boost/lexical_cast/try_lexical_convert.hpp
// Copyright Kevlin Henney, 2000-2005. // Copyright Alexander Nasonov, 2006-2010. // Copyright Antony Polukhin, 2011-2014. // // 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) // // what: lexical_cast custom keyword cast // who: contributed by Kevlin Henney, // enhanced with contributions from Terje Slettebo, // with additional fixes and suggestions from Gennaro Prota, // Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov, // Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann, // Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters // when: November 2000, March 2003, June 2005, June 2006, March 2011 - 2014 #ifndef BOOST_LEXICAL_CAST_TRY_LEXICAL_CONVERT_HPP #define BOOST_LEXICAL_CAST_TRY_LEXICAL_CONVERT_HPP #include <boost/config.hpp> #ifdef BOOST_HAS_PRAGMA_ONCE # pragma once #endif #include <string> #include <boost/mpl/if.hpp> #include <boost/type_traits/ice.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/type_traits/is_arithmetic.hpp> #include <boost/lexical_cast/detail/is_character.hpp> #include <boost/lexical_cast/detail/converter_numeric.hpp> #include <boost/lexical_cast/detail/converter_lexical.hpp> #include <boost/range/iterator_range_core.hpp> #include <boost/container/container_fwd.hpp> namespace boost { namespace detail { template<typename T> struct is_stdstring : boost::false_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_stdstring< std::basic_string<CharT, Traits, Alloc> > : boost::true_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_stdstring< boost::container::basic_string<CharT, Traits, Alloc> > : boost::true_type {}; template<typename Target, typename Source> struct is_arithmetic_and_not_xchars { BOOST_STATIC_CONSTANT(bool, value = ( boost::type_traits::ice_and< boost::type_traits::ice_not< boost::detail::is_character<Target>::value >::value, boost::type_traits::ice_not< boost::detail::is_character<Source>::value >::value, boost::is_arithmetic<Source>::value, boost::is_arithmetic<Target>::value >::value )); }; /* * is_xchar_to_xchar<Target, Source>::value is true, * Target and Souce are char types of the same size 1 (char, signed char, unsigned char). */ template<typename Target, typename Source> struct is_xchar_to_xchar { BOOST_STATIC_CONSTANT(bool, value = ( boost::type_traits::ice_and< boost::type_traits::ice_eq<sizeof(Source), sizeof(Target)>::value, boost::type_traits::ice_eq<sizeof(Source), sizeof(char)>::value, boost::detail::is_character<Target>::value, boost::detail::is_character<Source>::value >::value )); }; template<typename Target, typename Source> struct is_char_array_to_stdstring : boost::false_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_char_array_to_stdstring< std::basic_string<CharT, Traits, Alloc>, CharT* > : boost::true_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_char_array_to_stdstring< std::basic_string<CharT, Traits, Alloc>, const CharT* > : boost::true_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_char_array_to_stdstring< boost::container::basic_string<CharT, Traits, Alloc>, CharT* > : boost::true_type {}; template<typename CharT, typename Traits, typename Alloc> struct is_char_array_to_stdstring< boost::container::basic_string<CharT, Traits, Alloc>, const CharT* > : boost::true_type {}; template <typename Target, typename Source> struct copy_converter_impl { // MSVC fail to forward an array (DevDiv#555157 "SILENT BAD CODEGEN triggered by perfect forwarding", // fixed in 2013 RTM). #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined(BOOST_MSVC) || BOOST_MSVC >= 1800) template <class T> static inline bool try_convert(T&& arg, Target& result) { result = static_cast<T&&>(arg); // eqaul to `result = std::forward<T>(arg);` return true; } #else static inline bool try_convert(const Source& arg, Target& result) { result = arg; return true; } #endif }; } namespace conversion { namespace detail { template <typename Target, typename Source> inline bool try_lexical_convert(const Source& arg, Target& result) { typedef BOOST_DEDUCED_TYPENAME boost::detail::array_to_pointer_decay<Source>::type src; typedef BOOST_DEDUCED_TYPENAME boost::type_traits::ice_or< boost::detail::is_xchar_to_xchar<Target, src >::value, boost::detail::is_char_array_to_stdstring<Target, src >::value, boost::type_traits::ice_and< boost::is_same<Target, src >::value, boost::detail::is_stdstring<Target >::value >::value, boost::type_traits::ice_and< boost::is_same<Target, src >::value, boost::detail::is_character<Target >::value >::value > shall_we_copy_t; typedef boost::detail::is_arithmetic_and_not_xchars<Target, src > shall_we_copy_with_dynamic_check_t; // We do evaluate second `if_` lazily to avoid unnecessary instantiations // of `shall_we_copy_with_dynamic_check_t` and improve compilation times. typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c< shall_we_copy_t::value, boost::mpl::identity<boost::detail::copy_converter_impl<Target, src > >, boost::mpl::if_< shall_we_copy_with_dynamic_check_t, boost::detail::dynamic_num_converter_impl<Target, src >, boost::detail::lexical_converter_impl<Target, src > > >::type caster_type_lazy; typedef BOOST_DEDUCED_TYPENAME caster_type_lazy::type caster_type; return caster_type::try_convert(arg, result); } template <typename Target, typename CharacterT> inline bool try_lexical_convert(const CharacterT* chars, std::size_t count, Target& result) { BOOST_STATIC_ASSERT_MSG( boost::detail::is_character<CharacterT>::value, "This overload of try_lexical_convert is meant to be used only with arrays of characters." ); return ::boost::conversion::detail::try_lexical_convert( ::boost::iterator_range<const CharacterT*>(chars, chars + count), result ); } }} // namespace conversion::detail namespace conversion { // ADL barrier using ::boost::conversion::detail::try_lexical_convert; } } // namespace boost #endif // BOOST_LEXICAL_CAST_TRY_LEXICAL_CONVERT_HPP