Chris@16: // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
Chris@16: // (C) Copyright 2003-2007 Jonathan Turkanis
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
Chris@16: 
Chris@16: // See http://www.boost.org/libs/iostreams for documentation.
Chris@16: 
Chris@16: // To do: handle bidirection streams and output-seekable components.
Chris@16: 
Chris@16: #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED
Chris@16: #define BOOST_IOSTREAMS_SKIP_HPP_INCLUDED
Chris@16: 
Chris@16: #if defined(_MSC_VER) && (_MSC_VER >= 1020)
Chris@16: # pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/iostreams/char_traits.hpp>
Chris@16: #include <boost/iostreams/detail/ios.hpp>  // failure.
Chris@16: #include <boost/iostreams/operations.hpp>
Chris@16: #include <boost/iostreams/seek.hpp>
Chris@16: #include <boost/iostreams/traits.hpp>
Chris@16: #include <boost/mpl/and.hpp>
Chris@16: #include <boost/mpl/bool.hpp>
Chris@16: #include <boost/mpl/or.hpp>
Chris@16: #include <boost/throw_exception.hpp>
Chris@16: #include <boost/type_traits/is_convertible.hpp>
Chris@16: 
Chris@16: namespace boost { namespace iostreams {
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: template<typename Device>
Chris@16: void skip(Device& dev, stream_offset off, mpl::true_)
Chris@16: { iostreams::seek(dev, off, BOOST_IOS::cur); }
Chris@16: 
Chris@16: template<typename Device>
Chris@16: void skip(Device& dev, stream_offset off, mpl::false_)
Chris@16: {   // gcc 2.95 needs namespace qualification for char_traits.
Chris@16:     typedef typename char_type_of<Device>::type  char_type;
Chris@16:     typedef iostreams::char_traits<char_type>    traits_type;
Chris@16:     for (stream_offset z = 0; z < off; ) {
Chris@16:         typename traits_type::int_type c;
Chris@16:         if (traits_type::is_eof(c = iostreams::get(dev)))
Chris@16:             boost::throw_exception(BOOST_IOSTREAMS_FAILURE("bad skip offset"));
Chris@16:         if (!traits_type::would_block(c))
Chris@16:             ++z;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<typename Filter, typename Device>
Chris@16: void skip( Filter& flt, Device& dev, stream_offset off,
Chris@16:            BOOST_IOS::openmode which, mpl::true_ )
Chris@16: { boost::iostreams::seek(flt, dev, off, BOOST_IOS::cur, which); }
Chris@16: 
Chris@16: template<typename Filter, typename Device>
Chris@16: void skip( Filter& flt, Device& dev, stream_offset off,
Chris@16:            BOOST_IOS::openmode, mpl::false_ )
Chris@16: { 
Chris@16:     typedef typename char_type_of<Device>::type char_type;
Chris@16:     char_type c;
Chris@16:     for (stream_offset z = 0; z < off; ) {
Chris@16:         std::streamsize amt;
Chris@16:         if ((amt = iostreams::read(flt, dev, &c, 1)) == -1)
Chris@16:             boost::throw_exception(BOOST_IOSTREAMS_FAILURE("bad skip offset"));
Chris@16:         if (amt == 1)
Chris@16:             ++z;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: } // End namespace detail.
Chris@16: 
Chris@16: template<typename Device>
Chris@16: void skip(Device& dev, stream_offset off)
Chris@16: { 
Chris@16:     typedef typename mode_of<Device>::type     mode;
Chris@16:     typedef mpl::or_<
Chris@16:         is_convertible<mode, input_seekable>,
Chris@16:         is_convertible<mode, output_seekable>
Chris@16:     >                                          can_seek;
Chris@16:     BOOST_STATIC_ASSERT(
Chris@16:         (can_seek::value || is_convertible<mode, input>::value)
Chris@16:     );
Chris@16:     detail::skip(dev, off, can_seek());
Chris@16: }
Chris@16: 
Chris@16: template<typename Filter, typename Device>
Chris@16: void skip( Filter& flt, Device& dev, stream_offset off, 
Chris@16:            BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
Chris@16: { 
Chris@16:     typedef typename mode_of<Filter>::type                 filter_mode;
Chris@16:     typedef typename mode_of<Device>::type                 device_mode;
Chris@16:     typedef mpl::or_<
Chris@16:         mpl::and_<
Chris@16:             is_convertible<filter_mode, input_seekable>,
Chris@16:             is_convertible<device_mode, input_seekable>
Chris@16:         >,
Chris@16:         mpl::and_<
Chris@16:             is_convertible<filter_mode, output_seekable>,
Chris@16:             is_convertible<device_mode, output_seekable>
Chris@16:         >
Chris@16:     >                                                      can_seek;
Chris@16:     BOOST_STATIC_ASSERT(
Chris@16:         ( can_seek::value || 
Chris@16:           (is_convertible<filter_mode, input>::value &&
Chris@16:           is_convertible<device_mode, input>::value) )
Chris@16:     );
Chris@16:     detail::skip(flt, dev, off, which, can_seek());
Chris@16: }
Chris@16: 
Chris@16: } } // End namespaces iostreams, boost.
Chris@16: 
Chris@16: #endif // #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED //------------------------//