libconfig第二篇----两个小例子

本文只看粗体即可，太多catch语句。两个例子均来自libconfig包的example文件夹下面,.

例子一：

#include <iostream>

#include <iomanip>

#include <cstdlib>

#include <libconfig.h++>

using namespace std;

using namespace libconfig;

// This example reads the configuration file 'example.cfg' and display some of its contents.



int main(int argc, char **argv)

{

  Config cfg;

try

  {

    cfg.readFile("example.cfg"); //读配置文件

  }

  catch(const FileIOException &fioex)

  {

    std::cerr << "I/O error while reading file." << std::endl;

    return(EXIT_FAILURE);

  }

  catch(const ParseException &pex)

  {

    std::cerr << "Parse error at " << pex.getFile() << ":" << pex.getLine()

              << " - " << pex.getError() << std::endl;

    return(EXIT_FAILURE);

  }

// Get the store name.

  try

  {

    string name = cfg.lookup("name"); // 查询某个路径“name”，得到setting，存储到name

    cout << "Store name: " << name << endl << endl;

  }

  catch(const SettingNotFoundException &nfex)

  {

    cerr << "No 'name' setting in configuration file." << endl;

  }



  const Setting& root = cfg.getRoot();//得到根setting

 // Output a list of all books in the inventory.

  try

  {

    const Setting &books = root["inventory"]["books"];

    int count = books.getLength();   //得到某个setting的长度,从而循环读取

       for(int i = 0; i < count; ++i)

    {

      const Setting &book = books[i];

      // Only output the record if all of the expected fields are present.

      string title, author;

      double price;

      int qty;

      if(!(book.lookupValue("title", title)  //查询名字为title的setting存储到title中

           && book.lookupValue("author", author)

           && book.lookupValue("price", price)

           && book.lookupValue("qty", qty)))

        continue;

      cout << setw(30) << left << title << "  "

           << setw(30) << left << author << "  "

           << '$' << setw(6) << right << price << "  "

           << qty

           << endl;

    }

    cout << endl;

  }

  catch(const SettingNotFoundException &nfex)

  {

    // Ignore.

  }

  return(EXIT_SUCCESS);

}





// eof

例子二

头文件省略

// This example reads the configuration file 'example.cfg', adds a new

// movie record to the movies list, and writes the updated configuration to

// 'updated.cfg'.

int main(int argc, char **argv)

{

  static const char *output_file = "updated.cfg";



  Config cfg;

  // Read the file. If there is an error, report it and exit.

  try

  {

    cfg.readFile("example.cfg"); //读配置文件

  }

  catch(const FileIOException &fioex)

  {

    std::cerr << "I/O error while reading file." << std::endl;

    return(EXIT_FAILURE);

  }

  catch(const ParseException &pex)

  {

    std::cerr << "Parse error at " << pex.getFile() << ":" << pex.getLine()

              << " - " << pex.getError() << std::endl;

    return(EXIT_FAILURE);

  }

// Get the store name.

  try

  {

    string name = cfg.lookup("name");    //通过"name"这个路径查找 到某个setting（名字为 name） 存储到string name 中

    cout << "Store name: " << name << endl << endl;

  }

  catch(const SettingNotFoundException &nfex)

  {

    cerr << "No 'name' setting in configuration file." << endl;

  }





  // Find the 'movies' setting. Add intermediate settings if they don't yet

  // exist.

  Setting &root = cfg.getRoot(); //返回root setting

  if(! root.exists("inventory"))

    root.add("inventory", Setting::TypeGroup);

  Setting &inventory = root["inventory"];

  if(! inventory.exists("movies"))

    inventory.add("movies", Setting::TypeList);

  Setting &movies = inventory["movies"]；

// Create the new movie entry.

  Setting &movie = movies.add(Setting::TypeGroup); //增加一个Setting::TypeGroup类型的子setting

  movie.add("title", Setting::TypeString) = "Buckaroo Banzai"; //增加一个子setting

  movie.add("media", Setting::TypeString) = "DVD";

  movie.add("price", Setting::TypeFloat) = 12.99;

  movie.add("qty", Setting::TypeInt) = 20;



  // Write out the updated configuration.

  try

  {

    cfg.writeFile(output_file); //把配置写到一个文件中

    cerr << "Updated configuration successfully written to: " << output_file

         << endl;

  }

  catch(const FileIOException &fioex)

  {

    cerr << "I/O error while writing file: " << output_file << endl;

    return(EXIT_FAILURE);

  }

  return(EXIT_SUCCESS);

}



// eof

配置文件：

example.cfg:

// An example configuration file that stores information about a store.



// Basic store information:

name = "Books, Movies & More";





// Store inventory:

inventory =

{

  books = ( { title  = "Treasure Island";

              author = "Robert Louis Stevenson";

              price  = 29.99;

              qty    = 5; },

            { title  = "Snow Crash";

              author = "Neal Stephenson";

              price  = 9.99;

              qty    = 8; }

          );





  movies = ( { title = "Brazil";

               media = "DVD";

               price = 19.99;

               qty = 11; },

             { title = "The City of Lost Children";

               media = "DVD";

               price = 18.99;

               qty = 5; },

             { title = "Memento";

               media = "Blu-Ray";

               price = 24.99;

               qty = 20;

             },

             { title = "Howard the Duck"; }

           );

};





// Store hours:

hours =

{

  mon = { open =  9; close = 18; };

  tue = { open =  9; close = 18; };

  wed = { open =  9; close = 18; };

  thu = { open =  9; close = 18; };

  fri = { open =  9; close = 20; };

  sat = { open =  9; close = 20; };

  sun = { open = 11; close = 16; };

};