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

   1 //
   2 // detail/std_global.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2017 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_STD_GLOBAL_HPP
  12 #define BOOST_ASIO_DETAIL_STD_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 #if defined(BOOST_ASIO_HAS_STD_CALL_ONCE)
  21
  22 #include <exception>
  23 #include <mutex>
  24
  25 #include <boost/asio/detail/push_options.hpp>
  26
  27 namespace boost {
  28 namespace asio {
  29 namespace detail {
  30
  31 template <typename T>
  32 struct std_global_impl
  33 {
  34   // Helper function to perform initialisation.
  35   static void do_init()
  36   {
  37     instance_.ptr_ = new T;
  38   }
  39
  40   // Destructor automatically cleans up the global.
  41   ~std_global_impl()
  42   {
  43     delete ptr_;
  44   }
  45
  46   static std::once_flag init_once_;
  47   static std_global_impl instance_;
  48   T* ptr_;
  49 };
  50
  51 template <typename T>
  52 std::once_flag std_global_impl<T>::init_once_;
  53
  54 template <typename T>
  55 std_global_impl<T> std_global_impl<T>::instance_;
  56
  57 template <typename T>
  58 T& std_global()
  59 {
  60   std::call_once(std_global_impl<T>::init_once_, &std_global_impl<T>::do_init);
  61   return *std_global_impl<T>::instance_.ptr_;
  62 }
  63
  64 } // namespace detail
  65 } // namespace asio
  66 } // namespace boost
  67
  68 #include <boost/asio/detail/pop_options.hpp>
  69
  70 #endif // defined(BOOST_ASIO_HAS_STD_CALL_ONCE)
  71
  72 #endif // BOOST_ASIO_DETAIL_STD_GLOBAL_HPP