boost/iostreams/traits.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2003-2007 Jonathan Turkanis
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   5
   6 // See http://www.boost.org/libs/iostreams for documentation.
   7
   8 //
   9 // Contains metafunctions char_type_of, category_of and mode_of used for
  10 // deducing the i/o category and i/o mode of a model of Filter or Device.
  11 //
  12 // Also contains several utility metafunctions, functions and macros.
  13 //
  14
  15 #ifndef BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED
  16 #define BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED
  17
  18 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  19 # pragma once
  20 #endif
  21
  22 #include <iosfwd>            // stream types, char_traits.
  23 #include <boost/config.hpp>  // partial spec, deduced typename.
  24 #include <boost/detail/workaround.hpp>
  25 #include <boost/iostreams/categories.hpp>
  26 #include <boost/iostreams/detail/bool_trait_def.hpp>
  27 #include <boost/iostreams/detail/config/wide_streams.hpp>
  28 #include <boost/iostreams/detail/is_iterator_range.hpp>
  29 #include <boost/iostreams/detail/select.hpp>
  30 #include <boost/iostreams/detail/select_by_size.hpp>
  31 #include <boost/iostreams/detail/wrap_unwrap.hpp>
  32 #include <boost/iostreams/traits_fwd.hpp>
  33 #include <boost/mpl/bool.hpp>
  34 #include <boost/mpl/eval_if.hpp>
  35 #include <boost/mpl/identity.hpp>
  36 #include <boost/mpl/int.hpp>
  37 #include <boost/mpl/or.hpp>
  38 #if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
  39 # include <boost/range/iterator_range.hpp>
  40 # include <boost/range/value_type.hpp>
  41 #endif // #if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
  42 #include <boost/ref.hpp>
  43 #include <boost/type_traits/is_convertible.hpp>
  44
  45 // Must come last.
  46 #include <boost/iostreams/detail/config/disable_warnings.hpp>
  47
  48 namespace boost { namespace iostreams {
  49
  50 //----------Definitions of predicates for streams and stream buffers----------//
  51
  52 #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //--------------------------------//
  53
  54 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istream, std::basic_istream, 2)
  55 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostream, std::basic_ostream, 2)
  56 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_iostream, std::basic_iostream, 2)
  57 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_streambuf, std::basic_streambuf, 2)
  58 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ifstream, std::basic_ifstream, 2)
  59 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ofstream, std::basic_ofstream, 2)
  60 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_fstream, std::basic_fstream, 2)
  61 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_filebuf, std::basic_filebuf, 2)
  62 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istringstream, std::basic_istringstream, 3)
  63 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostringstream, std::basic_ostringstream, 3)
  64 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_stringstream, std::basic_stringstream, 3)
  65 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_stringbuf, std::basic_stringbuf, 3)
  66
  67 #else // #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //-----------------------//
  68
  69 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_istream, std::istream, 0)
  70 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_ostream, std::ostream, 0)
  71 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_iostream, std::iostream, 0)
  72 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_streambuf, std::streambuf, 0)
  73
  74 #endif // #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //----------------------//
  75
  76 template<typename T>
  77 struct is_std_io
  78     : mpl::or_< is_istream<T>, is_ostream<T>, is_streambuf<T> >
  79     { };
  80
  81 template<typename T>
  82 struct is_std_file_device
  83     : mpl::or_<
  84           is_ifstream<T>,
  85           is_ofstream<T>,
  86           is_fstream<T>,
  87           is_filebuf<T>
  88       >
  89     { };
  90
  91 template<typename T>
  92 struct is_std_string_device
  93     : mpl::or_<
  94           is_istringstream<T>,
  95           is_ostringstream<T>,
  96           is_stringstream<T>,
  97           is_stringbuf<T>
  98       >
  99     { };
 100
 101 template<typename Device, typename Tr, typename Alloc>
 102 struct stream;
 103
 104 template<typename T, typename Tr, typename Alloc, typename Mode>
 105 class stream_buffer;
 106
 107 template< typename Mode, typename Ch, typename Tr,
 108           typename Alloc, typename Access >
 109 class filtering_stream;
 110
 111 template< typename Mode, typename Ch, typename Tr,
 112           typename Alloc, typename Access >
 113 class wfiltering_stream;
 114
 115 template< typename Mode, typename Ch, typename Tr,
 116           typename Alloc, typename Access >
 117 class filtering_streambuf;
 118
 119 template< typename Mode, typename Ch, typename Tr,
 120           typename Alloc, typename Access >
 121 class filtering_wstreambuf;
 122
 123 namespace detail {
 124
 125 template<typename T, typename Tr>
 126 class linked_streambuf;
 127
 128 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_boost_stream,
 129                                 boost::iostreams::stream,
 130                                 3 )
 131 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_boost_stream_buffer,
 132                                 boost::iostreams::stream_buffer,
 133                                 4 )
 134 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_stream_impl,
