--- /dev/null
+#include <config.h>
+#include "calendar.h"
+#include <assert.h>
+#include <stdbool.h>
+#include "settings.h"
+#include "value.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+/* 14 Oct 1582. */
+#define EPOCH (-577734)
+
+/* Calculates and returns floor(a/b) for integer b > 0. */
+static int
+floor_div (int a, int b)
+{
+ assert (b > 0);
+ return (a >= 0 ? a : a - b + 1) / b;
+}
+
+/* Calculates floor(a/b) and the corresponding remainder and
+ stores them into *Q and *R. */
+static void
+floor_divmod (int a, int b, int *q, int *r)
+{
+ *q = floor_div (a, b);
+ *r = a - b * *q;
+}
+
+/* Returns true if Y is a leap year, false otherwise. */
+static bool
+is_leap_year (int y)
+{
+ return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0);
+}
+
+static int
+raw_gregorian_to_offset (int y, int m, int d)
+{
+ return (EPOCH - 1
+ + 365 * (y - 1)
+ + floor_div (y - 1, 4)
+ - floor_div (y - 1, 100)
+ + floor_div (y - 1, 400)
+ + floor_div (367 * m - 362, 12)
+ + (m <= 2 ? 0 : (m >= 2 && is_leap_year (y) ? -1 : -2))
+ + d);
+}
+
+/* Returns the number of days from 14 Oct 1582 to (Y,M,D) in the
+ Gregorian calendar. Returns SYSMIS for dates before 14 Oct
+ 1582. */
+double
+calendar_gregorian_to_offset (int y, int m, int d,
+ calendar_error_func *error, void *aux)
+{
+ /* Normalize year. */
+ if (y >= 0 && y < 100)
+ {
+ int epoch = get_epoch ();
+ int century = epoch / 100 + (y < epoch % 100);
+ y += century * 100;
+ }
+
+ /* Normalize month. */
+ if (m < 1 || m > 12)
+ {
+ if (m == 0)
+ {
+ y--;
+ m = 12;
+ }
+ else if (m == 13)
+ {
+ y++;
+ m = 1;
+ }
+ else
+ {
+ error (aux, _("Month %d is not in acceptable range of 0 to 13."), m);
+ return SYSMIS;
+ }
+ }
+
+ /* Normalize day. */
+ if (d < 0 || d > 31)
+ {
+ error (aux, _("Day %d is not in acceptable range of 0 to 31."), d);
+ return SYSMIS;
+ }
+
+ /* Validate date. */
+ if (y < 1582 || (y == 1582 && (m < 10 || (m == 10 && d < 15))))
+ {
+ error (aux, _("Date %04d-%d-%d is before the earliest acceptable "
+ "date of 1582-10-15."), y, m, d);
+ return SYSMIS;
+ }
+
+ /* Calculate offset. */
+ return raw_gregorian_to_offset (y, m, d);
+}
+
+/* Returns the number of days in the given YEAR from January 1 up
+ to (but not including) the first day of MONTH. */
+static int
+cum_month_days (int year, int month)
+{
+ static const int cum_month_days[12] =
+ {
+ 0,
+ 31, /* Jan */
+ 31 + 28, /* Feb */
+ 31 + 28 + 31, /* Mar */
+ 31 + 28 + 31 + 30, /* Apr */
+ 31 + 28 + 31 + 30 + 31, /* May */
+ 31 + 28 + 31 + 30 + 31 + 30, /* Jun */
+ 31 + 28 + 31 + 30 + 31 + 30 + 31, /* Jul */
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31, /* Aug */
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30, /* Sep */
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31, /* Oct */
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30, /* Nov */
+ };
+
+ assert (month >= 1 && month <= 12);
+ return cum_month_days[month - 1] + (month >= 3 && is_leap_year (year));
+}
+
+/* Takes a count of days from 14 Oct 1582 and returns the
+ Gregorian calendar year it is in. Dates both before and after
+ the epoch are supported. */
+int
+calendar_offset_to_year (int ofs)
+{
+ int d0;
+ int n400, d1;
+ int n100, d2;
+ int n4, d3;
+ int n1;
+ int y;
+
+ d0 = ofs - EPOCH;
+ floor_divmod (d0, 365 * 400 + 100 - 3, &n400, &d1);
+ floor_divmod (d1, 365 * 100 + 25 - 1, &n100, &d2);
+ floor_divmod (d2, 365 * 4 + 1, &n4, &d3);
+ n1 = floor_div (d3, 365);
+ y = 400 * n400 + 100 * n100 + 4 * n4 + n1;
+ if (n100 != 4 && n1 != 4)
+ y++;
+
+ return y;
+}
+
+/* Takes a count of days from 14 Oct 1582 and translates it into
+ a Gregorian calendar date in (*Y,*M,*D). Dates both before
+ and after the epoch are supported. */
+void
+calendar_offset_to_gregorian (int ofs, int *y, int *m, int *d)
+{
+ int year = *y = calendar_offset_to_year (ofs);
+ int january1 = raw_gregorian_to_offset (year, 1, 1);
+ int yday = ofs - january1 + 1;
+ int march1 = january1 + cum_month_days (year, 3);
+ int correction = ofs < march1 ? 0 : (is_leap_year (year) ? 1 : 2);
+ int month = *m = (12 * (yday - 1 + correction) + 373) / 367;
+ *d = yday - cum_month_days (year, month);
+}
+
+/* Takes a count of days from 14 Oct 1582 and returns the 1-based
+ year-relative day number, that is, the number of days from the
+ beginning of the year. */
+int
+calendar_offset_to_yday (int ofs)
+{
+ int year = calendar_offset_to_year (ofs);
+ int january1 = raw_gregorian_to_offset (year, 1, 1);
+ int yday = ofs - january1 + 1;
+ return yday;
+}
+
+/* Takes a count of days from 14 Oct 1582 and returns the
+ corresponding weekday 1...7, with 1=Sunday. */
+int
+calendar_offset_to_wday (int ofs)
+{
+ int wday = (ofs - EPOCH + 1) % 7 + 1;
+ if (wday <= 0)
+ wday += 7;
+ return wday;
+}
+
+/* Takes a count of days from 14 Oct 1582 and returns the month
+ it is in. */
+int
+calendar_offset_to_month (int ofs)
+{
+ int y, m, d;
+ calendar_offset_to_gregorian (ofs, &y, &m, &d);
+ return m;
+}
+
+/* Takes a count of days from 14 Oct 1582 and returns the
+ corresponding day of the month. */
+int
+calendar_offset_to_mday (int ofs)
+{
+ int y, m, d;
+ calendar_offset_to_gregorian (ofs, &y, &m, &d);
+ return d;
+}
projects / pspp-builds.git / blobdiff