1 files changed, 61 insertions, 0 deletions
diff --git a/boost/asio/detail/null_global.hpp b/boost/asio/detail/null_global.hpp
new file mode 100644
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+++ b/boost/asio/detail/null_global.hpp
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+//
+// detail/null_global.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2017 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