148 lines
3.8 KiB
C
148 lines
3.8 KiB
C
/* Originally released by the musl project (http://www.musl-libc.org/) under the
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* MIT license. Taken from the file /src/time/__secs_to_tm.c */
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#include <limits.h>
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#include "libc_time.h"
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/* 2000-03-01 (mod 400 year, immediately after feb29 */
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#define LEAPOCH (946684800LL + 86400*(31+29))
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#define DAYS_PER_400Y (365*400 + 97)
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#define DAYS_PER_100Y (365*100 + 24)
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#define DAYS_PER_4Y (365*4 + 1)
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int __secs_to_tm(long long t, struct mytm *tm) {
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long long days, secs, years;
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int remdays, remsecs, remyears;
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int qc_cycles, c_cycles, q_cycles;
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int months;
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static const char days_in_month[] = {31,30,31,30,31,31,30,31,30,31,31,29};
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/* Reject time_t values whose year would overflow int */
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if (t < INT_MIN * 31622400LL || t > INT_MAX * 31622400LL)
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return -1;
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secs = t - LEAPOCH;
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days = secs / 86400LL;
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remsecs = (int)(secs % 86400);
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if (remsecs < 0) {
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remsecs += 86400;
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--days;
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}
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qc_cycles = (int)(days / DAYS_PER_400Y);
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remdays = (int)(days % DAYS_PER_400Y);
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if (remdays < 0) {
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remdays += DAYS_PER_400Y;
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--qc_cycles;
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}
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c_cycles = remdays / DAYS_PER_100Y;
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if (c_cycles == 4) --c_cycles;
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remdays -= c_cycles * DAYS_PER_100Y;
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q_cycles = remdays / DAYS_PER_4Y;
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if (q_cycles == 25) --q_cycles;
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remdays -= q_cycles * DAYS_PER_4Y;
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remyears = remdays / 365;
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if (remyears == 4) --remyears;
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remdays -= remyears * 365;
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years = remyears + 4*q_cycles + 100*c_cycles + 400LL*qc_cycles;
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for (months=0; days_in_month[months] <= remdays; ++months)
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remdays -= days_in_month[months];
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if (years+100 > INT_MAX || years+100 < INT_MIN)
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return -1;
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tm->tm_year = (int)(years + 100);
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tm->tm_mon = months + 2;
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if (tm->tm_mon >= 12) {
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tm->tm_mon -=12;
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++tm->tm_year;
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}
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tm->tm_mday = remdays + 1;
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tm->tm_hour = remsecs / 3600;
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tm->tm_min = remsecs / 60 % 60;
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tm->tm_sec = remsecs % 60;
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return 0;
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}
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static const int secs_through_month[] =
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{0, 31*86400, 59*86400, 90*86400,
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120*86400, 151*86400, 181*86400, 212*86400,
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243*86400, 273*86400, 304*86400, 334*86400 };
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static int
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__month_to_secs(int month, int is_leap) {
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int t = secs_through_month[month];
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if (is_leap && month >= 2)
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t+=86400;
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return t;
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}
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static long long
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__year_to_secs(const long long year, int *is_leap) {
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int cycles, centuries, leaps, rem;
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int is_leap_val = 0;
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if (!is_leap) {
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is_leap = &is_leap_val;
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}
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cycles = (int)((year-100) / 400);
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rem = (int)((year-100) % 400);
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if (rem < 0) {
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cycles--;
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rem += 400;
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}
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if (!rem) {
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*is_leap = 1;
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centuries = 0;
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leaps = 0;
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} else {
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if (rem >= 200) {
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if (rem >= 300) centuries = 3, rem -= 300;
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else centuries = 2, rem -= 200;
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} else {
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if (rem >= 100) centuries = 1, rem -= 100;
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else centuries = 0;
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}
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if (!rem) {
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*is_leap = 0;
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leaps = 0;
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} else {
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leaps = (rem / (int)4U);
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rem %= (int)4U;
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*is_leap = !rem;
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}
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}
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leaps += 97*cycles + 24*centuries - *is_leap;
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return (year-100) * 31536000LL + leaps * 86400LL + 946684800 + 86400;
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}
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long long __tm_to_secs(const struct mytm *tm) {
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int is_leap;
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long long year = tm->tm_year;
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int month = tm->tm_mon;
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if (month >= 12 || month < 0) {
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int adj = month / 12;
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month %= 12;
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if (month < 0) {
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adj--;
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month += 12;
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}
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year += adj;
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}
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long long t = __year_to_secs(year, &is_leap);
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t += __month_to_secs(month, is_leap);
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t += 86400LL * (tm->tm_mday-1);
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t += 3600LL * tm->tm_hour;
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t += 60LL * tm->tm_min;
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t += tm->tm_sec;
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return t;
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}
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