#ifndef BOOST_STATE_SAVER_HPP

 #define BOOST_STATE_SAVER_HPP

 // MS compatible compilers support #pragma once

 #if defined(_MSC_VER) && (_MSC_VER >= 1020)

 # pragma once

 #endif

 /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8

 // state_saver.hpp:

 // (C) Copyright 2003-4 Pavel Vozenilek and Robert Ramey - http://www.rrsd.com.

 // Use, modification and distribution is subject to 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)

 //  See http://www.boost.org for updates, documentation, and revision history.

 // Inspired by Daryle Walker's iostate_saver concept.  This saves the original

 // value of a variable when a state_saver is constructed and restores

 // upon destruction.  Useful for being sure that state is restored to

 // variables upon exit from scope.

 #include <boost/config.hpp>

 #ifndef BOOST_NO_EXCEPTIONS

     #include <exception>

 #endif

 #include <boost/call_traits.hpp>

 #include <boost/noncopyable.hpp>

 #include <boost/type_traits/has_nothrow_copy.hpp>

 #include <boost/detail/no_exceptions_support.hpp>

 #include <boost/mpl/eval_if.hpp>

 #include <boost/mpl/identity.hpp>

 namespace boost {

 template<class T>

 // T requirements:

 //  - POD or object semantic (cannot be reference, function, ...)

 //  - copy constructor

 //  - operator = (no-throw one preferred)

 class state_saver : private boost::noncopyable

 {

 private:

     const T previous_value;

     T & previous_ref;

     struct restore {

         static void invoke(T & previous_ref, const T & previous_value){

             previous_ref = previous_value; // won't throw

         }

     };

     struct restore_with_exception {

         static void invoke(T & previous_ref, const T & previous_value){

             BOOST_TRY{

                 previous_ref = previous_value;

             } 

             BOOST_CATCH(::std::exception &) { 

                 // we must ignore it - we are in destructor

             }

             BOOST_CATCH_END

         }

     };

 public:

     state_saver(

         T & object

     ) : 

         previous_value(object),

         previous_ref(object) 

     {}

     ~state_saver() {

         #ifndef BOOST_NO_EXCEPTIONS

             typedef BOOST_DEDUCED_TYPENAME mpl::eval_if<

                 has_nothrow_copy<T>,

                 mpl::identity<restore>,

                 mpl::identity<restore_with_exception>

             >::type typex;

             typex::invoke(previous_ref, previous_value);

         #else

             previous_ref = previous_value;

         #endif

     }

 }; // state_saver<>

 } // boost

 #endif //BOOST_STATE_SAVER_HPP