| 1 | // last_value function object (documented as part of Boost.Signals) |
|---|---|
| 2 | |
| 3 | // Copyright Frank Mori Hess 2007. |
| 4 | // Copyright Douglas Gregor 2001-2003. Use, modification and |
| 5 | // distribution is subject to the Boost Software License, Version |
| 6 | // 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| 7 | // http://www.boost.org/LICENSE_1_0.txt) |
| 8 | |
| 9 | // For more information, see http://www.boost.org |
| 10 | |
| 11 | #ifndef BOOST_SIGNALS2_LAST_VALUE_HPP |
| 12 | #define BOOST_SIGNALS2_LAST_VALUE_HPP |
| 13 | |
| 14 | #include <boost/core/no_exceptions_support.hpp> |
| 15 | #include <boost/optional.hpp> |
| 16 | #include <boost/signals2/expired_slot.hpp> |
| 17 | #include <boost/throw_exception.hpp> |
| 18 | #include <stdexcept> |
| 19 | |
| 20 | namespace boost { |
| 21 | namespace signals2 { |
| 22 | |
| 23 | // no_slots_error is thrown when we are unable to generate a return value |
| 24 | // due to no slots being connected to the signal. |
| 25 | class no_slots_error: public std::exception |
| 26 | { |
| 27 | public: |
| 28 | virtual const char* what() const throw() {return "boost::signals2::no_slots_error";} |
| 29 | }; |
| 30 | |
| 31 | template<typename T> |
| 32 | class last_value { |
| 33 | public: |
| 34 | typedef T result_type; |
| 35 | |
| 36 | template<typename InputIterator> |
| 37 | T operator()(InputIterator first, InputIterator last) const |
| 38 | { |
| 39 | if(first == last) |
| 40 | { |
| 41 | boost::throw_exception(e: no_slots_error()); |
| 42 | } |
| 43 | optional<T> value; |
| 44 | while (first != last) |
| 45 | { |
| 46 | BOOST_TRY |
| 47 | { |
| 48 | value = *first; |
| 49 | } |
| 50 | BOOST_CATCH(const expired_slot &) {} |
| 51 | BOOST_CATCH_END |
| 52 | ++first; |
| 53 | } |
| 54 | if(value) return value.get(); |
| 55 | boost::throw_exception(e: no_slots_error()); |
| 56 | } |
| 57 | }; |
| 58 | |
| 59 | template<> |
| 60 | class last_value<void> { |
| 61 | public: |
| 62 | typedef void result_type; |
| 63 | template<typename InputIterator> |
| 64 | result_type operator()(InputIterator first, InputIterator last) const |
| 65 | { |
| 66 | while (first != last) |
| 67 | { |
| 68 | BOOST_TRY |
| 69 | { |
| 70 | *first; |
| 71 | } |
| 72 | BOOST_CATCH(const expired_slot &) {} |
| 73 | BOOST_CATCH_END |
| 74 | ++first; |
| 75 | } |
| 76 | return; |
| 77 | } |
| 78 | }; |
| 79 | } // namespace signals2 |
| 80 | } // namespace boost |
| 81 | #endif // BOOST_SIGNALS2_LAST_VALUE_HPP |
| 82 |