boost/iostreams/traits.hpp

0001 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
0002 // (C) Copyright 2003-2007 Jonathan Turkanis
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
0005
0006 // See http://www.boost.org/libs/iostreams for documentation.
0007
0008 //
0009 // Contains metafunctions char_type_of, category_of and mode_of used for
0010 // deducing the i/o category and i/o mode of a model of Filter or Device.
0011 //
0012 // Also contains several utility metafunctions, functions and macros.
0013 //
0014
0015 #ifndef BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED
0016 #define BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED
0017
0018 #if defined(_MSC_VER)
0019 # pragma once
0020 #endif
0021
0022 #include <iosfwd>            // stream types, char_traits.
0023 #include <boost/config.hpp>  // partial spec, deduced typename.
0024 #include <boost/detail/workaround.hpp>
0025 #include <boost/iostreams/categories.hpp>
0026 #include <boost/iostreams/detail/bool_trait_def.hpp>
0027 #include <boost/iostreams/detail/config/wide_streams.hpp>
0028 #include <boost/iostreams/detail/is_iterator_range.hpp>
0029 #include <boost/iostreams/detail/select.hpp>
0030 #include <boost/iostreams/detail/select_by_size.hpp>
0031 #include <boost/iostreams/detail/wrap_unwrap.hpp>
0032 #include <boost/iostreams/traits_fwd.hpp>
0033 #include <boost/mpl/bool.hpp>
0034 #include <boost/mpl/eval_if.hpp>
0035 #include <boost/mpl/identity.hpp>
0036 #include <boost/mpl/int.hpp>
0037 #include <boost/mpl/or.hpp>
0038 #include <boost/range/iterator_range.hpp>
0039 #include <boost/range/value_type.hpp>
0040 #include <boost/ref.hpp>
0041 #include <boost/type_traits/is_convertible.hpp>
0042
0043 // Must come last.
0044 #include <boost/iostreams/detail/config/disable_warnings.hpp>
0045
0046 namespace boost { namespace iostreams {
0047
0048 //----------Definitions of predicates for streams and stream buffers----------//
0049
0050 #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //--------------------------------//
0051
0052 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istream, std::basic_istream, 2)
0053 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostream, std::basic_ostream, 2)
0054 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_iostream, std::basic_iostream, 2)
0055 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_streambuf, std::basic_streambuf, 2)
0056 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ifstream, std::basic_ifstream, 2)
0057 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ofstream, std::basic_ofstream, 2)
0058 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_fstream, std::basic_fstream, 2)
0059 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_filebuf, std::basic_filebuf, 2)
0060 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istringstream, std::basic_istringstream, 3)
0061 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostringstream, std::basic_ostringstream, 3)
0062 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_stringstream, std::basic_stringstream, 3)
0063 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_stringbuf, std::basic_stringbuf, 3)
0064
0065 #else // #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //-----------------------//
0066
0067 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istream, std::istream, 0)
0068 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostream, std::ostream, 0)
0069 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_iostream, std::iostream, 0)
0070 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_streambuf, std::streambuf, 0)
0071
0072 #endif // #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //----------------------//
0073
0074 template<typename T>
0075 struct is_std_io
0076     : mpl::or_< is_istream<T>, is_ostream<T>, is_streambuf<T> >
0077     { };
0078
0079 template<typename T>
0080 struct is_std_file_device
0081     : mpl::or_<
0082           is_ifstream<T>,
0083           is_ofstream<T>,
0084           is_fstream<T>,
0085           is_filebuf<T>
0086       >
0087     { };
0088
0089 template<typename T>
0090 struct is_std_string_device
0091     : mpl::or_<
0092           is_istringstream<T>,
0093           is_ostringstream<T>,
0094           is_stringstream<T>,
0095           is_stringbuf<T>
0096       >
0097     { };
0098
0099 template<typename Device, typename Tr, typename Alloc>
0100 struct stream;
0101
0102 template<typename T, typename Tr, typename Alloc, typename Mode>
0103 class stream_buffer;
0104
0105 template< typename Mode, typename Ch, typename Tr,
0106           typename Alloc, typename Access >
0107 class filtering_stream;
0108
0109 template< typename Mode, typename Ch, typename Tr,
0110           typename Alloc, typename Access >
0111 class wfiltering_stream;
0112
0113 template< typename Mode, typename Ch, typename Tr,
0114           typename Alloc, typename Access >
0115 class filtering_streambuf;
0116
0117 template< typename Mode, typename Ch, typename Tr,
0118           typename Alloc, typename Access >
0119 class filtering_wstreambuf;
0120
0121 namespace detail {
0122
0123 template<typename T, typename Tr>
