Chris@16: /*
Chris@101:  *          Copyright Andrey Semashev 2007 - 2015.
Chris@16:  * Distributed under the Boost Software License, Version 1.0.
Chris@16:  *    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16:  *          http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  */
Chris@16: /*!
Chris@16:  * \file   singleton.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   20.04.2008
Chris@16:  *
Chris@16:  * \brief  This header is the Boost.Log library implementation, see the library documentation
Chris@16:  *         at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/utility/once_block.hpp>
Chris@16: #include <boost/log/detail/header.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: //! A base class for singletons, constructed on-demand
Chris@16: template< typename DerivedT, typename StorageT = DerivedT >
Chris@16: class lazy_singleton
Chris@16: {
Chris@16: public:
Chris@16:     BOOST_DEFAULTED_FUNCTION(lazy_singleton(), {})
Chris@16: 
Chris@16:     //! Returns the singleton instance
Chris@16:     static StorageT& get()
Chris@16:     {
Chris@16:         BOOST_LOG_ONCE_BLOCK()
Chris@16:         {
Chris@16:             DerivedT::init_instance();
Chris@16:         }
Chris@16:         return get_instance();
Chris@16:     }
Chris@16: 
Chris@16:     //! Initializes the singleton instance
Chris@16:     static void init_instance()
Chris@16:     {
Chris@16:         get_instance();
Chris@16:     }
Chris@16: 
Chris@16:     BOOST_DELETED_FUNCTION(lazy_singleton(lazy_singleton const&))
Chris@16:     BOOST_DELETED_FUNCTION(lazy_singleton& operator= (lazy_singleton const&))
Chris@16: 
Chris@16: protected:
Chris@16:     //! Returns the singleton instance (not thread-safe)
Chris@16:     static StorageT& get_instance()
Chris@16:     {
Chris@16:         static StorageT instance;
Chris@16:         return instance;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: //! A base class for singletons, constructed on namespace scope initialization stage
Chris@16: template< typename DerivedT, typename StorageT = DerivedT >
Chris@16: class singleton :
Chris@16:     public lazy_singleton< DerivedT, StorageT >
Chris@16: {
Chris@16: public:
Chris@16:     static StorageT& instance;
Chris@16: };
Chris@16: 
Chris@16: template< typename DerivedT, typename StorageT >
Chris@16: StorageT& singleton< DerivedT, StorageT >::instance =
Chris@16:     lazy_singleton< DerivedT, StorageT >::get();
Chris@16: 
Chris@16: } // namespace aux
Chris@16: 
Chris@16: BOOST_LOG_CLOSE_NAMESPACE // namespace log
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/log/detail/footer.hpp>
Chris@16: 
Chris@16: #endif // BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_