C++实现简单的日志记录

//dlogger.h
#ifndef DLOGGER_H
#define DLOGGER_H

#include <iostream>
#include <Mutex>
#include <ctime>
#include <string>

extern std::mutex mt;

//用于获取运行时间
class Duration
{
public:
    explicit Duration() : m_start(clock()){}

    inline double duration();

private:
    clock_t m_start;
};

double Duration::duration()
{
    return (double)(clock() - m_start) / CLOCKS_PER_SEC;
}

class DLogger
{
public:
    enum LogLevel
    {
        Log_Info = 0,
        Log_Debug,
        Log_Warning,
        Log_Error,
        Log_Fatal,
        Level_Num
    };

public:
    explicit DLogger(const std::string &dir = "");

    void log(const char* msg, const char* fileName, int line, LogLevel level = Log_Info);

private:
    std::string m_fileName;
    static const std::string m_levelMsg[Level_Num];
};

extern std::mutex mt;

#endif

//dlogger.cpp
#include "dlogger.h"
#include <cstring>

std::mutex mt;


const std::string DLogger::m_levelMsg[Level_Num] =
{
    "Info",
    "Debug",
    "Warning",
    "Error",
    "Fatal"
};

/**
 * 为日志文件提供一个目录，不提供目录则表示当前工作目录
 */
DLogger::DLogger(const std::string &dir)
{
    char buf[64];
    time_t now = time(0);
    tm* ltm = localtime(&now);

    sprintf(buf, "%d-%d-%d.log", ltm->tm_year + 1900, ltm->tm_mon + 1, ltm->tm_mday);

    if(dir.empty())
    {
        m_fileName = buf;
    }
    else
    {
        m_fileName = dir + "\\" + buf;
    }

}

/**
 * 记录日志
 * @param msg      [日志信息]
 * @param fileName [日志信息文件名]
 * @param line     [日志信息所在行]
 * @param level    [日志信息等级]
 */
void DLogger::log(const char* msg, const char* fileName, int line, LogLevel level)
{
    mt.lock();

    FILE* fp = ::fopen(m_fileName.data(), "a+");
    if(!fp)
    {
        mt.unlock();
        return;
    }
    char buf[1024];

    time_t now = time(0);
    tm *ltm = localtime(&now);

    ::sprintf(buf, "%d/%d/%d %d:%d:%d, %s, %d, %s, %s\n",
              1900+ltm->tm_year, ltm->tm_mon, ltm->tm_mday,
              ltm->tm_hour, ltm->tm_min, ltm->tm_sec,
              fileName, line, msg, m_levelMsg[level].data());

    ::fwrite(buf, sizeof(char),strlen(buf), fp);
    ::fclose(fp);

    mt.unlock();
}