C++如何实现一个简单的INI配置文件解析器？（代码示例）

#include <iostream>
#include <string>
#include <map>
#include <fstream>
#include <cctype>
#include <algorithm>
<p>// 去首尾空格
std::string trim(const std::string& s) {
size_t start = s.find_first_not_of(" \t\r\n");
if (start == std::string::npos) return "";
size_t end = s.find_last_not_of(" \t\r\n");
return s.substr(start, end - start + 1);
}</p><p>class IniParser {
public:
std::map<std::string, std::map<std::string, std::string>> data;
std::string current_section;</p><pre class='brush:php;toolbar:false;'>bool load(const std::string& filename) {
    std::ifstream file(filename);
    if (!file.is_open()) return false;

    std::string line;
    int line_num = 0;
    while (std::getline(file, line)) {
        line_num++;
        line = trim(line);
        if (line.empty() || line[0] == '#' || line[0] == ';') continue;

        // 匹配 [section]
        if (line[0] == '[' && line.back() == ']') {
            std::string sec = trim(line.substr(1, line.length()-2));
            if (!sec.empty()) current_section = sec;
            continue;
        }

        // 匹配 key=value
        size_t eq_pos = line.find('=');
        if (eq_pos != std::string::npos) {
            std::string key = trim(line.substr(0, eq_pos));
            std::string value = trim(line.substr(eq_pos + 1));
            if (!key.empty() && !current_section.empty()) {
                data[current_section][key] = value;
            }
        }
    }
    return true;
}

// 获取字符串值，未找到返回默认值
std::string get(const std::string& section, const std::string& key, const std::string& def = "") const {
    auto sec_it = data.find(section);
    if (sec_it == data.end()) return def;
    auto key_it = sec_it->second.find(key);
    if (key_it == sec_it->second.end()) return def;
    return key_it->second;
}

// 获取整数（简单转换，失败返回默认值）
int get_int(const std::string& section, const std::string& key, int def = 0) const {
    std::string s = get(section, key);
    if (s.empty()) return def;
    try {
        return std::stoi(s);
    } catch (...) {
        return def;
    }
}

std::cout << "Host: " << ini.get("database", "host", "localhost") << "\n";
std::cout << "Port: " << ini.get_int("database", "port", 3306) << "\n";
std::cout << "Debug: " << ini.get("app", "debug", "false") << "\n";