Source code sharing: C ++ configuration class

An enthusiastic Daniel on the Internet shared a C ++ configuration class, as shown below:
Config. h

    //Config.h      #pragma once            #include <string>      #include <map>      #include <iostream>      #include <fstream>      #include <sstream>                  /*     * \brief Generic configuration Class     *     */      class Config {          // Data      protected:          std::string m_Delimiter;  //!< separator between key and value          std::string m_Comment;    //!< separator between value and comments          std::map<std::string,std::string> m_Contents;  //!< extracted keys and values                typedef std::map<std::string,std::string>::iterator mapi;          typedef std::map<std::string,std::string>::const_iterator mapci;          // Methods      public:                Config( std::string filename,std::string delimiter = "=",std::string comment = "#" );          Config();          template<class T> T Read( const std::string& in_key ) const;  //!<Search for key and read value or optional default value, call as read<T>          template<class T> T Read( const std::string& in_key, const T& in_value ) const;          template<class T> bool ReadInto( T& out_var, const std::string& in_key ) const;          template<class T>          bool ReadInto( T& out_var, const std::string& in_key, const T& in_value ) const;          bool FileExist(std::string filename);          void ReadFile(std::string filename,std::string delimiter = "=",std::string comment = "#" );                // Check whether key exists in configuration          bool KeyExists( const std::string& in_key ) const;                // Modify keys and values          template<class T> void Add( const std::string& in_key, const T& in_value );          void Remove( const std::string& in_key );                // Check or change configuration syntax          std::string GetDelimiter() const { return m_Delimiter; }          std::string GetComment() const { return m_Comment; }          std::string SetDelimiter( const std::string& in_s )          { std::string old = m_Delimiter;  m_Delimiter = in_s;  return old; }            std::string SetComment( const std::string& in_s )          { std::string old = m_Comment;  m_Comment =  in_s;  return old; }                // Write or read configuration          friend std::ostream& operator<<( std::ostream& os, const Config& cf );          friend std::istream& operator>>( std::istream& is, Config& cf );            protected:          template<class T> static std::string T_as_string( const T& t );          template<class T> static T string_as_T( const std::string& s );          static void Trim( std::string& inout_s );                      // Exception types      public:          struct File_not_found {              std::string filename;              File_not_found( const std::string& filename_ = std::string() )                  : filename(filename_) {} };              struct Key_not_found {  // thrown only by T read(key) variant of read()                  std::string key;                  Key_not_found( const std::string& key_ = std::string() )                      : key(key_) {} };      };                  /* static */      template<class T>      std::string Config::T_as_string( const T& t )      {          // Convert from a T to a string          // Type T must support << operator          std::ostringstream ost;          ost << t;          return ost.str();      }                  /* static */      template<class T>      T Config::string_as_T( const std::string& s )      {          // Convert from a string to a T          // Type T must support >> operator          T t;          std::istringstream ist(s);          ist >> t;          return t;      }                  /* static */      template<>      inline std::string Config::string_as_T<std::string>( const std::string& s )      {          // Convert from a string to a string          // In other words, do nothing          return s;      }                  /* static */      template<>      inline bool Config::string_as_T<bool>( const std::string& s )      {          // Convert from a string to a bool          // Interpret "false", "F", "no", "n", "0" as false          // Interpret "true", "T", "yes", "y", "1", "-1", or anything else as true          bool b = true;          std::string sup = s;          for( std::string::iterator p = sup.begin(); p != sup.end(); ++p )              *p = toupper(*p);  // make string all caps          if( sup==std::string("FALSE") || sup==std::string("F") ||              sup==std::string("NO") || sup==std::string("N") ||              sup==std::string("0") || sup==std::string("NONE") )              b = false;          return b;      }                  template<class T>      T Config::Read( const std::string& key ) const      {          // Read the value corresponding to key          mapci p = m_Contents.find(key);          if( p == m_Contents.end() ) throw Key_not_found(key);          return string_as_T<T>( p->second );      }                  template<class T>      T Config::Read( const std::string& key, const T& value ) const      {          // Return the value corresponding to key or given default value          // if key is not found          mapci p = m_Contents.find(key);          if( p == m_Contents.end() ) return value;          return string_as_T<T>( p->second );      }                  template<class T>      bool Config::ReadInto( T& var, const std::string& key ) const      {          // Get the value corresponding to key and store in var          // Return true if key is found          // Otherwise leave var untouched          mapci p = m_Contents.find(key);          bool found = ( p != m_Contents.end() );          if( found ) var = string_as_T<T>( p->second );          return found;      }                  template<class T>      bool Config::ReadInto( T& var, const std::string& key, const T& value ) const      {          // Get the value corresponding to key and store in var          // Return true if key is found          // Otherwise set var to given default          mapci p = m_Contents.find(key);          bool found = ( p != m_Contents.end() );          if( found )              var = string_as_T<T>( p->second );          else              var = value;          return found;      }                  template<class T>      void Config::Add( const std::string& in_key, const T& value )      {          // Add a key with given value          std::string v = T_as_string( value );          std::string key=in_key;          trim(key);          trim(v);          m_Contents[key] = v;          return;      }  

