ceph/src/boost/boost/asio/detail/null_global.hpp

   1 //
   2 // detail/null_global.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #ifndef BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
  12 #define BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/config.hpp>
  19
  20 #include <boost/asio/detail/push_options.hpp>
  21
  22 namespace boost {
  23 namespace asio {
  24 namespace detail {
  25
  26 template <typename T>
  27 struct null_global_impl
  28 {
  29   null_global_impl()
  30     : ptr_(0)
  31   {
  32   }
  33
  34   // Destructor automatically cleans up the global.
  35   ~null_global_impl()
  36   {
  37     delete ptr_;
  38   }
  39
  40   static null_global_impl instance_;
  41   T* ptr_;
  42 };
  43
  44 template <typename T>
  45 null_global_impl<T> null_global_impl<T>::instance_;
  46
  47 template <typename T>
  48 T& null_global()
  49 {
  50   if (null_global_impl<T>::instance_.ptr_ == 0)
  51     null_global_impl<T>::instance_.ptr_ = new T;
  52   return *null_global_impl<T>::instance_.ptr_;
  53 }
  54
  55 } // namespace detail
  56 } // namespace asio
  57 } // namespace boost
  58
  59 #include <boost/asio/detail/pop_options.hpp>
  60
  61 #endif // BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP