82 lines
2.2 KiB
C++
82 lines
2.2 KiB
C++
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// last_value function object (documented as part of Boost.Signals)
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// Copyright Frank Mori Hess 2007.
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// Copyright Douglas Gregor 2001-2003. Use, modification and
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// distribution is subject to the Boost Software License, Version
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// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// For more information, see http://www.boost.org
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#ifndef BOOST_SIGNALS2_LAST_VALUE_HPP
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#define BOOST_SIGNALS2_LAST_VALUE_HPP
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#include <boost/core/no_exceptions_support.hpp>
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#include <boost/optional.hpp>
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#include <boost/signals2/expired_slot.hpp>
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#include <boost/throw_exception.hpp>
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#include <stdexcept>
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namespace boost {
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namespace signals2 {
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// no_slots_error is thrown when we are unable to generate a return value
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// due to no slots being connected to the signal.
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class no_slots_error: public std::exception
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{
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public:
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virtual const char* what() const throw() {return "boost::signals2::no_slots_error";}
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};
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template<typename T>
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class last_value {
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public:
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typedef T result_type;
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template<typename InputIterator>
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T operator()(InputIterator first, InputIterator last) const
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{
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if(first == last)
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{
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boost::throw_exception(no_slots_error());
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}
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optional<T> value;
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while (first != last)
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{
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BOOST_TRY
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{
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value = *first;
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}
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BOOST_CATCH(const expired_slot &) {}
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BOOST_CATCH_END
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++first;
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}
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if(value) return value.get();
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throw no_slots_error();
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}
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};
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template<>
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class last_value<void> {
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public:
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typedef void result_type;
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template<typename InputIterator>
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result_type operator()(InputIterator first, InputIterator last) const
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{
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while (first != last)
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{
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BOOST_TRY
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{
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*first;
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}
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BOOST_CATCH(const expired_slot &) {}
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BOOST_CATCH_END
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++first;
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}
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return;
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}
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};
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} // namespace signals2
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} // namespace boost
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#endif // BOOST_SIGNALS2_LAST_VALUE_HPP
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