_INTERLOCKED_EXCHANGE(&flag.status,0);
if(!event_handle)
{
event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
}
if(event_handle)
{
::boost::detail::win32::SetEvent(event_handle);
}
throw;
}
}
if(!counted)
{
BOOST_INTERLOCKED_INCREMENT(&flag.count);
counted=true;
status=::boost::detail::interlocked_read_acquire(&flag.status);
if(status==function_complete_flag_value)
{
break;
}
event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
if(!event_handle)
{
event_handle=::boost::detail::allocate_event_handle(flag.event_handle);
continue;
}
}
BOOST_VERIFY(!::boost::detail::win32::WaitForSingleObject(
event_handle,::boost::detail::win32::infinite));
}
if(counted || throw_count)
{
if(!BOOST_INTERLOCKED_EXCHANGE_ADD(&flag.count,(counted?-1:0)-throw_count))
{
if(!event_handle)
{
event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
}
if(event_handle)
{
BOOST_INTERLOCKED_EXCHANGE_POINTER(&flag.event_handle,0);
::boost::detail::win32::CloseHandle(event_handle);
}
}
}
}
}
#include <boost/config/abi_suffix.hpp>
#endif
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Swift