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Bug 630077 - GDateTime week number support

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Fully implement support for ISO 8601 week dates in GDateTime and
document that this is the case.

Add an exhaustive test case to ensure correctness.
This commit is contained in:
Ryan Lortie 2010-09-27 09:06:24 -04:00
parent fe1186a842
commit fff6814973
5 changed files with 239 additions and 48 deletions
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1
docs/reference/glib/glib-sections.txt
View File

@ -1491,6 +1491,7 @@ g_date_time_get_month
g_date_time_get_day_of_month
<SUBSECTION>
g_date_time_get_week_numbering_year
g_date_time_get_week_of_year
g_date_time_get_day_of_week

96
glib/gdatetime.c
View File

@ -1582,13 +1582,103 @@ g_date_time_get_day_of_month (GDateTime *datetime)
}
/* Week of year / day of week getters {{{1 */
/**
* g_date_time_get_week_numbering_year:
* @date: a #GDateTime
*
* Returns the ISO 8601 week-numbering year in which the week containing
* @datetime falls.
*
* This function, taken together with g_date_time_get_week_of_year() and
* g_date_time_get_day_of_week() can be used to determine the full ISO
* week date on which @datetime falls.
*
* This is usually equal to the normal Gregorian year (as returned by
* g_date_time_get_year()), except as detailed below:
*
* For Thursday, the week-numbering year is always equal to the usual
* calendar year. For other days, the number is such that every day
* within a complete week (Monday to Sunday) is contained within the
* same week-numbering year.
*
* For Monday, Tuesday and Wednesday occuring near the end of the year,
* this may mean that the week-numbering year is one greater than the
* calendar year (so that these days have the same week-numbering year
* as the Thursday occuring early in the next year).
*
* For Friday, Saturaday and Sunday occuring near the start of the year,
* this may mean that the week-numbering year is one less than the
* calendar year (so that these days have the same week-numbering year
* as the Thursday occuring late in the previous year).
*
* An equivalent description is that the week-numbering year is equal to
* the calendar year containing the majority of the days in the current
* week (Monday to Sunday).
*
* Note that January 1 0001 in the proleptic Gregorian calendar is a
* Monday, so this function never returns 0.
*
* Returns: the ISO 8601 week-numbering year for @datetime
*
* Since: 2.26
**/
gint
g_date_time_get_week_numbering_year (GDateTime *datetime)
{
gint year, month, day, weekday;
g_date_time_get_ymd (datetime, &year, &month, &day);
weekday = g_date_time_get_day_of_week (datetime);
/* January 1, 2, 3 might be in the previous year if they occur after
* Thursday.
*
* Jan 1: Friday, Saturday, Sunday => day 1: weekday 5, 6, 7
* Jan 2: Saturday, Sunday => day 2: weekday 6, 7
* Jan 3: Sunday => day 3: weekday 7
*
* So we have a special case if (day - weekday) <= -4
*/
if (month == 1 && (day - weekday) <= -4)
return year - 1;
/* December 29, 30, 31 might be in the next year if they occur before
* Thursday.
*
* Dec 31: Monday, Tuesday, Wednesday => day 31: weekday 1, 2, 3
* Dec 30: Monday, Tuesday => day 30: weekday 1, 2
* Dec 29: Monday => day 29: weekday 1
*
* So we have a special case if (day - weekday) >= 28
*/
else if (month == 12 && (day - weekday) >= 28)
return year + 1;
else
return year;
}
/**
* g_date_time_get_week_of_year:
* @datetime: a #GDateTime
*
* Returns the numeric week of the respective year.
* Returns the ISO 8601 week number for the week containing @datetime.
* The ISO 8601 week number is the same for every day of the week (from
* Moday through Sunday). That can produce some unusual results
* (described below).
*
* Return value: the week of the year
* The first week of the year is week 1. This is the week that contains
* the first Thursday of the year. Equivalently, this is the first week
* that has more than 4 of its days falling within the calendar year.
*
* The value 0 is never returned by this function. Days contained
* within a year but occuring before the first ISO 8601 week of that
* year are considered as being contained in the last week of the
* previous year. Similarly, the final days of a calendar year may be
* considered as being part of the first ISO 8601 week of the next year
* if 4 or more days of that week are contained within the new year.
*
* Returns: the ISO 8601 week number for @datetime.
*
* Since: 2.26
*/
@ -1608,7 +1698,7 @@ g_date_time_get_week_of_year (GDateTime *datetime)
* g_date_time_get_day_of_week:
* @datetime: a #GDateTime
*
* Retrieves the ISO 8601 day of the week represented by @datetime (1 is
* Retrieves the ISO 8601 day of the week on which @datetime falls (1 is
* Monday, 2 is Tuesday... 7 is Sunday).
*
* Return value: the day of the week

