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/* $OpenBSD: pom.c,v 1.21 2016/01/07 16:00:33 tb Exp $ */
/* $NetBSD: pom.c,v 1.6 1996/02/06 22:47:29 jtc Exp $ */
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software posted to USENET.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*/
/*
* Phase of the Moon. Calculates the current phase of the moon.
* Based on routines from `Practical Astronomy with Your Calculator',
* by Duffett-Smith. Comments give the section from the book that
* particular piece of code was adapted from.
*
* -- Keith E. Brandt VIII 1984
*
* Updated to the Third Edition of Duffett-Smith's book, IX 1998
*
*/
#include <ctype.h>
#include <err.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
#define EPOCH 90
#define EPSILONg 279.403303 /* solar ecliptic long at EPOCH */
#define RHOg 282.768422 /* solar ecliptic long of perigee at EPOCH */
#define ECCEN 0.016713 /* solar orbit eccentricity */
#define lzero 318.351648 /* lunar mean long at EPOCH */
#define Pzero 36.340410 /* lunar mean long of perigee at EPOCH */
#define Nzero 318.510107 /* lunar mean long of node at EPOCH */
#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
void adj360(double *);
double dtor(double);
double potm(double);
time_t parsetime(char *);
__dead void badformat(void);
int
main(int argc, char *argv[])
{
struct timeval tp;
struct timezone tzp;
struct tm *GMT;
time_t tmpt;
double days, today, tomorrow;
int cnt;
char buf[1024];
if (pledge("stdio", NULL) == -1)
err(1, "pledge");
if (argc > 1) {
tmpt = parsetime(argv[1]);
strftime(buf, sizeof(buf), "%a %Y %b %e %H:%M:%S (%Z)",
localtime(&tmpt));
printf("%s: ", buf);
} else {
if (gettimeofday(&tp,&tzp))
err(1, "gettimeofday");
tmpt = tp.tv_sec;
}
GMT = gmtime(&tmpt);
days = (GMT->tm_yday + 1) + ((GMT->tm_hour +
(GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0);
for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
days += isleap(cnt + 1900) ? 366 : 365;
/* Selected time could be before EPOCH */
for (cnt = GMT->tm_year; cnt < EPOCH; ++cnt)
days -= isleap(cnt + 1900) ? 366 : 365;
today = potm(days) + 0.5;
(void)printf("The Moon is ");
if ((int)today == 100)
(void)printf("Full\n");
else if (!(int)today)
(void)printf("New\n");
else {
tomorrow = potm(days + 1);
if ((int)today == 50)
(void)printf("%s\n", tomorrow > today ?
"at the First Quarter" : "at the Last Quarter");
/* today is 0.5 too big, but it doesn't matter here
* since the phase is changing fast enough
*/
else {
today -= 0.5; /* Now it might matter */
(void)printf("%s ", tomorrow > today ?
"Waxing" : "Waning");
if (today > 50)
(void)printf("Gibbous (%1.0f%% of Full)\n",
today);
else if (today < 50)
(void)printf("Crescent (%1.0f%% of Full)\n",
today);
}
}
return 0;
}
/*
* potm --
* return phase of the moon
*/
double
potm(double days)
{
double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
double A4, lprime, V, ldprime, D, Nm;
N = 360.0 * days / 365.242191; /* sec 46 #3 */
adj360(&N);
Msol = N + EPSILONg - RHOg; /* sec 46 #4 */
adj360(&Msol);
Ec = 360 / M_PI * ECCEN * sin(dtor(Msol)); /* sec 46 #5 */
LambdaSol = N + Ec + EPSILONg; /* sec 46 #6 */
adj360(&LambdaSol);
l = 13.1763966 * days + lzero; /* sec 65 #4 */
adj360(&l);
Mm = l - (0.1114041 * days) - Pzero; /* sec 65 #5 */
adj360(&Mm);
Nm = Nzero - (0.0529539 * days); /* sec 65 #6 */
adj360(&Nm);
Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 65 #7 */
Ac = 0.1858 * sin(dtor(Msol)); /* sec 65 #8 */
A3 = 0.37 * sin(dtor(Msol));
Mmprime = Mm + Ev - Ac - A3; /* sec 65 #9 */
Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 65 #10 */
A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 65 #11 */
lprime = l + Ev + Ec - Ac + A4; /* sec 65 #12 */
V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 65 #13 */
ldprime = lprime + V; /* sec 65 #14 */
D = ldprime - LambdaSol; /* sec 67 #2 */
return(50.0 * (1 - cos(dtor(D)))); /* sec 67 #3 */
}
/*
* dtor --
* convert degrees to radians
*/
double
dtor(double deg)
{
return(deg * M_PI / 180);
}
/*
* adj360 --
* adjust value so 0 <= deg <= 360
*/
void
adj360(double *deg)
{
for (;;)
if (*deg < 0.0)
*deg += 360.0;
else if (*deg > 360.0)
*deg -= 360.0;
else
break;
}
#define ATOI2(ar) ((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;
time_t
parsetime(char *p)
{
struct tm *lt;
int bigyear;
int yearset = 0;
time_t tval;
char *t;
for (t = p; *t; ++t) {
if (isdigit((unsigned char)*t))
continue;
badformat();
}
tval = time(NULL);
lt = localtime(&tval);
lt->tm_sec = 0;
lt->tm_min = 0;
switch (strlen(p)) {
case 10: /* yyyy */
bigyear = ATOI2(p);
lt->tm_year = (bigyear * 100) - 1900;
yearset = 1;
/* FALLTHROUGH */
case 8: /* yy */
if (yearset) {
lt->tm_year += ATOI2(p);
} else {
lt->tm_year = ATOI2(p);
if (lt->tm_year < 69) /* hack for 2000 */
lt->tm_year += 100;
}
/* FALLTHROUGH */
case 6: /* mm */
lt->tm_mon = ATOI2(p);
if ((lt->tm_mon > 12) || !lt->tm_mon)
badformat();
--lt->tm_mon; /* time struct is 0 - 11 */
/* FALLTHROUGH */
case 4: /* dd */
lt->tm_mday = ATOI2(p);
if ((lt->tm_mday > 31) || !lt->tm_mday)
badformat();
/* FALLTHROUGH */
case 2: /* HH */
lt->tm_hour = ATOI2(p);
if (lt->tm_hour > 23)
badformat();
break;
default:
badformat();
}
/* The calling code needs a valid tm_ydays and this is the easiest
* way to get one */
if ((tval = mktime(lt)) == -1)
errx(1, "specified date is outside allowed range");
return (tval);
}
void
badformat(void)
{
warnx("illegal time format");
(void)fprintf(stderr, "usage: pom [[[[[cc]yy]mm]dd]HH]\n");
exit(1);
}
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