【发布时间】：2015-02-04 06:20:23
【问题描述】：
我想解析一个类似 c-struct 的声明，它有一些标量或数组作为成员。然后可以为 HDF5 序列化生成具有此 c-struct 定义的 C++ 头文件。但是我在尝试同时使用 boost::spirit 处理标量和数组时发现了一些困难。
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <boost/foreach.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_stl.hpp>
#include <boost/spirit/include/phoenix_fusion.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;
namespace fusion = boost::fusion;
struct struct_field
{
std::string type;
std::string name;
int dim;
};
struct struct_body
{
std::string name;
std::vector<struct_field> fields;
};
BOOST_FUSION_ADAPT_STRUCT(
struct_field,
(std::string, type)
(std::string, name)
(int, dim)
)
BOOST_FUSION_ADAPT_STRUCT(
struct_body,
(std::string, name)
(std::vector<struct_field>, fields)
)
template <typename Iterator, typename Skipper>
struct preprocessor :
qi::grammar<Iterator, struct_body(), Skipper>
{
preprocessor() :
preprocessor::base_type(body)
{
using namespace qi::labels;
using qi::eol;
using qi::lit;
using qi::lexeme;
using qi::int_;
using ascii::char_;
using phoenix::at_c;
using phoenix::push_back;
vartype =
*lit(' ') >> lexeme[+(char_ - ' ') [_val += _1]];
varname =
(*lit(' ') >> lexeme[+(char_ - '[') [_val += _1]]) |
(*lit(' ') >> lexeme[+(char_ - ';') [_val += _1]] >> ';');
vardim = '[' >> int_ [_val += _1] >> "];";
strucname =
"declare(" >>
lexeme[+(char_ - ')')[_val += _1]] >>
')' >>
eol;
field =
vartype [at_c<0>(_val) = _1] >>
varname [at_c<1>(_val) = _1] >>
-vardim [at_c<2>(_val) = _1] >>
eol;
body =
strucname [at_c<0>(_val) = _1] >>
'(' >> eol >>
*(field [push_back(at_c<1>(_val), _1)]) >>
')' >> -eol;
}
qi::rule<Iterator, struct_body(), Skipper> body;
qi::rule<Iterator, struct_field(), Skipper> field;
qi::rule<Iterator, std::string(), Skipper> strucname;
qi::rule<Iterator, std::string(), Skipper> vartype, varname;
qi::rule<Iterator, int(), Skipper> vardim;
};
template<typename Iterator, typename Skipper>
bool parse(Iterator &first, Iterator end, Skipper const &skipper, struct_body &mystruct)
{
preprocessor<Iterator, Skipper> g;
return qi::phrase_parse(first, end, g, skipper, mystruct);
}
int main(int argc, char **argv)
{
std::string storage = "declare(grid_point)\r\n(\r\n int id[1];\r\n int cp[1];\r\n double pos[3];\r\n)";
std::string::const_iterator iter = storage.begin();
std::string::const_iterator end = storage.end();
struct_body mystruct;
bool result = parse(iter, end, qi::blank, mystruct);
if (result && iter == end)
{
std::cout << mystruct.fields.size() << " fields are parsed." << std::endl;
BOOST_FOREACH(struct_field const& field, mystruct.fields)
{
std::cout << field.type << " : " << field.name << " [ " << field.dim << " ] ;" << std::endl;
}
}
}
正如我们所见，所有成员都被声明为数组。否则，无法正确解析标量。
declare(grid_point)
(
int id;
int cp;
double pos[3];
)
上述声明无法解析。似乎 boost::spirit 总是在 [dim] 上执行积极的匹配。实际上 [dim] 只需要数组而不是标量。那么如何解决这个问题呢？
【问题讨论】：
-
为什么是近距离投票？这个问题对 SO 来说是完全没有意义的。更重要的是，它问得很好。很好，有一个目标描述，一个问题描述和一个完整的SSCCE。
标签： c++ boost boost-spirit boost-spirit-qi