29.线程的互斥与同步（三）-EW帮帮网

池化技术：预制，减少系统调用的次数，提高效率。

日志

完整代码：

#ifndef __LOG_HPP__
#define __LOG_HPP__

#include <iostream>
#include <string>
#include <filesystem>
#include <fstream>
#include <memory>
#include <unistd.h>
#include <sys/types.h>
#include <ctime>
#include "Mutex.hpp"

namespace LogModule
{
    using namespace MutexModule;
    // 日志刷新策略
    class LogStrategy
    {
    public:
        ~LogStrategy() = default;
        virtual void SyncLog(const std::string &message) = 0;
    };
    // 控制台刷新
    class ConsoleLogStrategy : public LogStrategy
    {
    public:
        ConsoleLogStrategy()
        {
        }
        ~ConsoleLogStrategy()
        {
        }
        virtual void SyncLog(const std::string &message) override
        {
            MutexGuard mutexguard(_mutex);
            std::cout << message << std::endl;
        }

    private:
        Mutex _mutex;
    };
    static const std::string default_path = "./log";
    static const std::string default_file = "my.log";
    static const std::string sep = "\r\n";
    // 文件刷新
    class FileLogStrategy : public LogStrategy
    {
    public:
        FileLogStrategy(const std::string &path = default_path, const std::string &file = default_file)
            : _path(path), _file(file)
        {
            {
                // 保证多线程时的线程安全
                MutexGuard mutexguard(_mutex);
                // 如果已经存在目录，返回
                if (std::filesystem::exists(_path))
                    return;
                try
                {
                    // 创建目录结构
                    std::filesystem::create_directories(_path);
                }
                catch (const std::filesystem::filesystem_error &e)
                {
                    std::cerr << e.what() << std::endl;
                }
            }
        }
        ~FileLogStrategy()
        {
        }
        virtual void SyncLog(const std::string &message) override
        {
            std::string pathname = _path + (_path.back() == '/' ? "" : "/") + _file;
            // 以追加方式打开文件
            std::ofstream ofs(pathname, std::ios::app);
            ofs << message << sep;
            ofs.close();
        }

    private:
        std::string _path;
        std::string _file;
        Mutex _mutex;
    };

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

    std::string GetLevel(LogLevel level)
    {
        switch (level)
        {
        case LogLevel::DEBUG:
            return "DEBUG";
        case LogLevel::INFO:
            return "INFO";
        case LogLevel::WARNING:
            return "WARNING";
        case LogLevel::ERROR:
            return "ERROR";
        case LogLevel::FATAL:
            return "FATAL";
        default:
            return "UNKNOWN";
        }
    }

    std::string GetTime()
    {
        time_t timestamp = time(nullptr);
        struct tm data;
        localtime_r(&timestamp, &data);
        char buff[128];
        snprintf(buff, 128, "%4d-%02d-%02d %02d:%02d:%02d",
                 data.tm_year + 1900,
                 data.tm_mon + 1,
                 data.tm_mday,
                 data.tm_hour,
                 data.tm_min,
                 data.tm_sec);
        return buff;
    }

    class Log
    {
    public:
        Log()
        {
        }
        ~Log()
        {
        }
        void EnableConsoleLogStrategy()
        {
            _sl = std::make_unique<ConsoleLogStrategy>();
        }
        void EnableFileLogStrategy()
        {
            _sl = std::make_unique<FileLogStrategy>();
        }
        // 格式化的左边消息
        class LogInfo
        {
        public:
            LogInfo(Log *log, LogLevel level, const std::string &filename, const unsigned int line)
                : _time(GetTime()), _level(level), _pid(getpid()), _filename(filename), _line(line), _log(log)
            {
                std::stringstream ss;
                ss << "[" << _time << "] "
                   << "[" << GetLevel(_level) << "] "
                   << "[" << _pid << "] "
                   << "[" << _filename << "] "
                   << "[" << _line << "] "
                   << "- ";
                _message = ss.str();
            }
            // LogInfo销毁时，刷新
            ~LogInfo()
            {
                if (_log->_sl)
                {
                    _log->_sl->SyncLog(_message);
                }
            }

            template <typename T>
            LogInfo &operator<<(const T &data)
            {
                std::stringstream ss;
                ss << data;
                _message += ss.str();
                return *this;
            }

        private:
            std::string _time;     // 时间，年月日时分秒
            LogLevel _level;       // 日志等级
            pid_t _pid;            // 进程pid
            std::string _filename; // 打印日志对应的文件名
            unsigned int _line;    // 行号
            std::string _message;  // 整条信息,左边+右边
            // Log的指针
            Log *_log;
        };
        // 重载函数调用，用仿函数的形式调用，且隐式传递自己的this指针
        // 返回LogInfo的匿名对象，生命周期只有一行，一行结束就调用析构，刷新。
        LogInfo operator()(LogLevel level, const std::string &filename, const unsigned int line)
        {
            return LogInfo(this, level, filename, line);
        }

    private:
        std::unique_ptr<LogStrategy> _sl; // 策略基类指针
    };

    Log log;
#define Enable_Console_log_Strategy() log.EnableConsoleLogStrategy()
#define Enable_File_log_Strategy() log.EnableFileLogStrategy()
#define LOG(level) log(level, __FILE__, __LINE__)
}

#endif

效果：