c++怎么实现一个简单的日志系统_c++日志系统实现方法

enum class LogLevel {
    DEBUG,
    INFO,
    WARNING,
    ERROR
};

#include 
#include 
#include 
#include 
#include 

class Logger {
public:
    static Logger& instance() {
        static Logger logger;
        return logger;
    }

    void setLevel(LogLevel level) {
        m_level = level;
    }

    void setFileOutput(const std::string& filename) {
        m_file.open(filename, std::ios::app);
    }

    void log(LogLevel level, const std::string& msg) {
        if (level < m_level) return;

        std::lock_guard lock(m_mutex);
        std::time_t now = std::time(nullptr);
        char timeStr[64];
        std::strftime(timeStr, sizeof(timeStr), "%Y-%m-%d %H:%M:%S", std::localtime(&now));

        std::string levelStr[] = {"DEBUG", "INFO", "WARNING", "ERROR"};
        std::string line = "[" + std::string(timeStr) + "] [" + levelStr[static_cast(level)] + "] " + msg + "\n";

        std::cout << line;
        if (m_file.is_open()) {
            m_file << line;
            m_file.flush();
        }
    }

private:
    Logger() : m_level(LogLevel::DEBUG) {}
    ~Logger() {
        if (m_file.is_open()) m_file.close();
    }

    LogLevel m_level;
    std::ofstream m_file;
    std::mutex m_mutex;
};

#define LOG_DEBUG(msg) Logger::instance().log(LogLevel::DEBUG, msg)
#define LOG_INFO(msg)  Logger::instance().log(LogLevel::INFO, msg)
#define LOG_WARN(msg)  Logger::instance().log(LogLevel::WARNING, msg)
#define LOG_ERROR(msg) Logger::instance().log(LogLevel::ERROR, msg)

int main() {
    Logger::instance().setLevel(LogLevel::INFO);
    Logger::instance().setFileOutput("app.log");

    LOG_DEBUG("This won't show"); // 被级别过滤
    LOG_INFO("Program started");
    LOG_WARN("Something unusual happened");
    LOG_ERROR("A critical error occurred");

    return 0;
}