#include #include "calendar.h" #include #include "bool.h" #include "settings.h" #include "val.h" /* 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; }