Chris@16: #ifndef BOOST_SERIALIZATION_STATE_SAVER_HPP
Chris@16: #define BOOST_SERIALIZATION_STATE_SAVER_HPP
Chris@16: 
Chris@16: // MS compatible compilers support #pragma once
Chris@101: #if defined(_MSC_VER)
Chris@16: # pragma once
Chris@16: #endif
Chris@16: 
Chris@16: /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
Chris@16: // state_saver.hpp:
Chris@16: 
Chris@16: // (C) Copyright 2003-4 Pavel Vozenilek and Robert Ramey - http://www.rrsd.com.
Chris@16: // Use, modification and distribution is subject to the Boost Software
Chris@16: // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: //  See http://www.boost.org/libs/serialization for updates, documentation, and revision history.
Chris@16: 
Chris@16: // Inspired by Daryle Walker's iostate_saver concept.  This saves the original
Chris@16: // value of a variable when a state_saver is constructed and restores
Chris@16: // upon destruction.  Useful for being sure that state is restored to
Chris@16: // variables upon exit from scope.
Chris@16: 
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: #ifndef BOOST_NO_EXCEPTIONS
Chris@16:     #include <exception>
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/call_traits.hpp>
Chris@16: #include <boost/noncopyable.hpp>
Chris@16: #include <boost/type_traits/has_nothrow_copy.hpp>
Chris@101: #include <boost/core/no_exceptions_support.hpp>
Chris@16: 
Chris@16: #include <boost/mpl/eval_if.hpp>
Chris@16: #include <boost/mpl/identity.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace serialization {
Chris@16: 
Chris@16: template<class T>
Chris@16: // T requirements:
Chris@16: //  - POD or object semantic (cannot be reference, function, ...)
Chris@16: //  - copy constructor
Chris@16: //  - operator = (no-throw one preferred)
Chris@16: class state_saver : private boost::noncopyable
Chris@16: {
Chris@16: private:
Chris@16:     const T previous_value;
Chris@16:     T & previous_ref;
Chris@16: 
Chris@16:     struct restore {
Chris@16:         static void invoke(T & previous_ref, const T & previous_value){
Chris@16:             previous_ref = previous_value; // won't throw
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     struct restore_with_exception {
Chris@16:         static void invoke(T & previous_ref, const T & previous_value){
Chris@16:             BOOST_TRY{
Chris@16:                 previous_ref = previous_value;
Chris@16:             } 
Chris@16:             BOOST_CATCH(::std::exception &) { 
Chris@16:                 // we must ignore it - we are in destructor
Chris@16:             }
Chris@16:             BOOST_CATCH_END
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16: public:
Chris@16:     state_saver(
Chris@16:         T & object
Chris@16:     ) : 
Chris@16:         previous_value(object),
Chris@16:         previous_ref(object) 
Chris@16:     {}
Chris@16:     
Chris@16:     ~state_saver() {
Chris@16:         #ifndef BOOST_NO_EXCEPTIONS
Chris@101:             typedef typename mpl::eval_if<
Chris@16:                 has_nothrow_copy< T >,
Chris@16:                 mpl::identity<restore>,
Chris@16:                 mpl::identity<restore_with_exception>
Chris@16:             >::type typex;
Chris@16:             typex::invoke(previous_ref, previous_value);
Chris@16:         #else
Chris@16:             previous_ref = previous_value;
Chris@16:         #endif
Chris@16:     }
Chris@16: 
Chris@16: }; // state_saver<>
Chris@16: 
Chris@16: } // serialization
Chris@16: } // boost
Chris@16: 
Chris@16: #endif //BOOST_SERIALIZATION_STATE_SAVER_HPP