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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);}

使用

include”Config.h”

std::string URLaddress;const char ConfigFile[] = "config.txt";Config configSettings(ConfigFile);URLaddress = configSettings.Read("URLaddress", URLaddress);