boost/iostreams/checked_operations.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2005-2007 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 // Contains implementations of get, read, put, write and seek which
   9 // check a device's mode at runtime instead of compile time.
  10
  11 #ifndef BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED
  12 #define BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED
  13
  14 #include <boost/iostreams/categories.hpp>
  15 #include <boost/iostreams/detail/dispatch.hpp>
  16 #include <boost/iostreams/detail/error.hpp>
  17 #include <boost/iostreams/get.hpp>
  18 #include <boost/iostreams/put.hpp>
  19 #include <boost/iostreams/read.hpp>
  20 #include <boost/iostreams/seek.hpp>
  21 #include <boost/iostreams/traits.hpp>
  22 #include <boost/iostreams/write.hpp>
  23
  24 // Must come last.
  25 #include <boost/iostreams/detail/config/disable_warnings.hpp>  // MSVC.
  26
  27 namespace boost { namespace iostreams {
  28
  29 namespace detail {
  30
  31 template<typename T>
  32 struct read_write_if_impl;
  33
  34 template<typename T>
  35 struct seek_if_impl;
  36
  37 } // End namespace detail.
  38
  39 template<typename T>
  40 typename int_type_of<T>::type get_if(T& t)
  41 {
  42     typedef typename detail::dispatch<T, input, output>::type tag;
  43     return detail::read_write_if_impl<tag>::get(t);
  44 }
  45
  46 template<typename T>
  47 inline std::streamsize
  48 read_if(T& t, typename char_type_of<T>::type* s, std::streamsize n)
  49 {
  50     typedef typename detail::dispatch<T, input, output>::type tag;
  51     return detail::read_write_if_impl<tag>::read(t, s, n);
  52 }
  53
  54 template<typename T>
  55 bool put_if(T& t, typename char_type_of<T>::type c)
  56 {
  57     typedef typename detail::dispatch<T, output, input>::type tag;
  58     return detail::read_write_if_impl<tag>::put(t, c);
  59 }
  60
  61 template<typename T>
  62 inline std::streamsize write_if
  63     (T& t, const typename char_type_of<T>::type* s, std::streamsize n)
  64 {
  65     typedef typename detail::dispatch<T, output, input>::type tag;
  66     return detail::read_write_if_impl<tag>::write(t, s, n);
  67 }
  68
  69 template<typename T>
  70 inline std::streampos
  71 seek_if( T& t, stream_offset off, BOOST_IOS::seekdir way,
  72          BOOST_IOS::openmode which = BOOST_IOS::in | BOOST_IOS::out )
  73 {
  74     using namespace detail;
  75     typedef typename dispatch<T, random_access, any_tag>::type tag;
  76     return seek_if_impl<tag>::seek(t, off, way, which);
  77 }
  78
  79 namespace detail {
  80
  81 //------------------Specializations of read_write_if_impl---------------------//
  82
  83 template<>
  84 struct read_write_if_impl<input> {
  85     template<typename T>
  86     static typename int_type_of<T>::type get(T& t)
  87     { return iostreams::get(t); }
  88
  89     template<typename T>
  90     static std::streamsize
  91     read(T& t, typename char_type_of<T>::type* s, std::streamsize n)
  92     { return iostreams::read(t, s, n); }
  93
  94     template<typename T>
  95     static bool put(T&, typename char_type_of<T>::type)
  96     { throw cant_write(); }
  97
  98     template<typename T>
  99     static std::streamsize
 100     write(T&, const typename char_type_of<T>::type*, std::streamsize)
 101     { throw cant_write(); }
 102 };
 103
 104 template<>
 105 struct read_write_if_impl<output> {
 106     template<typename T>
 107     static typename int_type_of<T>::type get(T&)
 108     { throw cant_read(); }
 109
 110     template<typename T>
 111     static std::streamsize
 112     read(T&, typename char_type_of<T>::type*, std::streamsize)
 113     { throw cant_read(); }
 114
 115     template<typename T>
 116     static bool put(T& t, typename char_type_of<T>::type c)
 117     { return iostreams::put(t, c); }
 118
 119     template<typename T>
 120     static std::streamsize
 121     write( T& t, const typename char_type_of<T>::type* s,
 122            std::streamsize n )
 123     { return iostreams::write(t, s, n); }
 124 };
 125
 126 //------------------Specializations of seek_if_impl---------------------------//
 127
 128 template<>
 129 struct seek_if_impl<random_access> {
 130     template<typename T>
 131     static std::streampos
 132     seek( T& t, stream_offset off, BOOST_IOS::seekdir way,
 133           BOOST_IOS::openmode which )
 134     { return iostreams::seek(t, off, way, which); }
 135 };
 136
 137 template<>
 138 struct seek_if_impl<any_tag> {
 139     template<typename T>
 140     static std::streampos
 141     seek(T&, stream_offset, BOOST_IOS::seekdir, BOOST_IOS::openmode)
 142     { throw cant_seek(); }
 143 };
 144
 145 } // End namespace detail.
 146
 147 } } // End namespaces iostreams, boost.
 148
 149 #include <boost/iostreams/detail/config/enable_warnings.hpp>  // MSVC.
 150
 151 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_CHECKED_OPERATIONS_HPP_INCLUDED