__year_to_secs.c raw

   1  long long __year_to_secs(long long year, int *is_leap)
   2  {
   3  	if (year-2ULL <= 136) {
   4  		int y = year;
   5  		int leaps = (y-68)>>2;
   6  		if (!((y-68)&3)) {
   7  			leaps--;
   8  			if (is_leap) *is_leap = 1;
   9  		} else if (is_leap) *is_leap = 0;
  10  		return 31536000*(y-70) + 86400*leaps;
  11  	}
  12  
  13  	int cycles, centuries, leaps, rem;
  14  
  15  	if (!is_leap) is_leap = &(int){0};
  16  	cycles = (year-100) / 400;
  17  	rem = (year-100) % 400;
  18  	if (rem < 0) {
  19  		cycles--;
  20  		rem += 400;
  21  	}
  22  	if (!rem) {
  23  		*is_leap = 1;
  24  		centuries = 0;
  25  		leaps = 0;
  26  	} else {
  27  		if (rem >= 200) {
  28  			if (rem >= 300) centuries = 3, rem -= 300;
  29  			else centuries = 2, rem -= 200;
  30  		} else {
  31  			if (rem >= 100) centuries = 1, rem -= 100;
  32  			else centuries = 0;
  33  		}
  34  		if (!rem) {
  35  			*is_leap = 0;
  36  			leaps = 0;
  37  		} else {
  38  			leaps = rem / 4U;
  39  			rem %= 4U;
  40  			*is_leap = !rem;
  41  		}
  42  	}
  43  
  44  	leaps += 97*cycles + 24*centuries - *is_leap;
  45  
  46  	return (year-100) * 31536000LL + leaps * 86400LL + 946684800 + 86400;
  47  }
  48