学习Boost.Spirit:解析INI [英] Learning Boost.Spirit: parsing INI
问题描述
I started to learn Boost.Spirit and finish reading Qi - Writing Parsers section. When reading, everything is easy and understandable. But when I try to do something, there are a lot of errors, because there are too many includes and namespaces and I need to know when to include/use them. As the practice, I want to write simple INI parser.
这是代码(包括来自Spirit lib内部示例之一)的所有代码:
Here is the code (includes are from one of examples inside Spirit lib as almost everything else):
#include <boost/config/warning_disable.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/fusion/adapted/std_pair.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/spirit/include/phoenix_object.hpp>
#include <iostream>
#include <string>
#include <vector>
#include <map>
namespace client
{
typedef std::map<std::string, std::string> key_value_map_t;
struct mini_ini
{
std::string name;
key_value_map_t key_values_map;
};
} // client
BOOST_FUSION_ADAPT_STRUCT(
client::mini_ini,
(std::string, name)
(client::key_value_map_t, key_values_map)
)
namespace client
{
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;
template <typename Iterator>
struct ini_grammar : qi::grammar<Iterator, mini_ini(), ascii::space_type>
{
ini_grammar() : ini_grammar::base_type(section_, "section")
{
using qi::char_;
using qi::on_error;
using qi::fail;
using namespace qi::labels;
using phoenix::construct;
using phoenix::val;
key_ = +char_("a-zA-Z_0-9");
pair_ = key_ >> '=' >> *char_;
section_ = '[' >> key_ >> ']' >> '\n' >> *(pair_ >> '\n');
key_.name("key");
pair_.name("pair");
section_.name("section");
on_error<fail>
(
section_
, std::cout
<< val("Error! Expecting ")
<< _4 // what failed?
<< val(" here: \"")
<< construct<std::string>(_3, _2) // iterators to error-pos, end
<< val("\"")
<< std::endl
);
}
qi::rule<Iterator, std::string(), ascii::space_type> key_;
qi::rule<Iterator, mini_ini(), ascii::space_type> section_;
qi::rule<Iterator, std::pair<std::string, std::string>(), ascii::space_type> pair_;
};
} // client
int
main()
{
std::string storage =
"[section]\n"
"key1=val1\n"
"key2=val2\n";
client::mini_ini ini;
typedef client::ini_grammar<std::string::const_iterator> ini_grammar;
ini_grammar grammar;
using boost::spirit::ascii::space;
std::string::const_iterator iter = storage.begin();
std::string::const_iterator end = storage.end();
bool r = phrase_parse(iter, end, grammar, space, ini);
if (r && iter == end)
{
std::cout << "-------------------------\n";
std::cout << "Parsing succeeded\n";
std::cout << "-------------------------\n";
return 0;
}
else
{
std::cout << "-------------------------\n";
std::cout << "Parsing failed\n";
std::cout << "-------------------------\n";
std::cout << std::string(iter, end) << "\n";
return 1;
}
return 0;
}
如您所见,我想将下一个文本解析为mini_ini
结构:
As u can see I want to parse next text into mini_ini
struct:
"[section]"
"key1=val1"
"key2=val2";
我失败了,并且std::string(iter, end)
是完整的输入字符串.
I have the fail and std::string(iter, end)
is full input string.
我的问题:
- 为什么我看到失败但看不到
on_error<fail>
处理程序? - 您是否对如何学习Boost.Spirit有任何建议(我对理论上的文档有很好的了解,但实际上我有很多为什么?)?
- Why I see fail but don't see
on_error<fail>
handler ? - Have you any recommendations how to learn Boost.Spirit (I have good understanding of documentation in theory, but in practice I have a lot of WHY ???) ?
谢谢
推荐答案
问.为什么我看到失败但看不到on_error处理程序
Q. Why I see fail but don't see on_error handler
The on_error handler is only fired for the registered rule (section_) and if an expectation point is failed.
您的语法不包含期望点(仅使用>>
,不使用>
).
Your grammar doesn't contain expectation points (only >>
are used, not >
).
问.您对如何学习Boost.Spirit有什么建议(我对理论上的文档有很好的了解,但实际上我有很多的理由?)?
Q. Have you any recommendations how to learn Boost.Spirit (I have good understanding of documentation in theory, but in practice I have a lot of WHY ???) ?
只需构建所需的解析器即可.从docs和SO答案中复制良好的约定.有很多.如您所见,相当多的示例包含Ini解析器的完整示例,并且错误报告的级别也有所不同.
Just build the parsers you need. Copy good conventions from the docs and SO answers. There are a lot of them. As you have seen, quite a number contain full examples of Ini parsers with varying levels of error reporting too.
