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implement week-based-year year numbers in strftime

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in the process, I refactored the week-number code so it can be used by
the week-based-year formats to determine year adjustments at the
boundary values. this also improves indention/code readability.
This commit is contained in:
Rich Felker 2013-06-28 12:38:42 -04:00
parent 062446a85d
commit aea7919032
1 changed files with 34 additions and 27 deletions
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61
src/time/strftime.c
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@ -17,6 +17,32 @@ static int is_leap(int y)
return !(y%4) && ((y%100) || !(y%400));
}
static int week_num(const struct tm *tm)
{
int val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
/* If 1 Jan is just 1-3 days past Monday,
* the previous week is also in this year. */
if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
val++;
if (!val) {
val = 52;
/* If 31 December of prev year a Thursday,
* or Friday of a leap year, then the
* prev year has 53 weeks. */
int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
val++;
} else if (val == 53) {
/* If 1 January is not a Thursday, and not
* a Wednesday of a leap year, then this
* year has only 52 weeks. */
int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
val = 1;
}
return val;
}
size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
{
nl_item item;
@ -67,14 +93,15 @@ do_fmt:
fmt = "%Y-%m-%d";
goto recu_strftime;
case 'g':
// FIXME
val = 0; //week_based_year(tm)%100;
fmt = "%02d";
goto number;
case 'G':
// FIXME
val = 0; //week_based_year(tm);
fmt = "%04d";
val = tm->tm_year + 1900;
if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
if (*f=='g') {
fmt = "%02d";
val %= 100;
}
goto number;
case 'H':
val = tm->tm_hour;
@ -133,27 +160,7 @@ do_fmt:
fmt = "%02d";
goto number;
case 'V':
val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
/* If 1 Jan is just 1-3 days past Monday,
* the previous week is also in this year. */
if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
val++;
if (!val) {
val = 52;
/* If 31 December of prev year a Thursday,
* or Friday of a leap year, then the
* prev year has 53 weeks. */
int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
val++;
} else if (val == 53) {
/* If 1 January is not a Thursday, and not
* a Wednesday of a leap year, then this
* year has only 52 weeks. */
int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
val = 1;
}
val = week_num(tm);
fmt = "%02d";
goto number;
case 'w':