From 1cc81f5cb0df2b66a795ff0c26d7bbc4d16e13c6 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 17 Jul 2013 05:24:50 -0400 Subject: the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested. --- src/time/__secs_to_tm.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 src/time/__secs_to_tm.c (limited to 'src/time/__secs_to_tm.c') diff --git a/src/time/__secs_to_tm.c b/src/time/__secs_to_tm.c new file mode 100644 index 00000000..f3c1cf92 --- /dev/null +++ b/src/time/__secs_to_tm.c @@ -0,0 +1,81 @@ +#include "time_impl.h" +#include + +/* 2000-03-01 (mod 400 year, immediately after feb29 */ +#define LEAPOCH (946684800LL + 86400*(31+29)) + +#define DAYS_PER_400Y (365*400 + 97) +#define DAYS_PER_100Y (365*100 + 24) +#define DAYS_PER_4Y (365*4 + 1) + +int __secs_to_tm(long long t, struct tm *tm) +{ + long long days, secs; + int remdays, remsecs, remyears; + int qc_cycles, c_cycles, q_cycles; + int years, months; + int wday, yday, leap; + static const char days_in_month[] = {31,30,31,30,31,31,30,31,30,31,31,29}; + + /* Reject time_t values whose year would overflow int */ + if (t < INT_MIN * 31622400LL || t > INT_MAX * 31622400LL) + return -1; + + secs = t - LEAPOCH; + days = secs / 86400; + remsecs = secs % 86400; + if (remsecs < 0) { + remsecs += 86400; + days--; + } + + wday = (3+days)%7; + if (wday < 0) wday += 7; + + qc_cycles = days / DAYS_PER_400Y; + remdays = days % DAYS_PER_400Y; + if (remdays < 0) { + remdays += DAYS_PER_400Y; + qc_cycles--; + } + + c_cycles = remdays / DAYS_PER_100Y; + if (c_cycles == 4) c_cycles--; + remdays -= c_cycles * DAYS_PER_100Y; + + q_cycles = remdays / DAYS_PER_4Y; + if (q_cycles == 25) q_cycles--; + remdays -= q_cycles * DAYS_PER_4Y; + + remyears = remdays / 365; + if (remyears == 4) remyears--; + remdays -= remyears * 365; + + leap = !remyears && (q_cycles || !c_cycles); + yday = remdays + 31 + 28 + leap; + if (yday >= 365+leap) yday -= 365+leap; + + years = remyears + 4*q_cycles + 100*c_cycles + 400*qc_cycles; + + for (months=0; days_in_month[months] <= remdays; months++) + remdays -= days_in_month[months]; + + if (years+100 > INT_MAX || years+100 < INT_MIN) + return -1; + + tm->tm_year = years + 100; + tm->tm_mon = months + 2; + if (tm->tm_mon >= 12) { + tm->tm_mon -=12; + tm->tm_year++; + } + tm->tm_mday = remdays + 1; + tm->tm_wday = wday; + tm->tm_yday = yday; + + tm->tm_hour = remsecs / 3600; + tm->tm_min = remsecs / 60 % 60; + tm->tm_sec = remsecs % 60; + + return 0; +} -- cgit v1.2.1