1 #include "time_impl.h" 2 #include <limits.h> 3 4 /* 2000-03-01 (mod 400 year, immediately after feb29 */ 5 #define LEAPOCH (946684800LL + 86400*(31+29)) 6 7 #define DAYS_PER_400Y (365*400 + 97) 8 #define DAYS_PER_100Y (365*100 + 24) 9 #define DAYS_PER_4Y (365*4 + 1) 10 11 int __secs_to_tm(long long t, struct tm *tm) 12 { 13 long long days, secs, years; 14 int remdays, remsecs, remyears; 15 int qc_cycles, c_cycles, q_cycles; 16 int months; 17 int wday, yday, leap; 18 static const char days_in_month[] = {31,30,31,30,31,31,30,31,30,31,31,29}; 19 20 /* Reject time_t values whose year would overflow int */ 21 if (t < INT_MIN * 31622400LL || t > INT_MAX * 31622400LL) 22 return -1; 23 24 secs = t - LEAPOCH; 25 days = secs / 86400; 26 remsecs = secs % 86400; 27 if (remsecs < 0) { 28 remsecs += 86400; 29 days--; 30 } 31 32 wday = (3+days)%7; 33 if (wday < 0) wday += 7; 34 35 qc_cycles = days / DAYS_PER_400Y; 36 remdays = days % DAYS_PER_400Y; 37 if (remdays < 0) { 38 remdays += DAYS_PER_400Y; 39 qc_cycles--; 40 } 41 42 c_cycles = remdays / DAYS_PER_100Y; 43 if (c_cycles == 4) c_cycles--; 44 remdays -= c_cycles * DAYS_PER_100Y; 45 46 q_cycles = remdays / DAYS_PER_4Y; 47 if (q_cycles == 25) q_cycles--; 48 remdays -= q_cycles * DAYS_PER_4Y; 49 50 remyears = remdays / 365; 51 if (remyears == 4) remyears--; 52 remdays -= remyears * 365; 53 54 leap = !remyears && (q_cycles || !c_cycles); 55 yday = remdays + 31 + 28 + leap; 56 if (yday >= 365+leap) yday -= 365+leap; 57 58 years = remyears + 4*q_cycles + 100*c_cycles + 400LL*qc_cycles; 59 60 for (months=0; days_in_month[months] <= remdays; months++) 61 remdays -= days_in_month[months]; 62 63 if (months >= 10) { 64 months -= 12; 65 years++; 66 } 67 68 if (years+100 > INT_MAX || years+100 < INT_MIN) 69 return -1; 70 71 tm->tm_year = years + 100; 72 tm->tm_mon = months + 2; 73 tm->tm_mday = remdays + 1; 74 tm->tm_wday = wday; 75 tm->tm_yday = yday; 76 77 tm->tm_hour = remsecs / 3600; 78 tm->tm_min = remsecs / 60 % 60; 79 tm->tm_sec = remsecs % 60; 80 81 return 0; 82 } 83