text: // (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_DETAIL_MODE_ADAPTER_HPP_INCLUDED
  #define BOOST_IOSTREAMS_DETAIL_MODE_ADAPTER_HPP_INCLUDED
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  # pragma once
  #endif              
  
  // Contains the definition of the class template mode_adapter, which allows
  // a filter or device to function as if it has a different i/o mode than that
  // deduced by the metafunction mode_of.
  
  #include <boost/config.hpp>                // BOOST_MSVC.
  #include <boost/detail/workaround.hpp>
  #include <boost/iostreams/categories.hpp>
  #include <boost/iostreams/detail/ios.hpp>  // openmode, seekdir, int types. 
  #include <boost/iostreams/traits.hpp>
  #include <boost/iostreams/operations.hpp> 
  #include <boost/mpl/if.hpp> 
  
  namespace boost { namespace iostreams { namespace detail {
  
  template<typename Mode, typename T>
  class mode_adapter {
  private:
      struct empty_base { };
  public:
      typedef typename wrapped_type<T>::type  policy_type;
      typedef typename char_type_of<T>::type  char_type;
      struct category 
          : Mode, 
            device_tag,
            mpl::if_<is_filter<T>, filter_tag, device_tag>,
            mpl::if_<is_filter<T>, multichar_tag, empty_base>,
            #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
                closable_tag, // VC6 can't see member close()!
            #endif
            localizable_tag
          { };
      explicit mode_adapter(const policy_type& t) : t_(t) { }
  
          // Device member functions.
  
      std::streamsize read(char_type* s, std::streamsize n);
      std::streamsize write(const char_type* s, std::streamsize n);
      std::streampos seek( stream_offset off, BOOST_IOS::seekdir way,
                           BOOST_IOS::openmode which = 
                               BOOST_IOS::in | BOOST_IOS::out );
  #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
      void close(BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out);
  #endif
  
          // Filter member functions.
  
      template<typename Source>
      std::streamsize read(Source& src, char_type* s, std::streamsize n)
      { return iostreams::read(t_, src, s, n); }
  
      template<typename Sink>
      std::streamsize write(Sink& snk, const char_type* s, std::streamsize n)
      { return iostreams::write(t_, snk, s, n); }
  
      template<typename Device>
      std::streampos seek(Device& dev, stream_offset off, BOOST_IOS::seekdir way)
      { return iostreams::seek(t_, dev, off, way); }
  
      template<typename Device>
      std::streampos seek( Device& dev, stream_offset off, 
                           BOOST_IOS::seekdir way, BOOST_IOS::openmode which  )
      { return iostreams::seek(t_, dev, off, way, which); }
  
      template<typename Device>
      void close(Device& dev)
      { iostreams::close(t_, dev); }
  
      template<typename Device>
      void close(Device& dev, BOOST_IOS::openmode which)
      { iostreams::close(t_, dev, which); }
  
      template<typename Locale>
      void imbue(const Locale& loc)
      { iostreams::imbue(t_, loc); }
  private:
      policy_type t_;
  };
                      
  //------------------Implementation of mode_adapter----------------------------//
  
  template<typename Mode, typename T>
  std::streamsize mode_adapter<Mode, T>::read
      (char_type* s, std::streamsize n)
  { return boost::iostreams::read(t_, s, n); }
  
  template<typename Mode, typename T>
  std::streamsize mode_adapter<Mode, T>::write
      (const char_type* s, std::streamsize n)
  { return boost::iostreams::write(t_, s, n); }
  
  template<typename Mode, typename T>
  std::streampos mode_adapter<Mode, T>::seek
      (stream_offset off, BOOST_IOS::seekdir way, BOOST_IOS::openmode which)
  { return boost::iostreams::seek(t_, off, way, which); }
  
  #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
      template<typename Mode, typename T>
      void mode_adapter<Mode, T>::close(BOOST_IOS::openmode which) 
      { iostreams::close(t_, which); }
  #endif
  
  } } } // End namespaces detail, iostreams, boost.
  
  #endif // #ifndef BOOST_IOSTREAMS_DETAIL_MODE_ADAPTER_HPP_INCLUDED //-----//
  