// (C) Copyright Jonathan Turkanis 2004.

 // 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.

 // Inspired by Daryle Walker's nullbuf from his More I/O submission.

 #ifndef BOOST_IOSTREAMS_NULL_HPP_INCLUDED

 #define BOOST_IOSTREAMS_NULL_HPP_INCLUDED

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

 # pragma once

 #endif

 #include <boost/iostreams/categories.hpp>

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

 #include <boost/iostreams/positioning.hpp>

 namespace boost { namespace iostreams {

 template<typename Ch, typename Mode>

 class basic_null_device {

 public:

     typedef Ch char_type;

     struct category

         : public Mode,

           public device_tag,

           public closable_tag

         { };

     std::streamsize read(Ch*, std::streamsize) { return 0; }

     std::streamsize write(const Ch*, std::streamsize n) { return n; }

     stream_offset seek( stream_offset, BOOST_IOS::seekdir,

                         BOOST_IOS::openmode = 

                             BOOST_IOS::in | BOOST_IOS::out ) 

     { return -1; }

     void close(BOOST_IOS::openmode = BOOST_IOS::in | BOOST_IOS::out) { }

 };

 template<typename Ch>

 struct basic_null_source : private basic_null_device<Ch, input> {

     typedef Ch          char_type;

     typedef source_tag  category;

     using basic_null_device<Ch, input>::read;

     using basic_null_device<Ch, input>::close;

 };

 typedef basic_null_source<char>     null_source;

 typedef basic_null_source<wchar_t>  wnull_source;

 template<typename Ch>

 struct basic_null_sink : private basic_null_device<Ch, output> {

     typedef Ch        char_type;

     typedef sink_tag  category;

     using basic_null_device<Ch, output>::write;

     using basic_null_device<Ch, output>::close;

 };

 typedef basic_null_sink<char>     null_sink;

 typedef basic_null_sink<wchar_t>  wnull_sink;

 } } // End namespaces iostreams, boost.

 #endif // #ifndef BOOST_IOSTREAMS_NULL_HPP_INCLUDED