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