[glib] gdatetime: Use proleptic gregorian
- From: Emmanuele Bassi <ebassi src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib] gdatetime: Use proleptic gregorian
- Date: Mon, 6 Sep 2010 10:55:13 +0000 (UTC)
commit 875ad12345e22b3189e524d9bede58f6e7b5cf88
Author: Thiago Santos <thiago sousa santos collabora co uk>
Date: Fri Sep 3 14:43:11 2010 +0100
gdatetime: Use proleptic gregorian
Use Proleptic Gregorian calendar instead of the Julian calendar
as the internal representation.
https://bugzilla.gnome.org/show_bug.cgi?id=50076
Signed-off-by: Emmanuele Bassi <ebassi linux intel com>
glib/gdatetime.c | 227 +++++++++++++++++++++++++++--------------------
glib/tests/gdatetime.c | 32 +++++++
2 files changed, 162 insertions(+), 97 deletions(-)
---
diff --git a/glib/gdatetime.c b/glib/gdatetime.c
index d3aa2eb..7ec336f 100644
--- a/glib/gdatetime.c
+++ b/glib/gdatetime.c
@@ -76,18 +76,25 @@
* reference count drops to 0, the resources allocated by the #GDateTime
* structure are released.
*
- * Internally, #GDateTime uses the Julian Day Number since the
- * initial Julian Period (-4712 BC). However, the public API uses the
+ * Internally, #GDateTime uses the Proleptic Gregorian Calendar, the first
+ * representable date is 0001-01-01. However, the public API uses the
* internationally accepted Gregorian Calendar.
*
* #GDateTime is available since GLib 2.26.
*/
+#define UNIX_EPOCH_START 719163
+
+#define DAYS_IN_4YEARS 1461 /* days in 4 years */
+#define DAYS_IN_100YEARS 36524 /* days in 100 years */
+#define DAYS_IN_400YEARS 146097 /* days in 400 years */
+
#define USEC_PER_SECOND (G_GINT64_CONSTANT (1000000))
#define USEC_PER_MINUTE (G_GINT64_CONSTANT (60000000))
#define USEC_PER_HOUR (G_GINT64_CONSTANT (3600000000))
#define USEC_PER_MILLISECOND (G_GINT64_CONSTANT (1000))
#define USEC_PER_DAY (G_GINT64_CONSTANT (86400000000))
+#define SEC_PER_DAY (G_GINT64_CONSTANT (86400))
#define GREGORIAN_LEAP(y) ((((y) % 4) == 0) && (!((((y) % 100) == 0) && (((y) % 400) != 0))))
#define JULIAN_YEAR(d) ((d)->julian / 365.25)
@@ -113,16 +120,10 @@ typedef struct _GTimeZone GTimeZone;
struct _GDateTime
{
- /* Julian Period, 0 is Initial Epoch */
- gint period : 3;
-
- /* Day within Julian Period */
- guint julian : 22;
-
+ /* 1 is 0001-01-01 in Proleptic Gregorian */
+ guint32 days;
/* Microsecond timekeeping within Day */
- guint64 usec : 37;
-
- gint reserved : 2;
+ guint64 usec;
/* TimeZone information, NULL is UTC */
GTimeZone *tz;
@@ -281,40 +282,29 @@ get_weekday_name_abbr (gint day)
}
static inline gint
-date_to_julian (gint year,
+date_to_proleptic_gregorian (gint year,
gint month,
gint day)
{
- gint a = (14 - month) / 12;
- gint y = year + 4800 - a;
- gint m = month + (12 * a) - 3;
+ gint64 days;
+
+ days = (year - 1) * 365 + ((year - 1) / 4) - ((year - 1) / 100)
+ + ((year - 1) / 400);
- return day
- + (((153 * m) + 2) / 5)
- + (y * 365)
- + (y / 4)
- - (y / 100)
- + (y / 400)
- - 32045;
+ days += days_in_year[0][month - 1];
+ if (GREGORIAN_LEAP (year) && month > 2)
+ day++;
+
+ days += day;
+
+ return days;
}
static inline void
g_date_time_add_days_internal (GDateTime *datetime,
gint64 days)
{
- gint __day = datetime->julian + days;
- if (__day < 1)
- {
- datetime->period += -1 + (__day / DAYS_PER_PERIOD);
- datetime->period += DAYS_PER_PERIOD + (__day % DAYS_PER_PERIOD);
- }
- else if (__day > DAYS_PER_PERIOD)
- {
- datetime->period += (datetime->julian + days) / DAYS_PER_PERIOD;
- datetime->julian = (datetime->julian + days) % DAYS_PER_PERIOD;
- }
- else
- datetime->julian += days;
+ datetime->days += days;
}
static inline void
@@ -392,10 +382,7 @@ g_date_time_add_ymd (GDateTime *datetime,
if (max_days[m] < d)
d = max_days[m];
