C++编写Config类读取配置文件

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。

原文地址：http://cooker.iteye.com/blog/777455