/*** *gmtime.c - breaks down a time value into GMT date/time info * * Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved. * *Purpose: * defines gmtime() - breaks the clock value down into GMT time/date * information; return pointer to structure with the data. * *******************************************************************************/ #include #include #include #include #include #include #ifdef _MT #include #include #endif /* _MT */ #include static struct tm tb = { 0 }; /* time block */ /*** *struct tm *gmtime(timp) - convert *timp to a structure (UTC) * *Purpose: * Converts the calendar time value, in internal format (time_t), to * broken-down time (tm structure) with the corresponding UTC time. * *Entry: * const time_t *timp - pointer to time_t value to convert * *Exit: * returns pointer to filled-in tm structure. * returns NULL if *timp < 0L * *Exceptions: * *******************************************************************************/ struct tm * __cdecl gmtime ( const time_t *timp ) { long caltim = *timp; /* calendar time to convert */ int islpyr = 0; /* is-current-year-a-leap-year flag */ REG1 int tmptim; REG3 int *mdays; /* pointer to days or lpdays */ #ifdef _MT REG2 struct tm *ptb; /* will point to gmtime buffer */ _ptiddata ptd = _getptd(); #else /* _MT */ REG2 struct tm *ptb = &tb; #endif /* _MT */ if ( caltim < 0L ) return(NULL); #ifdef _MT /* Use per thread buffer area (malloc space, if necessary) */ if ( (ptd->_gmtimebuf != NULL) || ((ptd->_gmtimebuf = _malloc_crt(sizeof(struct tm))) != NULL) ) ptb = ptd->_gmtimebuf; else ptb = &tb; /* malloc error: use static buffer */ #endif /* _MT */ /* * Determine years since 1970. First, identify the four-year interval * since this makes handling leap-years easy (note that 2000 IS a * leap year and 2100 is out-of-range). */ tmptim = (int)(caltim / _FOUR_YEAR_SEC); caltim -= ((long)tmptim * _FOUR_YEAR_SEC); /* * Determine which year of the interval */ tmptim = (tmptim * 4) + 70; /* 1970, 1974, 1978,...,etc. */ if ( caltim >= _YEAR_SEC ) { tmptim++; /* 1971, 1975, 1979,...,etc. */ caltim -= _YEAR_SEC; if ( caltim >= _YEAR_SEC ) { tmptim++; /* 1972, 1976, 1980,...,etc. */ caltim -= _YEAR_SEC; /* * Note, it takes 366 days-worth of seconds to get past a leap * year. */ if ( caltim >= (_YEAR_SEC + _DAY_SEC) ) { tmptim++; /* 1973, 1977, 1981,...,etc. */ caltim -= (_YEAR_SEC + _DAY_SEC); } else { /* * In a leap year after all, set the flag. */ islpyr++; } } } /* * tmptim now holds the value for tm_year. caltim now holds the * number of elapsed seconds since the beginning of that year. */ ptb->tm_year = tmptim; /* * Determine days since January 1 (0 - 365). This is the tm_yday value. * Leave caltim with number of elapsed seconds in that day. */ ptb->tm_yday = (int)(caltim / _DAY_SEC); caltim -= (long)(ptb->tm_yday) * _DAY_SEC; /* * Determine months since January (0 - 11) and day of month (1 - 31) */ if ( islpyr ) mdays = _lpdays; else mdays = _days; for ( tmptim = 1 ; mdays[tmptim] < ptb->tm_yday ; tmptim++ ) ; ptb->tm_mon = --tmptim; ptb->tm_mday = ptb->tm_yday - mdays[tmptim]; /* * Determine days since Sunday (0 - 6) */ ptb->tm_wday = ((int)(*timp / _DAY_SEC) + _BASE_DOW) % 7; /* * Determine hours since midnight (0 - 23), minutes after the hour * (0 - 59), and seconds after the minute (0 - 59). */ ptb->tm_hour = (int)(caltim / 3600); caltim -= (long)ptb->tm_hour * 3600L; ptb->tm_min = (int)(caltim / 60); ptb->tm_sec = (int)(caltim - (ptb->tm_min) * 60); ptb->tm_isdst = 0; return( (struct tm *)ptb ); }