boost/boost/iostreams/seek.hpp

   1 // (C) Copyright Jonathan Turkanis 2003.
   2 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   4
   5 // See http://www.boost.org/libs/iostreams for documentation.
   6
   7 #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED
   8 #define BOOST_IOSTREAMS_SEEK_HPP_INCLUDED
   9
  10 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  11 # pragma once
  12 #endif
  13
  14 #include <boost/config.hpp>  // DEDUCED_TYPENAME, MSVC.
  15 #include <boost/integer_traits.hpp>
  16 #include <boost/iostreams/categories.hpp>
  17 #include <boost/iostreams/detail/dispatch.hpp>
  18 #include <boost/iostreams/detail/ios.hpp>       // streamsize, seekdir, openmode.
  19 #include <boost/iostreams/detail/streambuf.hpp>
  20 #include <boost/iostreams/detail/wrap_unwrap.hpp>
  21 #include <boost/iostreams/operations_fwd.hpp>
  22 #include <boost/iostreams/positioning.hpp>
  23 #include <boost/mpl/if.hpp>
  24
  25 // Must come last.
  26 #include <boost/iostreams/detail/config/disable_warnings.hpp>
  27
  28 namespace boost { namespace iostreams {
  29
  30 namespace detail {
  31
  32 template<typename T>
  33 struct seek_device_impl;
  34
  35 template<typename T>
  36 struct seek_filter_impl;
  37
  38 } // End namespace detail.
  39
  40 template<typename T>
  41 inline std::streampos
  42 seek( T& t, stream_offset off, BOOST_IOS::seekdir way,
  43       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
  44 {
  45     using namespace detail;
  46     return seek_device_impl<T>::seek(detail::unwrap(t), off, way, which);
  47 }
  48
  49 template<typename T, typename Device>
  50 inline std::streampos
  51 seek( T& t, Device& dev, stream_offset off, BOOST_IOS::seekdir way,
  52       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
  53 {
  54     using namespace detail;
  55     return seek_filter_impl<T>::seek(detail::unwrap(t), dev, off, way, which);
  56 }
  57
  58 namespace detail {
  59
  60 //------------------Definition of seek_device_impl----------------------------//
  61
  62 template<typename T>
  63 struct seek_device_impl
  64     : mpl::if_<
  65           is_custom<T>,
  66           operations<T>,
  67           seek_device_impl<
  68               BOOST_DEDUCED_TYPENAME
  69               dispatch<
  70                   T, iostream_tag, istream_tag, ostream_tag,
  71                   streambuf_tag, two_head, any_tag
  72               >::type
  73           >
  74       >::type
  75     { };
  76
  77 struct seek_impl_basic_ios {
  78     template<typename T>
  79     static std::streampos seek( T& t, stream_offset off,
  80                                 BOOST_IOS::seekdir way,
  81                                 BOOST_IOS::openmode which )
  82     {
  83         if ( way == BOOST_IOS::beg &&
  84              ( off < integer_traits<std::streamoff>::const_min ||
  85                off > integer_traits<std::streamoff>::const_max ) )
  86         {
  87             return t.rdbuf()->pubseekpos(offset_to_position(off));
  88         } else {
  89             return t.rdbuf()->pubseekoff(off, way, which);
  90         }
  91     }
  92 };
  93
  94 template<>
  95 struct seek_device_impl<iostream_tag> : seek_impl_basic_ios { };
  96
  97 template<>
  98 struct seek_device_impl<istream_tag> : seek_impl_basic_ios { };
  99
 100 template<>
 101 struct seek_device_impl<ostream_tag> : seek_impl_basic_ios { };
 102
 103 template<>
 104 struct seek_device_impl<streambuf_tag> {
 105     template<typename T>
 106     static std::streampos seek( T& t, stream_offset off,
 107                                 BOOST_IOS::seekdir way,
 108                                 BOOST_IOS::openmode which )
 109     {
 110         if ( way == BOOST_IOS::beg &&
 111              ( off < integer_traits<std::streamoff>::const_min ||
 112                off > integer_traits<std::streamoff>::const_max ) )
 113         {
 114             return t.BOOST_IOSTREAMS_PUBSEEKPOS(offset_to_position(off));
 115         } else {
 116             return t.BOOST_IOSTREAMS_PUBSEEKOFF(off, way, which);
 117         }
 118     }
 119 };
 120
 121 template<>
 122 struct seek_device_impl<two_head> {
 123     template<typename T>
 124     static std::streampos seek( T& t, stream_offset off,
 125                                 BOOST_IOS::seekdir way,
 126                                 BOOST_IOS::openmode which )
 127     { return t.seek(off, way, which); }
 128 };
 129
 130 template<>
 131 struct seek_device_impl<any_tag> {
 132     template<typename T>
 133     static std::streampos seek( T& t, stream_offset off,
 134                                 BOOST_IOS::seekdir way,
 135                                 BOOST_IOS::openmode )
 136     { return t.seek(off, way); }
 137 };
 138
 139 //------------------Definition of seek_filter_impl----------------------------//
 140
 141 template<typename T>
 142 struct seek_filter_impl
 143     : mpl::if_<
 144           is_custom<T>,
 145           operations<T>,
 146           seek_filter_impl<
 147               BOOST_DEDUCED_TYPENAME
 148               dispatch<T, two_head, any_tag>::type
 149           >
 150       >::type
 151     { };
 152
 153 template<>
 154 struct seek_filter_impl<two_head> {
 155     template<typename T, typename Device>
 156     static std::streampos seek( T& t, Device& d,
 157                                 stream_offset off,
 158                                 BOOST_IOS::seekdir way,
 159                                 BOOST_IOS::openmode which )
 160     { return t.seek(d, off, way, which); }
 161 };
 162
 163 template<>
 164 struct seek_filter_impl<any_tag> {
 165     template<typename T, typename Device>
 166     static std::streampos seek( T& t, Device& d,
 167                                 stream_offset off,
 168                                 BOOST_IOS::seekdir way,
 169                                 BOOST_IOS::openmode )
 170     { return t.seek(d, off, way); }
 171 };
 172
 173 } // End namespace detail.
 174
 175 } } // End namespaces iostreams, boost.
 176
 177 #include <boost/iostreams/detail/config/enable_warnings.hpp>
 178
 179 #endif // #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED