void
g_date_subtract_months (GDate *d,
guint nmonths)
{
guint years, months;
gint index;
g_return_if_fail (g_date_valid (d));
if (!d->dmy)
g_date_update_dmy (d);
g_return_if_fail (d->dmy);
years = nmonths/12;
months = nmonths%12;
g_return_if_fail (d->year > years);
d->year -= years;
if (d->month > months) d->month -= months;
else
{
months -= d->month;
d->month = 12 - months;
d->year -= 1;
}
index = g_date_is_leap_year (d->year) ? 1 : 0;
if (d->day > days_in_months[index][d->month])
d->day = days_in_months[index][d->month];
d->julian = FALSE;
g_return_if_fail (g_date_valid (d));
}
void
g_date_to_struct_tm (GDate *d,
struct tm *tm)
{
GDateWeekday day;
g_return_if_fail (d != NULL);
g_return_if_fail (g_date_valid (d));
g_return_if_fail (tm != NULL);
if (!d->dmy)
{
g_date_update_dmy (d);
}
g_return_if_fail (d->dmy);
/* zero all the irrelevant fields to be sure they're valid */
/* On Linux and maybe other systems, there are weird non-POSIX
* fields on the end of struct tm that choke strftime if they
* contain garbage. So we need to 0 the entire struct, not just the
* fields we know to exist.
*/
memset (tm, 0x0, sizeof (struct tm));
tm->tm_mday = d->day;
tm->tm_mon = d->month - 1; /* 0-11 goes in tm */
tm->tm_year = ((int)d->year) - 1900; /* X/Open says tm_year can be negative */
day = g_date_weekday (d);
if (day == 7) day = 0; /* struct tm wants days since Sunday, so Sunday is 0 */
tm->tm_wday = (int)day;
tm->tm_yday = g_date_day_of_year (d) - 1; /* 0 to 365 */
tm->tm_isdst = -1; /* -1 means "information not available" */
}
guint
g_date_get_monday_week_of_year (const GDate *d)
{
GDateWeekday wd;
guint day;
GDate first;
g_return_val_if_fail (g_date_valid (d), 0);
if (!d->dmy)
g_date_update_dmy (d);
g_return_val_if_fail (d->dmy, 0);
g_date_clear (&first, 1);
g_date_set_dmy (&first, 1, 1, d->year);
wd = g_date_get_weekday (&first) - 1; /* make Monday day 0 */
day = g_date_get_day_of_year (d) - 1;
return ((day + wd)/7U + (wd == 0 ? 1 : 0));
}
