| 1 | // (C) Copyright Jonathan Turkanis 2003. |
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| 2 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
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| 3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.) |
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| 4 | |
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| 5 | // See http://www.boost.org/libs/iostreams for documentation. |
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| 6 | |
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| 7 | // To do: handle bidirection streams and output-seekable components. |
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| 8 | |
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| 9 | #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED |
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| 10 | #define BOOST_IOSTREAMS_SKIP_HPP_INCLUDED |
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| 11 | |
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| 12 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
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| 13 | # pragma once |
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| 14 | #endif |
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| 15 | |
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| 16 | #include <boost/iostreams/char_traits.hpp> |
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| 17 | #include <boost/iostreams/detail/ios.hpp> // failure. |
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| 18 | #include <boost/iostreams/operations.hpp> |
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| 19 | #include <boost/iostreams/traits.hpp> |
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| 20 | #include <boost/mpl/and.hpp> |
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| 21 | #include <boost/mpl/bool.hpp> |
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| 22 | #include <boost/type_traits/is_convertible.hpp> |
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| 23 | |
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| 24 | namespace boost { namespace iostreams { |
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| 25 | |
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| 26 | namespace detail { |
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| 27 | |
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| 28 | template<typename Device> |
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| 29 | void skip(Device& dev, stream_offset off, mpl::true_) |
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| 30 | { iostreams::seek(dev, off, BOOST_IOS::cur); } |
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| 31 | |
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| 32 | template<typename Device> |
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| 33 | void skip(Device& dev, stream_offset off, mpl::false_) |
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| 34 | { // gcc 2.95 needs namespace qualification for char_traits. |
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| 35 | typedef typename char_type_of<Device>::type char_type; |
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| 36 | typedef iostreams::char_traits<char_type> traits_type; |
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| 37 | for (stream_offset z = 0; z < off; ) { |
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| 38 | typename traits_type::int_type c; |
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| 39 | if (traits_type::is_eof(c = iostreams::get(dev))) |
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| 40 | throw BOOST_IOSTREAMS_FAILURE("bad skip offset"); |
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| 41 | if (!traits_type::would_block(c)) |
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| 42 | ++z; |
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| 43 | } |
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| 44 | } |
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| 45 | |
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| 46 | template<typename Filter, typename Device> |
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| 47 | void skip(Filter& flt, Device& dev, stream_offset off, mpl::true_) |
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| 48 | { flt.seek(dev, off, BOOST_IOS::cur); } |
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| 49 | |
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| 50 | template<typename Filter, typename Device> |
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| 51 | void skip(Filter& flt, Device& dev, stream_offset off, mpl::false_) |
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| 52 | { |
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| 53 | typedef typename char_type_of<Device>::type char_type; |
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| 54 | char_type c; |
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| 55 | for (stream_offset z = 0; z < off; ) { |
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| 56 | std::streamsize amt; |
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| 57 | if ((amt = iostreams::read(flt, dev, &c, 1)) == -1) |
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| 58 | throw BOOST_IOSTREAMS_FAILURE("bad skip offset"); |
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| 59 | if (amt == 1) |
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| 60 | ++z; |
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| 61 | } |
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| 62 | } |
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| 63 | |
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| 64 | } // End namespace detail. |
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| 65 | |
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| 66 | template<typename Device> |
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| 67 | void skip(Device& dev, stream_offset off) |
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| 68 | { |
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| 69 | typedef typename mode_of<Device>::type mode; |
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| 70 | detail::skip(dev, off, is_convertible<mode, seekable>()); |
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| 71 | } |
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| 72 | |
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| 73 | template<typename Filter, typename Device> |
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| 74 | void skip(Filter& flt, Device& dev, stream_offset off) |
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| 75 | { |
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| 76 | typedef typename mode_of<Filter>::type filter_mode; |
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| 77 | typedef typename mode_of<Device>::type device_mode; |
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| 78 | typedef mpl::and_< |
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| 79 | is_convertible<filter_mode, output_seekable>, |
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| 80 | is_convertible<device_mode, output_seekable> |
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| 81 | > can_seek; |
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| 82 | detail::skip(flt, dev, off, can_seek()); |
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| 83 | } |
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| 84 | |
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| 85 | } } // End namespaces iostreams, boost. |
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| 86 | |
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| 87 | #endif // #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED //------------------------// |
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