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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 //------------------------// |