[337] | 1 | #include "time_impl.h"
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| 2 | #include <limits.h>
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| 3 |
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| 4 | /* 2000-03-01 (mod 400 year, immediately after feb29 */
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| 5 | #define LEAPOCH (946684800LL + 86400*(31+29))
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| 6 |
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| 7 | #define DAYS_PER_400Y (365*400 + 97)
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| 8 | #define DAYS_PER_100Y (365*100 + 24)
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| 9 | #define DAYS_PER_4Y (365*4 + 1)
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| 10 |
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| 11 | int __secs_to_tm(long long t, struct tm *tm)
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| 12 | {
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| 13 | long long days, secs, years;
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| 14 | int remdays, remsecs, remyears;
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| 15 | int qc_cycles, c_cycles, q_cycles;
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| 16 | int months;
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| 17 | int wday, yday, leap;
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| 18 | static const char days_in_month[] = {31,30,31,30,31,31,30,31,30,31,31,29};
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| 19 |
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| 20 | /* Reject time_t values whose year would overflow int */
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| 21 | if (t < INT_MIN * 31622400LL || t > INT_MAX * 31622400LL)
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| 22 | return -1;
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| 23 |
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| 24 | secs = t - LEAPOCH;
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| 25 | days = secs / 86400;
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| 26 | remsecs = secs % 86400;
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| 27 | if (remsecs < 0) {
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| 28 | remsecs += 86400;
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| 29 | days--;
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| 30 | }
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| 31 |
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| 32 | wday = (3+days)%7;
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| 33 | if (wday < 0) wday += 7;
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| 34 |
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| 35 | qc_cycles = days / DAYS_PER_400Y;
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| 36 | remdays = days % DAYS_PER_400Y;
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| 37 | if (remdays < 0) {
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| 38 | remdays += DAYS_PER_400Y;
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| 39 | qc_cycles--;
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| 40 | }
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| 41 |
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| 42 | c_cycles = remdays / DAYS_PER_100Y;
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| 43 | if (c_cycles == 4) c_cycles--;
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| 44 | remdays -= c_cycles * DAYS_PER_100Y;
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| 45 |
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| 46 | q_cycles = remdays / DAYS_PER_4Y;
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| 47 | if (q_cycles == 25) q_cycles--;
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| 48 | remdays -= q_cycles * DAYS_PER_4Y;
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| 49 |
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| 50 | remyears = remdays / 365;
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| 51 | if (remyears == 4) remyears--;
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| 52 | remdays -= remyears * 365;
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| 53 |
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| 54 | leap = !remyears && (q_cycles || !c_cycles);
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| 55 | yday = remdays + 31 + 28 + leap;
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| 56 | if (yday >= 365+leap) yday -= 365+leap;
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| 57 |
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| 58 | years = remyears + 4*q_cycles + 100*c_cycles + 400LL*qc_cycles;
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| 59 |
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| 60 | for (months=0; days_in_month[months] <= remdays; months++)
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| 61 | remdays -= days_in_month[months];
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| 62 |
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| 63 | if (months >= 10) {
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| 64 | months -= 12;
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| 65 | years++;
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| 66 | }
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| 67 |
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| 68 | if (years+100 > INT_MAX || years+100 < INT_MIN)
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| 69 | return -1;
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| 70 |
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| 71 | tm->tm_year = years + 100;
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| 72 | tm->tm_mon = months + 2;
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| 73 | tm->tm_mday = remdays + 1;
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| 74 | tm->tm_wday = wday;
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| 75 | tm->tm_yday = yday;
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| 76 |
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| 77 | tm->tm_hour = remsecs / 3600;
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| 78 | tm->tm_min = remsecs / 60 % 60;
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| 79 | tm->tm_sec = remsecs % 60;
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| 80 |
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| 81 | return 0;
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| 82 | }
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