 135                                 boost::iostreams::filtering_stream,
 136                                 5 )
 137 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_wstream_impl,
 138                                 boost::iostreams::wfiltering_stream,
 139                                 5 )
 140 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_streambuf_impl,
 141                                 boost::iostreams::filtering_streambuf,
 142                                 5 )
 143 BOOST_IOSTREAMS_BOOL_TRAIT_DEF( is_filtering_wstreambuf_impl,
 144                                 boost::iostreams::filtering_wstreambuf,
 145                                 5 )
 146 BOOST_IOSTREAMS_BOOL_TRAIT_DEF(is_linked, linked_streambuf, 2)
 147
 148 template<typename T>
 149 struct is_filtering_stream
 150     : mpl::or_<
 151           is_filtering_stream_impl<T>,
 152           is_filtering_wstream_impl<T>
 153       >
 154     { };
 155
 156 template<typename T>
 157 struct is_filtering_streambuf
 158     : mpl::or_<
 159           is_filtering_streambuf_impl<T>,
 160           is_filtering_wstreambuf_impl<T>
 161       >
 162     { };
 163
 164 template<typename T>
 165 struct is_boost
 166     : mpl::or_<
 167           is_boost_stream<T>,
 168           is_boost_stream_buffer<T>,
 169           is_filtering_stream<T>,
 170           is_filtering_streambuf<T>
 171       >
 172     { };
 173
 174 } // End namespace detail.
 175
 176 //------------------Definitions of char_type_of-------------------------------//
 177
 178 namespace detail {
 179
 180 template<typename T>
 181 struct member_char_type { typedef typename T::char_type type; };
 182
 183 } // End namespace detail.
 184
 185 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //---------------------------//
 186 # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //-------------------------------//
 187
 188 template<typename T>
 189 struct char_type_of
 190     : detail::member_char_type<
 191           typename detail::unwrapped_type<T>::type
 192       >
 193     { };
 194
 195 # else // # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //---------------------//
 196
 197 template<typename T>
 198 struct char_type_of {
 199     typedef typename detail::unwrapped_type<T>::type U;
 200     typedef typename
 201             mpl::eval_if<
 202                 is_std_io<U>,
 203                 mpl::identity<char>,
 204                 detail::member_char_type<U>
 205             >::type type;
 206 };
 207
 208 # endif // # ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES //--------------------//
 209
 210 template<typename Iter>
 211 struct char_type_of< iterator_range<Iter> > {
 212     typedef typename iterator_value<Iter>::type type;
 213 };
 214
 215 #else // #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //------------------//
 216
 217 template<typename T>
 218 struct char_type_of {
 219     template<typename U>
 220     struct get_value_type {
 221         #if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
 222             typedef typename range_value<U>::type type;
 223         #endif // #if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
 224     };
 225     typedef typename
 226             mpl::eval_if<
 227                 is_iterator_range<T>,
 228                 get_value_type<T>,
 229                 detail::member_char_type<
 230                     BOOST_DEDUCED_TYPENAME detail::unwrapped_type<T>::type
 231                 >
 232             >::type type;
 233 };
 234
 235 #endif // #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //-----------------//
 236
 237 //------------------Definitions of category_of--------------------------------//
 238
 239 namespace detail {
 240
 241 template<typename T>
 242 struct member_category { typedef typename T::category type; };
 243
 244 } // End namespace detail.
 245
 246 template<typename T>
 247 struct category_of {
 248     template<typename U>
 249     struct member_category {
 250         typedef typename U::category type;
 251     };
 252     typedef typename detail::unwrapped_type<T>::type U;
 253     typedef typename
 254             mpl::eval_if<
 255                 mpl::and_<
 256                     is_std_io<U>,
 257                     mpl::not_< detail::is_boost<U> >
 258                 >,
 259                 iostreams::select<  // Disambiguation for Tru64
 260                     is_filebuf<U>,        filebuf_tag,
 261                     is_ifstream<U>,       ifstream_tag,
 262                     is_ofstream<U>,       ofstream_tag,
 263                     is_fstream<U>,        fstream_tag,
 264                     is_stringbuf<U>,      stringbuf_tag,
 265                     is_istringstream<U>,  istringstream_tag,
 266                     is_ostringstream<U>,  ostringstream_tag,
 267                     is_stringstream<U>,   stringstream_tag,
 268                     is_streambuf<U>,      generic_streambuf_tag,
 269                     is_iostream<U>,       generic_iostream_tag,
 270                     is_istream<U>,        generic_istream_tag,
 271                     is_ostream<U>,        generic_ostream_tag
 272                 >,
 273                 detail::member_category<U>
 274             >::type type;
 275 };
 276
 277 // Partial specialization for reference wrappers
 278 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //---------------------------//
 279
 280 template<typename T>
 281 struct category_of< reference_wrapper<T> >
 282     : category_of<T>
 283     { };
 284
 285 #endif // #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //-----------------//
 286
 287 //------------------Definition of get_category--------------------------------//
 288
 289 //
 290 // Returns an object of type category_of<T>::type.
