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os/ossrv/ossrv_pub/boost_apis/boost/iostreams/skip.hpp
author sl@SLION-WIN7.fritz.box
Fri, 15 Jun 2012 03:10:57 +0200
changeset 0 bde4ae8d615e
permissions -rw-r--r--
First public contribution. 
     1 // (C) Copyright Jonathan Turkanis 2003.

     2 // Distributed under the Boost Software License, Version 1.0. (See accompanying

     3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)

     4 

     5 // See http://www.boost.org/libs/iostreams for documentation.

     6 

     7 // To do: handle bidirection streams and output-seekable components.

     8 

     9 #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED

    10 #define BOOST_IOSTREAMS_SKIP_HPP_INCLUDED

    11 

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

    13 # pragma once

    14 #endif

    15 

    16 #include <boost/iostreams/char_traits.hpp>

    17 #include <boost/iostreams/detail/ios.hpp>  // failure.

    18 #include <boost/iostreams/operations.hpp>

    19 #include <boost/iostreams/traits.hpp>

    20 #include <boost/mpl/and.hpp>

    21 #include <boost/mpl/bool.hpp>

    22 #include <boost/type_traits/is_convertible.hpp>

    23 

    24 namespace boost { namespace iostreams {

    25 

    26 namespace detail {

    27 

    28 template<typename Device>

    29 void skip(Device& dev, stream_offset off, mpl::true_)

    30 { iostreams::seek(dev, off, BOOST_IOS::cur); }

    31 

    32 template<typename Device>

    33 void skip(Device& dev, stream_offset off, mpl::false_)

    34 {   // gcc 2.95 needs namespace qualification for char_traits.

    35     typedef typename char_type_of<Device>::type  char_type;

    36     typedef iostreams::char_traits<char_type>    traits_type;

    37     for (stream_offset z = 0; z < off; ) {

    38         typename traits_type::int_type c;

    39         if (traits_type::is_eof(c = iostreams::get(dev)))

    40             throw BOOST_IOSTREAMS_FAILURE("bad skip offset");

    41         if (!traits_type::would_block(c))

    42             ++z;

    43     }

    44 }

    45 

    46 template<typename Filter, typename Device>

    47 void skip(Filter& flt, Device& dev, stream_offset off, mpl::true_)

    48 { flt.seek(dev, off, BOOST_IOS::cur); }

    49 

    50 template<typename Filter, typename Device>

    51 void skip(Filter& flt, Device& dev, stream_offset off, mpl::false_)

    52 { 

    53     typedef typename char_type_of<Device>::type char_type;

    54     char_type c;

    55     for (stream_offset z = 0; z < off; ) {

    56         std::streamsize amt;

    57         if ((amt = iostreams::read(flt, dev, &c, 1)) == -1)

    58             throw BOOST_IOSTREAMS_FAILURE("bad skip offset");

    59         if (amt == 1)

    60             ++z;

    61     }

    62 }

    63 

    64 } // End namespace detail.

    65 

    66 template<typename Device>

    67 void skip(Device& dev, stream_offset off)

    68 { 

    69     typedef typename mode_of<Device>::type mode;

    70     detail::skip(dev, off, is_convertible<mode, seekable>());

    71 }

    72 

    73 template<typename Filter, typename Device>

    74 void skip(Filter& flt, Device& dev, stream_offset off)

    75 { 

    76     typedef typename mode_of<Filter>::type                     filter_mode;

    77     typedef typename mode_of<Device>::type                     device_mode;

    78     typedef mpl::and_<

    79                 is_convertible<filter_mode, output_seekable>,

    80                 is_convertible<device_mode, output_seekable>

    81             >                                                  can_seek;

    82     detail::skip(flt, dev, off, can_seek());

    83 }

    84 

    85 } } // End namespaces iostreams, boost.

    86 

    87 #endif // #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED //------------------------//
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