1 files changed, 89 insertions, 0 deletions
diff --git a/boost/log/detail/singleton.hpp b/boost/log/detail/singleton.hpp
new file mode 100644
index 0000000000..ac1ac1afe0
--- /dev/null
+++ b/boost/log/detail/singleton.hpp
@@ -0,0 +1,89 @@
+/*
+ *          Copyright Andrey Semashev 2007 - 2014.
+ * 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)
+ */
+/*!
+ * \file   singleton.hpp
+ * \author Andrey Semashev
+ * \date   20.04.2008
+ *
+ * \brief  This header is the Boost.Log library implementation, see the library documentation
+ *         at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html.
+ */
+
+#ifndef BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_
+#define BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_
+
+#include <boost/log/detail/config.hpp>
+#include <boost/log/utility/once_block.hpp>
+#include <boost/log/detail/header.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#pragma once
+#endif
+
+namespace boost {
+
+BOOST_LOG_OPEN_NAMESPACE
+
+namespace aux {
+
+//! A base class for singletons, constructed on-demand
+template< typename DerivedT, typename StorageT = DerivedT >
+class lazy_singleton
+{
+public:
+    BOOST_DEFAULTED_FUNCTION(lazy_singleton(), {})
+
+    //! Returns the singleton instance
+    static StorageT& get()
+    {
+        BOOST_LOG_ONCE_BLOCK()
+        {
+            DerivedT::init_instance();
+        }
+        return get_instance();
+    }
+
+    //! Initializes the singleton instance
+    static void init_instance()
+    {
+        get_instance();
+    }
+
+    BOOST_DELETED_FUNCTION(lazy_singleton(lazy_singleton const&))
+    BOOST_DELETED_FUNCTION(lazy_singleton& operator= (lazy_singleton const&))
+
+protected:
+    //! Returns the singleton instance (not thread-safe)
+    static StorageT& get_instance()
+    {
+        static StorageT instance;
+        return instance;
+    }
+};
+
+//! A base class for singletons, constructed on namespace scope initialization stage
+template< typename DerivedT, typename StorageT = DerivedT >
+class singleton :
+    public lazy_singleton< DerivedT, StorageT >
+{
+public:
+    static StorageT& instance;
+};
+
+template< typename DerivedT, typename StorageT >
+StorageT& singleton< DerivedT, StorageT >::instance =
+    lazy_singleton< DerivedT, StorageT >::get();
+
+} // namespace aux
+
+BOOST_LOG_CLOSE_NAMESPACE // namespace log
+
+} // namespace boost
+
+#include <boost/log/detail/footer.hpp>
+
+#endif // BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_