我有一个像下面这样的字符串：
[GENERAL]
FMax Antenna = 3000
FMin Antenna = 2000
Invalid key = Invalid value
EMin Antenna = -50
EMax Antenna = 80
我想解析它，以便在结构中保存FMin Antenna，FMax Antenna，EMin Antenna，EMax Antenna的值。我已经创建了一个Spirit解析器，但它可以部分工作。
由于该文件可以包含许多key = value行，因此我只需要解析我需要的内容（我必须阅读的键值），忽略其他对。
key和value都可以是包含空格和制表符的字母数字字符串。
我在解析器中定义了我想要读取的键但是当我遇到未知键时，我无法读取其后面的键（在示例中，我无法读取EMin Antenna和{ {1}}因为是在未知密钥之后定义的。）
我已经尝试过以下代码：如果我解析EMax Antenna，它只包含我想要读取的键，它可以工作，但如果我在文件中间添加了未知的file1对，就像在key = value中一样，它停止阅读所有后续行。
如何修复它并在未知的键值对后继续解析文件？
file2输出继电器：
#include <boost/optional/optional_io.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_io.hpp>
#include <boost/fusion/adapted/struct.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
namespace qi = boost::spirit::qi;
const std::string file1 = R"xx(
[GENERAL]
FMax Antenna = 3000
FMin Antenna = 2000
EMin Antenna = -50
EMax Antenna = 80
)xx";
const std::string file2 = R"xx(
[GENERAL]
FMax Antenna = 3000
FMin Antenna = 2000
EMin Antenna = -50
pappa pio = po po
EMax Antenna = 80
Ciao = 55
)xx";
struct Data {
double minFrequency = 0.0;
double maxFrequency = 0.0;
double minElevation = 0.0;
double maxElevation = 0.0;
};
BOOST_FUSION_ADAPT_STRUCT(
Data,
(double, minFrequency)
(double, maxFrequency)
(double, minElevation)
(double, maxElevation)
)
template <typename It, typename Skipper = qi::space_type>
struct grammar : qi::grammar<It, Data(), Skipper> {
grammar() : grammar::base_type(start) {
auto minFrequency = bind(&Data::minFrequency, qi::_val);
auto maxFrequency = bind(&Data::maxFrequency, qi::_val);
auto minElevation = bind(&Data::minElevation, qi::_val);
auto maxElevation = bind(&Data::maxElevation, qi::_val);
start = qi::no_case["[GENERAL]"] >> *(
("FMin Antenna" >> qi::lit('=') >> qi::int_)[minFrequency = qi::_1] |
("FMax Antenna" >> qi::lit('=') >> qi::int_)[maxFrequency = qi::_1] |
("EMin Antenna" >> qi::lit('=') >> qi::int_)[minElevation = qi::_1] |
("EMax Antenna" >> qi::lit('=') >> qi::int_)[maxElevation = qi::_1] |
(+(qi::alnum | qi::blank) >> qi::lit('=') >> +(qi::alnum | qi::blank)) // Issue here?
