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; };
};