initial commit

AUTHORS

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+Steffen Vogel <post@steffenvogel.de>

INSTALL

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+/usr/share/automake-1.11/INSTALL

Makefile.am

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+SUBDIRS = src
+
+dist_doc_DATA = README

README

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+libastro is a collection of functions for time, date and ephemeris calculus

configure.ac

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+#                                               -*- Autoconf -*-
+# Process this file with autoconf to produce a configure script.
+
+AC_PREREQ([2.69])
+AC_INIT(astro, 0.1, stv0g@0l.de)
+AC_CONFIG_SRCDIR([include/sun.h])
+AC_CONFIG_HEADERS([config.h])
+
+# Checks for programs.
+AC_PROG_CC
+
+# Checks for libraries.
+
+# Checks for header files.
+
+# Checks for typedefs, structures, and compiler characteristics.
+
+# Checks for library functions.
+
+# Automake
+AM_INIT_AUTOMAKE
+AM_PROG_CC_C_O
+
+AC_CONFIG_FILES([
+  Makefile
+  src/Makefile
+])
+
+AC_OUTPUT

src/Makefile.am

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+bin_PROGRAMS = astro
+
+astro_SOURCES = calendar.c astro.c
+astro_LDADD = -lm

src/astro.c

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+#include <stdio.h>
+#include <time.h>
+
+#include "calendar.h"
+
+extern const char* weekdays[];
+extern const char* months[];
+
+int main(int argc, char *argv[]) {
+	time_t u = time(NULL);
+	struct tm *n = localtime(&u); /* current time and date */
+
+	struct date d;
+	struct time t;
+
+	if (argc == 2) {
+		sscanf(argv[1], "%d.%d.%d", &d.day, &d.month, &d.year);
+	}
+	else {
+		d.day = n->tm_mday;
+		d.month = n->tm_mon+1;
+		d.year = n->tm_year+1900;
+	}
+
+	t.hour = n->tm_hour;
+	t.minute = n->tm_min;
+	t.second = n->tm_sec;
+
+
+	printf("Berechne für %d.%d.%d %d:%0d\n", d.day, d.month, d.year, t.hour, t.minute);
+
+	struct date e = eastern(d.year);
+	enum weekday wday = weekday(d);
+	bool leap = leapyear(d.year);
+	double dec = hms2decimal(t);
+	int day = daynumber(d);
+	int week = weeknumber(d); // TODO fix
+
+	printf("In year %d, eastern is on %s the %d. %s\n", e.year, weekdays[weekday(e)], e.day, months[e.month-1]);
+	printf("The year %d %s a leapyear\n", d.year, (leap) ? "is" : "is not");
+	printf("Daynumber: %d\n", day);
+	printf("Today is a %s\n", weekdays[wday]);
+	printf("%.1f %% of the day are over :-%c\n", dec*1e2, (dec > 0.5) ? '(' : ')');
+	printf("Weeknumber: %d\n", week);
+
+
+	return 0;
+}

