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