boost/iostreams/seek.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 #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED
0009 #define BOOST_IOSTREAMS_SEEK_HPP_INCLUDED
0010
0011 #if defined(_MSC_VER)
0012 # pragma once
0013 #endif
0014
0015 #include <boost/config.hpp>  // DEDUCED_TYPENAME, MSVC.
0016 #include <boost/integer_traits.hpp>
0017 #include <boost/iostreams/categories.hpp>
0018 #include <boost/iostreams/detail/dispatch.hpp>
0019 #include <boost/iostreams/detail/ios.hpp>       // streamsize, seekdir, openmode.
0020 #include <boost/iostreams/detail/streambuf.hpp>
0021 #include <boost/iostreams/detail/wrap_unwrap.hpp>
0022 #include <boost/iostreams/operations_fwd.hpp>
0023 #include <boost/iostreams/positioning.hpp>
0024 #include <boost/mpl/if.hpp>
0025
0026 // Must come last.
0027 #include <boost/iostreams/detail/config/disable_warnings.hpp>
0028
0029 namespace boost { namespace iostreams {
0030
0031 namespace detail {
0032
0033 template<typename T>
0034 struct seek_device_impl;
0035
0036 template<typename T>
0037 struct seek_filter_impl;
0038
0039 } // End namespace detail.
0040
0041 template<typename T>
0042 inline std::streampos
0043 seek( T& t, stream_offset off, BOOST_IOS::seekdir way,
0044       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
0045 {
0046     using namespace detail;
0047     return seek_device_impl<T>::seek(detail::unwrap(t), off, way, which);
0048 }
0049
0050 template<typename T, typename Device>
0051 inline std::streampos
0052 seek( T& t, Device& dev, stream_offset off, BOOST_IOS::seekdir way,
0053       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
0054 {
0055     using namespace detail;
0056     return seek_filter_impl<T>::seek(detail::unwrap(t), dev, off, way, which);
0057 }
0058
0059 namespace detail {
0060
0061 //------------------Definition of seek_device_impl----------------------------//
0062
0063 template<typename T>
0064 struct seek_device_impl
0065     : mpl::if_<
0066           is_custom<T>,
0067           operations<T>,
0068           seek_device_impl<
0069               BOOST_DEDUCED_TYPENAME
0070               dispatch<
0071                   T, iostream_tag, istream_tag, ostream_tag,
0072                   streambuf_tag, two_head, any_tag
0073               >::type
0074           >
0075       >::type
0076     { };
0077
0078 struct seek_impl_basic_ios {
0079     template<typename T>
0080     static std::streampos seek( T& t, stream_offset off,
0081                                 BOOST_IOS::seekdir way,
0082                                 BOOST_IOS::openmode which )
0083     {
0084         if ( way == BOOST_IOS::beg &&
0085              ( off < integer_traits<std::streamoff>::const_min ||
0086                off > integer_traits<std::streamoff>::const_max ) )
0087         {
0088             return t.rdbuf()->pubseekpos(offset_to_position(off));
0089         } else {
0090             return t.rdbuf()->pubseekoff(off, way, which);
0091         }
0092     }
0093 };
0094
0095 template<>
0096 struct seek_device_impl<iostream_tag> : seek_impl_basic_ios { };
0097
0098 template<>
0099 struct seek_device_impl<istream_tag> : seek_impl_basic_ios { };
0100
0101 template<>
0102 struct seek_device_impl<ostream_tag> : seek_impl_basic_ios { };
0103
0104 template<>
0105 struct seek_device_impl<streambuf_tag> {
0106     template<typename T>
0107     static std::streampos seek( T& t, stream_offset off,
0108                                 BOOST_IOS::seekdir way,
0109                                 BOOST_IOS::openmode which )
0110     {
0111         if ( way == BOOST_IOS::beg &&
0112              ( off < integer_traits<std::streamoff>::const_min ||
0113                off > integer_traits<std::streamoff>::const_max ) )
0114         {
0115             return t.BOOST_IOSTREAMS_PUBSEEKPOS(offset_to_position(off));
0116         } else {
0117             return t.BOOST_IOSTREAMS_PUBSEEKOFF(off, way, which);
0118         }
0119     }
0120 };
0121
0122 template<>
0123 struct seek_device_impl<two_head> {
0124     template<typename T>
0125     static std::streampos seek( T& t, stream_offset off,
0126                                 BOOST_IOS::seekdir way,
0127                                 BOOST_IOS::openmode which )
0128     { return t.seek(off, way, which); }
0129 };
0130
0131 template<>
0132 struct seek_device_impl<any_tag> {
0133     template<typename T>
0134     static std::streampos seek( T& t, stream_offset off,
0135                                 BOOST_IOS::seekdir way,
0136                                 BOOST_IOS::openmode )
0137     { return t.seek(off, way); }
0138 };
0139
0140 //------------------Definition of seek_filter_impl----------------------------//
0141
0142 template<typename T>
0143 struct seek_filter_impl
0144     : mpl::if_<
0145           is_custom<T>,
0146           operations<T>,
0147           seek_filter_impl<
0148               BOOST_DEDUCED_TYPENAME
0149               dispatch<T, two_head, any_tag>::type
0150           >
0151       >::type
0152     { };
0153
0154 template<>
0155 struct seek_filter_impl<two_head> {
0156     template<typename T, typename Device>
0157     static std::streampos seek( T& t, Device& d,
0158                                 stream_offset off,
0159                                 BOOST_IOS::seekdir way,
0160                                 BOOST_IOS::openmode which )
0161     { return t.seek(d, off, way, which); }
0162 };
0163
0164 template<>
0165 struct seek_filter_impl<any_tag> {
0166     template<typename T, typename Device>
0167     static std::streampos seek( T& t, Device& d,
0168                                 stream_offset off,
0169                                 BOOST_IOS::seekdir way,
0170                                 BOOST_IOS::openmode )
0171     { return t.seek(d, off, way); }
0172 };
0173
0174 } // End namespace detail.
0175
0176 } } // End namespaces iostreams, boost.
0177
0178 #include <boost/iostreams/detail/config/enable_warnings.hpp>
0179
0180 #endif // #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED