以下是转载于网上的一个很好的config文件的实现，留存以备案
//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("") || 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 #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(,'=') ), m_Comment( string(,'#') )
{
// 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( , 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() > )
{
// Read an entire line at a time
string line;
if( nextline.length() > )
{
line = nextline; // we read ahead; use it now
nextline = "";
}
else
{
std::getline( is, line );
} // Ignore comments
line = line.substr( , 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( , delimPos );
line.replace( , 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( , 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);
}
//main.cpp
#include "Config.h"
int main()
{
int port;
std::string ipAddress;
std::string username;
std::string password;
const char ConfigFile[]= "config.txt";
Config configSettings(ConfigFile); port = configSettings.Read("port", );
ipAddress = configSettings.Read("ipAddress", ipAddress);
username = configSettings.Read("username", username);
password = configSettings.Read("password", password);
std::cout<<"port:"<<port<<std::endl;
std::cout<<"ipAddress:"<<ipAddress<<std::endl;
std::cout<<"username:"<<username<<std::endl;
std::cout<<"password:"<<password<<std::endl; return ;
}
config.txt的文件内容：
ipAddress=10.10.90.125
port=3001
username=mark
password=2d2df5a
编译运行输出:
port:3001
ipAddress:10.10.90.125
username:mark
password:2d2df5a