Config. cpp

    // Config.cpp            #include "Config.h"            using namespace std;                  Config::Config( string filename, string delimiter,                     string comment )                     : m_Delimiter(delimiter), m_Comment(comment)      {          // Construct a Config, getting keys and values from given file                std::ifstream in( filename.c_str() );                if( !in ) throw File_not_found( filename );                 in >> (*this);      }                  Config::Config()      : m_Delimiter( string(1,'=') ), m_Comment( string(1,'#') )      {          // Construct a Config without a file; empty      }                        bool Config::KeyExists( const string& key ) const      {          // Indicate whether key is found          mapci p = m_Contents.find( key );          return ( p != m_Contents.end() );      }                  /* static */      void Config::Trim( string& inout_s )      {          // Remove leading and trailing whitespace          static const char whitespace[] = " \n\t\v\r\f";          inout_s.erase( 0, inout_s.find_first_not_of(whitespace) );          inout_s.erase( inout_s.find_last_not_of(whitespace) + 1U );      }                  std::ostream& operator<<( std::ostream& os, const Config& cf )      {          // Save a Config to os          for( Config::mapci p = cf.m_Contents.begin();              p != cf.m_Contents.end();              ++p )          {              os << p->first << " " << cf.m_Delimiter << " ";              os << p->second << std::endl;          }          return os;      }            void Config::Remove( const string& key )      {          // Remove key and its value          m_Contents.erase( m_Contents.find( key ) );          return;      }            std::istream& operator>>( std::istream& is, Config& cf )      {          // Load a Config from is          // Read in keys and values, keeping internal whitespace          typedef string::size_type pos;          const string& delim  = cf.m_Delimiter;  // separator          const string& comm   = cf.m_Comment;    // comment          const pos skip = delim.length();        // length of separator                string nextline = "";  // might need to read ahead to see where value ends                while( is || nextline.length() > 0 )          {              // Read an entire line at a time              string line;              if( nextline.length() > 0 )              {                  line = nextline;  // we read ahead; use it now                  nextline = "";              }              else              {                  std::getline( is, line );              }                    // Ignore comments              line = line.substr( 0, line.find(comm) );                    // Parse the line if it contains a delimiter              pos delimPos = line.find( delim );              if( delimPos < string::npos )              {                  // Extract the key                  string key = line.substr( 0, delimPos );                  line.replace( 0, delimPos+skip, "" );                        // See if value continues on the next line                  // Stop at blank line, next line with a key, end of stream,                  // or end of file sentry                  bool terminate = false;                  while( !terminate && is )                  {                      std::getline( is, nextline );                      terminate = true;                            string nlcopy = nextline;                      Config::Trim(nlcopy);                      if( nlcopy == "" ) continue;                            nextline = nextline.substr( 0, nextline.find(comm) );                      if( nextline.find(delim) != string::npos )                          continue;                            nlcopy = nextline;                      Config::Trim(nlcopy);                      if( nlcopy != "" ) line += "\n";                      line += nextline;                      terminate = false;                  }                        // Store key and value                  Config::Trim(key);                  Config::Trim(line);                  cf.m_Contents[key] = line;  // overwrites if key is repeated              }          }                return is;      }      bool Config::FileExist(std::string filename)      {          bool exist= false;          std::ifstream in( filename.c_str() );          if( in )               exist = true;          return exist;      }            void Config::ReadFile( string filename, string delimiter,                            string comment )      {          m_Delimiter = delimiter;          m_Comment = comment;          std::ifstream in( filename.c_str() );                if( !in ) throw File_not_found( filename );                 in >> (*this);      }  

From: http://cooker.iteye.com/blog/777455

On the basis of the package:

Main_config.h

// Main_config.h: interface for the main_config class. //////////////////////////////////////// /// // If! Defined (DEFINE _) # define afx_main_config_h1_b4beee3f_3d800004428_a25f_66e6b56318f200000000ded _ # include "Const. H "# include" config. H "// The main configuration file encapsulates class main_config {public: // @ brief to get the instance static main_config & instance (); // @ brief get the config object const config & get_config (); // @ brief import the configuration file bool load_config (); Private: main_config (); Virtual ~ Main_config (); // config * _ config; // configuration file path char _ conf_path [path_size]; // configure the file name char _ conf_name [path_size];}; # endif //! Defined (afx_main_config_hsf-b4beee3f_3d800004428_a25f_66e6b56318f200000000ded _)

Main_config.cpp

// Main_config.cpp: implementation of the Main_config class.////////////////////////////////////////////////////////////////////////#include "Main_config.h"#include "const.h"//////////////////////////////////////////////////////////////////////// Construction/Destruction//////////////////////////////////////////////////////////////////////Main_config::Main_config(){snprintf(_conf_path, sizeof(_conf_path), "%s", "../conf");snprintf(_conf_name, sizeof(_conf_name), "%s/%s.%s", _conf_path, execname, "conf");}Main_config::~Main_config(){if(_config){delete _config;}}bool Main_config::load_config(){bool ret = true;_config = new(std::nothrow) Config(_conf_name);if (_config == NULL){return false;}return ret;}Main_config& Main_config::instance(){static Main_config main_config;return main_config;}const Config& Main_config::get_config(){return *_config;}

Usage:

# Include "main_config.h"... // load the main configuration file if (! Main_config: instance (). load_config () {STD: cout <"main_config: load_config () failed" <STD: Endl; return false ;} // read the port number _ Port = main_config: instance () from the configuration file (). get_config (). read ("Port", 0 );....

Simple and reliable!