c++ - 序列化和反序列化time_t变量后的结果不正确

这个小程序重现了我项目中的错误。 time_t变量转换为struct_tm，然后转换为字符串，并序列化为file。稍后，此字符串将从文件加载，并应转换回time_t。结果time_t与原始时间相差一小时（可能是因为夏令时）。我只能更改反序列化部分，因为文件格式应保持不变。

#include "stdafx.h"
#include <iostream>
#include <string>
#include <time.h>

using namespace std;

string FormatDateTime(struct tm* time);
void Test();


int _tmain(int argc, _TCHAR* argv[])
{
    Test();
    return 0;
}


string FormatDateTime(struct tm* time)
{
    static const char* months[] =
    {
        "Jan", "Feb",  "Mar", "Apr", "May", "Jun",  "Jul", "Aug",  "Sep", "Oct",  "Nov", "Dec"
    };

    char s[30];
    const char* month;

    if ( time->tm_mon >= 0  &&  time->tm_mon < 12 )
    {
        month = months[time->tm_mon];
    }
    else
    {
        month = "??";
    }

    sprintf(s, "%d-%s-%02d %02d:%02d:%02d",
        time->tm_year + 1900,
        month,
        time->tm_mday,
        time->tm_hour,
        time->tm_min,
        time->tm_sec);

    return s;
}

void Test()
{
    // time_t variable is initialized with current time
    time_t t = time(NULL);

    // time_t variable is converted to struct tm and then to string
    struct tm* ptm = localtime(&t);

    char buffer[100];

    sprintf(buffer, "%d %d %d %d %d %d",
        ptm->tm_mday, ptm->tm_mon + 1, ptm->tm_year + 1900, ptm->tm_hour, ptm->tm_min, ptm->tm_sec);

    cout << buffer << endl;         // string is OK


    // string is saved to the file

    // *********************************************************************************************

    // later this string is restored from the file

    // **** I can change something only after this line **** //

    struct tm stm;
    memset(&stm, 0, sizeof(stm));

    sscanf(buffer, "%d %d %d %d %d %d",
        &stm.tm_mday, &stm.tm_mon, &stm.tm_year, &stm.tm_hour, &stm.tm_min, &stm.tm_sec);

    stm.tm_mon -= 1;
    stm.tm_year -= 1900;

    string s = FormatDateTime(ptm);

    cout << s << endl;              // OK

    // *********************************************************************************************
    // Now I need to convert struct tm to time_t and keep it in the variable

    time_t t1 = mktime(&stm);       // not the same time - 1 hour difference

    if ( t1 == t )
    {
        cout << "t1 == t" << endl;
    }
    else
    {
        cout << "t1 != t   !!!!!" << endl;
    }

    // time_t is printed - result is incorrect

    // Utilities::FormatDateTime
    struct tm* ptm1 = localtime(&t1);

    s = FormatDateTime(ptm1);

    cout << s << endl;
}

当地时间是11.33。结果：

19 7 2012 11 33 17
2012-Jul-19 11:33:17
t1 != t   !!!!!
2012-Jul-19 12:33:17

如何更改此程序的最后一部分以获得正确的结果？

序列化和反序列化time_t变量后的结果不正确

2 个答案: