Simple INI reading and writing in C++ (Public Domain)

config.cpp

#include "config.hpp"

#include <fstream>

namespace config
{

std::map<std::string, std::map<std::string, std::string>> tree{};
const std::string filePath{"config.ini"};

bool exists(const std::string& section, const std::string& name)
{
    return tree.count(section) > 0 && tree[section].count(name) > 0;
}

void load()
{
    tree.clear();

    std::ifstream ifs{};
    ifs.exceptions(std::ifstream::badbit);
    ifs.open(filePath);

    std::string line;
    std::string section{};
    while (std::getline(ifs, line))
    {
        if (line.empty() || line[0] == ';') continue;

        if (line[0] == '[' && line[line.size() - 1] == ']')
        {
            section = line.substr(1, line.size() - 2);
            continue;
        }

        auto delimiterPos = line.find_first_of('=');
        if (delimiterPos != std::string::npos)
        {
            auto key = line.substr(0, delimiterPos);
            auto value = line.substr(delimiterPos + 1, line.size() - delimiterPos);
            tree[section][key] = value;
        }
    }
}

void save()
{
    std::ofstream ofs{};
    ofs.exceptions(std::ifstream::badbit);
    ofs.open(filePath);

    for (auto [section, property] : tree)
    {
        ofs << '[' << section << "]\n";
        for (auto [key, value] : property)
        {
            ofs << key << '=' << value << '\n';
        }
        ofs << '\n';
    }

    ofs.close();
}

}

config.hpp

#pragma once

#include <map>
#include <string>

namespace config
{

extern std::map<std::string, std::map<std::string, std::string>> tree;
extern const std::string filePath;

void load();
void save();

bool exists(const std::string& section, const std::string& name);

template<typename T>
T set(const std::string& section, const std::string& name, T value)
{
    std::ostringstream oss{};
    oss << value;
    tree[section][name] = oss.str();
    return value;
}

template<typename T>
T get(const std::string& section, const std::string& name, T defaultValue = {})
{
    if (!exists(section, name))
        return set(section, name, defaultValue);

    std::istringstream iss{tree[section][name]};
    T ret;
    iss >> ret;
    return ret;
}

}