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3rdparty/boost_1_81_0/boost/signals2/last_value.hpp 2.11 KB
0b6a182c   Hu Chunming   添加无鉴权注册和注销
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  // last_value function object (documented as part of Boost.Signals)
  
  // Copyright Frank Mori Hess 2007.
  // Copyright Douglas Gregor 2001-2003. 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)
  
  // For more information, see http://www.boost.org
  
  #ifndef BOOST_SIGNALS2_LAST_VALUE_HPP
  #define BOOST_SIGNALS2_LAST_VALUE_HPP
  
  #include <boost/core/no_exceptions_support.hpp>
  #include <boost/optional.hpp>
  #include <boost/signals2/expired_slot.hpp>
  #include <boost/throw_exception.hpp>
  #include <stdexcept>
  
  namespace boost {
    namespace signals2 {
  
      // no_slots_error is thrown when we are unable to generate a return value
      // due to no slots being connected to the signal.
      class no_slots_error: public std::exception
      {
      public:
        virtual const char* what() const throw() {return "boost::signals2::no_slots_error";}
      };
  
      template<typename T>
      class last_value {
      public:
        typedef T result_type;
  
        template<typename InputIterator>
        T operator()(InputIterator first, InputIterator last) const
        {
          if(first == last)
          {
            boost::throw_exception(no_slots_error());
          }
          optional<T> value;
          while (first != last)
          {
            BOOST_TRY
            {
              value = *first;
            }
            BOOST_CATCH(const expired_slot &) {}
            BOOST_CATCH_END
            ++first;
          }
          if(value) return value.get();
          boost::throw_exception(no_slots_error());
        }
      };
  
      template<>
      class last_value<void> {
      public:
        typedef void result_type;
        template<typename InputIterator>
          result_type operator()(InputIterator first, InputIterator last) const
        {
          while (first != last)
          {
            BOOST_TRY
            {
              *first;
            }
            BOOST_CATCH(const expired_slot &) {}
            BOOST_CATCH_END
            ++first;
          }
          return;
        }
      };
    } // namespace signals2
  } // namespace boost
  #endif // BOOST_SIGNALS2_LAST_VALUE_HPP