sl@0: #ifndef BOOST_STATE_SAVER_HPP
sl@0: #define BOOST_STATE_SAVER_HPP
sl@0: 
sl@0: // MS compatible compilers support #pragma once
sl@0: #if defined(_MSC_VER) && (_MSC_VER >= 1020)
sl@0: # pragma once
sl@0: #endif
sl@0: 
sl@0: /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
sl@0: // state_saver.hpp:
sl@0: 
sl@0: // (C) Copyright 2003-4 Pavel Vozenilek and Robert Ramey - http://www.rrsd.com.
sl@0: // Use, modification and distribution is subject to the Boost Software
sl@0: // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: 
sl@0: //  See http://www.boost.org for updates, documentation, and revision history.
sl@0: 
sl@0: // Inspired by Daryle Walker's iostate_saver concept.  This saves the original
sl@0: // value of a variable when a state_saver is constructed and restores
sl@0: // upon destruction.  Useful for being sure that state is restored to
sl@0: // variables upon exit from scope.
sl@0: 
sl@0: 
sl@0: #include <boost/config.hpp>
sl@0: #ifndef BOOST_NO_EXCEPTIONS
sl@0:     #include <exception>
sl@0: #endif
sl@0: 
sl@0: #include <boost/call_traits.hpp>
sl@0: #include <boost/noncopyable.hpp>
sl@0: #include <boost/type_traits/has_nothrow_copy.hpp>
sl@0: #include <boost/detail/no_exceptions_support.hpp>
sl@0: 
sl@0: #include <boost/mpl/eval_if.hpp>
sl@0: #include <boost/mpl/identity.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: template<class T>
sl@0: // T requirements:
sl@0: //  - POD or object semantic (cannot be reference, function, ...)
sl@0: //  - copy constructor
sl@0: //  - operator = (no-throw one preferred)
sl@0: class state_saver : private boost::noncopyable
sl@0: {
sl@0: private:
sl@0:     const T previous_value;
sl@0:     T & previous_ref;
sl@0: 
sl@0:     struct restore {
sl@0:         static void invoke(T & previous_ref, const T & previous_value){
sl@0:             previous_ref = previous_value; // won't throw
sl@0:         }
sl@0:     };
sl@0: 
sl@0:     struct restore_with_exception {
sl@0:         static void invoke(T & previous_ref, const T & previous_value){
sl@0:             BOOST_TRY{
sl@0:                 previous_ref = previous_value;
sl@0:             } 
sl@0:             BOOST_CATCH(::std::exception &) { 
sl@0:                 // we must ignore it - we are in destructor
sl@0:             }
sl@0:             BOOST_CATCH_END
sl@0:         }
sl@0:     };
sl@0: 
sl@0: public:
sl@0:     state_saver(
sl@0:         T & object
sl@0:     ) : 
sl@0:         previous_value(object),
sl@0:         previous_ref(object) 
sl@0:     {}
sl@0:     
sl@0:     ~state_saver() {
sl@0:         #ifndef BOOST_NO_EXCEPTIONS
sl@0:             typedef BOOST_DEDUCED_TYPENAME mpl::eval_if<
sl@0:                 has_nothrow_copy<T>,
sl@0:                 mpl::identity<restore>,
sl@0:                 mpl::identity<restore_with_exception>
sl@0:             >::type typex;
sl@0:             typex::invoke(previous_ref, previous_value);
sl@0:         #else
sl@0:             previous_ref = previous_value;
sl@0:         #endif
sl@0:     }
sl@0: 
sl@0: }; // state_saver<>
sl@0: 
sl@0: } // boost
sl@0: 
sl@0: #endif //BOOST_STATE_SAVER_HPP