Added thirdparty: boost library

thirdparty/include/boost/convert/spirit.hpp

@@ -0,0 +1,50 @@
+// Copyright (c) 2009-2020 Vladimir Batov.
+// Use, modification and distribution are subject to the Boost Software License,
+// Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
+
+#ifndef BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
+#define BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
+
+#include <boost/convert/base.hpp>
+#include <boost/convert/detail/config.hpp>
+#include <boost/spirit/include/qi.hpp>
+#include <boost/spirit/include/karma.hpp>
+
+namespace boost { namespace cnv { struct spirit; }}
+
+struct boost::cnv::spirit : boost::cnv::cnvbase<boost::cnv::spirit>
+{
+    using this_type = boost::cnv::spirit;
+    using base_type = boost::cnv::cnvbase<this_type>;
+
+    using base_type::operator();
+
+    template<typename string_type, typename out_type>
+    void
+    str_to(cnv::range<string_type> range, optional<out_type>& result_out) const
+    {
+        using parser = typename boost::spirit::traits::create_parser<out_type>::type;
+
+        auto    beg = range.begin();
+        auto    end = range.end();
+        auto result = out_type();
+
+        if (boost::spirit::qi::parse(beg, end, parser(), result))
+            if (beg == end) // ensure the whole string has been parsed
+                result_out = result;
+    }
+    template<typename in_type, typename char_type>
+    cnv::range<char_type*>
+    to_str(in_type value_in, char_type* beg) const
+    {
+        using generator = typename boost::spirit::traits::create_generator<in_type>::type;
+
+        auto  end = beg;
+        bool good = boost::spirit::karma::generate(end, generator(), value_in);
+
+        return cnv::range<char_type*>(beg, good ? end : beg);
+    }
+};
+
+#endif // BOOST_CONVERT_SPIRIT_BASED_CONVERTER_HPP
+