// (C) Copyright Jonathan Turkanis 2003.

 // Distributed under the Boost Software License, Version 1.0. (See accompanying

 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)

 // See http://www.boost.org/libs/iostreams for documentation.

 #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED

 #define BOOST_IOSTREAMS_SEEK_HPP_INCLUDED

 #if defined(_MSC_VER) && (_MSC_VER >= 1020)

 # pragma once

 #endif

 #include <boost/config.hpp>  // DEDUCED_TYPENAME, MSVC.

 #include <boost/integer_traits.hpp>

 #include <boost/iostreams/categories.hpp>

 #include <boost/iostreams/detail/dispatch.hpp>

 #include <boost/iostreams/detail/ios.hpp>       // streamsize, seekdir, openmode.

 #include <boost/iostreams/detail/streambuf.hpp>

 #include <boost/iostreams/detail/wrap_unwrap.hpp>

 #include <boost/iostreams/operations_fwd.hpp>

 #include <boost/iostreams/positioning.hpp>

 #include <boost/mpl/if.hpp>

 // Must come last.

 #include <boost/iostreams/detail/config/disable_warnings.hpp>

 namespace boost { namespace iostreams {

 namespace detail {

 template<typename T>

 struct seek_device_impl;

 template<typename T>

 struct seek_filter_impl;

 } // End namespace detail.

 template<typename T>

 inline std::streampos

 seek( T& t, stream_offset off, BOOST_IOS::seekdir way,

       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )

 { 

     using namespace detail;

     return seek_device_impl<T>::seek(detail::unwrap(t), off, way, which); 

 }

 template<typename T, typename Device>

 inline std::streampos

 seek( T& t, Device& dev, stream_offset off, BOOST_IOS::seekdir way,

       BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )

 { 

     using namespace detail;

     return seek_filter_impl<T>::seek(detail::unwrap(t), dev, off, way, which);

 }

 namespace detail {

 //------------------Definition of seek_device_impl----------------------------//

 template<typename T>

 struct seek_device_impl

     : mpl::if_<

           is_custom<T>,

           operations<T>,

           seek_device_impl<

               BOOST_DEDUCED_TYPENAME

               dispatch<

                   T, iostream_tag, istream_tag, ostream_tag,

                   streambuf_tag, two_head, any_tag

               >::type

           >

       >::type

     { };

 struct seek_impl_basic_ios {

     template<typename T>

     static std::streampos seek( T& t, stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode which )

     {

         if ( way == BOOST_IOS::beg &&

              ( off < integer_traits<std::streamoff>::const_min ||

                off > integer_traits<std::streamoff>::const_max ) )

         {

             return t.rdbuf()->pubseekpos(offset_to_position(off));

         } else {

             return t.rdbuf()->pubseekoff(off, way, which);

         }

     }

 };

 template<>

 struct seek_device_impl<iostream_tag> : seek_impl_basic_ios { };

 template<>

 struct seek_device_impl<istream_tag> : seek_impl_basic_ios { };

 template<>

 struct seek_device_impl<ostream_tag> : seek_impl_basic_ios { };

 template<>

 struct seek_device_impl<streambuf_tag> {

     template<typename T>

     static std::streampos seek( T& t, stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode which )

     {

         if ( way == BOOST_IOS::beg &&

              ( off < integer_traits<std::streamoff>::const_min ||

                off > integer_traits<std::streamoff>::const_max ) )

         {

             return t.BOOST_IOSTREAMS_PUBSEEKPOS(offset_to_position(off));

         } else {

             return t.BOOST_IOSTREAMS_PUBSEEKOFF(off, way, which);

         }

     }

 };

 template<>

 struct seek_device_impl<two_head> {

     template<typename T>

     static std::streampos seek( T& t, stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode which )

     { return t.seek(off, way, which); }

 };

 template<>

 struct seek_device_impl<any_tag> {

     template<typename T>

     static std::streampos seek( T& t, stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode )

     { return t.seek(off, way); }

 };

 //------------------Definition of seek_filter_impl----------------------------//

 template<typename T>

 struct seek_filter_impl

     : mpl::if_<

           is_custom<T>,

           operations<T>,

           seek_filter_impl<

               BOOST_DEDUCED_TYPENAME

               dispatch<T, two_head, any_tag>::type

           >

       >::type

     { };

 template<>

 struct seek_filter_impl<two_head> {

     template<typename T, typename Device>

     static std::streampos seek( T& t, Device& d,

                                 stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode which )

     { return t.seek(d, off, way, which); }

 };

 template<>

 struct seek_filter_impl<any_tag> {

     template<typename T, typename Device>

     static std::streampos seek( T& t, Device& d,

                                 stream_offset off,

                                 BOOST_IOS::seekdir way,

                                 BOOST_IOS::openmode )

     { return t.seek(d, off, way); }

 };

 } // End namespace detail.

 } } // End namespaces iostreams, boost.

 #include <boost/iostreams/detail/config/enable_warnings.hpp>

 #endif // #ifndef BOOST_IOSTREAMS_SEEK_HPP_INCLUDED