diff options
| -rw-r--r-- | lib/libcalendar/Makefile | 20 | ||||
| -rw-r--r-- | lib/libcalendar/calendar.3 | 180 | ||||
| -rw-r--r-- | lib/libcalendar/calendar.c | 327 | ||||
| -rw-r--r-- | lib/libcalendar/calendar.h | 41 | ||||
| -rw-r--r-- | lib/libcalendar/easter.c | 82 |
5 files changed, 650 insertions, 0 deletions
diff --git a/lib/libcalendar/Makefile b/lib/libcalendar/Makefile new file mode 100644 index 0000000..fe41148 --- /dev/null +++ b/lib/libcalendar/Makefile @@ -0,0 +1,20 @@ +# $Id$ + +LIB= calendar + +SRCS= calendar.c easter.c + +MAN3= calendar.3 + +MLINKS= calendar.3 easterg.3 calendar.3 easterj.3 \ + calendar.3 gdate.3 calendar.3 jdate.3 \ + calendar.3 ndaysg.3 calendar.3 ndaysj.3 \ + calendar.3 week.3 calendar.3 weekday.3 + +CFLAGS+=-I. -I${.CURDIR} -Wall + +beforeinstall: + ${INSTALL} -C -m 444 -o $(BINOWN) -g $(BINGRP) ${.CURDIR}/calendar.h \ + ${DESTDIR}/usr/include + +.include <bsd.lib.mk> diff --git a/lib/libcalendar/calendar.3 b/lib/libcalendar/calendar.3 new file mode 100644 index 0000000..4f51a02 --- /dev/null +++ b/lib/libcalendar/calendar.3 @@ -0,0 +1,180 @@ +.\" Copyright (c) 1997 Wolfgang Helbig +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $Id$ +.\" +.Dd November 29, 1997 +.Dt CALENDAR 3 +.Os +.Sh NAME +.Nm easterg , +.Nm easterj , +.Nm gdate , +.Nm jdate , +.Nm ndaysg , +.Nm ndaysj , +.Nm week , +.Nm weekday +.Nd Calendar arithmetic for the Christian era. +.Sh SYNOPSIS +.Fd #include <calendar.h> +.Ft date * +.Fn easterg "int year" "date *dt" +.Ft date * +.Fn easterj "int year" "date *dt" +.Ft date * +.Fn gdate "int nd" "date *dt" +.Ft date * +.Fn jdate "int nd" "date *dt" +.Ft int +.Fn ndaysg "date *dt" +.Ft int +.Fn ndaysj "date *dt" +.Ft int +.Fn week "int nd" "int *year" +.Ft int +.Fn weekday "int nd" +.Sh DESCRIPTION +These functions provide calendar arithmetic for a large range of years, +starting at March 1st, year zero (i. e. 1 B.C.) and ending way beyond +year 100000. + +Programs should be linked with +.Fl lcalendar . + +The functions +.Fn easterg +and +.Fn easterj +store the date of Easter Sunday into the structure pointed at by +.Fa dt +and return a pointer to this structure. +The function +.Fn easterg +assumes Gregorian Calendar (adopted by most western churches after 1582) and +.Fn easterj +assumes Julian Calendar (Western churches before 1582 and Greek Church +until today). + +The functions +.Fn gdate , +.Fn jdate , +.Fn ndaysg +and +.Fn ndaysj +provide conversions between the common "year, month, day" notation +of a date and the "number of days" representation, which is better suited +for calculations. The days are numbered from March 1st year 1 B.C., starting +with zero, so the number of a day gives the number of days since March 1st, +year 1 B.C. The conversions work for nonnegative day numbers only. + +The +.Fn gdate +and +.Fn jdate +functions +store the date corresponding to the day number +.Fa nd +into the structure pointed at by +.Fa dt +and return a pointer to this structure. + +The +.Fn ndaysg +and +.Fn ndaysj +functions +return the day number of the date pointed at by +.Fa dt . + +The +.Fn gdate +and +.Fn ndaysg +functions +assume Gregorian Calendar after October 4th 1582 and Julian Calendar before, +whereas +.Fn jdate +and +.Fn ndaysj +assume Julian Calendar throughout. + +The two calendars differ by the definition of the leap year. The +Julian Calendar says every year that is a multiple of four is a +leap year. The Gregorian Calendar excludes years that are multiples of +100 and not multiples of 400. +This means the years 1700, 1800, 1900, 2100 are not leap years +and the year 2000 is +a leap year. +The new rules were inaugurated on October 4th 1582 by deleting ten +days following this date. + +The function +.Fn week +returns the number of the week which contains the day numbered +.Fa nd . +The argument +.Fa *year +is set with the year that contains (the greater part of) the week. +The weeks are numbered per year starting with week 1, which is the +first week in a year that includes more than three days of the year. +Weeks start on Monday. +This function is defined for Gregorian Calendar only. + +The function +.Fn weekday +returns the weekday (Mo = 0 .. Su = 6) of the day numbered +.Fa nd . + +The type +.Fa date +is a structure defined in +.Aq Pa calendar.h . +It contains these fields: +.Bd -literal -offset indent +int y; /\(** year (0000 - ????) \(**/ +int m; /\(** month (1 - 12) \(**/ +int d; /\(** day of month (1 - 31) \(**/ +.Ed + +The year zero is written as "1 B.C." by historians and "0" by astronomers +and in this library. +.Sh SEE ALSO +.Xr ncal 1 , +.Xr strftime 3 +.Rs +.%A A. B. Author +.%D November 1997 +.Sh STANDARDS +The week number conforms to ISO 8601: 1988. +.Sh HISTORY +The +.Nm calendar +library first appeared in +.Fx 3.0 . +.Sh AUTHOR +This manual page and the library was written by +.An Wolfgang Helbig Aq helbig@FreeBSD.ORG . +.Sh BUGS +The library was coded with great care so there are no bugs left. diff --git a/lib/libcalendar/calendar.c b/lib/libcalendar/calendar.c new file mode 100644 index 0000000..41e79b2 --- /dev/null +++ b/lib/libcalendar/calendar.c @@ -0,0 +1,327 @@ +/*- + * Copyright (c) 1997 Wolfgang Helbig + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $Id$ + */ + +#include "calendar.h" + +#ifndef NULL +#define NULL 0 +#endif + +/* + * For each month tabulate the number of days elapsed in a year before the + * month. This assumes the internal date representation, where a year + * starts on March 1st. So we don't need a special table for leap years. + * But we do need a special table for the year 1582, since 10 days are + * deleted in October. This is month1s for the switch from Julian to + * Gregorian calendar. + */ +static int const month1[] = + {0, 31, 61, 92, 122, 153, 184, 214, 245, 275, 306, 337}; + /* M A M J J A S O N D J */ +static int const month1s[]= + {0, 31, 61, 92, 122, 153, 184, 214, 235, 265, 296, 327}; + +/* The last day of Julian calendar, in internal and ndays representation */ +static int nswitch; /* The last day of Julian calendar */ +static date jiswitch = {1582, 7, 3}; + +static date *date2idt(date *idt, date *dt); +static date *idt2date(date *dt, date *idt); +static int ndaysji(date *idt); +static int ndaysgi(date *idt); +static int firstweek(int year); + +/* + * Compute the Julian date from the number of days elapsed since + * March 1st of year zero. + */ +date * +jdate(int ndays, date *dt) +{ + date idt; /* Internal date representation */ + int r; /* hold the rest of days */ + + /* + * Compute the year by starting with an approximation not smaller + * than the answer and using linear search for the greatest + * year which does not begin after ndays. + */ + idt.y = ndays / 365; + idt.m = 0; + idt.d = 0; + while ((r = ndaysji(&idt)) > ndays) + idt.y--; + + /* + * Set r to the days left in the year and compute the month by + * linear search as the largest month that does not begin after r + * days. + */ + r = ndays - r; + for (idt.m = 11; month1[idt.m] > r; idt.m--) + ; + + /* Compute the days left in the month */ + idt.d = r - month1[idt.m]; + + /* return external representation of the date */ + return (idt2date(dt, &idt)); +} + +/* + * Return the number of days since March 1st of the year zero. + * The date is given according to Julian calendar. + */ +int +ndaysj(date *dt) +{ + date idt; /* Internal date representation */ + + if (date2idt(&idt, dt) == NULL) + return (-1); + else + return (ndaysji(&idt)); +} + +/* + * Same as above, where the Julian date is given in internal notation. + * This formula shows