时间相关函数的实现

#include <stdio.h>

/**/
typedef struct _date_time_{
    unsigned char year;/*[0,99]*/
    unsigned char mon;/*[1,12]*/
    unsigned char mday;/*[1,31]*/
    unsigned char hour;/*[0,23]*/
    unsigned char min;/*[0,59]*/
    unsigned char sec;/*[0,59]*/
    unsigned char week;/*[0,6]*/
}date_time_t;


/*
    这个函数将时间转换成从1970年1月1日0小时0分0秒到你输入的时间所经过的秒数，溢出时间为2106-02-07 06:28:16。
    若你要计算2000-02-07 06:28:16 到2000-02-09 06:28:16 所经过的秒数：
    unsigned long time1 = Dt_mktime_abs(2000, 2, 7, 6, 28, 16) - Dt_mktime_abs(2000, 2, 9, 6, 28, 16)
*/
unsigned long Dt_mktime_abs(date_time_t *pTm)
{
    int year/*[2000, 2099]*/ = pTm->tm_year/*[00, 99]*/ + 2000;
    int mon/*[1, 12]*/ = pTm->tm_mon/*[1, 12]*/;
    int day/*[1, 31]*/ = pTm->tm_mday/*[1, 31]*/;
    int hour = pTm->tm_hour/*[0, 23]*/;
    int min = pTm->tm_min/*[0, 59]*/;
    int sec = pTm->tm_sec/*[0, 59]*/;

    /**/
    if(((int)(mon -= 2)) <= 0)
    {
        mon += 12;/* Puts Feb last since it has leap day */
        year -= 1;
    }

    return ((((unsigned long)(year / 4 - year / 100 + year / 400 + 367 * mon / 12 + day) + year * 365 - 719499) * 24
                    + hour /* now have hours */) * 60 + min /* now have minutes */)*60 + sec; /* finally seconds */
}


/**/
int Calc_week_day( unsigned int year/*[2000, 2099]*/, unsigned int mon/*[1, 12]*/, unsigned int day/*[1, 31]*/)
{
    int week = 0;
    unsigned int y = 0;
    unsigned int c = 0;
    unsigned int m = 0;
    unsigned int d = 0;

    if((mon == 1) || (mon == 2))
    {
        c = ( year - 1 ) / 100;
        y = ( year - 1 ) % 100;
        m = mon + 12;
        d = day;
    }
    else
    {
        c = year / 100;
        y = year % 100;
        m = mon;
        d = day;
    }

    week = y + y / 4 + c / 4 - 2 * c + 26 * ( m + 1 ) / 10 + d - 1; //蔡勒公式
    week = week >= 0 ? ( week % 7 ) : ( week % 7 + 7 ); //week为负时取模

    return week;
}


/*
    1:leap year
    0:not leap year
*/
int Is_leap_year(unsigned int year)
{
    if(((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0))
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

/*
 The number of days in the month.
*/
unsigned char Get_days_in_month(unsigned int year, unsigned int mon/*[1,12]*/)
{
    unsigned char day_table[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    if((mon == 2) && (is_leap_year(year) == 1))
    {
        return 29;
    }
    else
    {
        return day_table[mon];
    }
}

/*
 * Convert seconds since 01-01-1970 00:00:00 to date.
 */
void Dt_time_to_tm(unsigned long time, date_time_t *pTm)
{
    unsigned int month = 0;
    unsigned int year = 0;
    int days = 0;
    int tm_year = 0;
    int tm_mon = 0;
    int tm_mday = 0;
    int tm_hour = 0;
    int tm_min = 0;
    int tm_sec = 0;
    int newdays = 0;

    /**/
#define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)

    /**/
    days = time / 86400;
    time -= (unsigned int)days * 86400;
    year = 1970 + days / 365;
    days -= (year - 1970) * 365 + LEAPS_THRU_END_OF(year - 1) - LEAPS_THRU_END_OF(1970 - 1);
    if (days < 0)
    {
        year -= 1;
        days += 365 + is_leap_year(year);
    }
    tm_year = year - 1900;
    for (month = 0; month < 11; month++)
    {
        newdays = days - rtc_month_days(month, year);
        if (newdays < 0)
        {
            break;
        }
        days = newdays;
    }
    tm_mon = month;
    tm_mday = days + 1;
    tm_hour = time / 3600;
    time -= tm_hour * 3600;
    tm_min = time / 60;
    tm_sec = time - tm_min * 60;

    /**/
    pTm->year = (unsigned char)(tm_year - 100);
    pTm->mon = (unsigned char)(tm_mon + 1);
    pTm->mday = (unsigned char)(tm_mday);
    pTm->hour = (unsigned char)(tm_hour);
    pTm->min = (unsigned char)(tm_min);
    pTm->sec = (unsigned char)(tm_sec);

    /**/
    pTm->week = (unsigned char)Calc_week_day(pTm->year + 2000, pTm->mon, pTm->mday);
}


/**/
int Dt_get_day_by_week(unsigned char year/*[0, 99]*/, unsigned char month/*[1, 12]*/,
                                unsigned char week_index/*>= 1*/, unsigned char week_day/*[0, 6]*/)
{
    /**/
    unsigned char week_day_ = 0;
    unsigned char day = 0;

    /**/
    if(!((year <= 99) && ((month >= 1) && (month <= 12)) && (week_index >= 1) &&
                                (week_day <= 6)))
    {
        printf("Invalid parameter(%d, %d, %d, %d)\r\n", year, month, week_index, week_day);
        return -1;
    }
    /*计算这个月的1号是星期几*/
    week_day_ = Calc_week_day(year + 2000, month, 1);
    /**/
    if(week_day >= week_day_)
    {
        day = week_day - week_day_ + 1;
    }
    else
    {
        day = 8 - week_day_ + week_day;
    }
    /**/
    day += (week_index - 1) * 7;

    /**/
    if(day > Get_days_in_month(year, month))
    {
        printf("Invalid result(%d, %d, %d, %d, %d)\r\n", year, month, week_index, week_day, day);
        return -1;
    }

    /**/
    return day;
}