How can I get the line number of an INI file where a specific option or section is found using C ?

Cross-platform way to get line number of an INI file where given option was found

Problem:

Looking for a C library (like boost::program_options) that can return the line number of an INI file where a given option or section was found.

Use cases:

1. Ask the library to find the value "vvv" in the section "[SSS]." The library should return the line number where "vvv" is found in the "[SSS]" section or -1. This allows us to say, for example, "line 55: vvv must be < 256."
2. Iterate through the INI file for sections and validate their names. When an unknown section is found, we can report "line 55: section [Hahaha] is unknown."

Response:

Exploiting the possibilities of Boost Spirit, a solution was crafted using line_pos_iterator.

Implementation Details:

• POSITIONSINFO = 0:

  • Input is streaming.
  • Output is in raw string format, or map> for sections.

  • POSITIONSINFO = 1:

    • Input is buffered.
    • Output is in textnode_t format:

    <code class="cpp">struct textnode_t {
      int sline, eline, scol, ecol;
      string_t text;
    };</code>

    • This enables the resulting map> to report the exact line and column starting and ending points for individual text elements.
    • Comments (#, / ... / style) are implemented.
    • Whitespace is tolerated.
    • De-escaping of slashes is left as an exercise.
    • Errors are reported with full position information when enabled.

  Code Snippet:

  <code class="cpp">#include <map>
  #include <string>
  #include <iterator>
  #include <boost/tuple/tuple_comparison.hpp>
  
  template <typename S = std::string, typename Cmp = std::less<S>>
  class IniFile {
  public:
      IniFile(Cmp cmp = Cmp()) : _cmp(cmp) {}
  
      IniFile(const std::string& filename, Cmp cmp = Cmp()) : _cmp(cmp) { open(filename); }
  
      void open(const std::string& filename);
  
  typedef S string_t;
  #if POSITIONINFO
      struct textnode_t {
          int sline, eline,
              scol, ecol;
          string_t text;
  
          // ...
      };
  #else
      typedef string_t textnode_t;
  #endif
  
  typedef std::pair<textnode_t, textnode_t> keyvalue_t;
  typedef std::map<textnode_t, textnode_t> section_t;
  typedef std::map<textnode_t, section_t> sections_t;
  
  private:
      Cmp _cmp;
  };</code>

  Additional Resources:

  • [Gist with complete code, makefile, and example.ini](https://gist.github.com/1425972)
  • [Boost Spirit documentation](https://www.boost.org/doc/libs/1_65_1/libs/spirit/doc/)

  Important Note: The provided solution does not require C 11 support, but it was used to dump the result of the parse.

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