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   once_block.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   23.06.2010
Chris@16:  *
Chris@16:  * \brief  The header defines classes and macros for once-blocks.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_UTILITY_ONCE_BLOCK_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_UTILITY_ONCE_BLOCK_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/utility/unique_identifier_name.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: #ifndef BOOST_LOG_NO_THREADS
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A flag to detect if a code block has already been executed.
Chris@16:  *
Chris@16:  * This structure should be used in conjunction with the \c BOOST_LOG_ONCE_BLOCK_FLAG
Chris@16:  * macro. Usage example:
Chris@16:  *
Chris@16:  * <code>
Chris@16:  * once_block_flag flag = BOOST_LOG_ONCE_BLOCK_INIT;
Chris@16:  *
Chris@16:  * void foo()
Chris@16:  * {
Chris@16:  *     BOOST_LOG_ONCE_BLOCK_FLAG(flag)
Chris@16:  *     {
Chris@16:  *         puts("Hello, world once!");
Chris@16:  *     }
Chris@16:  * }
Chris@16:  * </code>
Chris@16:  */
Chris@16: struct once_block_flag
Chris@16: {
Chris@16: #ifndef BOOST_LOG_DOXYGEN_PASS
Chris@16:     // Do not use, implementation detail
Chris@16:     enum
Chris@16:     {
Chris@16:         uninitialized = 0, // this must be zero, so that zero-initialized once_block_flag is equivalent to the one initialized with uninitialized
Chris@16:         being_initialized,
Chris@16:         initialized
Chris@16:     };
Chris@16:     unsigned char status;
Chris@16: #endif // BOOST_LOG_DOXYGEN_PASS
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * \def BOOST_LOG_ONCE_BLOCK_INIT
Chris@16:  *
Chris@16:  * The static initializer for \c once_block_flag.
Chris@16:  */
Chris@16: #define BOOST_LOG_ONCE_BLOCK_INIT { boost::log::once_block_flag::uninitialized }
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: class once_block_sentry
Chris@16: {
Chris@16: private:
Chris@16:     once_block_flag& m_flag;
Chris@16: 
Chris@16: public:
Chris@16:     explicit once_block_sentry(once_block_flag& f) BOOST_NOEXCEPT : m_flag(f)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     ~once_block_sentry() BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         if (m_flag.status != once_block_flag::initialized)
Chris@16:             rollback();
Chris@16:     }
Chris@16: 
Chris@16:     bool executed() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return (m_flag.status == once_block_flag::initialized || enter_once_block());
Chris@16:     }
Chris@16: 
Chris@16:     BOOST_LOG_API void commit() BOOST_NOEXCEPT;
Chris@16: 
Chris@16: private:
Chris@16:     BOOST_LOG_API bool enter_once_block() const BOOST_NOEXCEPT;
Chris@16:     BOOST_LOG_API void rollback() BOOST_NOEXCEPT;
Chris@16: 
Chris@16:     //  Non-copyable, non-assignable
Chris@16:     BOOST_DELETED_FUNCTION(once_block_sentry(once_block_sentry const&))
Chris@16:     BOOST_DELETED_FUNCTION(once_block_sentry& operator= (once_block_sentry const&))
Chris@16: };
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: #else // BOOST_LOG_NO_THREADS
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: struct once_block_flag
Chris@16: {
Chris@16:     bool status;
Chris@16: };
Chris@16: 
Chris@16: #define BOOST_LOG_ONCE_BLOCK_INIT { false }
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: class once_block_sentry
Chris@16: {
Chris@16: private:
Chris@16:     once_block_flag& m_flag;
Chris@16: 
Chris@16: public:
Chris@16:     explicit once_block_sentry(once_block_flag& f) BOOST_NOEXCEPT : m_flag(f)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     bool executed() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return m_flag.status;
Chris@16:     }
Chris@16: 
Chris@16:     void commit() BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         m_flag.status = true;
Chris@16:     }
Chris@16: 
Chris@16:     //  Non-copyable, non-assignable
Chris@16:     BOOST_DELETED_FUNCTION(once_block_sentry(once_block_sentry const&))
Chris@16:     BOOST_DELETED_FUNCTION(once_block_sentry& operator= (once_block_sentry const&))
Chris@16: };
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: #endif // BOOST_LOG_NO_THREADS
Chris@16: 
Chris@16: #ifndef BOOST_LOG_DOXYGEN_PASS
Chris@16: 
Chris@16: #define BOOST_LOG_ONCE_BLOCK_FLAG_INTERNAL(flag_var, sentry_var)\
Chris@16:     for (boost::log::aux::once_block_sentry sentry_var((flag_var));\
Chris@16:         BOOST_UNLIKELY(!sentry_var.executed()); sentry_var.commit())
Chris@16: 
Chris@16: // NOTE: flag_var deliberately doesn't have an initializer so that it is zero-initialized at the static initialization stage
Chris@16: #define BOOST_LOG_ONCE_BLOCK_INTERNAL(flag_var, sentry_var)\
Chris@16:     static boost::log::once_block_flag flag_var;\
Chris@16:     BOOST_LOG_ONCE_BLOCK_FLAG_INTERNAL(flag_var, sentry_var)
Chris@16: 
Chris@16: #endif // BOOST_LOG_DOXYGEN_PASS
Chris@16: 
Chris@16: /*!
Chris@16:  * \def BOOST_LOG_ONCE_BLOCK_FLAG(flag_var)
Chris@16:  *
Chris@16:  * Begins a code block to be executed only once, with protection against thread concurrency.
Chris@16:  * User has to provide the flag variable that controls whether the block has already
Chris@16:  * been executed.
Chris@16:  */
Chris@16: #define BOOST_LOG_ONCE_BLOCK_FLAG(flag_var)\
Chris@16:     BOOST_LOG_ONCE_BLOCK_FLAG_INTERNAL(\
Chris@16:         flag_var,\
Chris@16:         BOOST_LOG_UNIQUE_IDENTIFIER_NAME(_boost_log_once_block_sentry_))
Chris@16: 
Chris@16: /*!
Chris@16:  * \def BOOST_LOG_ONCE_BLOCK()
Chris@16:  *
Chris@16:  * Begins a code block to be executed only once, with protection against thread concurrency.
Chris@16:  */
Chris@16: #define BOOST_LOG_ONCE_BLOCK()\
Chris@16:     BOOST_LOG_ONCE_BLOCK_INTERNAL(\
Chris@16:         BOOST_LOG_UNIQUE_IDENTIFIER_NAME(_boost_log_once_block_flag_),\
Chris@16:         BOOST_LOG_UNIQUE_IDENTIFIER_NAME(_boost_log_once_block_sentry_))
Chris@16: 
Chris@16: #include <boost/log/detail/footer.hpp>
Chris@16: 
Chris@16: #endif // BOOST_LOG_UTILITY_ONCE_BLOCK_HPP_INCLUDED_