boost/iostreams/checked_operations.hpp

0001 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
0002 // (C) Copyright 2005-2007 Jonathan Turkanis
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
0005
0006 // See http://www.boost.org/libs/iostreams for documentation.
0007
0008 // Contains implementations of get, read, put, write and seek which
0009 // check a device's mode at runtime instead of compile time.
0010
0011 #ifndef BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED
0012 #define BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED
0013
0014 #include <boost/iostreams/categories.hpp>
0015 #include <boost/iostreams/detail/dispatch.hpp>
0016 #include <boost/iostreams/detail/error.hpp>
0017 #include <boost/iostreams/detail/config/unreachable_return.hpp>
0018 #include <boost/iostreams/get.hpp>
0019 #include <boost/iostreams/put.hpp>
0020 #include <boost/iostreams/read.hpp>
0021 #include <boost/iostreams/seek.hpp>
0022 #include <boost/iostreams/traits.hpp>
0023 #include <boost/iostreams/write.hpp>
0024 #include <boost/throw_exception.hpp>
0025
0026 // Must come last.
0027 #include <boost/iostreams/detail/config/disable_warnings.hpp>  // MSVC.
0028
0029 namespace boost { namespace iostreams {
0030
0031 namespace detail {
0032
0033 template<typename T>
0034 struct read_write_if_impl;
0035
0036 template<typename T>
0037 struct seek_if_impl;
0038
0039 } // End namespace detail.
0040
0041 template<typename T>
0042 typename int_type_of<T>::type get_if(T& t)
0043 {
0044     typedef typename detail::dispatch<T, input, output>::type tag;
0045     return detail::read_write_if_impl<tag>::get(t);
0046 }
0047
0048 template<typename T>
0049 inline std::streamsize
0050 read_if(T& t, typename char_type_of<T>::type* s, std::streamsize n)
0051 {
0052     typedef typename detail::dispatch<T, input, output>::type tag;
0053     return detail::read_write_if_impl<tag>::read(t, s, n);
0054 }
0055
0056 template<typename T>
0057 bool put_if(T& t, typename char_type_of<T>::type c)
0058 {
0059     typedef typename detail::dispatch<T, output, input>::type tag;
0060     return detail::read_write_if_impl<tag>::put(t, c);
0061 }
0062
0063 template<typename T>
0064 inline std::streamsize write_if
0065     (T& t, const typename char_type_of<T>::type* s, std::streamsize n)
0066 {
0067     typedef typename detail::dispatch<T, output, input>::type tag;
0068     return detail::read_write_if_impl<tag>::write(t, s, n);
0069 }
0070
0071 template<typename T>
0072 inline std::streampos
0073 seek_if( T& t, stream_offset off, BOOST_IOS::seekdir way,
0074          BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
0075 {
0076     using namespace detail;
0077     typedef typename dispatch<T, random_access, any_tag>::type tag;
0078     return seek_if_impl<tag>::seek(t, off, way, which);
0079 }
0080
0081 namespace detail {
0082
0083 //------------------Specializations of read_write_if_impl---------------------//
0084
0085 template<>
0086 struct read_write_if_impl<input> {
0087     template<typename T>
0088     static typename int_type_of<T>::type get(T& t)
0089     { return iostreams::get(t); }
0090
0091     template<typename T>
0092     static std::streamsize
0093     read(T& t, typename char_type_of<T>::type* s, std::streamsize n)
0094     { return iostreams::read(t, s, n); }
0095
0096     template<typename T>
0097     static bool put(T&, typename char_type_of<T>::type)
0098     { boost::throw_exception(cant_write());
0099       BOOST_IOSTREAMS_UNREACHABLE_RETURN(false) }
0100
0101     template<typename T>
0102     static std::streamsize
0103     write(T&, const typename char_type_of<T>::type*, std::streamsize)
0104     { boost::throw_exception(cant_write());
0105       BOOST_IOSTREAMS_UNREACHABLE_RETURN(0) }
0106 };
0107
0108 template<>
0109 struct read_write_if_impl<output> {
0110     template<typename T>
0111     static typename int_type_of<T>::type get(T&)
0112     { boost::throw_exception(cant_read());
0113       BOOST_IOSTREAMS_UNREACHABLE_RETURN(0) }
0114
0115     template<typename T>
0116     static std::streamsize
0117     read(T&, typename char_type_of<T>::type*, std::streamsize)
0118     { boost::throw_exception(cant_read());
0119       BOOST_IOSTREAMS_UNREACHABLE_RETURN(0) }
0120
0121     template<typename T>
0122     static bool put(T& t, typename char_type_of<T>::type c)
0123     { return iostreams::put(t, c); }
0124
0125     template<typename T>
0126     static std::streamsize
0127     write( T& t, const typename char_type_of<T>::type* s,
0128            std::streamsize n )
0129     { return iostreams::write(t, s, n); }
0130 };
0131
0132 //------------------Specializations of seek_if_impl---------------------------//
0133
0134 template<>
0135 struct seek_if_impl<random_access> {
0136     template<typename T>
0137     static std::streampos
0138     seek( T& t, stream_offset off, BOOST_IOS::seekdir way,
0139           BOOST_IOS::openmode which )
0140     { return iostreams::seek(t, off, way, which); }
0141 };
0142
0143 template<>
0144 struct seek_if_impl<any_tag> {
0145     template<typename T>
0146     static std::streampos
0147     seek(T&, stream_offset, BOOST_IOS::seekdir, BOOST_IOS::openmode)
0148     { boost::throw_exception(cant_seek());
0149       BOOST_IOSTREAMS_UNREACHABLE_RETURN(std::streampos()) }
0150 };
0151
0152 } // End namespace detail.
0153
0154 } } // End namespaces iostreams, boost.
0155
0156 #include <boost/iostreams/detail/config/enable_warnings.hpp>  // MSVC.
0157
0158 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED