計算時間差

time_t tr_timediff(const tm * ptm1, const tm * ptm2) {     uint16_t year;     uint32_t days = 0;     uint8_t n;     uint64_t time = 0;     tm * pendtm = NULL;     uint8_t nptm1monthday = 0;     assert(ptm1 != NULL);     if (NULL == ptm2)     {         //計算本地時間         tr_time(pendtm);assert(pendtm != NULL);     }     else     {         pendtm = ptm2;     }          if     if (pendtm->tm_year != ptm1->tm_year)     {         //不是同一年         year = pendtm->tm_year - 1;         while (year > ptm1->tm_year)         {             //計算全年天數             if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)             {                 days += 366;             }             else             {                 days += 365;             }             year -= 1;         }         for (n = 12; n >= ptm1->tm_month; --n)         {             //計算開始時間月數             switch (n)             {                 case 1:                 case 3:                 case 5:                 case 7:                 case 8:                 case 10:                 case 12:                 {                     if (n == ptm1->tm_month)                     {                         nptm1monthday = 31;                     }                     else                     {                         days += 31;                     }                 }                     break;                 case 4:                 case 6:                 case 9:                 case 11:                 {                     if (n == ptm1->tm_month)                     {                         nptm1monthday = 30;                     }                     else                     {                         days += 30;                     }                 }                     break;                 case 2:                 {                     if (n == ptm1->tm_month)                     {                         if (((ptm1->tm_year) % 4 == 0 && (ptm1->tm_year) % 100                                 != 0) || (ptm1->tm_year) % 400 == 0)                         {                             nptm1monthday = 29;                         }                         else                         {                             nptm1monthday = 28;                         }                     }                     else                     {                         if (((ptm1->tm_year) % 4 == 0 && (ptm1->tm_year) % 100                                 != 0) || (ptm1->tm_year) % 400 == 0)                         {                             days += 29;                         }                         else                         {                             days += 28;                         }                     }                 }             }         }         for (n = 1; n < pendtm->tm_month; ++n)         {             //計算結束時間月數             switch (n)             {                 case 1:                 case 3:                 case 5:                 case 7:                 case 8:                 case 10:                 case 12:                 {                     days += 31;                 }                     break;                 case 4:                 case 6:                 case 9:                 case 11:                 {                     days += 30;                 }                     break;                 case 2:                 {                     if (((pendtm->tm_year) % 4 == 0 && (pendtm->tm_year) % 100 != 0)                             || (pendtm->tm_year) % 400 == 0)                     {                         days += 29;                     }                     else                     {                         days += 28;                     }                 }             }         }         days += pendtm->tm_day - 1;//累加結束時間天數         days += nptm1monthday - ptm1->tm_day;//累加開始時間天數         time = (days * 24 * 60 * 60) + (pendtm->tm_hour * 3600 + pendtm->tm_minute                 * 60 + pendtm->tm_second) + ((24 - ptm1->tm_hour - 1) * 3600                 + ((60 - ptm1->tm_minute - 1) * 60) + 60 - ptm1->tm_second);     }     else     {         //開始時間和結束時間是同一年         for (n = ptm1->tm_month; n < pendtm->tm_month; ++n)         {             //計算開始和結束月份             switch (n)             {                 case 1:                 case 3:                 case 5:                 case 7:                 case 8:                 case 10:                 case 12:                 {                     if (n == ptm1->tm_month)                     {                         nptm1monthday = 31;                     }                     else                     {                         days += 31;                     }                 }                     break;                 case 4:                 case 6:                 case 9:                 case 11:                 {                     if (n == ptm1->tm_month)                     {                         nptm1monthday = 30;                     }                     else                     {                         days += 30;                     }                 }                     break;                 case 2:                 {                     if (n == ptm1->tm_month)                     {                         if (((ptm1->tm_year) % 4 == 0 && (ptm1->tm_year) % 100                                 != 0) || (ptm1->tm_year) % 400 == 0)                         {                             nptm1monthday = 29;                         }                         else                         {                             nptm1monthday = 28;                         }                     }                     else                     {                         if (((ptm1->tm_year) % 4 == 0 && (ptm1->tm_year) % 100                                 != 0) || (ptm1->tm_year) % 400 == 0)                         {                             days += 29;                         }                         else                         {                             days += 28;                         }                     }                 }             }         }         if (ptm1->tm_month != pendtm->tm_month)         {             //若是開始時間和結束時間不是同一月             days += pendtm->tm_day;//累加結束時間天數             days += nptm1monthday - ptm1->tm_day;//累加開始時間天數         }         else         {             //同年同月中             days += pendtm->tm_day - ptm1->tm_day;         }         time = (days * 24 * 60 * 60) + ((pendtm->tm_hour - ptm1->tm_hour) * 3600                 + (pendtm->tm_minute - ptm1->tm_minute) * 60 + pendtm->tm_second                 - ptm1->tm_second);     }     return time; }