60 lines
1.2 KiB
C++
60 lines
1.2 KiB
C++
|
//
|
||
|
|
// detail/null_global.hpp
|
||
|
|
// ~~~~~~~~~~~~~~~~~~~~~~
|
||
|
|
//
|
||
|
|
// Copyright (c) 2003-2023 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 ASIO_DETAIL_NULL_GLOBAL_HPP
|
||
|
|
#define ASIO_DETAIL_NULL_GLOBAL_HPP
|
||
|
|
|
||
|
|
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
|
||
|
|
# pragma once
|
||
|
|
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
|
||
|
|
|
||
|
|
#include "asio/detail/config.hpp"
|
||
|
|
|
||
|
|
#include "asio/detail/push_options.hpp"
|
||
|
|
|
||
|
|
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
|
||
|
|
|
||
|
|
#include "asio/detail/pop_options.hpp"
|
||
|
|
|
||
|
|
#endif // ASIO_DETAIL_NULL_GLOBAL_HPP
|