time_string_to_time_t time_t_to_tm

前言

工程中要用到几个时间转换的函数，写了个demo, 验证一下。
实验环境：debian8.8

实验

// @file time_convert.h
// @brief 时间转换

#ifndef __TIME_CONVERT_H__
#define __TIME_CONVERT_H__

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string>

/**
 Returns the difference between gmt and local time in seconds.
 Use gmtime() and localtime() to keep things simple.
 */
long get_offset_from_gmt_to_local(time_t tm_in);

time_t time_t_add_offset(time_t tm_in, long l_offset);
std::string get_time_t_string(time_t tm_in);

// "2018-07-09 10:12:00" to time_t
time_t time_string_to_time_t(const char* date_time_y_m_d_h_m_s);
time_t get_current_time_t();
struct tm time_t_to_tm(time_t in);

#endif // #ifndef __TIME_CONVERT_H__

// @file time_convert.cpp
// @brief syslog日志宏的实现

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "time_convert.h"

long get_offset_from_gmt_to_local(time_t tm_in)
{
    long dt = 0;
    long dir = 0;
    struct tm *gmt = NULL;
    struct tm*loc = NULL;
    struct tm sgmt;

    if (tm_in == 0) {
        tm_in = time(NULL);
    }

    gmt = &sgmt;
    *gmt = *gmtime(&tm_in);
    loc = localtime(&tm_in);

    dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60
        + (loc->tm_min - gmt->tm_min) * 60;

    /**
     If the year or julian day is different, we span 00:00 GMT
     and must add or subtract a day. Check the year first to
     avoid problems when the julian day wraps.
     */
    dir = loc->tm_year - gmt->tm_year;
    if (dir == 0) {
        dir = loc->tm_yday - gmt->tm_yday;
    }

    dt += dir * 24 * 60 * 60;

    return (dt);
}

time_t time_t_add_offset(time_t tm_in, long l_offset)
{
    time_t tm_rc = tm_in;

    tm_rc += l_offset;

    return tm_rc;
}

std::string get_time_t_string(time_t tm_in)
{
    char sz_buf[0x100] = {'\0'};
    time_t tm_tmp = tm_in;
    std::string str_rc = "";
    tm* p_tm_gmt = NULL;

    p_tm_gmt = gmtime(&tm_tmp);
    if (NULL != p_tm_gmt) {
        sprintf(sz_buf, "%04d-%02d-%02d %02d:%02d:%02d",
              p_tm_gmt->tm_year + 1900,
              p_tm_gmt->tm_mon + 1,
              p_tm_gmt->tm_mday,
              p_tm_gmt->tm_hour,
              p_tm_gmt->tm_min,
              p_tm_gmt->tm_sec);

        str_rc = sz_buf;
    }

    return str_rc;
}

time_t time_string_to_time_t(const char* date_time_y_m_d_h_m_s)
{
    time_t rc;
    struct tm tm;

    if (NULL != date_time_y_m_d_h_m_s) {
        strptime(date_time_y_m_d_h_m_s, "%Y-%m-%d %H:%M:%S", &tm);
        rc = mktime(&tm);  // t is now your desired time_t
    } else {
        rc = get_current_time_t();
    }

    return rc;
}

time_t get_current_time_t()
{
    time_t rawtime;
    time_t rc;
    struct tm* timeinfo = NULL;

    time(&rawtime);
    timeinfo = localtime(&rawtime);

    // if do other case, can modify time now
    // e.g. 
    //  timeinfo->tm_year = year - 1900;
    //  timeinfo->tm_mon = month - 1;
    //  timeinfo->tm_mday = day;

    /* call mktime: timeinfo->tm_wday will be set */
    rc = mktime(timeinfo);

    return rc;
}

struct tm time_t_to_tm(time_t in)
{
    struct tm* timeinfo = NULL;
    struct tm rc;

    timeinfo = localtime(&in);
    memcpy(&rc, timeinfo, sizeof(struct tm));
    return rc;
}

// @file main.cpp

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h> // daemon
#include <signal.h>
#include <time.h>

#include "my_syslog.h"
#include "time_convert.h"

#ifndef SAFE_DELETE
#define SAFE_DELETE(p) \
    if (NULL != (p)) { \
        delete (p); \
        (p) = NULL; \
    }
#endif // #ifndef SAFE_DELETE

void init(const char* psz_log_owner_name);
void uninit();
void proc_sig_term(int num);
void show_time_stamp(const char* psz_tip, long ts);
int fn_test();

int main(int argc, char** argv)
{
    char sz_buf[1024] = {'\0'};

#ifdef MAKE_FILE_MACRO__BIN_NAME
    sprintf(sz_buf, "%s", MAKE_FILE_MACRO__BIN_NAME);
    init(sz_buf);
    MYLOG_D("MAKE_FILE_MACRO__BIN_NAME = [%s]", MAKE_FILE_MACRO__BIN_NAME);
#else
    init(NULL);
#endif // #ifdef MAKE_FILE_MACRO__BIN_NAME

    fn_test();
    uninit();

    MYLOG_D("THE END");
    return EXIT_SUCCESS;
}

void init(const char* psz_log_owner_name)
{
    int i = 0;

    daemon(0, 0);

    ns_syslog::open_syslog((NULL != psz_log_owner_name) ? psz_log_owner_name : "ns_syslog");

