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//
// detail/null_global.hpp
// ~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// 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)
//
#ifndef BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
#define BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
template <typename T>
struct null_global_impl
{
null_global_impl()
: ptr_(0)
{
}
// Destructor automatically cleans up the global.
~null_global_impl()
{
delete ptr_;
}
static null_global_impl instance_;
T* ptr_;
};
template <typename T>
null_global_impl<T> null_global_impl<T>::instance_;
template <typename T>
T& null_global()
{
if (null_global_impl<T>::instance_.ptr_ == 0)
null_global_impl<T>::instance_.ptr_ = new T;
return *null_global_impl<T>::instance_.ptr_;
}
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
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