Spirit Qi : rule for char [5]

问题

I have the following structure

struct MyStruct 
{
    char CODE;
    char NAME[5];
};

I make it a fusion struct

BOOST_FUSION_ADAPT_STRUCT
(
MyStruct,
(char, MARKET_CODE)
(char, NAME[5])
)

My grammar is implemented as follow:

MyStruct_parser() : ticker_parser::base_type(start)
    {
        using qi::lexeme;
        using ascii::char_;

        a_word %= lexeme[+(char_)];
        start %=  a_word >> a_word;
    }
    qi::rule<Iterator, std::string(), ascii::space_type> quoted_string;
    qi::rule<Iterator, Ticker(), ascii::space_type> start;

Unfortunately it does not compile. Now I use std::string instead of char[5] I have no problem. Can you please tell me how to tell Spirit to read char[5]?

Thank you

回答1:

You can supply custom attribute transformations using boost::spirit::traits::transform_attribute<>:

See it Live On Coliru or indeed Live for C++03

#include <boost/spirit/include/qi.hpp>
#include <boost/array.hpp>

namespace qi = boost::spirit::qi;

typedef char name_t[5];
// typedef boost::array<char, 5> name_t;

struct MyStruct {
    char   code;
    name_t name;
};

namespace boost { namespace spirit { namespace traits {

    template <>
        struct transform_attribute<name_t, std::vector<char>, qi::domain> {
            typedef std::vector<char> type;

            static type pre(name_t&) { return {}; }

            static void post(name_t& val, type const& attr) {
                static_assert(sizeof(val)==5, "");
                assert(attr.size() == sizeof(val));

                using boost::begin;
                using boost::end;
                std::copy(attr.begin(), attr.end(), begin(val));
            }
            static void fail(name_t&) { }
        };

} } }

int main()
{
    std::string const input("123456");

    using It = std::string::const_iterator;
    It f(input.begin()), l(input.end());

    MyStruct data;
    qi::rule<It, std::vector<char>()> c5 = qi::repeat(5) [ qi::char_ ];
    bool ok = qi::parse(f,l, qi::char_ >> c5, data.code, data.name);

    if (ok)
    {
        std::cout << "Parse success: " << data.code << ", '" << std::string(std::begin(data.name), std::end(data.name)) << "'\n";
    } else
    {
        std::cout << "Parse failed\n";
    }

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

Prints

Parse success: 1, '23456'

in both the c++11 and c++03 versions

来源：https://stackoverflow.com/questions/24493589/spirit-qi-rule-for-char-5