执行更详细的状态报告:
Do more detailed status reporting:
bool ok = phrase_parse(iter, end, grammar, space, ini);
if (ok) {
std::cout << "Parse success\n";
} else {
std::cout << "Parse failure\n";
}
if (iter != end) {
std::cout << "Remaining unparsed: '" << std::string(iter, end) << "'\n";
}
return ok && (iter==end)? 0 : 1;
使用BOOST_SPIRIT_DEBUG:
Use BOOST_SPIRIT_DEBUG:
#define BOOST_SPIRIT_DEBUG
// and later
BOOST_SPIRIT_DEBUG_NODES((key_)(pair_)(section_))
打印:
<section_>
<try>[section]\nkey1=val1\n</try>
<key_>
<try>section]\nkey1=val1\nk</try>
<success>]\nkey1=val1\nkey2=val</success>
<attributes>[[s, e, c, t, i, o, n]]</attributes>
</key_>
<fail/>
</section_>
Parse failure
Remaining unparsed: '[section]
key1=val1
key2=val2
'
您会注意到,由于不匹配换行符,因此未解析节标题.您的船长(space_type
) 跳过 换行符,因此它将永远不匹配:
You'll notice that the section header isn't parsed because the newline is not matched. Your skipper (space_type
) skips the newline, hence it will never match: Boost spirit skipper issues
使用blank_type
做为船长时,您将获得成功的解析:
When using blank_type
as the skipper you'll get a successful parse:
<section_>
<try>[section]\nkey1=val1\n</try>
<key_>
<try>section]\nkey1=val1\nk</try>
<success>]\nkey1=val1\nkey2=val</success>
<attributes>[[s, e, c, t, i, o, n]]</attributes>
</key_>
<pair_>
<try>key1=val1\nkey2=val2\n</try>
<key_>
<try>key1=val1\nkey2=val2\n</try>
<success>=val1\nkey2=val2\n</success>
<attributes>[[k, e, y, 1]]</attributes>
</key_>
<success></success>
<attributes>[[[k, e, y, 1], [v, a, l, 1,
, k, e, y, 2, =, v, a, l, 2,
]]]</attributes>
</pair_>
<success>key1=val1\nkey2=val2\n</success>
<attributes>[[[s, e, c, t, i, o, n], []]]</attributes>
</section_>
Parse success
Remaining unparsed: 'key1=val1
key2=val2
注意:解析成功,但是没有执行您想要的操作.这是因为
*char_
包含换行符.所以做
NOTE: The parse succeeds but doesn't do what you want. This is because
*char_
includes newlines. So make that
pair_ = key_ >> '=' >> *(char_ - qi::eol); // or
pair_ = key_ >> '=' >> *~char_("\r\n"); // etc
完整代码
#define BOOST_SPIRIT_DEBUG
#include <boost/config/warning_disable.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/fusion/adapted/std_pair.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/spirit/include/phoenix_object.hpp>
#include <iostream>
#include <string>
#include <vector>
#include <map>
namespace client
{
typedef std::map<std::string, std::string> key_value_map_t;
struct mini_ini
{
std::string name;
key_value_map_t key_values_map;
};
} // client
BOOST_FUSION_ADAPT_STRUCT(
client::mini_ini,
(std::string, name)
(client::key_value_map_t, key_values_map)
)
namespace client
{
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;
template <typename Iterator>
struct ini_grammar : qi::grammar<Iterator, mini_ini(), ascii::blank_type>
{
ini_grammar() : ini_grammar::base_type(section_, "section")
{
using qi::char_;
using qi::on_error;
using qi::fail;
using namespace qi::labels;
using phoenix::construct;
using phoenix::val;
key_ = +char_("a-zA-Z_0-9");
pair_ = key_ >> '=' >> *char_;
section_ = '[' >> key_ >> ']' >> '\n' >> *(pair_ >> '\n');
BOOST_SPIRIT_DEBUG_NODES((key_)(pair_)(section_))
on_error<fail>
(
section_
, std::cout
<< val("Error! Expecting ")
<< _4 // what failed?
<< val(" here: \"")
<< construct<std::string>(_3, _2) // iterators to error-pos, end
<< val("\"")
<< std::endl
);
}
qi::rule<Iterator, std::string(), ascii::blank_type> key_;
qi::rule<Iterator, mini_ini(), ascii::blank_type> section_;
qi::rule<Iterator, std::pair<std::string, std::string>(), ascii::blank_type> pair_;
};
} // client
int
main()
{
std::string storage =
"[section]\n"
"key1=val1\n"
"key2=val2\n";
client::mini_ini ini;
typedef client::ini_grammar<std::string::const_iterator> ini_grammar;
ini_grammar grammar;
using boost::spirit::ascii::blank;
std::string::const_iterator iter = storage.begin();
std::string::const_iterator end = storage.end();
bool ok = phrase_parse(iter, end, grammar, blank, ini);
if (ok) {
std::cout << "Parse success\n";
} else {
std::cout << "Parse failure\n";
}
if (iter != end) {
std::cout << "Remaining unparsed: '" << std::string(iter, end) << "'\n";
}
return ok && (iter==end)? 0 : 1;
}
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