tokenizing string , accepting everything between given set of characters in CPP - c++

Question

I have the following code:
int main()
{
string s = "server ('m1.labs.teradata.com') username ('use\\')r_*5') password('u\" er 5') dbname ('default')";
regex re("(\'[!-~]+\')");
sregex_token_iterator i(s.begin(), s.end(), re, 1);
sregex_token_iterator j;
unsigned count = 0;
while(i != j)
{
cout << "the token is "<<*i<< endl;
count++;
}
cout << "There were " << count << " tokens found." << endl;
return 0;
}
Using the above regex, I wanted to extract the string between the paranthesis and single quote:, The out put should look like :
the token is 'm1.labs.teradata.com'
the token is 'use\')r_*5'
the token is 'u" er 5'
the token is 'default'
There were 4 tokens found.
Basically, the regex supposed to extract everything between " (' " and " ') ". It can be anything space , special character, quote or a closing parathesis.
I has earlier used the following regex:
boost::regex re_arg_values("(\'[!-~]+\')");
But is was not accepting space. Please can someone help me out with this. Thanks in advance.

Answer 1

Here's a sample of using Spirit X3 to create grammar to actually parse this. I'd like to parse into a map of (key->value) pairs, which makes a lot more sense than just blindly assuming the names are always the same:
using Config = std::map<std::string, std::string>;
using Entry = std::pair<std::string, std::string>;
Now, we setup some grammar rules using X3:
namespace parser {
using namespace boost::spirit::x3;
auto value = quoted("'") | quoted('"');
auto key = lexeme[+alpha];
auto pair = key >> '(' >> value >> ')';
auto config = skip(space) [ *as<Entry>(pair) ];
}
The helpers as<> and quoted are simple lambdas:
template <typename T> auto as = [](auto p) { return rule<struct _, T> {} = p; };
auto quoted = [](auto q) { return lexeme[q >> *('\\' >> char_ | char_ - q) >> q]; };
Now we can parse the string into a map directly:
Config parse_config(std::string const& cfg) {
Config parsed;
auto f = cfg.begin(), l = cfg.end();
if (!parse(f, l, parser::config, parsed))
throw std::invalid_argument("Parse failed at " + std::string(f,l));
return parsed;
}
And the demo program
int main() {
Config cfg = parse_config("server ('m1.labs.teradata.com') username ('use\\')r_*5') password('u\" er 5') dbname ('default')");
for (auto& setting : cfg)
std::cout << "Key " << setting.first << " has value " << setting.second << "\n";
}
Prints
Key dbname has value default
Key password has value u" er 5
Key server has value m1.labs.teradata.com
Key username has value use')r_*5
LIVE DEMO
Live On Coliru
#include <iostream>
#include <boost/spirit/home/x3.hpp>
#include <boost/fusion/adapted/std_pair.hpp>
#include <map>
using Config = std::map<std::string, std::string>;
using Entry = std::pair<std::string, std::string>;
namespace parser {
using namespace boost::spirit::x3;
template <typename T> auto as = [](auto p) { return rule<struct _, T> {} = p; };
auto quoted = [](auto q) { return lexeme[q >> *(('\\' >> char_) | (char_ - q)) >> q]; };
auto value = quoted("'") | quoted('"');
auto key = lexeme[+alpha];
auto pair = key >> '(' >> value >> ')';
auto config = skip(space) [ *as<Entry>(pair) ];
}
Config parse_config(std::string const& cfg) {
Config parsed;
auto f = cfg.begin(), l = cfg.end();
if (!parse(f, l, parser::config, parsed))
throw std::invalid_argument("Parse failed at " + std::string(f,l));
return parsed;
}
int main() {
Config cfg = parse_config("server ('m1.labs.teradata.com') username ('use\\')r_*5') password('u\" er 5') dbname ('default')");
for (auto& setting : cfg)
std::cout << "Key " << setting.first << " has value " << setting.second << "\n";
}
Bonus
If you want to learn how to extract the raw input: just try
auto source = skip(space) [ *raw [ pair ] ];
as in this:
using RawSettings = std::vector<std::string>;
RawSettings parse_raw_config(std::string const& cfg) {
RawSettings parsed;
auto f = cfg.begin(), l = cfg.end();
if (!parse(f, l, parser::source, parsed))
throw std::invalid_argument("Parse failed at " + std::string(f,l));
return parsed;
}
int main() {
for (auto& setting : parse_raw_config(text))
std::cout << "Raw: " << setting << "\n";
}
Which prints: Live On Coliru
Raw: server ('m1.labs.teradata.com')
Raw: username ('use\')r_*5')
Raw: password('u" er 5')
Raw: dbname ('default')

Answer 2

Fixing a few syntax and style issues:
you need to escape \ in C strings
you had a " in s, making a syntax error
#include <boost/regex.hpp>
#include <boost/range/iterator_range.hpp>
#include <iostream>
int main() {
std::string s = "server ('m1.labs.teradata.com') username ('use\')r_*5') password('u' er 5') dbname ('default')";
boost::regex re(R"(('([^'\\]*(?:\\[\s\S][^'\\]*)*)'))");
size_t count = 0;
for (auto tok : boost::make_iterator_range(boost::sregex_token_iterator(s.begin(), s.end(), re, 1), {})) {
std::cout << "Token " << ++count << " is " << tok << "\n";
}
}
Prints
Token 1 is 'm1.labs.teradata.com'
Token 2 is 'use'
Token 3 is ') password('
Token 4 is ' er 5'
Token 5 is 'default'