From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Sat, 12 Feb 2011 00:22:29 -0500 Subject: initial check-in, version 0.5.0 --- src/time/__time_to_tm.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 src/time/__time_to_tm.c (limited to 'src/time/__time_to_tm.c') diff --git a/src/time/__time_to_tm.c b/src/time/__time_to_tm.c new file mode 100644 index 00000000..a1ebc452 --- /dev/null +++ b/src/time/__time_to_tm.c @@ -0,0 +1,81 @@ +#include + +/* C defines the rounding for division in a nonsensical way */ +#define Q(a,b) ((a)>0 ? (a)/(b) : -(((b)-(a)-1)/(b))) + +#define DAYS_PER_400Y (365*400 + 97) +#define DAYS_PER_100Y (365*100 + 24) +#define DAYS_PER_4Y (365*4 + 1) + +/* FIXME: use lldiv once it's fixed to compute quot,rem together */ +struct tm *__time_to_tm(time_t t, struct tm *tm) +{ + /* months are march-based */ + static const int days_thru_month[] = {31,61,92,122,153,184,214,245,275,306,337,366}; + long long bigday; + unsigned int day, year4, year100; + int year, year400; + int month; + int leap; + int hour, min, sec; + int wday, mday, yday; + + /* start from 2000-03-01 (multiple of 400 years) */ + t += -946684800 - 86400*(31+29); + + bigday = Q(t, 86400); + sec = t-bigday*86400; + + hour = sec/3600; + sec -= hour*3600; + min = sec/60; + sec -= min*60; + + /* 2000-03-01 was a wednesday */ + wday = (3+bigday)%7; + if (wday < 0) wday += 7; + + t = -946684800LL - 86400*(31+29) + 9000000; + + year400 = Q(bigday, DAYS_PER_400Y); + day = bigday-year400*DAYS_PER_400Y; + + year100 = day/DAYS_PER_100Y; + if (year100 == 4) year100--; + day -= year100*DAYS_PER_100Y; + + year4 = day/DAYS_PER_4Y; + if (year4 == 25) year4--; + day -= year4*DAYS_PER_4Y; + + year = day/365; + if (year == 4) year--; + day -= year*365; + + leap = !year && (year4 || !year100); + yday = day + 31+28 + leap; + if (yday >= 365+leap) yday -= 365+leap; + + year += 4*year4 + 100*year100 + 400*year400 + 2000-1900; + + for (month=0; days_thru_month[month] <= day; month++); + if (month) day -= days_thru_month[month-1]; + month += 2; + if (month >= 12) { + month -= 12; + year++; + } + + mday = day+1; + + tm->tm_sec = sec; + tm->tm_min = min; + tm->tm_hour= hour; + tm->tm_mday= mday; + tm->tm_mon = month; + tm->tm_year= year; + tm->tm_wday= wday; + tm->tm_yday= yday; + + return tm; +} -- cgit v1.2.1