 291 //
 292 template<typename T>
 293 inline typename category_of<T>::type get_category(const T&)
 294 { typedef typename category_of<T>::type category; return category(); }
 295
 296 //------------------Definition of int_type_of---------------------------------//
 297
 298 template<typename T>
 299 struct int_type_of {
 300 #ifndef BOOST_IOSTREAMS_NO_STREAM_TEMPLATES
 301     typedef std::char_traits<
 302                 BOOST_DEDUCED_TYPENAME char_type_of<T>::type
 303             > traits_type;
 304     typedef typename traits_type::int_type type;
 305 #else
 306     typedef int                            type;
 307 #endif
 308 };
 309
 310 //------------------Definition of mode_of-------------------------------------//
 311
 312 namespace detail {
 313
 314 template<int N> struct io_mode_impl;
 315
 316 #define BOOST_IOSTREAMS_MODE_HELPER(tag_, id_) \
 317     case_<id_> io_mode_impl_helper(tag_); \
 318     template<> struct io_mode_impl<id_> { typedef tag_ type; }; \
 319     /**/
 320 BOOST_IOSTREAMS_MODE_HELPER(input, 1)
 321 BOOST_IOSTREAMS_MODE_HELPER(output, 2)
 322 BOOST_IOSTREAMS_MODE_HELPER(bidirectional, 3)
 323 BOOST_IOSTREAMS_MODE_HELPER(input_seekable, 4)
 324 BOOST_IOSTREAMS_MODE_HELPER(output_seekable, 5)
 325 BOOST_IOSTREAMS_MODE_HELPER(seekable, 6)
 326 BOOST_IOSTREAMS_MODE_HELPER(dual_seekable, 7)
 327 BOOST_IOSTREAMS_MODE_HELPER(bidirectional_seekable, 8)
 328 BOOST_IOSTREAMS_MODE_HELPER(dual_use, 9)
 329 #undef BOOST_IOSTREAMS_MODE_HELPER
 330
 331 template<typename T>
 332 struct io_mode_id {
 333     typedef typename category_of<T>::type category;
 334     BOOST_SELECT_BY_SIZE(int, value, detail::io_mode_impl_helper(category()));
 335 };
 336
 337 } // End namespace detail.
 338
 339 template<typename T> // Borland 5.6.4 requires this circumlocution.
 340 struct mode_of : detail::io_mode_impl< detail::io_mode_id<T>::value > { };
 341
 342 // Partial specialization for reference wrappers
 343 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //---------------------------//
 344
 345 template<typename T>
 346 struct mode_of< reference_wrapper<T> >
 347     : mode_of<T>
 348     { };
 349
 350 #endif // #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION //-----------------//
 351
 352 //------------------Definition of is_device, is_filter and is_direct----------//
 353
 354 namespace detail {
 355
 356 template<typename T, typename Tag>
 357 struct has_trait_impl {
 358     typedef typename category_of<T>::type category;
 359     BOOST_STATIC_CONSTANT(bool, value = (is_convertible<category, Tag>::value));
 360 };
 361
 362 template<typename T, typename Tag>
 363 struct has_trait
 364     : mpl::bool_<has_trait_impl<T, Tag>::value>
 365     { };
 366
 367 } // End namespace detail.
 368
 369 template<typename T>
 370 struct is_device : detail::has_trait<T, device_tag> { };
 371
 372 template<typename T>
 373 struct is_filter : detail::has_trait<T, filter_tag> { };
 374
 375 template<typename T>
 376 struct is_direct : detail::has_trait<T, direct_tag> { };
 377
 378 //------------------Definition of BOOST_IOSTREAMS_STREAMBUF_TYPEDEFS----------//
 379
 380 #define BOOST_IOSTREAMS_STREAMBUF_TYPEDEFS(Tr) \
 381     typedef Tr                              traits_type; \
 382     typedef typename traits_type::int_type  int_type; \
 383     typedef typename traits_type::off_type  off_type; \
 384     typedef typename traits_type::pos_type  pos_type; \
 385     /**/
 386
 387 } } // End namespaces iostreams, boost.
 388
 389 #include <boost/iostreams/detail/config/enable_warnings.hpp>
 390
 391 #endif // #ifndef BOOST_IOSTREAMS_IO_TRAITS_HPP_INCLUDED