[Boost-users] [boost] [iostreams] Pipelined reference_wrappers of filters/device

Subject: [Boost-users] [boost] [iostreams] Pipelined reference_wrappers of filters/device
From: feverzsj (feverzsj_at_[hidden])
Date: 2010-04-21 12:00:14

hi all,
  BOOST_IOSTREAMS_PIPABLE generate something like :
          template<..., typename component>
          pipeline<...> operator|(your_filter const& , component const&);
  It is proper for plan use, e.g. filter1 | filter2 | ... | device.
  But for boost::reference_wrapper, ref(filter1) | ref(filter2)
|...|ref(device), after type conversion, will be : filter1 | ref(filter2)
|...|ref(device), which may confuse the user.
  So, will it be a good idea to make another reloaded
operator|(reference_wrapper<your_filter> const&, component const&)) ?
  I have written a macro to handle this( simply copy and modify
BOOST_IOSTREAMS_PIPABLE):

#define BOOST_IOSTREAMS_EXTENDED_PIPABLE(filter, arity)													\
template< BOOST_PP_ENUM_PARAMS(arity, typename T)														\
                BOOST_PP_COMMA_IF(arity) typename Component>													\
::boost::iostreams::pipeline<																			\
                ::boost::iostreams::detail::pipeline_segment<filter
BOOST_IOSTREAMS_TEMPLATE_ARGS(arity, T)>	\
                ,Component																						\
>																										\
operator|(const filter BOOST_IOSTREAMS_TEMPLATE_ARGS(arity, T)& f, const
Component& c)					\
{																										\
        typedef																								\
                ::boost::iostreams::detail::pipeline_segment<													\
                        filter BOOST_IOSTREAMS_TEMPLATE_ARGS(arity, T)												\
		> segment;																						\
        return ::boost::iostreams::pipeline<segment, Component>												\
        (segment(f), c);																					\
}																										\
template<BOOST_PP_ENUM_PARAMS(arity, typename T)														\
                BOOST_PP_COMMA_IF(arity)typename Component>														\
::boost::iostreams::pipeline<																			\
                ::boost::iostreams::detail::pipeline_segment<													\
                                                        boost::reference_wrapper<filter BOOST_IOSTREAMS_TEMPLATE_ARGS(arity,
T)> >	\
                ,Component																						\
>																										\
operator|(const boost::reference_wrapper<filter
BOOST_IOSTREAMS_TEMPLATE_ARGS(arity, T)>& wf			\
                ,const Component& c)																			\
{																										\
        typedef																								\
                ::boost::iostreams::detail::pipeline_segment<													\
                        boost::reference_wrapper<filter BOOST_IOSTREAMS_TEMPLATE_ARGS(arity, T)>				
\
		> segment;																						\
        return ::boost::iostreams::pipeline<segment, Component>(segment(wf), c);						
\
}																										\
/**/

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