    // 设置控制变量中的日志条件, 实际应用中, 是从配置文件读取的控制开关
    ns_syslog::g_log_condition.b_EMERG = false;
    ns_syslog::g_log_condition.b_CRIT = true;
    ns_syslog::g_log_condition.b_ALERT = true;
    ns_syslog::g_log_condition.b_ERR = true;
    ns_syslog::g_log_condition.b_WARNING = true;
    ns_syslog::g_log_condition.b_NOTICE = true;
    ns_syslog::g_log_condition.b_INFO = true;
    ns_syslog::g_log_condition.b_DEBUG = true;

    // 根据控制变量, 设置日志的mask
    // 在实际应用中, 这里可以是动态设置, e.g. 配置文件检测线程发现配置变了, 需要变更某些级别的日志记录结果
    ns_syslog::set_log_level(
        ns_syslog::g_log_condition.b_EMERG, 
        ns_syslog::g_log_condition.b_ALERT,
        ns_syslog::g_log_condition.b_CRIT,
        ns_syslog::g_log_condition.b_ERR,
        ns_syslog::g_log_condition.b_WARNING,
        ns_syslog::g_log_condition.b_NOTICE,
        ns_syslog::g_log_condition.b_INFO,
        ns_syslog::g_log_condition.b_DEBUG);

    // clear screen (print 25 empty line)
    for (i = 0; i < 25; i++) {
        MYLOG_D("");
    }

    signal(SIGTERM, proc_sig_term);
}

void uninit()
{
    ns_syslog::close_syslog();
}

void proc_sig_term(int num)
{
    MYLOG_D("SIGTERM = %d, num = %d", SIGTERM, num);
    MYLOG_D("maybe can do some clean task before quit");
    exit(1);    
}

int fn_test()
{
    time_t time_t_give_by_user;
    struct tm tm_give_by_user;

    time_t time_t_cur;
    struct tm tm_cur;

    MYLOG_D(">> fn_test()");

    time_t_give_by_user = time_string_to_time_t("2018-07-08 10:46:06");
    tm_give_by_user = time_t_to_tm(time_t_give_by_user);

    // https://en.cppreference.com/w/c/chrono/tm
    MYLOG_D("tm_give_by_user = %d-%d-%d %d:%d:%d",
        tm_give_by_user.tm_year + 1900,
        tm_give_by_user.tm_mon + 1,
        tm_give_by_user.tm_mday,
        tm_give_by_user.tm_hour,
        tm_give_by_user.tm_min,
        tm_give_by_user.tm_sec);

    time_t_cur = get_current_time_t();
    tm_cur = time_t_to_tm(time_t_cur);

    MYLOG_D("tm_cur = %d-%d-%d %d:%d:%d",
        tm_cur.tm_year + 1900,
        tm_cur.tm_mon + 1,
        tm_cur.tm_mday,
        tm_cur.tm_hour,
        tm_cur.tm_min,
        tm_cur.tm_sec);

    /* run result
    Jul  9 11:01:24 localhost test_timezone[1663]: [DEBUG : main.cpp.34 : main()] : MAKE_FILE_MACRO__BIN_NAME = [test_timezone]
    Jul  9 11:01:24 localhost test_timezone[1663]: [DEBUG : main.cpp.104 : fn_test()] : >> fn_test()
    Jul  9 11:01:24 localhost test_timezone[1663]: [DEBUG : main.cpp.116 : fn_test()] : tm_give_by_user = 2018-7-8 10:46:6
    Jul  9 11:01:24 localhost test_timezone[1663]: [DEBUG : main.cpp.127 : fn_test()] : tm_cur = 2018-7-9 11:1:24
    Jul  9 11:01:24 localhost test_timezone[1663]: [DEBUG : main.cpp.42 : main()] : THE END
    */

    // tm_now = time(NULL); // 1521255156, 这种是秒数
    // MYLOG_D("tm_now = %lld", (long long)tm_now);

    // show_time_stamp("current local time", tm_now);

    // 1520906625610 这种是时间戳，是毫秒数
    // show_time_stamp("3rd give time 1", 1520906625610 / 1000);
    // show_time_stamp("3rd give time 2", 1520920367484 / 1000);

    return 0;
}

void show_time_stamp(const char* psz_tip, long ts)
{
    time_t tm_fixed;
    long l_offset = 0;

    MYLOG_D("%s", (NULL != psz_tip) ? psz_tip : "show_time_stamp");

    // 28800 is 8hours(8 * 60 * 60 second)
    l_offset = get_offset_from_gmt_to_local(ts);

    tm_fixed = time_t_add_offset(ts, l_offset);
    MYLOG_D("tm_fixed = %lld => %s", (long long)tm_fixed, get_time_t_string(tm_fixed).c_str());
}

2018_0709_1418

还需要比较2个time_t, 验证了一下。

    time_t_begin = get_current_time_t();
    sleep(2);
    time_t_end = get_current_time_t();

    db_offset = difftime(time_t_end, time_t_begin);
    MYLOG_D("difftime(time_t_end, time_t_begin) = %d", (int)db_offset);

    db_offset = difftime(time_t_begin, time_t_end);
    MYLOG_D("difftime(time_t_begin, time_t_end) = %d", (int)db_offset);

    /* run result
    Jul  9 14:16:03 localhost test_timezone[2406]: [DEBUG : main.cpp.118 : fn_test()] : difftime(time_t_end, time_t_begin) = 2
    Jul  9 14:16:03 localhost test_timezone[2406]: [DEBUG : main.cpp.121 : fn_test()] : difftime(time_t_begin, time_t_end) = -2
    */