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use more straightforward ngx_gmtime() implementation

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This commit is contained in:
Igor Sysoev 2008-04-13 13:33:12 +00:00
parent a8372d8a84
commit 4611ad3dea
1 changed files with 46 additions and 35 deletions
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81
src/core/ngx_times.c
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@ -203,14 +203,17 @@ ngx_http_cookie_time(u_char *buf, time_t t)
void
ngx_gmtime(time_t t, ngx_tm_t *tp)
{
ngx_uint_t n, sec, min, hour, mday, mon, year, wday, yday, days;
ngx_int_t yday;
ngx_uint_t n, sec, min, hour, mday, mon, year, wday, days, leap;
/* the calculation is valid for positive time_t only */
n = (ngx_uint_t) t;
days = n / 86400;
/* Jaunary 1, 1970 was Thursday */
wday = (4 + days) % 7;
n %= 86400;
@ -219,57 +222,65 @@ ngx_gmtime(time_t t, ngx_tm_t *tp)
min = n / 60;
sec = n % 60;
/* the algorithm based on Gauss's formula */
/*
* the algorithm based on Gauss' formula,
* see src/http/ngx_http_parse_time.c
*/
/* days since March 1, 1 BC */
days = days - (31 + 28) + 719527;
year = days * 400 / (365 * 400 + 100 - 4 + 1);
/*
* The "days" should be adjusted to 1 only, however, some March 1st's go
* to previous year, so we adjust them to 2. This causes also shift of the
* last Feburary days to next year, but we catch the case when "yday"
* becomes negative.
*/
year = (days + 2) * 400 / (365 * 400 + 100 - 4 + 1);
yday = days - (365 * year + year / 4 - year / 100 + year / 400);
mon = (yday + 31) * 12 / 367;
mday = yday - (mon * 367 / 12 - 31);
if (yday < 0) {
leap = (year % 4 == 0) && (year % 100 || (year % 400 == 0));
yday = 365 + leap + yday;
year--;
}
mon += 2;
/*
* The empirical formula that maps "yday" to month.
* There are at least 10 variants, some of them are:
* mon = (yday + 31) * 15 / 459
* mon = (yday + 31) * 17 / 520
* mon = (yday + 31) * 20 / 612
*/
mon = (yday + 31) * 10 / 306;
/* the Gauss' formula that evaluates days before the month */
mday = yday - (367 * mon / 12 - 30) + 1;
if (yday >= 306) {
year++;
mon -= 10;
/*
* there is no "yday" in Win32 SYSTEMTIME
*
* yday -= 306;
*/
year++;
mon -= 12;
} else {
if (mday == 0) {
/* Jaunary 31 */
mon = 1;
mday = 31;
mon += 2;
} else if (mon == 2) {
if ((year % 4 == 0) && (year % 100 || (year % 400 == 0))) {
if (mday > 29) {
mon = 3;
mday -= 29;
}
} else if (mday > 28) {
mon = 3;
mday -= 28;
}
}
/*
* there is no "yday" in Win32 SYSTEMTIME
*
* } else {
* yday += 31 + 28;
*
* if ((year % 4 == 0) && (year % 100 || (year % 400 == 0))) {
* yday++;
* }
*/
/*
* there is no "yday" in Win32 SYSTEMTIME
*
* yday += 31 + 28 + leap;
*/
}
tp->ngx_tm_sec = (ngx_tm_sec_t) sec;