(转)C++编写Config类读取配置文件

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转载最新推荐文章于 2026-04-08 10:29:12 发布 2.9k 阅读 AI 写同款· GEO 优化 ›

独家解读：简单又强大的配置文件 Config 读写类一、引言在项目过程中，难免会需要一个方便的配置文件读写类，它可以像游戏的存档文件一样，记录着我们当前项目的配置信息，以至于方便我们每次初始化运行的时候可以从这个配置文件读取上一次的配置信息，当然也可以在程序运行过程中记录用户的配置设置信息。我们理想中的这个配置文件读写类，它要有以下这些方法：1. 支持读入一个指定配置文件的能力2. 支持随时加入一个配置项的能力3. 足够强大，能够写入各种数据结构的配阅读详情

老外写的一段代码，在Server中编写这个类读取配置文件比较实用

C++代码

//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 ;
}

C++代码

// 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 );
}

C++代码

//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" , 0);
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 0;
}

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

这个类还有很多其他的方法，可以调用试试。

转载出处: http://cooker.javaeye.com/blog/777455

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