Re: X3: Using dynamic Repetition Parser Directives

On 01-02-16 08:50, Seth wrote:
>
> That said, I think you're far better off writing a custom parser here.

Just for fun, added that too:

http://coliru.stacked-crooked.com/a/87053f2f3f00862d

    #include <iostream>
    #include <boost/spirit/home/x3.hpp>
    #include <boost/fusion/adapted/std_tuple.hpp>
    #include <boost/spirit/home/x3/binary.hpp>

    namespace x3 = boost::spirit::x3;

    namespace hessian {

        typedef std::string string_t;

        namespace parser {

            struct bstring : x3::parser<bstring> {
                using attribute_type = hessian::string_t;

                // string ::= s b1 b0 <utf8-data> string
                //       ::= S b1 b0 <utf8-data>
                //       ::= [x00-x1f] <utf8-data>
                // NOTE: The length means number of UTF16 characters but
    the content is given in UTF8 characters!
                template <typename It, typename Ctx, typename Attr>
                    bool parse(It& f, It const& l, Ctx&,
    x3::unused_type, Attr& attr) const {
                        auto saved = f;
                        char type;
                        size_t len;
                        auto tied = std::tie(type, len);

                        while (x3::parse(f,l,x3::char_("sS") >>
    x3::big_word,tied)) {
                            if
    (!x3::parse(f,l,x3::repeat(len)[x3::char_],attr))
                                break;
                            if (type == 'S')
                                return true;
                        }

                        f = saved;
                        return false;
                    }
            };

        }
    }

    #include <iomanip>

    std::string as_hex(std::string const& what) {
        std::ostringstream oss;
        oss << std::hex << std::setfill('0');
        for (uint8_t ch : what) {
            if (std::isprint(ch)) oss << ch;
            else                  oss << "\\x" << std::setw(2) << int{ch};
        }

        return oss.str();
    }

    void test_string() {
        const std::string text("s\x00\x07hello, S\x00\x05world", 18);
        try {
            hessian::string_t attr;
            auto f = text.begin(), l = text.end();
            bool ok = x3::parse(f, l, x3::eps >
    hessian::parser::bstring{}, attr);

            if (ok)
                std::cout << "Parsed: '" << as_hex(attr) << "'\n";
            else
                std::cout << "Failed\n";

            if(f!=l)
                std::cout << "Remaining: '" << as_hex({f,l}) << "'\n";

        } catch (const
    x3::expectation_failure<std::string::const_iterator> &exception) {
            std::cout << exception.what() << " " << exception.which() <<
    " " << std::string(exception.where(), text.end())
                      << std::endl;
        }
    }

    int main()
    {
        test_string();
    }

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