1
glib/gdatetime.h
View File

@ -184,6 +184,7 @@ gint g_date_time_get_year (GDateTi
gint g_date_time_get_month (GDateTime *datetime);
gint g_date_time_get_day_of_month (GDateTime *datetime);
gint g_date_time_get_week_numbering_year (GDateTime *datetime);
gint g_date_time_get_week_of_year (GDateTime *datetime);
gint g_date_time_get_day_of_week (GDateTime *datetime);

1
glib/glib.symbols
View File

@ -349,6 +349,7 @@ g_date_time_get_second
g_date_time_get_seconds
g_date_time_get_timezone_abbreviation
g_date_time_get_utc_offset
g_date_time_get_week_numbering_year
g_date_time_get_week_of_year
g_date_time_get_year
g_date_time_get_ymd

188
glib/tests/gdatetime.c
View File

@ -230,50 +230,6 @@ test_GDateTime_get_day_of_month (void)
g_date_time_unref (dt);
}
static void
test_GDateTime_get_ymd (void)
{
GDateTime *dt;
struct tm tm;
time_t t;
gint d, m, y;
gint d2, m2, y2;
gint days[2][13] = {{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
t = time (NULL);
memset (&tm, 0, sizeof (struct tm));
get_localtime_tm (t, &tm);
dt = g_date_time_new_from_unix_local (t);
g_date_time_get_ymd(dt, &y, &m, &d);
g_assert_cmpint(y, ==, tm.tm_year + 1900);
g_assert_cmpint(m, ==, tm.tm_mon + 1);
g_assert_cmpint(d, ==, tm.tm_mday);
/* exaustive test */
for (y = 1750; y < 2250; y++)
{
gint leap = ((y % 4) == 0) && (!(((y % 100) == 0) && ((y % 400) != 0)))
? 1
: 0;
for (m = 1; m <= 12; m++)
{
for (d = 1; d <= days[leap][m]; d++)
{
GDateTime *dt1 = g_date_time_new_utc (y, m, d, 0, 0, 0);
g_date_time_get_ymd (dt1, &y2, &m2, &d2);
g_assert_cmpint (y, ==, y2);
g_assert_cmpint (m, ==, m2);
g_assert_cmpint (d, ==, d2);
g_date_time_unref (dt1);
}
}
}
}
static void
test_GDateTime_get_hour (void)
{
@ -898,6 +854,148 @@ test_GDateTime_dst (void)
g_time_zone_unref (tz);
}
static inline gboolean
is_leap_year (gint year)
{
g_assert (1 <= year && year <= 9999);
return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
}
static inline gint
days_in_month (gint year, gint month)
{
const gint table[2][13] = {
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
g_assert (1 <= month && month <= 12);
return table[is_leap_year (year)][month];
}
static void
test_all_dates (void)
{
gint year, month, day;
GTimeZone *timezone;
gint64 unix_time;
gint day_of_year;
gint week_year;
gint week_num;
gint weekday;
/* save some time by hanging on to this. */
timezone = g_time_zone_new_utc ();
unix_time = G_GINT64_CONSTANT(-62135596800);
/* 0001-01-01 is 0001-W01-1 */
week_year = 1;
week_num = 1;
weekday = 1;
/* The calendar makes a full cycle every 400 years, so we could
* theoretically just test years 1 through 400. That assumes that our
* software has no bugs, so probably we should just test them all. :)
*/
for (year = 1; year <= 9999; year++)
{
day_of_year = 1;
for (month = 1; month <= 12; month++)
for (day = 1; day <= days_in_month (year, month); day++)
{
GDateTime *dt;
dt = g_date_time_new (timezone, year, month, day, 0, 0, 0);
#if 0
g_print ("%04d-%02d-%02d = %04d-W%02d-%d = %04d-%03d\n",
year, month, day,
week_year, week_num, weekday,
year, day_of_year);
#endif
/* sanity check */