- /* since the add_days_internal() uses the julian date we need to
- * update it using the new year/month/day and then add the days
- */
- datetime->julian = date_to_julian (y, m, d);
+ datetime->days = date_to_proleptic_gregorian (y, m, d);
g_date_time_add_days_internal (datetime, days);
}
@@ -1052,15 +1039,13 @@ g_date_time_compare (gconstpointer dt1,
a = dt1;
b = dt2;
- if ((a->period == b->period) &&
- (a->julian == b->julian) &&
+ if ((a->days == b->days )&&
(a->usec == b->usec))
{
return 0;
}
- else if ((a->period > b->period) ||
- ((a->period == b->period) && (a->julian > b->julian)) ||
- ((a->period == b->period) && (a->julian == b->julian) && a->usec > b->usec))
+ else if ((a->days > b->days) ||
+ ((a->days == b->days) && a->usec > b->usec))
{
return 1;
}
@@ -1087,8 +1072,7 @@ g_date_time_copy (const GDateTime *datetime)
g_return_val_if_fail (datetime != NULL, NULL);
copied = g_date_time_new ();
- copied->period = datetime->period;
- copied->julian = datetime->julian;
+ copied->days = datetime->days;
copied->usec = datetime->usec;
copied->tz = g_time_zone_copy (datetime->tz);
@@ -1141,13 +1125,8 @@ g_date_time_difference (const GDateTime *begin,
g_return_val_if_fail (begin != NULL, 0);
g_return_val_if_fail (end != NULL, 0);
- if (begin->period != 0 || end->period != 0)
- {
- g_warning ("GDateTime only supports the current Julian period");
- return 0;
- }
-
- return ((end->julian - begin->julian) * USEC_PER_DAY) + (end->usec - begin->usec);
+ return (GTimeSpan) (((gint64) end->days - (gint64) begin->days)
+ * USEC_PER_DAY) + ((gint64) end->usec - (gint64) begin->usec);
}
/**
@@ -1298,23 +1277,81 @@ g_date_time_get_dmy (const GDateTime *datetime,
gint *month,
gint *year)
{
- gint a, b, c, d, e, m;
+ gint the_year;
+ gint the_month;
+ gint the_day;
+ gint remaining_days;
+ gint y100_cycles;
+ gint y4_cycles;
+ gint y1_cycles;
+ gint preceding;
+ gboolean leap;
- a = datetime->julian + 32044;
- b = ((4 * a) + 3) / 146097;
- c = a - ((b * 146097) / 4);
- d = ((4 * c) + 3) / 1461;
- e = c - (1461 * d) / 4;
- m = (5 * e + 2) / 153;
+ g_return_if_fail (datetime != NULL);
+
+ remaining_days = datetime->days;
+
+ /*
+ * We need to convert an offset in days to its year/month/day representation.
+ * Leap years makes this a little trickier than it should be, so we use
+ * 400, 100 and 4 years cycles here to get to the correct year.
+ */
- if (day != NULL)
- *day = e - (((153 * m) + 2) / 5) + 1;
+ /* Our days offset starts sets 0001-01-01 as day 1, if it was day 0 our
+ * math would be simpler, so let's do it */
+ remaining_days--;
- if (month != NULL)
- *month = m + 3 - (12 * (m / 10));
+ the_year = (remaining_days / DAYS_IN_400YEARS) * 400 + 1;
+ remaining_days = remaining_days % DAYS_IN_400YEARS;
- if (year != NULL)
- *year = (b * 100) + d - 4800 + (m / 10);
+ y100_cycles = remaining_days / DAYS_IN_100YEARS;
+ remaining_days = remaining_days % DAYS_IN_100YEARS;
+ the_year += y100_cycles * 100;
+
+ y4_cycles = remaining_days / DAYS_IN_4YEARS;
+ remaining_days = remaining_days % DAYS_IN_4YEARS;
+ the_year += y4_cycles * 4;
+
+ y1_cycles = remaining_days / 365;
+ the_year += y1_cycles;
+ remaining_days = remaining_days % 365;
+
+ if (y1_cycles == 4 || y100_cycles == 4) {
+ g_assert (remaining_days == 0);
+
+ /* special case that indicates that the date is actually one year before,
+ * in the 31th of December */
+ the_year--;
+ the_month = 12;
+ the_day = 31;
+ goto end;
+ }
+
+ /* now get the month and the day */
+ leap = y1_cycles == 3 && (y4_cycles != 24 || y100_cycles == 3);
+
+ g_assert (leap == GREGORIAN_LEAP(the_year));
+
+ the_month = (remaining_days + 50) >> 5;
+ preceding = (days_in_year[0][the_month - 1] + (the_month > 2 && leap));
+ if (preceding > remaining_days) {
