[glib] Bug 630077 - GDateTime week number support
- From: Ryan Lortie <ryanl src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib] Bug 630077 - GDateTime week number support
- Date: Fri, 1 Oct 2010 15:25:31 +0000 (UTC)
commit fff6814973356ac23b1022113632441110825283
Author: Ryan Lortie <desrt desrt ca>
Date: Mon Sep 27 09:06:24 2010 -0400
Bug 630077 - GDateTime week number support
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.
docs/reference/glib/glib-sections.txt | 1 +
glib/gdatetime.c | 96 ++++++++++++++++-
glib/gdatetime.h | 1 +
glib/glib.symbols | 1 +
glib/tests/gdatetime.c | 188 +++++++++++++++++++++++++--------
5 files changed, 239 insertions(+), 48 deletions(-)
---
diff --git a/docs/reference/glib/glib-sections.txt b/docs/reference/glib/glib-sections.txt
index 344e2d4..0a818b8 100644
--- a/docs/reference/glib/glib-sections.txt
+++ b/docs/reference/glib/glib-sections.txt
@@ -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
diff --git a/glib/gdatetime.c b/glib/gdatetime.c
index 1115495..4ad3807 100644
--- a/glib/gdatetime.c
+++ b/glib/gdatetime.c
@@ -1583,12 +1583,102 @@ 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).
+ *
+ * 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.
*
- * Return value: the week of the 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
diff --git a/glib/gdatetime.h b/glib/gdatetime.h
index f668fde..b76df89 100644
--- a/glib/gdatetime.h
+++ b/glib/gdatetime.h
@@ -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);
diff --git a/glib/glib.symbols b/glib/glib.symbols
index f4b45a0..52d0519 100644
--- a/glib/glib.symbols
+++ b/glib/glib.symbols
@@ -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
diff --git a/glib/tests/gdatetime.c b/glib/tests/gdatetime.c
index e6b1c4d..20f7cda 100644
--- a/glib/tests/gdatetime.c
+++ b/glib/tests/gdatetime.c
@@ -231,50 +231,6 @@ test_GDateTime_get_day_of_month (void)
}
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)
{
GDateTime *dt;
@@ -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 ();
}
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