detail/utility/traits_utils.hpp

0001 ///////////////////////////////////////////////////////////////////////////////
0002 // traits_utils.hpp
0003 //
0004 //  Copyright 2008 Eric Niebler. Distributed under the Boost
0005 //  Software License, Version 1.0. (See accompanying file
0006 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007
0008 #ifndef BOOST_XPRESSIVE_DETAIL_UTILITY_TRAITS_UTILS_HPP_EAN_10_04_2005
0009 #define BOOST_XPRESSIVE_DETAIL_UTILITY_TRAITS_UTILS_HPP_EAN_10_04_2005
0010
0011 // MS compatible compilers support #pragma once
0012 #if defined(_MSC_VER)
0013 # pragma once
0014 # pragma warning(push)
0015 # pragma warning(disable : 4100) // unreferenced formal parameter
0016 #endif
0017
0018 #include <string>
0019 #include <boost/mpl/bool.hpp>
0020 #include <boost/mpl/assert.hpp>
0021 #include <boost/utility/enable_if.hpp>
0022 #include <boost/type_traits/is_same.hpp>
0023 #include <boost/iterator/transform_iterator.hpp>
0024 #include <boost/xpressive/detail/utility/algorithm.hpp>
0025
0026 namespace boost { namespace xpressive { namespace detail
0027 {
0028
0029     ///////////////////////////////////////////////////////////////////////////////
0030     // char_cast
0031     //
0032     template<typename ToChar, typename FromChar, typename Traits>
0033     inline ToChar
0034     char_cast(FromChar from, Traits const &, typename enable_if<is_same<ToChar, FromChar> >::type * = 0)
0035     {
0036         return from;
0037     }
0038
0039     template<typename ToChar, typename FromChar, typename Traits>
0040     inline ToChar
0041     char_cast(FromChar from, Traits const &tr, typename disable_if<is_same<ToChar, FromChar> >::type * = 0)
0042     {
0043         BOOST_MPL_ASSERT((is_same<FromChar, char>));
0044         return tr.widen(from);
0045     }
0046
0047     ///////////////////////////////////////////////////////////////////////////////
0048     // widen_fun
0049     //
0050     template<typename Traits>
0051     struct widen_fun
0052     {
0053         typedef typename Traits::char_type result_type;
0054         explicit widen_fun(Traits const &tr)
0055           : traits_(tr)
0056         {}
0057
0058         result_type operator()(char ch) const
0059         {
0060             return this->traits_.widen(ch);
0061         }
0062
0063         Traits const &traits_;
0064     };
0065
0066     ///////////////////////////////////////////////////////////////////////////////
0067     // string_cast_
0068     //
0069     template<
0070         typename To
0071       , typename From
0072       , typename ToChar = typename detail::range_data<To>::type
0073       , typename FromChar = typename detail::range_data<From>::type
0074     >
0075     struct string_cast_
0076     {
0077         BOOST_MPL_ASSERT((is_same<FromChar, char>));
0078         typedef To const result_type;
0079         template<typename Traits>
0080         result_type operator()(From const &from, Traits const &tr) const
0081         {
0082             widen_fun<Traits> widen(tr);
0083             To to(
0084                 boost::make_transform_iterator(detail::data_begin(from), widen)
0085               , boost::make_transform_iterator(detail::data_end(from), widen)
0086             );
0087             return to;
0088         }
0089     };
0090
0091     template<typename To, typename From, typename Char>
0092     struct string_cast_<To, From, Char, Char>
0093     {
0094         typedef To const result_type;
0095         template<typename Traits>
0096         result_type operator()(From const &from, Traits const &) const
0097         {
0098             To to(detail::data_begin(from), detail::data_end(from));
0099             return to;
0100         }
0101     };
0102
0103     template<typename From, typename Char>
0104     struct string_cast_<From, From, Char, Char>
0105     {
0106         typedef From const &result_type;
0107         template<typename Traits>
0108         result_type operator()(From const &from, Traits const &) const
0109         {
0110             return from;
0111         }
0112     };
0113
0114     ///////////////////////////////////////////////////////////////////////////////
0115     // string_cast
0116     //
0117     template<typename To, typename From, typename Traits>
0118     typename string_cast_<To, From>::result_type
0119     string_cast(From const &from, Traits const &tr)
0120     {
0121         return string_cast_<To, From>()(from, tr);
0122     }
0123
0124     ///////////////////////////////////////////////////////////////////////////////
0125     // translate
0126     //
0127     template<typename Char, typename Traits>
0128     inline Char translate(Char ch, Traits const &tr, mpl::false_) // case-sensitive
0129     {
0130         return tr.translate(ch);
0131     }
0132
0133     template<typename Char, typename Traits>
0134     inline Char translate(Char ch, Traits const &tr, mpl::true_) // case-insensitive
0135     {
0136         return tr.translate_nocase(ch);
0137     }
0138
0139 }}} // namespace boost::xpressive::detail
0140
0141 #if defined(_MSC_VER)
0142 # pragma warning(pop)
0143 #endif
0144
0145 #endif