1 | #ifndef BOOST_SERIALIZATION_STATE_SAVER_HPP |
2 | #define BOOST_SERIALIZATION_STATE_SAVER_HPP |
3 | |
4 | // MS compatible compilers support #pragma once |
5 | #if defined(_MSC_VER) |
6 | # pragma once |
7 | #endif |
8 | |
9 | /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8 |
10 | // state_saver.hpp: |
11 | |
12 | // (C) Copyright 2003-4 Pavel Vozenilek and Robert Ramey - http://www.rrsd.com. |
13 | // Use, modification and distribution is subject to the Boost Software |
14 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
15 | // http://www.boost.org/LICENSE_1_0.txt) |
16 | |
17 | // See http://www.boost.org/libs/serialization for updates, documentation, and revision history. |
18 | |
19 | // Inspired by Daryle Walker's iostate_saver concept. This saves the original |
20 | // value of a variable when a state_saver is constructed and restores |
21 | // upon destruction. Useful for being sure that state is restored to |
22 | // variables upon exit from scope. |
23 | |
24 | |
25 | #include <boost/config.hpp> |
26 | #ifndef BOOST_NO_EXCEPTIONS |
27 | #include <exception> |
28 | #endif |
29 | |
30 | #include <boost/call_traits.hpp> |
31 | #include <boost/noncopyable.hpp> |
32 | #include <boost/type_traits/has_nothrow_copy.hpp> |
33 | #include <boost/core/no_exceptions_support.hpp> |
34 | |
35 | #include <boost/mpl/eval_if.hpp> |
36 | #include <boost/mpl/identity.hpp> |
37 | |
38 | namespace boost { |
39 | namespace serialization { |
40 | |
41 | template<class T> |
42 | // T requirements: |
43 | // - POD or object semantic (cannot be reference, function, ...) |
44 | // - copy constructor |
45 | // - operator = (no-throw one preferred) |
46 | class state_saver : private boost::noncopyable |
47 | { |
48 | private: |
49 | const T previous_value; |
50 | T & previous_ref; |
51 | |
52 | struct restore { |
53 | static void invoke(T & previous_ref, const T & previous_value){ |
54 | previous_ref = previous_value; // won't throw |
55 | } |
56 | }; |
57 | |
58 | struct restore_with_exception { |
59 | static void invoke(T & previous_ref, const T & previous_value){ |
60 | BOOST_TRY{ |
61 | previous_ref = previous_value; |
62 | } |
63 | BOOST_CATCH(::std::exception &) { |
64 | // we must ignore it - we are in destructor |
65 | } |
66 | BOOST_CATCH_END |
67 | } |
68 | }; |
69 | |
70 | public: |
71 | state_saver( |
72 | T & object |
73 | ) : |
74 | previous_value(object), |
75 | previous_ref(object) |
76 | {} |
77 | |
78 | ~state_saver() { |
79 | #ifndef BOOST_NO_EXCEPTIONS |
80 | typedef typename mpl::eval_if< |
81 | has_nothrow_copy< T >, |
82 | mpl::identity<restore>, |
83 | mpl::identity<restore_with_exception> |
84 | >::type typex; |
85 | typex::invoke(previous_ref, previous_value); |
86 | #else |
87 | previous_ref = previous_value; |
88 | #endif |
89 | } |
90 | |
91 | }; // state_saver<> |
92 | |
93 | } // serialization |
94 | } // boost |
95 | |
96 | #endif //BOOST_SERIALIZATION_STATE_SAVER_HPP |
97 | |