);
}
private:
qi::rule<It, Data(), Skipper> start;
};
int main() {
using It = std::string::const_iterator;
Data parsed1, parsed2;
bool ok = qi::phrase_parse(file1.begin(), file1.end(), grammar<It>(), qi::space, parsed1);
std::cout << "--- File 1 ---" << std::endl;
std::cout << "parsed = " << std::boolalpha << ok << std::endl;
std::cout << "min freq = " << parsed1.minFrequency << std::endl;
std::cout << "max freq = " << parsed1.maxFrequency << std::endl;
std::cout << "min elev = " << parsed1.minElevation << std::endl;
std::cout << "max elev = " << parsed1.maxElevation << std::endl;
std::cout << "--- File 2 ---" << std::endl;
ok = qi::phrase_parse(file2.begin(), file2.end(), grammar<It>(), qi::space, parsed2);
std::cout << "parsed = " << std::boolalpha << ok << std::endl;
std::cout << "min freq = " << parsed2.minFrequency << std::endl;
std::cout << "max freq = " << parsed2.maxFrequency << std::endl;
std::cout << "min elev = " << parsed2.minElevation << std::endl;
std::cout << "max elev = " << parsed2.maxElevation << std::endl;
return 0;
}
答案 0 :(得分：3)
你对船长感到困惑。
+(alnum|blank)，这是永远无法工作的，因为船长会吃掉与blank相匹配的所有内容（有关背景，请参阅Boost spirit skipper issues）
其他说明：
我做得非常明确：
known =
("FMin Antenna" >> lit('=') >> int_)[minFrequency = _1] |
("FMax Antenna" >> lit('=') >> int_)[maxFrequency = _1] |
("EMin Antenna" >> lit('=') >> int_)[minElevation = _1] |
("EMax Antenna" >> lit('=') >> int_)[maxElevation = _1]
;
unknown = +alnum >> '=' >> +alnum;
setting = (known(_r1) | unknown) >> +eol;
start =
no_case["[GENERAL]"] >> eol
>> *setting(_val);
在规则中拆分有点棘手，因为*setting会尝试合成容器属性，从而无法传播到实际的Data属性。
我通过在继承属性中通过引用传递属性来解决它，该属性禁用自动属性传播。
或者，您可以添加任何类型的语义操作来禁止自动属性传播
<强> Live On Coliru
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iomanip>
namespace qi = boost::spirit::qi;
struct Data {
double minFrequency = 0.0;
double maxFrequency = 0.0;
double minElevation = 0.0;
double maxElevation = 0.0;
};
template <typename It, typename Skipper = qi::blank_type>
struct grammar : qi::grammar<It, Data(), Skipper> {
grammar() : grammar::base_type(start) {
using namespace qi;
auto minFrequency = bind(&Data::minFrequency, _r1);
auto maxFrequency = bind(&Data::maxFrequency, _r1);
auto minElevation = bind(&Data::minElevation, _r1);
auto maxElevation = bind(&Data::maxElevation, _r1);
known =
("FMin Antenna" >> lit('=') >> int_)[minFrequency = _1] |
("FMax Antenna" >> lit('=') >> int_)[maxFrequency = _1] |
("EMin Antenna" >> lit('=') >> int_)[minElevation = _1] |
("EMax Antenna" >> lit('=') >> int_)[maxElevation = _1]
;
unknown = +alnum >> '=' >> +alnum;
setting = (known(_r1) | unknown) >> +eol;
start =
no_case["[GENERAL]"] >> eol
>> *setting(_val);
}
private:
qi::rule<It, Data(), Skipper> start;
qi::rule<It, void(Data&), Skipper> setting, known;
qi::rule<It, Skipper> unknown;
};
int main() {
using It = std::string::const_iterator;
grammar<It> const g;
for (std::string const file : {
"[GENERAL]\nFMax Antenna = 3000\nFMin Antenna = 2000\nEMin Antenna = -50\nEMax Antenna = 80\n",
"[GENERAL]\nFMax Antenna = 3000\nFMin Antenna = 2000\nEMin Antenna = -50\npappa pio = po po\nEMax Antenna = 80\nCiao = 55\n",
})
{
Data parsed;
It f = begin(file), l = end(file);
bool ok = qi::phrase_parse(f, l, g, qi::blank, parsed);
std::cout << "--- File ---" << "\n";
std::cout << "parsed = " << std::boolalpha << ok << "\n";
if (ok) {
std::cout << "min freq = " << parsed.minFrequency << "\n";
std::cout << "max freq = " << parsed.maxFrequency << "\n";
std::cout << "min elev = " << parsed.minElevation << "\n";
std::cout << "max elev = " << parsed.maxElevation << "\n";
}
if (f!=l) {
std::cout << "Remaining unparsed: ";
while (f!=l) {
char c = *f++;
if (isprint(c)) std::cout << c;
else std::cout << "\\x" << std::setw(2) << std::setfill('0') << std::hex << static_cast<int>(c);
}
}
}
}
打印
--- File ---
parsed = true
min freq = 2000
max freq = 3000
min elev = -50
max elev = 80
--- File ---
parsed = true
min freq = 2000
max freq = 3000
min elev = -50
max elev = 80