How to Get Line Numbers for INI File Options Using the Boost Spirit Library?

How to Obtain Line Numbers of INI File Options

Problem Description

To locate specific options within an INI file, you may need a C library that provides line numbers for a given option or section. This capability allows you to pinpoint the location of a value or section in the file.

Use Cases

• Identify the line number where a specific value (vvv) exists within a section ([SSS]) to provide precise error messages or warnings (line 55: vvv must be < 256).
• Iterate through an INI file to validate section names and report any unknown sections (line 55: section [Hahaha] is unknown).

Available Solution

Boost Spirit Library:

The Boost Spirit library provides a robust solution for parsing INI files. This library allows you to not only parse INI files but also obtain line numbers for specific options or sections.

Code Sample

#include 
#include 

using namespace qi;

struct IniGrammar : grammar()>
{
    IniGrammar() : IniGrammar::base_type(start)
    {
        using namespace qi;

        // Define the grammar rules
        key     = lexeme[+(char_ - char_('='))];
        value   = lexeme[+(char_ - eol)];
        pair    = key > '=' > value;
        section = '[' > lexeme[+(char_ - char_(']'))] > ']' > *pair;
        start   = *(section % eol);
    }

    rule key;
    rule value;
    rule()> pair;
    rule>()> section;
    rule()> start;
};

int main()
{
    // Parse the INI file
    std::string ini_file = "[Main]\nkey1 = value1\nkey2 = value2";
    std::map ini_data;
    parse(ini_file.begin(), ini_file.end(), IniGrammar(), ini_data);

    // Print the line number for a specific option
    auto it = ini_data.find("key1");
    if (it != ini_data.end())
    {
        std::cout << "Line number for key1: " << it->second << std::endl;
    }

    return 0;
}
Conclusion
Using the Boost Spirit library, you can parse INI files and obtain line numbers for specific options or sections. This capability enhances your ability to analyze and validate INI files or report precise error messages and warnings.
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