0124 class linked_streambuf;
0125
0126 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_boost_stream,
0127                                 boost::iostreams::stream,
0128                                 3 )
0129 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_boost_stream_buffer,
0130                                 boost::iostreams::stream_buffer,
0131                                 4 )
0132 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_stream_impl,
0133                                 boost::iostreams::filtering_stream,
0134                                 5 )
0135 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_wstream_impl,
0136                                 boost::iostreams::wfiltering_stream,
0137                                 5 )
0138 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_streambuf_impl,
0139                                 boost::iostreams::filtering_streambuf,
0140                                 5 )
0141 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_wstreambuf_impl,
0142                                 boost::iostreams::filtering_wstreambuf,
0143                                 5 )
0144 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_linked, linked_streambuf, 2)
0145
0146 template<typename T>
0147 struct is_filtering_stream
0148     : mpl::or_<
0149           is_filtering_stream_impl<T>,
0150           is_filtering_wstream_impl<T>
0151       >
0152     { };
0153
0154 template<typename T>
0155 struct is_filtering_streambuf
0156     : mpl::or_<
0157           is_filtering_streambuf_impl<T>,
0158           is_filtering_wstreambuf_impl<T>
0159       >
0160     { };
0161
0162 template<typename T>
0163 struct is_boost
0164     : mpl::or_<
0165           is_boost_stream<T>,
0166           is_boost_stream_buffer<T>,
0167           is_filtering_stream<T>,
0168           is_filtering_streambuf<T>
0169       >
0170     { };
0171
0172 } // End namespace detail.
0173
0174 //------------------Definitions of char_type_of-------------------------------//
0175
0176 namespace detail {
0177
0178 template<typename T>
0179 struct member_char_type { typedef typename T::char_type type; };
0180
0181 } // End namespace detail.
0182
0183 # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //-------------------------------//
0184
0185 template<typename T>
0186 struct char_type_of
0187     : detail::member_char_type<
0188           typename detail::unwrapped_type<T>::type
0189       >
0190     { };
0191
0192 # else // # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //---------------------//
0193
0194 template<typename T>
0195 struct char_type_of {
0196     typedef typename detail::unwrapped_type<T>::type U;
0197     typedef typename
0198             mpl::eval_if<
0199                 is_std_io<U>,
0200                 mpl::identity<char>,
0201                 detail::member_char_type<U>
0202             >::type type;
0203 };
0204
0205 # endif // # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //--------------------//
0206
0207 template<typename Iter>
0208 struct char_type_of< iterator_range<Iter> > {
0209     typedef typename iterator_value<Iter>::type type;
0210 };
0211
0212
0213 //------------------Definitions of category_of--------------------------------//
0214
0215 namespace detail {
0216
0217 template<typename T>
0218 struct member_category { typedef typename T::category type; };
0219
0220 } // End namespace detail.
0221
0222 template<typename T>
0223 struct category_of {
0224     template<typename U>
0225     struct member_category {
0226         typedef typename U::category type;
0227     };
0228     typedef typename detail::unwrapped_type<T>::type U;
0229     typedef typename
0230             mpl::eval_if<
0231                 mpl::and_<
0232                     is_std_io<U>,
0233                     mpl::not_< detail::is_boost<U> >
0234                 >,
0235                 iostreams::select<  // Disambiguation for Tru64
0236                     is_filebuf<U>,        filebuf_tag,
0237                     is_ifstream<U>,       ifstream_tag,
0238                     is_ofstream<U>,       ofstream_tag,
0239                     is_fstream<U>,        fstream_tag,
0240                     is_stringbuf<U>,      stringbuf_tag,
0241                     is_istringstream<U>,  istringstream_tag,
0242                     is_ostringstream<U>,  ostringstream_tag,
0243                     is_stringstream<U>,   stringstream_tag,
0244                     is_streambuf<U>,      generic_streambuf_tag,
0245                     is_iostream<U>,       generic_iostream_tag,
0246                     is_istream<U>,        generic_istream_tag,
0247                     is_ostream<U>,        generic_ostream_tag
0248                 >,
0249                 detail::member_category<U>
0250             >::type type;
0251 };
0252
0253 // Partial specialization for reference wrappers
0254
0255 template<typename T>
0256 struct category_of< reference_wrapper<T> >
0257     : category_of<T>
0258     { };
0259
0260
0261 //------------------Definition of get_category--------------------------------//
0262
0263 //
0264 // Returns an object of type category_of<T>::type.
