libconfig C++ 学习笔记

1. C++API 头文件 #include <libconfig.h++> ，命名空间：using namespace libconfig;

2.多线程使用问题：

　　（1）libconfig是完全可重入的,库中函数不使用全局变量和不保持成功调用间的状态。所以两个独立配置文件在两个不同线程间并发操作可以是安全的；

　　（2）libconfig是线程不安全，libconfig不考虑系统线程模型。所以一个配置文件的实例被多个线程获取，必须使用同步机制（例如读写锁或互斥锁）来保护。

　　（3）libconfig不是异步安全，不能在信号句柄中调用

　　（4）libconfig不能保证取消安全。因为它不知道主机系统的线程模型，库不包含任何线程取消点。在大多数情况下这将不是多线程程序的问题。但是，请注意一些库中的例程（即那些从/到文件读取/写入配置的程序）流）使用可能会阻止的C库例程执行I/O；是否这些C库例程是取消安全的，取决于主机系统。

3.C++API

　　C++API使用Config类和Setting类，因为不提供公有的copy constructor or assignment operator，所以在函数参数中传递时使用引用或指针方式
4.使用方法（使用官方example）：

配置文件：

// 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    = ; },

            { title  = "Snow Crash";

              author = "Neal Stephenson";

              price  = 9.99;

              qty    = ; }

          );

  movies = ( { title = "Brazil";

               media = "DVD";

               price = 19.99;

               qty = ; },

             { title = "The City of Lost Children";

               media = "DVD";

               price = 18.99;

               qty = ; },

             { title = "Memento";

               media = "Blu-Ray";

               price = 24.99;

               qty = ;

             },

             { title = "Howard the Duck"; }

           );

};

// Store hours:

hours =

{

  mon = { open =  ; close = ; };

  tue = { open =  ; close = ; };

  wed = { open =  ; close = ; };

  thu = { open =  ; close = ; };

  fri = { open =  ; close = ; };

  sat = { open =  ; close = ; };

  sun = { open = ; close = ; };

};

C++读取配置程序：

#include <cstdlib>

#include <libconfig.h++>

#include <iostream>

#include <iomanip>

using namespace std;

using namespace libconfig;

int main(){

    Config cfg;     //1.声明 Config对象

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

    // Get the store name.

    try

    {

        string name = cfg.lookup("name");

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

    }

    catch(const SettingNotFoundException &nfex)         //配置没找到会有SettingNotFoundException 异常

    {

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

    }

    // Get the store name.

  try

  {

    string name = cfg.lookup("name");

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

  }

  catch(const SettingNotFoundException &nfex)

  {

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

  }

  const Setting& root = cfg.getRoot();

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

  try

  {

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

    int count = books.getLength();

    cout << setw() << left << "TITLE" << "  "

         << setw() << left << "AUTHOR" << "   "

         << setw() << left << "PRICE" << "  "

         << "QTY"

         << endl;

    for(int i = ; 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)

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

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

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

        continue;

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

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

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

           << qty

           << endl;

    }

    cout << endl;

  }

  catch(const SettingNotFoundException &nfex)

  {

    // Ignore.

  }

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

  try

  {

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

    int count = movies.getLength();

    cout << setw() << left << "TITLE" << "  "

         << setw() << left << "MEDIA" << "   "

         << setw() << left << "PRICE" << "  "

         << "QTY"

         << endl;

    for(int i = ; i < count; ++i)

    {

      const Setting &movie = movies[i];

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

      string title, media;

      double price;

      int qty;

      if(!(movie.lookupValue("title", title)

           && movie.lookupValue("media", media)

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

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

        continue;

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

           << setw() << left << media << "  "

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

           << qty

           << endl;

    }

    cout << endl;

  }

  catch(const SettingNotFoundException &nfex)

  {

    // Ignore.

  }

    return ;

}

5.常用Config类方法：

（1）Method on Config: Setting & getRoot () const

This method returns the root setting for the configuration, which is a group.

（2）

Method on Config: Setting & lookup (const std::string &path) constMethod on Config: Setting & lookup (const char * path) const

These methods locate the setting specified by the path path. If the requested setting is not found, a SettingNotFoundException is thrown.

（3）

Method on Config: bool lookupValue (const char *path, bool &value) constMethod on Config: bool lookupValue (const std::string &path, bool &value) constMethod on Config: bool lookupValue (const char *path, int &value) constMethod on Config: bool lookupValue (const std::string &path, int &value) constMethod on Config: bool lookupValue (const char *path, unsigned int &value) constMethod on Config: bool lookupValue (const std::string &path, unsigned int &value) constMethod on Config: bool lookupValue (const char *path, long long &value) constMethod on Config: bool lookupValue (const std::string &path, long long &value) constMethod on Config: bool lookupValue (const char *path, float &value) constMethod on Config: bool lookupValue (const std::string &path, float &value) constMethod on Config: bool lookupValue (const char *path, double &value) constMethod on Config: bool lookupValue (const std::string &path, double &value) constMethod on Config: bool lookupValue (const char *path, const char *&value) constMethod on Config: bool lookupValue (const std::string &path, const char *&value) constMethod on Config: bool lookupValue (const char *path, std::string &value) constMethod on Config: bool lookupValue (const std::string &path, std::string &value) const

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libconfig C++ 学习笔记

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