有一个解析conf配置文件的代码，写的非常精简。贴出来，供大家借鉴。
不说了。上代码
//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;
}
// 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);
}
使用的方式：
这里只演示从sstream获取配置的方式，从文件获取内容只需要在构造函数中，给一个文件路径。
Config(std::string filename)
#include <sstream>
#include "config.h"
using namespace std;
int main(int argc, const char * argv[]) {
string str = " action=blacklist \r\n nodeid=XXXXX1234 \r\n pi=3.141 ";
Config cfg;
//Config cfg("prog.conf"); //从文件获取配置
stringstream stream(str);
stream >> cfg;
auto actionStr = cfg.Read("action", string("bbb"));//bbb是默认值
auto pi = cfg.Read("pi", 9999);//9999是默认值，如果找不到pi，就用这个默认值
auto nodeid = cfg.Read("nodeid", string("sss"));
cfg.Add("key", "value");
stringstream ostream;
ostream <<cfg ;
string ostr = ostream.str();
return 0;
}