0265 //
0266 template<typename T>
0267 inline typename category_of<T>::type get_category(const T&)
0268 { typedef typename category_of<T>::type category; return category(); }
0269
0270 //------------------Definition of int_type_of---------------------------------//
0271
0272 template<typename T>
0273 struct int_type_of {
0274 #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES
0275     typedef std::char_traits<
0276                 BOOST_DEDUCED_TYPENAME char_type_of<T>::type
0277             > traits_type;
0278     typedef typename traits_type::int_type type;
0279 #else
0280     typedef int                            type;
0281 #endif
0282 };
0283
0284 //------------------Definition of mode_of-------------------------------------//
0285
0286 namespace detail {
0287
0288 template<int N> struct io_mode_impl;
0289
0290 #define BOOST_IOSTREAMS_MODE_HELPER(tag_, id_) \
0291     case_<id_> io_mode_impl_helper(tag_); \
0292     template<> struct io_mode_impl<id_> { typedef tag_ type; }; \
0293     /**/
0294 BOOST_IOSTREAMS_MODE_HELPER(input, 1)
0295 BOOST_IOSTREAMS_MODE_HELPER(output, 2)
0296 BOOST_IOSTREAMS_MODE_HELPER(bidirectional, 3)
0297 BOOST_IOSTREAMS_MODE_HELPER(input_seekable, 4)
0298 BOOST_IOSTREAMS_MODE_HELPER(output_seekable, 5)
0299 BOOST_IOSTREAMS_MODE_HELPER(seekable, 6)
0300 BOOST_IOSTREAMS_MODE_HELPER(dual_seekable, 7)
0301 BOOST_IOSTREAMS_MODE_HELPER(bidirectional_seekable, 8)
0302 BOOST_IOSTREAMS_MODE_HELPER(dual_use, 9)
0303 #undef BOOST_IOSTREAMS_MODE_HELPER
0304
0305 template<typename T>
0306 struct io_mode_id {
0307     typedef typename category_of<T>::type category;
0308     BOOST_SELECT_BY_SIZE(int, value, detail::io_mode_impl_helper(category()));
0309 };
0310
0311 } // End namespace detail.
0312
0313 template<typename T> // Borland 5.6.4 requires this circumlocution.
0314 struct mode_of : detail::io_mode_impl< detail::io_mode_id<T>::value > { };
0315
0316 // Partial specialization for reference wrappers
0317
0318 template<typename T>
0319 struct mode_of< reference_wrapper<T> >
0320     : mode_of<T>
0321     { };
0322
0323
0324 //------------------Definition of is_device, is_filter and is_direct----------//
0325
0326 namespace detail {
0327
0328 template<typename T, typename Tag>
0329 struct has_trait_impl {
0330     typedef typename category_of<T>::type category;
0331     BOOST_STATIC_CONSTANT(bool, value = (is_convertible<category, Tag>::value));
0332 };
0333
0334 template<typename T, typename Tag>
0335 struct has_trait
0336     : mpl::bool_<has_trait_impl<T, Tag>::value>
0337     { };
0338
0339 } // End namespace detail.
0340
0341 template<typename T>
0342 struct is_device : detail::has_trait<T, device_tag> { };
0343
0344 template<typename T>
0345 struct is_filter : detail::has_trait<T, filter_tag> { };
0346
0347 template<typename T>
0348 struct is_direct : detail::has_trait<T, direct_tag> { };
0349
0350 //------------------Definition of BOOST_IOSTREAMS_STREAMBUF_TYPEDEFS----------//
0351
0352 #define BOOST_IOSTREAMS_STREAMBUF_TYPEDEFS(Tr) \
0353     typedef Tr                              traits_type; \
0354     typedef typename traits_type::int_type  int_type; \
0355     typedef typename traits_type::off_type  off_type; \
0356     typedef typename traits_type::pos_type  pos_type; \
0357     /**/
0358
0359 } } // End namespaces iostreams, boost.
0360
0361 #include <boost/iostreams/detail/config/enable_warnings.hpp>
0362
0363 #endif // #ifndef BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED