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