boot 词汇分析器

比眉伴天荒 2022-06-05 09:21 68阅读 0赞

这是一个简单的json语法分析器,也可以定义自己的分析器,先学习了

#include <boost/spirit.hpp> 
    #include <string> 
    #include <fstream> 
    #include <sstream> 
    #include <iostream> 
    
    struct json_grammar 
      : public boost::spirit::grammar<json_grammar> 
    { 
      struct print 
      { 
        void operator()(const char *begin, const char *end) const 
        { 
          std::cout << std::string(begin, end) << std::endl; 
        } 
      }; 
    
      template <typename Scanner> 
      struct definition 
      { 
        boost::spirit::rule<Scanner> object, member, string, value, number, array; 
    
        definition(const json_grammar &self) 
        { 
          using namespace boost::spirit; 
          object = "{" >> member >> *("," >> member) >> "}"; 
          member = string[print()] >> ":" >> value; 
          string = "\"" >> *~ch_p("\"") >> "\""; 
          value = string | number | object | array | "true" | "false" | "null"; 
          number = real_p; 
          array = "[" >> value >> *("," >> value) >> "]"; 
        } 
    
        const boost::spirit::rule<Scanner> &start() 
        { 
          return object; 
        } 
      }; 
    }; 
    
    int main(int argc, char *argv[]) 
    { 
      std::ifstream fs(argv[1]); 
      std::ostringstream ss; 
      ss << fs.rdbuf(); 
      std::string data = ss.str(); 
    
      json_grammar g; 
      boost::spirit::parse_info<> pi = boost::spirit::parse(data.c_str(), g, boost::spirit::space_p); 
      if (pi.hit) 
      { 
        if (pi.full) 
          std::cout << "parsing all data successfully" << std::endl; 
        else 
          std::cout << "parsing data partially" << std::endl; 
        std::cout << pi.length << " characters parsed" << std::endl; 
      } 
      else 
        std::cout << "parsing failed; stopped at '" << pi.stop << "'" << std::endl; 
    }