1 | // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com) |
2 | // (C) Copyright 2003-2007 Jonathan Turkanis |
3 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
4 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.) |
5 | |
6 | // See http://www.boost.org/libs/iostreams for documentation. |
7 | |
8 | // To do: handle bidirection streams and output-seekable components. |
9 | |
10 | #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED |
11 | #define BOOST_IOSTREAMS_SKIP_HPP_INCLUDED |
12 | |
13 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
14 | # pragma once |
15 | #endif |
16 | |
17 | #include <boost/iostreams/char_traits.hpp> |
18 | #include <boost/iostreams/detail/ios.hpp> // failure. |
19 | #include <boost/iostreams/operations.hpp> |
20 | #include <boost/iostreams/seek.hpp> |
21 | #include <boost/iostreams/traits.hpp> |
22 | #include <boost/mpl/and.hpp> |
23 | #include <boost/mpl/bool.hpp> |
24 | #include <boost/mpl/or.hpp> |
25 | #include <boost/throw_exception.hpp> |
26 | #include <boost/type_traits/is_convertible.hpp> |
27 | |
28 | namespace boost { namespace iostreams { |
29 | |
30 | namespace detail { |
31 | |
32 | template<typename Device> |
33 | void skip(Device& dev, stream_offset off, mpl::true_) |
34 | { iostreams::seek(dev, off, BOOST_IOS::cur); } |
35 | |
36 | template<typename Device> |
37 | void skip(Device& dev, stream_offset off, mpl::false_) |
38 | { // gcc 2.95 needs namespace qualification for char_traits. |
39 | typedef typename char_type_of<Device>::type char_type; |
40 | typedef iostreams::char_traits<char_type> traits_type; |
41 | for (stream_offset z = 0; z < off; ) { |
42 | typename traits_type::int_type c; |
43 | if (traits_type::is_eof(c = iostreams::get(dev))) |
44 | boost::throw_exception(BOOST_IOSTREAMS_FAILURE("bad skip offset" )); |
45 | if (!traits_type::would_block(c)) |
46 | ++z; |
47 | } |
48 | } |
49 | |
50 | template<typename Filter, typename Device> |
51 | void skip( Filter& flt, Device& dev, stream_offset off, |
52 | BOOST_IOS::openmode which, mpl::true_ ) |
53 | { boost::iostreams::seek(flt, dev, off, BOOST_IOS::cur, which); } |
54 | |
55 | template<typename Filter, typename Device> |
56 | void skip( Filter& flt, Device& dev, stream_offset off, |
57 | BOOST_IOS::openmode, mpl::false_ ) |
58 | { |
59 | typedef typename char_type_of<Device>::type char_type; |
60 | char_type c; |
61 | for (stream_offset z = 0; z < off; ) { |
62 | std::streamsize amt; |
63 | if ((amt = iostreams::read(flt, dev, &c, 1)) == -1) |
64 | boost::throw_exception(BOOST_IOSTREAMS_FAILURE("bad skip offset" )); |
65 | if (amt == 1) |
66 | ++z; |
67 | } |
68 | } |
69 | |
70 | } // End namespace detail. |
71 | |
72 | template<typename Device> |
73 | void skip(Device& dev, stream_offset off) |
74 | { |
75 | typedef typename mode_of<Device>::type mode; |
76 | typedef mpl::or_< |
77 | is_convertible<mode, input_seekable>, |
78 | is_convertible<mode, output_seekable> |
79 | > can_seek; |
80 | BOOST_STATIC_ASSERT( |
81 | (can_seek::value || is_convertible<mode, input>::value) |
82 | ); |
83 | detail::skip(dev, off, can_seek()); |
84 | } |
85 | |
86 | template<typename Filter, typename Device> |
87 | void skip( Filter& flt, Device& dev, stream_offset off, |
88 | BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out ) |
89 | { |
90 | typedef typename mode_of<Filter>::type filter_mode; |
91 | typedef typename mode_of<Device>::type device_mode; |
92 | typedef mpl::or_< |
93 | mpl::and_< |
94 | is_convertible<filter_mode, input_seekable>, |
95 | is_convertible<device_mode, input_seekable> |
96 | >, |
97 | mpl::and_< |
98 | is_convertible<filter_mode, output_seekable>, |
99 | is_convertible<device_mode, output_seekable> |
100 | > |
101 | > can_seek; |
102 | BOOST_STATIC_ASSERT( |
103 | ( can_seek::value || |
104 | (is_convertible<filter_mode, input>::value && |
105 | is_convertible<device_mode, input>::value) ) |
106 | ); |
107 | detail::skip(flt, dev, off, which, can_seek()); |
108 | } |
109 | |
110 | } } // End namespaces iostreams, boost. |
111 | |
112 | #endif // #ifndef BOOST_IOSTREAMS_SKIP_HPP_INCLUDED //------------------------// |
113 | |