iterate over ini file on c++, probably using boost::property_tree::ptree?

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执念已碎 2021-02-10 16:09

My task is trivial - i just need to parse such file:

Apple = 1
Orange = 2
XYZ = 3950

But i do not know the set of available keys. I was parsing

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故里飘歌 (楼主)

2021-02-10 16:16
For the moment, I've simplified the problem a bit, leaving out the logic for comments (which looks broken to me anyway).
```
#include 
#include 
#include 
#include 

typedef std::pair entry;

// This isn't officially allowed (it's an overload, not a specialization) but is
// fine with every compiler of which I'm aware.
namespace std {
std::istream &operator>>(std::istream &is,  entry &d) { 
    std::getline(is, d.first, '=');
    std::getline(is, d.second);
    return is;
}
}

int main() {
    // open an input file.
    std::ifstream in("myfile.ini");

    // read the file into our map:
    std::map dict((std::istream_iterator(in)),
                                            std::istream_iterator());

    // Show what we read:
    for (entry const &e : dict) 
        std::cout << "Key: " << e.first << "\tvalue: " << e.second << "\n";
}
```
Personally, I think I'd write the comment skipping as a filtering stream buffer, but for those unfamiliar with the C++ standard library, it's open to argument that would be a somewhat roundabout solution. Another possibility would be a comment_iterator that skips the remainder of a line, starting from a designated comment delimiter. I don't like that as well, but it's probably simpler in some ways.

Note that the only code we really write here is to read one, single entry from the file into a pair. The istream_iterator handles pretty much everything from there. As such, there's little real point in writing a direct analog of your function -- we just initialize the map from the iterators, and we're done.
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