| // |
| // detail/null_global.hpp |
| // ~~~~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2016 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 |