src/calendar.c

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+#include <math.h>
+
+#include "calendar.h"
+
+/** Constants */
+const double DELTA_T = 66.7; /* seconds */
+
+const char *weekdays[] = { "Monday", "Tuesday", "Wednesday",
+	"Thursday", "Friday", "Saturday", "Sunday" };
+
+const char *holidays[] = { };
+
+const char *months[] = { "January", "February", "March",
+	"April", "May", "June", "July", "August",
+	"October", "November", "December" };
+
+const char *signs[] = { "Aries", "Taurus", "Gemini", "Cancer",
+	"Leo", "Virgo", "Libra", "Scorpio",
+	"Ophiuchus", "Sagittarius", "Capricorn",
+	"Aquarius", "Pisces" };
+
+double frac(double x) {
+	return x - floor(x);
+}
+
+struct date eastern(int year) {
+	int k = year / 100;				/* Säkularzahl */
+	int m = 15 + (3*k + 3) / 4 - (8*k + 13) / 25;	/* säkulare Mondschaltung */
+	int s = 2 - (3*k + 3) / 4;			/* säkulare Sonnenschaltung */
+	int a = year % 19;				/* den Mondparameter */
+	int d = (19*a + m) % 30;			/* Keim für den ersten Vollmond im Frühling */
+	int r = (d + a/11) / 29;			/* kalendarische Korrekturgröße */
+	int og = 21 + d - r;				/* Ostergrenze */
+	int sz = 7 - (year + year/4 + s) % 7;		/* erster Sonntag im März */
+	int oe = 7 - (og - sz) % 7;			/* Osterentfernung in Tagen */
+	int os = os = og + oe;				/* Datum des Ostersonntags als Märzdatum */
+
+	struct date eastern = {
+		.year = year,
+		.month = (os > 31) ? 4 : 3,
+		.day = (os > 31) ? os - 31 : os
+	};
+
+	return eastern;
+}
+
+struct date holiday(struct date date, enum holiday type) {
+	switch (type) {
+		case EASTER_SUNDAY:
+			return eastern(date.year);
+			break;
+
+		case NEWYEAR: {
+			struct date ny;
+			ny.year = date.year;
+			ny.month = 1;
+			ny.day = 1;
+			return ny;
+		}
+
+		case SILVESTER: {
+			struct date sv;
+			sv.year = date.year;
+			sv.month = 12;
+			sv.day = 31;
+			return sv;
+		}
+	}
+}
+
+int weekday(struct date date) {
+	const int century_code[] = { 6, 4, 2, 0 };
+	const int month_code[] = { 6, 2, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
+
+	int l = (leapyear(date.year) && date.month <= 2) ? 1 : 0;
+	int x = date.year % 100;
+	int y = date.year / 100;
+	int a = century_code[(y - 16) % 4];
+	int b = month_code[(date.month-1) % 12] - l;
+	int c = x + x/4;
+	int d = date.day;
+
+	return (a + b + c + d) % 7;
+}
+
+bool leapyear(int year) {
+	if ((year % 400) == 0)
+		return true;
+	else if ((year % 100) == 0)
+		return false;
+	else if ((year % 4) == 0)
+		return true;
+	else
+		return false;
+}
+
+int daynumber(struct date date) {
+	int days = date.month;
+
+	if (date.month <= 2) {
+		days--;
+		days *= leapyear(date.year) ? 62 : 63;
+		days /= 2;
+	}
+	else {
+		days++;
+		days *= 30.6;
+		days -= leapyear(date.year)? 62 : 63;
+	}
+
+	return days + date.day;
+}
+
+int weeknumber(struct date date) {
+	int dn = daynumber(date);
+
+	struct date ny = { /* new year */
+		.year = date.year,
+		.month = 1, .day = 1
+	};
+	int wdny = weekday(ny);
+
+	// Sonderfälle Freitag und Samstag
+	if (wdny >= 5) {
+		wdny -= 7;
+	}
+
+	// Sonderfälle "Jahresanfang mit KW-Nummer aus dem Vorjahr"
+	if (dn + wdny <= 1) {
+		struct date sv = { /* silvester last year */
+			.year = date.year - 1,
+			.month = 12, .day = 31
+		};
+		return weeknumber(sv);
+	}
+
+	int wn = (dn + wdny + 5) / 7;
+
+	/* 53 Kalenderwochen hat grundsätzlich nur ein Jahr, 
+	   welches mit einem Donnerstag anfängt !
+	   In Schaltjahren ist es auch mit einem Mittwoch möglich, z.B. 1992
+	   Andernfalls ist diese KW schon die KW1 des Folgejahres. */
+	if (wn == 53) {
+		bool ly = leapyear(date.year);
+
+		if ( (wdny + 7 ) % 7 ==  4 || ((wdny + 7) % 7 == 3 && ly)) {
+			return wn;
+		}
+		else {
+			return 1; // Korrektur des Wertes
+		}
+	}
+	else {
+		return wn;
+	}
+}
+
+double hms2decimal(struct time t) {
+	return (((t.second / 60.0) + t.minute) / 60.0 + t.hour) / 24.0;
+}
+
+struct time decimal2hms(double decimal) {
+	double hours = decimal * 24;
+	double minutes = frac(hours) * 60;
+	double seconds = frac(minutes) * 60;
+
+	struct time time = { hours, minutes, seconds };
+	return time;
+}
+
+int gregorian2julian(struct date d) {
+	if (d.month <= 2) {
+		d.year--;
+		d.month += 12;
+	}
+
+	struct date x = { .day = 15, .month = 10, .year = 1582 };
+	if (datecmp(d, x) > 0) {
+		int a = d.year / 100;
+		int b = 2 - a + 
+	}
+
+	return b + c + d + d.day + 1720994.5
+}
+
+struct date julian2gregorian(int jd) {
+
+}
+
+struct time utc2et(struct time d) {
+	
+}
+
+int datecmp(struct date a, struct date b) {
+	if (a.year == b.year) {
+		if (a.month == b.month) {
+			if (a.day == b.day) return 0;
+			else return a.day - b.day;
+		}
+		else return a.month - b.month;
+	}
+	else return a.year - b.year;
+}