+ /* estimate is too large */
+ the_month -= 1;
+ preceding -= leap ? days_in_months[1][the_month] :
+ days_in_months[0][the_month];
+ }
+ remaining_days -= preceding;
+ g_assert(0 <= remaining_days);
+
+ the_day = remaining_days + 1;
+
+end:
+ if (year)
+ *year = the_year;
+ if (month)
+ *month = the_month;
+ if (day)
+ *day = the_day;
}
/**
@@ -1357,13 +1394,26 @@ g_date_time_get_julian (const GDateTime *datetime,
gint *minute,
gint *second)
{
+ gint y, m, d, a, b, c, e, f, j;
g_return_if_fail (datetime != NULL);
+ g_date_time_get_dmy (datetime, &d, &m, &y);
+
+ /* FIXME: This is probably not optimal and doesn't handle the fact that the
+ * julian calendar has its 0 hour on midday */
+
+ a = y / 100;
+ b = a / 4;
+ c = 2 - a + b;
+ e = 365.25 * (y + 4716);
+ f = 30.6001 * (m + 1);
+ j = c + d + e + f - 1524;
+
if (period)
- *period = datetime->period;
+ *period = 0;
if (julian)
- *julian = datetime->julian;
+ *julian = j;
if (hour)
*hour = (datetime->usec / USEC_PER_HOUR);
@@ -1630,7 +1680,8 @@ g_date_time_new_from_date (gint year,
g_return_val_if_fail (day > 0 && day <= 31, NULL);
dt = g_date_time_new ();
- dt->julian = date_to_julian (year, month, day);
+
+ dt->days = date_to_proleptic_gregorian (year, month, day);
dt->tz = g_date_time_create_time_zone (dt, NULL);
return dt;
@@ -2104,33 +2155,18 @@ g_date_time_to_local (const GDateTime *datetime)
gint64
g_date_time_to_epoch (const GDateTime *datetime)
{
- struct tm tm;
- gint year,
- month,
- day;
+ gint64 result;
g_return_val_if_fail (datetime != NULL, 0);
- g_return_val_if_fail (datetime->period == 0, 0);
- g_date_time_get_dmy (datetime, &day, &month, &year);
+ if (datetime->days <= 0)
+ return G_MININT64;
- /* FIXME we use gint64, we shold expand these limits */
- if (year < 1970)
- return 0;
- else if (year > 2037)
- return G_MAXINT64;
+ result = (datetime->days - UNIX_EPOCH_START) * SEC_PER_DAY
+ + datetime->usec / USEC_PER_SECOND
+ - g_date_time_get_utc_offset (datetime) / 1000000;
- memset (&tm, 0, sizeof (tm));
-
- tm.tm_year = year - 1900;
- tm.tm_mon = month - 1;
- tm.tm_mday = day;
- tm.tm_hour = g_date_time_get_hour (datetime);
- tm.tm_min = g_date_time_get_minute (datetime);
- tm.tm_sec = g_date_time_get_second (datetime);
- tm.tm_isdst = -1;
-
- return (gint64) mktime (&tm);
+ return result;
}
/**
@@ -2151,11 +2187,8 @@ g_date_time_to_timeval (const GDateTime *datetime,
tv->tv_sec = 0;
tv->tv_usec = 0;
- if (G_LIKELY (datetime->period == 0))
- {
- tv->tv_sec = g_date_time_to_epoch (datetime);
- tv->tv_usec = datetime->usec % USEC_PER_SECOND;
- }
+ tv->tv_sec = g_date_time_to_epoch (datetime);
+ tv->tv_usec = datetime->usec % USEC_PER_SECOND;
}
/**
diff --git a/glib/tests/gdatetime.c b/glib/tests/gdatetime.c
index 828b537..1f4cb3c 100644
--- a/glib/tests/gdatetime.c
+++ b/glib/tests/gdatetime.c
@@ -293,6 +293,9 @@ test_GDateTime_get_dmy (void)
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));
@@ -303,6 +306,28 @@ test_GDateTime_get_dmy (void)
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_from_date (y, m, d);
+
+ g_date_time_get_dmy (dt1, &d2, &m2, &y2);
+ g_assert_cmpint (y, ==, y2);
+ g_assert_cmpint (m, ==, m2);
+ g_assert_cmpint (d, ==, d2);
+ g_date_time_unref (dt1);
+ }
+ }
+ }
}
static void
@@ -410,6 +435,13 @@ test_GDateTime_new_from_timeval (void)
g_get_current_time (&tv);
dt = g_date_time_new_from_timeval (&tv);
+
+ if (g_test_verbose ())
+ g_print ("\nDT%d/%d/%d\n",
+ g_date_time_get_year (dt),
+ g_date_time_get_month (dt),
+ g_date_time_get_day_of_month (dt));
+
g_date_time_to_timeval (dt, &tv2);
g_assert_cmpint (tv.tv_sec, ==, tv2.tv_sec);
g_assert_cmpint (tv.tv_usec, ==, tv2.tv_usec);
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