前言
系统程序一般需要读取参数文件，看到一个很好的Config类记录在此。
头文件Config.h
//Config.h //re: https://blog.csdn.net/David_xtd/article/details/9320549 #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; }