the beauty of this notation. + */ +static int +ndaysji(date * idt) +{ + + return (idt->d + month1[idt->m] + idt->y * 365 + idt->y / 4); +} + +/* + * Compute the date according to the Gregorian calendar from the number of + * days since March 1st, year zero. The date computed will be Julian if it + * is older than 1582-10-05. This is the reverse of the function ndaysg(). + */ +date * +gdate(int ndays, date *dt) +{ + int const *montht; /* month-table */ + date idt; /* for internal date representation */ + int r; /* holds the rest of days */ + + /* + * Compute the year by starting with an approximation not smaller + * than the answer and search linearly for the greatest year not + * starting after ndays. + */ + idt.y = ndays / 365; + idt.m = 0; + idt.d = 0; + while ((r = ndaysgi(&idt)) > ndays) + idt.y--; + + /* + * Set ndays to the number of days left and compute by linear + * search the greatest month which does not start after ndays. We + * use the table month1 which provides for each month the number + * of days that elapsed in the year before that month. Here the + * year 1582 is special, as 10 days are left out in October to + * resynchronize the calendar with the earth's orbit. October 4th + * 1582 is followed by October 15th 1582. We use the "switch" + * table month1s for this year. + */ + ndays = ndays - r; + if (idt.y == 1582) + montht = month1s; + else + montht = month1; + + for (idt.m = 11; montht[idt.m] > ndays; idt.m--) + ; + + idt.d = ndays - montht[idt.m]; /* the rest is the day in month */ + + /* Advance ten days deleted from October if after switch in Oct 1582 */ + if (idt.y == jiswitch.y && idt.m == jiswitch.m && jiswitch.d < idt.d) + idt.d += 10; + + /* return external representation of found date */ + return (idt2date(dt, &idt)); +} + +/* + * Return the number of days since March 1st of the year zero. The date is + * assumed Gregorian if younger than 1582-10-04 and Julian otherwise. This + * is the reverse of gdate. + */ +int +ndaysg(date *dt) +{ + date idt; /* Internal date representation */ + + if (date2idt(&idt, dt) == NULL) + return (-1); + return (ndaysgi(&idt)); +} + +/* + * Same as above, but with the Gregorian date given in internal + * representation. + */ +static int +ndaysgi(date *idt) +{ + int nd; /* Number of days--return value */ + + /* Cache nswitch if not already done */ + if (nswitch == 0) + nswitch = ndaysji(&jiswitch); + + /* + * Assume Julian calendar and adapt to Gregorian if necessary, i. e. + * younger than nswitch. Gregori deleted + * the ten days from Oct 5th to Oct 14th 1582. + * Thereafter years which are multiples of 100 and not multiples + * of 400 were not leap years anymore. + * This makes the average length of a year + * 365d +.25d - .01d + .0025d = 365.2425d. But the tropical + * year measures 365.2422d. So in 10000/3 years we are + * again one day ahead of the earth. Sigh :-) + * (d is the average length of a day and tropical year is the + * time from one spring point to the next.) + */ + if ((nd = ndaysji(idt)) == -1) + return (-1); + if (idt->y >= 1600) + nd = (nd - 10 - (idt->y - 1600) / 100 + (idt->y - 1600) / 400); + else if (nd > nswitch) + nd -= 10; + return (nd); +} + +/* + * Compute the week number from the number of days since March 1st year 0. + * The weeks are numbered per year starting with 1. If the first + * week of a year includes at least four days of that year it is week 1, + * otherwise it gets the number of the last week of the previous year. + * The variable y will be filled with the year that contains the greater + * part of the week. + */ +int +week(int nd, int *y) +{ + date dt; + int fw; /* 1st day of week 1 of previous, this and + * next year */ + gdate(nd, &dt); + for (*y = dt.y + 1; nd < (fw = firstweek(*y)); (*y)--) + ; + return ((nd - fw) / 