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