boost/convert/spirit.hpp

0001 // Copyright (c) 2009-2020 Vladimir Batov.
0002 // Use, modification and distribution are subject to the Boost Software License,
0003 // Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
0004
0005 #ifndef BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
0006 #define BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
0007
0008 #include <boost/convert/base.hpp>
0009 #include <boost/convert/detail/config.hpp>
0010 #include <boost/spirit/include/qi.hpp>
0011 #include <boost/spirit/include/karma.hpp>
0012
0013 namespace boost { namespace cnv { struct spirit; }}
0014
0015 struct boost::cnv::spirit : boost::cnv::cnvbase<boost::cnv::spirit>
0016 {
0017     using this_type = boost::cnv::spirit;
0018     using base_type = boost::cnv::cnvbase<this_type>;
0019
0020     using base_type::operator();
0021
0022     template<typename string_type, typename out_type>
0023     void
0024     str_to(cnv::range<string_type> range, optional<out_type>& result_out) const
0025     {
0026         using parser = typename boost::spirit::traits::create_parser<out_type>::type;
0027
0028         auto    beg = range.begin();
0029         auto    end = range.end();
0030         auto result = out_type();
0031
0032         if (boost::spirit::qi::parse(beg, end, parser(), result))
0033             if (beg == end) // ensure the whole string has been parsed
0034                 result_out = result;
0035     }
0036     template<typename in_type, typename char_type>
0037     cnv::range<char_type*>
0038     to_str(in_type value_in, char_type* beg) const
0039     {
0040         using generator = typename boost::spirit::traits::create_generator<in_type>::type;
0041
0042         auto  end = beg;
0043         bool good = boost::spirit::karma::generate(end, generator(), value_in);
0044
0045         return cnv::range<char_type*>(beg, good ? end : beg);
0046     }
0047 };
0048
0049 #endif // BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
0050