src/calendar.h

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+/**
+ * Time and Calender calculus
+ *
+ * based on Practical astronomy with your calculator or spreadsheet
+ *   from Peter Duffett-Smith, Jonathan Zwart. – 4th ed. (Cambridge University Press, 2011)
+ *
+ * @copyright	2012 Steffen Vogel
+ * @license	http://www.gnu.org/licenses/gpl.txt GNU Public License
+ * @author	Steffen Vogel <post@steffenvogel.de>
+ * @author	Arnold Barmettler <barmettler@astronomie.info>
+ * @link	http://www.steffenvogel.de
+ */
+/*
+ * This file is part of libastro
+ *
+ * libastro is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * any later version.
+ *
+ * libastro is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libastro. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+/* TODO
+christliche Feiertage
+Advent
+Sommer/Frühlings/Herbstanfang
+Längster/Kürzester Tag
+Vollmond
+*/
+
+#ifndef _TIME_H_
+#define _TIME_H_
+
+#include <stdbool.h>
+#include <time.h>
+
+/** Types */
+struct date {
+	int day;
+	int month;
+	int year;
+};
+
+struct time {
+	int second;
+	int minute;
+	int hour;
+};
+
+/* helper to convert libastro types to struct tm */
+struct tma {
+	struct time time;
+	struct date date;
+	int wday;		/* day of the week */
+	int yday;		/* day in the year */
+	int isdst;		/* daylight saving time */
+};
+
+union datetime {
+	struct tma libastro;
+	struct tm posix;
+};
+
+enum weekday {
+	MONDAY, TUESDAY, WEDNESDAY,
+	THURSDAY, FRIDAY, SATURDAY, SUNDAY
+};
+
+enum holiday {
+	EASTER_SUNDAY,
+	CHRISTMAS,
+	ADVENT_1, ADVENT_2, ADVENT_3, ADVENT_4,
+	SILVESTER, NEWYEAR
+};
+
+/** Prototypes */
+
+/** Helper functions */
+double frac(double x);
+
+/**
+ * Compare to dates like strcmp()
+ */
+int datecmp(struct date a, struct date b);
+
+struct date dateadd(struct date a, struct date b);
+
+
+struct date holiday(struct date d, enum holiday type);
+
+/**
+ * Calculate the date of eastern
+ *
+ * @see http://de.wikipedia.org/wiki/Gau%C3%9Fsche_Osterformel
+ */
+struct date eastern(int year);
+
+/**
+ * Checks if year is a leapyear
+ */
+bool leapyear(int year);
+
+/**
+ * Calculate the daynumber of a gregorian date
+ *  e.g the number of days after 1.1. of the current year
+ */
+int daynumber(struct date d);
+
+/**
+ * Calculate the weeknumber of a gregorian date
+ *
+ * according to DIN1355
+ */
+int weeknumber(struct date d);
+
+/**
+ * Return english weekday name
+ */
+int weekday(struct date d);
+
+/**
+ * Return sign
+ */
+const char * sign(struct date d, int mode);
+
+/**
+ * Convert a gregorian date to a julian date
+ */
+int gregorian2julian(struct date d);
+struct date julian2gregorian(int jd);
+
+/**
+ * Convert HH:MM:SS to decimal day
+ */
+double hms2decimal(struct time t);
+struct time decimal2hms(double decimal);
+
+/**
+ * Universial to Local Time
+ */
+//utc2local(struct date, int zone);
+
+/**
+ * Universal to Greenwich Sidereal Time
+ */
+//utc2gmst();
+
+/**
+ * Greenwich Sidereal to Universal Time
+ */
+//gmst2utc();
+
+/**
+ * Local Sidereal to Univeral Time
+ */
+//lmst2utc();
+
+/**
+ * Universal to Terrestrial (dynamic) Time
+ */
+//utc2tdt(utc);
+
+/**
+ * Ephimeris Time
+ */
+//struct time utc2et(struct time d);
+
+#endif /* _TIME_H_ */