Boost.Spirit - 如何使用repeat解析成结构？

Question

我正在尝试编写一个小程序来使用 Boost.Spirit 解析来自 /proc/stat 的 cpu 使用信息。它主要工作，但我无法在使用 repeat 时编译我的语法。我错过了什么？

全部代码：

#include <vector>

#include "boost/fusion/include/adapt_struct.hpp"
#define BOOST_SPIRIT_DEBUG
#include "boost/spirit/include/qi.hpp"
#include "boost/iostreams/device/mapped_file.hpp"

namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;

struct Cpu
{
   unsigned int user;
   unsigned int nice;
   unsigned int system;
   unsigned int idle;
   unsigned int iowait;
   unsigned int irq;
   unsigned int softirq;
   unsigned int steal;
   unsigned int guest;
   unsigned int guest_nice;
};

BOOST_FUSION_ADAPT_STRUCT(
   Cpu,
   (unsigned int, user)
   (unsigned int, nice)
   (unsigned int, system)
   (unsigned int, idle)
   (unsigned int, iowait)
   (unsigned int, irq)
   (unsigned int, softirq)
   (unsigned int, steal)
   (unsigned int, guest)
   (unsigned int, guest_nice)
)

template< typename Iter, typename Skip = ascii::blank_type >
struct Cpu_parser : qi::grammar< Iter, Cpu(), Skip >
{
   qi::rule< Iter, Cpu(), Skip > start;

   Cpu_parser() : Cpu_parser::base_type(start)
   {
      using namespace qi;

      start = lexeme[lit("cpu") >> omit[-uint_]] >> repeat(10)[uint_];
      //start = lexeme[lit("cpu") >> omit[-uint_]] >> uint_ >> uint_ >> uint_ >> uint_ >> uint_ >> uint_ >> uint_ >> uint_ >> uint_ >> uint_;

      BOOST_SPIRIT_DEBUG_NODE(start);
   }
};

int main(int argc, char** argv)
{
   std::vector< Cpu > cpus;

   {
      std::ifstream ifs("/proc/stat");
      ifs >> std::noskipws;

      Cpu_parser< boost::spirit::istream_iterator > cpu_parser;

      std::cout << phrase_parse(
         boost::spirit::istream_iterator(ifs),
         boost::spirit::istream_iterator(),
         cpu_parser % qi::eol,
         ascii::blank,
         cpus) << std::endl;
   }

   return 0;
}

所有个人 uint_s 的注释行工作正常，但我想知道我在重复时做错了什么。

如果我用无符号整数向量替换 Cpu 结构，我也可以重复工作。

Answer 1

你不能。容易地。那是因为repeat()[]合成了一个容器属性。你的结构是一个融合序列，而不是一个容器。

你/可以/通过

伪造它

不使用FUSION_ADAPT_STRUCT
定义自定义点（例如 is_container<Cpu>。这里有一个描述如何在文档中执行操作的示例：http://www.boost.org/doc/libs/1_60_0/libs/spirit/doc/html/spirit/advanced/customize/iterate/container_iterator.html#spirit.advanced.customize.iterate.container_iterator.example。还有一个答案描述了如何使其与std::array)

不过，有个好消息：

“好消息”

对于融合序列，qi::auto_ 解析器知道该怎么做！

这去除了 80% 的脂肪：

Live On Coliru

#include "boost/fusion/include/adapt_struct.hpp"
#include "boost/spirit/include/qi.hpp"
#include <fstream>

struct Cpu {
   unsigned user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice;
};

BOOST_FUSION_ADAPT_STRUCT(Cpu, user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice)

int main() {

    std::vector<Cpu> cpus;
    bool ok = [&cpus] {
        using It = boost::spirit::istream_iterator;
        using namespace boost::spirit::qi;

        std::ifstream ifs("/proc/stat");

        return parse(
                It(ifs >> std::noskipws), {},
                ("cpu" >> -omit[uint_] >> skip(blank)[auto_]) % eol,
                cpus);
    }();

    std::cout << std::boolalpha << ok << std::endl;
}

NOTE

The output is true. Just not on Coliru (/proc/cpu is not accessible there).

The lambda trick is there to make the using namespace scoped, while being able to return the value for ok.

Boost.Spirit - 如何使用repeat解析成结构？

Boost.Spirit - How to use repeat to parse into a struct?

c++

parsing

boost

boost-spirit-qi

全部代码：

“好消息”