7 + 1); +} + +/* return the first day of week 1 of year y */ +static int +firstweek(int y) +{ + date idt; + int nd, wd; + + idt.y = y - 1; /* internal representation of y-1-1 */ + idt.m = 10; + idt.d = 0; + + nd = ndaysgi(&idt); + /* + * If more than 3 days of this week are in the preceding year, the + * next week is week 1 (and the next monday is the answer), + * otherwise this week is week 1 and the last monday is the + * answer. + */ + if ((wd = weekday(nd)) > 3) + return (nd - wd + 7); + else + return (nd - wd); +} + +/* return the weekday (Mo = 0 .. Su = 6) */ +int +weekday(int nd) +{ + date dmondaygi = {1997, 8, 16}; /* Internal repr. of 1997-11-17 */ + static int nmonday; /* ... which is a monday */ + + /* Cache the daynumber of one monday */ + if (nmonday == 0) + nmonday = ndaysgi(&dmondaygi); + + /* return (nd - nmonday) modulo 7 which is the weekday */ + nd = (nd - nmonday) % 7; + if (nd < 0) + return (nd + 7); + else + return (nd); +} + +/* + * Convert a date to internal date representation: The year starts on + * March 1st, month and day numbering start at zero. E. g. March 1st of + * year zero is written as y=0, m=0, d=0. + */ +static date * +date2idt(date *idt, date *dt) +{ + + idt->d = dt->d - 1; + if (dt->m > 2) { + idt->m = dt->m - 3; + idt->y = dt->y; + } else { + idt->m = dt->m + 9; + idt->y = dt->y - 1; + } + if (idt->m < 0 || idt->m > 11 || idt->y < 0) + return (NULL); + else + return idt; +} + +/* Reverse of date2idt */ +static date * +idt2date(date *dt, date *idt) +{ + + dt->d = idt->d + 1; + if (idt->m < 10) { + dt->m = idt->m + 3; + dt->y = idt->y; + } else { + dt->m = idt->m - 9; + dt->y = idt->y + 1; + } + if (dt->m < 1) + return (NULL); + else + return (dt); +} diff --git a/lib/libcalendar/calendar.h b/lib/libcalendar/calendar.h new file mode 100644 index 0000000..6c8d8f9 --- /dev/null +++ b/lib/libcalendar/calendar.h @@ -0,0 +1,41 @@ +/*- + * Copyright (c) 1997 Wolfgang Helbig + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $Id$ + */ +typedef struct date { + int y; /* year */ + int m; /* month */ + int d; /* day */ +} date; + +date *easterg(int _year, date *_dt); +date *easterj(int _year, date *_dt); +date *gdate(int _nd, date *_dt); +date *jdate(int _nd, date *_dt); +int ndaysg(date *_dt); +int ndaysj(date *_dt); +int week(int _nd, int *_year); +int weekday(int _nd); diff --git a/lib/libcalendar/easter.c b/lib/libcalendar/easter.c new file mode 100644 index 0000000..53021f7 --- /dev/null +++ b/lib/libcalendar/easter.c @@ -0,0 +1,82 @@ +/*- + * Copyright (c) 1997 Wolfgang Helbig + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $Id$ + */ + +#include "calendar.h" + +/* Compute Easter Sunday in Gregorian Calendar */ +date * +easterg(int y, date *dt) +{ + int c, i, j, k, l, n; + + n = y % 19; + c = y / 100; + k = (c - 17) / 25; + i = (c - c/4 -(c-k)/3 + 19 * n + 15) % 30; + i = i -(i/28) * (1 - (i/28) * (29/(i + 1)) * ((21 - n)/11)); + j = (y + y/4 + i + 2 - c + c/4) % 7; + l = i - j; + dt->m = 3 + (l + 40) / 44; + dt->d = l + 28 - 31*(dt->m / 4); + dt->y = y; + return (dt); +} + +/* Compute Easter Sunday in Julian Calendar */ +date * +easterj(int y, date * dt) +{ + + /* + * Table for the easter limits in one metonic (19-year) cycle. 21 + * to 31 is in March, 1 through 18 in April. Easter is the first + * sunday after the easter limit. + */ + int mc[] = {5, 25, 13, 2, 22, 10, 30, 18, 7, 27, 15, 4, + 24, 12, 1, 21, 9, 29, 17}; + + /* Offset from a weekday to next sunday */ + int ns[] = {6, 5, 4, 3, 2, 1, 7}; + int dn; + + /* Assign the easter limit of y to *dt */ + dt->d = mc[y % 19]; + + if (dt->d < 21) + dt->m = 4; + else + dt->m = 3; + + dt->y = y; + + /* Compute the next sunday after the easter limit */ + dn = ndaysj(dt); + dn += ns[weekday(dn)]; + + return (jdate(dn, dt)); +} |
