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Annotation of coherent/b/bin/zip/mktime.c, revision 1.1.1.1

1.1       root        1: /* free mktime function
                      2:    Copyright 1988, 1989 by David MacKenzie <[email protected]>
                      3:    and Michael Haertel <[email protected]>
                      4:    Unlimited distribution permitted provided this copyright notice is
                      5:    retained and any functional modifications are prominently identified.  */
                      6: 
                      7: /* Note: This version of mktime is ignorant of the tzfile; it does not
                      8:    return correct results during the few hours around when daylight savings
                      9:    time goes in to or out of effect.  It also does not allow or adjust
                     10:    for invalid values in any of the fields, contrary to the ANSI C
                     11:    specification. */
                     12: 
                     13: #ifdef MKTIME_MISSING
                     14: #include <sys/types.h>
                     15: #include <time.h>
                     16: 
                     17: time_t mkgmtime ();
                     18: 
                     19: /* Return the equivalent in seconds past 12:00:00 a.m. Jan 1, 1970 GMT
                     20:    of the local time and date in the exploded time structure `tm',
                     21:    and set `tm->tm_yday', `tm->tm_wday', and `tm->tm_isdst'.
                     22:    Return -1 if any of the other fields in `tm' has an invalid value. */
                     23: 
                     24: time_t
                     25: mktime (tm)
                     26:      struct tm *tm;
                     27: {
                     28:   struct tm save_tm;            /* Copy of contents of `*tm'. */
                     29:   struct tm *ltm;               /* Local time. */
                     30:   time_t then;                  /* The time to return. */
                     31: 
                     32:   then = mkgmtime (tm);
                     33:   if (then == -1)
                     34:     return -1;
                     35: 
                     36:   /* In case `tm' points to the static area used by localtime,
                     37:      save its contents and restore them later. */
                     38:   save_tm = *tm;
                     39:   /* Correct for the timezone and any daylight savings time.
                     40:      If a change to or from daylight savings time occurs between when
                     41:      it is the time in `tm' locally and when it is that time in Greenwich,
                     42:      the change to or from dst is ignored, but that is a rare case. */
                     43:   then += then - mkgmtime (localtime (&then));
                     44: 
                     45:   ltm = localtime (&then);
                     46:   save_tm.tm_yday = ltm->tm_yday;
                     47:   save_tm.tm_wday = ltm->tm_wday;
                     48:   save_tm.tm_isdst = ltm->tm_isdst;
                     49:   *tm = save_tm;
                     50: 
                     51:   return then;
                     52: }
                     53: 
                     54: /* Nonzero if `y' is a leap year, else zero. */
                     55: #define leap(y) (((y) % 4 == 0 && (y) % 100 != 0) || (y) % 400 == 0)
                     56: 
                     57: /* Number of leap years from 1970 to `y' (not including `y' itself). */
                     58: #define nleap(y) (((y) - 1969) / 4 - ((y) - 1901) / 100 + ((y) - 1601) / 400)
                     59: 
                     60: /* Number of days in each month of the year. */
                     61: static char monlens[] =
                     62: {
                     63:   31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
                     64: };
                     65: 
                     66: /* Return the equivalent in seconds past 12:00:00 a.m. Jan 1, 1970 GMT
                     67:    of the Greenwich Mean time and date in the exploded time structure `tm',
                     68:    and set `tm->tm_yday', `tm->tm_wday', and `tm->tm_isdst'.
                     69:    Return -1 if any of the other fields in `tm' has an invalid value. */
                     70: 
                     71: time_t
                     72: mkgmtime (tm)
                     73:      struct tm *tm;
                     74: {
                     75:   int years, months, days, hours, minutes, seconds;
                     76: 
                     77:   years = tm->tm_year + 1900;   /* year - 1900 -> year */
                     78:   months = tm->tm_mon;          /* 0..11 */
                     79:   days = tm->tm_mday - 1;       /* 1..31 -> 0..30 */
                     80:   hours = tm->tm_hour;          /* 0..23 */
                     81:   minutes = tm->tm_min;         /* 0..59 */
                     82:   seconds = tm->tm_sec;         /* 0..61 in ANSI C. */
                     83: 
                     84:   if (years < 1970
                     85:       || months < 0 || months > 11
                     86:       || days < 0
                     87:       || days > monlens[months] + (months == 1 && leap (years)) - 1
                     88:       || hours < 0 || hours > 23
                     89:       || minutes < 0 || minutes > 59
                     90:       || seconds < 0 || seconds > 61)
                     91:   return -1;
                     92: 
                     93:   /* Set `days' to the number of days into the year. */
                     94:   if (months > 1 && leap (years))
                     95:     ++days;
                     96:   while (months-- > 0)
                     97:     days += monlens[months];
                     98:   tm->tm_yday = days;
                     99: 
                    100:   /* Now set `days' to the number of days since Jan 1, 1970. */
                    101:   days += 365 * (years - 1970) + nleap (years);
                    102:   tm->tm_wday = (days + 4) % 7; /* Jan 1, 1970 was Thursday. */
                    103:   tm->tm_isdst = 0;
                    104: 
                    105:   return 86400 * days + 3600 * hours + 60 * minutes + seconds;
                    106: }
                    107: #endif

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