fix(core): Simplify time conversion and fix an edge case for negative dates

deps/libc_time.c

@@ -16,7 +16,6 @@ int __secs_to_tm(long long t, struct mytm *tm) {
     int remdays, remsecs, remyears;
     int qc_cycles, c_cycles, q_cycles;
     int 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 */
@@ -31,9 +30,6 @@ int __secs_to_tm(long long t, struct mytm *tm) {
         --days;
     }
 
-    wday = (int)((3+days)%7);
-    if (wday < 0) wday += 7;
-
     qc_cycles = (int)(days / DAYS_PER_400Y);
     remdays = (int)(days % DAYS_PER_400Y);
     if (remdays < 0) {
@@ -53,10 +49,6 @@ int __secs_to_tm(long long t, struct mytm *tm) {
     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 + 400LL*qc_cycles;
 
     for (months=0; days_in_month[months] <= remdays; ++months)
@@ -72,9 +64,6 @@ int __secs_to_tm(long long t, struct mytm *tm) {
         ++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;
@@ -82,42 +71,32 @@ int __secs_to_tm(long long t, struct mytm *tm) {
     return 0;
 }
 
-int __month_to_secs(int month, int is_leap) {
-    static const int secs_through_month[] =
-        {0, 31*86400, 59*86400, 90*86400,
-         120*86400, 151*86400, 181*86400, 212*86400,
-         243*86400, 273*86400, 304*86400, 334*86400 };
+static const int secs_through_month[] =
+    {0, 31*86400, 59*86400, 90*86400,
+     120*86400, 151*86400, 181*86400, 212*86400,
+     243*86400, 273*86400, 304*86400, 334*86400 };
+
+static int
+__month_to_secs(int month, int is_leap) {
     int t = secs_through_month[month];
     if (is_leap && month >= 2)
         t+=86400;
     return t;
 }
 
-long long __year_to_secs(long long year, int *is_leap) {
-    if (year-(int)2ULL <= 136) {
-        long long y = (int)year;
-        long long leaps = (y-68)>>2;
-        if (!((y-8)&3)) {
-            leaps--;
-            if (is_leap) *is_leap = 1;
-        } else if (is_leap) *is_leap = 0;
-        return 31536000*(y-70) + 86400*leaps;
-    }
-
+static long long
+__year_to_secs(const long long year, int *is_leap) {
     int cycles, centuries, leaps, rem;
-
-    //if (!is_leap) is_leap = &(int){0};
     int is_leap_val = 0;
     if (!is_leap) {
         is_leap = &is_leap_val;
     }
     cycles = (int)((year-100) / 400);
     rem = (int)((year-100) % 400);
-    /* Comparison is always false because rem >= 0.
     if (rem < 0) {
         cycles--;
         rem += 400;
-    } */
+    }
     if (!rem) {
         *is_leap = 1;
         centuries = 0;

deps/libc_time.h

@@ -8,13 +8,9 @@ struct mytm {
     int tm_mday;
     int tm_mon;
     int tm_year;
-    int tm_wday;
-    int tm_yday;
 };
 
 int __secs_to_tm(long long t, struct mytm *tm);
-int __month_to_secs(int month, int is_leap);
-long long __year_to_secs(long long year, int *is_leap);
 long long __tm_to_secs(const struct mytm *tm);
 
 #endif /* LIBC_TIME_H_ */