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Make isleap faster #4852

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Make isleap faster #4852

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12 changes: 8 additions & 4 deletions Sources/CoreFoundation/CFDate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -240,10 +240,14 @@ static const uint8_t daysInMonth[16] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 3
static const uint16_t daysBeforeMonth[16] = {INVALID_MONTH_RESULT, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365, INVALID_MONTH_RESULT, INVALID_MONTH_RESULT};
static const uint16_t daysAfterMonth[16] = {365, 334, 306, 275, 245, 214, 184, 153, 122, 92, 61, 31, 0, 0, 0, 0};

CF_INLINE bool isleap(int64_t year) {
int64_t y = (year + 1) % 400; /* correct to nearest multiple-of-400 year, then find the remainder */
if (y < 0) y = -y;
return (0 == (y & 3) && 100 != y && 200 != y && 300 != y);
CF_INLINE bool isleap(int64_t year)
{
year++; // year is current year minus 1, so add 1 back
if (year < 0) year = -year;
if ((year & 3) != 0) return false;
if (year % 400) return true;
if (year % 100) return false;
return true;
}

/* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
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