if G_UNLIKELY (g_date_time_get_year (dt) != year ||
g_date_time_get_month (dt) != month ||
g_date_time_get_day_of_month (dt) != day)
g_error ("%04d-%02d-%02d comes out as %04d-%02d-%02d",
year, month, day,
g_date_time_get_year (dt),
g_date_time_get_month (dt),
g_date_time_get_day_of_month (dt));
if G_UNLIKELY (g_date_time_get_week_numbering_year (dt) != week_year ||
g_date_time_get_week_of_year (dt) != week_num ||
g_date_time_get_day_of_week (dt) != weekday)
g_error ("%04d-%02d-%02d should be %04d-W%02d-%d but "
"comes out as %04d-W%02d-%d", year, month, day,
week_year, week_num, weekday,
g_date_time_get_week_numbering_year (dt),
g_date_time_get_week_of_year (dt),
g_date_time_get_day_of_week (dt));
if G_UNLIKELY (g_date_time_to_unix (dt) != unix_time)
g_error ("%04d-%02d-%02d 00:00:00 UTC should have unix time %"
G_GINT64_FORMAT " but comes out as %"G_GINT64_FORMAT,
year, month, day, unix_time, g_date_time_to_unix (dt));
if G_UNLIKELY (g_date_time_get_day_of_year (dt) != day_of_year)
g_error ("%04d-%02d-%02d should be day of year %d"
" but comes out as %d", year, month, day,
day_of_year, g_date_time_get_day_of_year (dt));
if G_UNLIKELY (g_date_time_get_hour (dt) != 0 ||
g_date_time_get_minute (dt) != 0 ||
g_date_time_get_seconds (dt) != 0)
g_error ("%04d-%02d-%02d 00:00:00 UTC comes out "
"as %02d:%02d:%02.6f", year, month, day,
g_date_time_get_hour (dt),
g_date_time_get_minute (dt),
g_date_time_get_seconds (dt));
/* done */
/* add 24 hours to unix time */
unix_time += 24 * 60 * 60;
/* move day of year forward */
day_of_year++;
/* move the week date forward */
if (++weekday == 8)
{
weekday = 1; /* Sunday -> Monday */
/* NOTE: year/month/day is the final day of the week we
* just finished.
*
* If we just finished the last week of last year then
* we are definitely starting the first week of this
* year.
*
* Otherwise, if we're still in this year, but Sunday
* fell on or after December 28 then December 29, 30, 31
* could be days within the next year's first year.
*/
if (year != week_year || (month == 12 && day >= 28))
{
/* first week of the new year */
week_num = 1;
week_year++;
}
else
week_num++;
}
}
}
g_time_zone_unref (timezone);
}
gint
main (gint argc,
gchar *argv[])
@ -920,7 +1018,6 @@ main (gint argc,
g_test_add_func ("/GDateTime/get_day_of_week", test_GDateTime_get_day_of_week);
g_test_add_func ("/GDateTime/get_day_of_month", test_GDateTime_get_day_of_month);
g_test_add_func ("/GDateTime/get_day_of_year", test_GDateTime_get_day_of_year);
g_test_add_func ("/GDateTime/get_ymd", test_GDateTime_get_ymd);
g_test_add_func ("/GDateTime/get_hour", test_GDateTime_get_hour);
g_test_add_func ("/GDateTime/get_microsecond", test_GDateTime_get_microsecond);
g_test_add_func ("/GDateTime/get_minute", test_GDateTime_get_minute);
@ -940,6 +1037,7 @@ main (gint argc,
g_test_add_func ("/GDateTime/to_utc", test_GDateTime_to_utc);
g_test_add_func ("/GDateTime/now_utc", test_GDateTime_now_utc);
g_test_add_func ("/GDateTime/dst", test_GDateTime_dst);
g_test_add_func ("/GDateTime/test-all-dates", test_all_dates);
return g_test_run ();
}