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 Hu Chunming
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/*
* Copyright Andrey Semashev 2007 - 2015.
* 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_
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