pom/pom.c

   1 /*      $NetBSD: pom.c,v 1.12 1999/09/14 20:00:07 jsm Exp $     */
   2
   3 /*
   4  * Copyright (c) 1989, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software posted to USENET.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  */
  37
  38 #include <sys/cdefs.h>
  39 #ifndef lint
  40 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
  41         The Regents of the University of California.  All rights reserved.\n");
  42 #endif /* not lint */
  43
  44 #ifndef lint
  45 #if 0
  46 static char sccsid[] = "@(#)pom.c       8.1 (Berkeley) 5/31/93";
  47 #else
  48 __RCSID("$NetBSD: pom.c,v 1.12 1999/09/14 20:00:07 jsm Exp $");
  49 #endif
  50 #endif /* not lint */
  51
  52 /*
  53  * Phase of the Moon.  Calculates the current phase of the moon.
  54  * Based on routines from `Practical Astronomy with Your Calculator',
  55  * by Duffett-Smith.  Comments give the section from the book that
  56  * particular piece of code was adapted from.
  57  *
  58  * -- Keith E. Brandt  VIII 1984
  59  *
  60  * Updated to the Third Edition of Duffett-Smith's book, Paul Janzen, IX 1998
  61  *
  62  */
  63
  64 #include <ctype.h>
  65 #include <err.h>
  66 #include <math.h>
  67 #include <stdio.h>
  68 #include <string.h>
  69 #include <stdlib.h>
  70 #include <time.h>
  71 #include <unistd.h>
  72
  73 #ifndef PI
  74 #define PI        3.14159265358979323846
  75 #endif
  76
  77 /*
  78  * The EPOCH in the third edition of the book is 1990 Jan 0.0 TDT.
  79  * In this program, we do not bother to correct for the differences
  80  * between UTC (as shown by the UNIX clock) and TDT.  (TDT = TAI + 32.184s;
  81  * TAI-UTC = 32s in Jan 1999.)
  82  */
  83 #define EPOCH_MINUS_1970        (20 * 365 + 5 - 1) /* 20 years, 5 leaps, back 1 day to Jan 0 */
  84 #define EPSILONg  279.403303    /* solar ecliptic long at EPOCH */
  85 #define RHOg      282.768422    /* solar ecliptic long of perigee at EPOCH */
  86 #define ECCEN     0.016713      /* solar orbit eccentricity */
  87 #define lzero     318.351648    /* lunar mean long at EPOCH */
  88 #define Pzero     36.340410     /* lunar mean long of perigee at EPOCH */
  89 #define Nzero     318.510107    /* lunar mean long of node at EPOCH */
  90
  91 void    adj360 __P((double *));
  92 double  dtor __P((double));
  93 int     main __P((int, char *[]));
  94 double  potm __P((double));
  95 time_t  parsetime __P((char *));
  96 void    badformat __P((void)) __attribute__((__noreturn__));
  97
  98 int
  99 main(argc, argv)
 100         int argc;
 101         char *argv[];
 102 {
 103         time_t tmpt, now;
 104         double days, today, tomorrow;
 105         char buf[1024];
 106
 107         if (time(&now) == (time_t)-1)
 108                 err(1, "time");
 109         if (argc > 1) {
 110                 tmpt = parsetime(argv[1]);
 111                 strftime(buf, sizeof(buf), "%a %Y %b %e %H:%M:%S (%Z)",
 112                         localtime(&tmpt));
 113                 printf("%s:  ", buf);
 114         } else {
 115                 tmpt = now;
 116         }
 117         days = (tmpt - EPOCH_MINUS_1970 * 86400) / 86400.0;
 118         today = potm(days) + .5;
 119         if (tmpt < now)
 120                 (void)printf("The Moon was ");
 121         else if (tmpt == now)
 122                 (void)printf("The Moon is ");
 123         else
 124                 (void)printf("The Moon will be ");
 125         if ((int)today == 100)
 126                 (void)printf("Full\n");
 127         else if (!(int)today)
 128                 (void)printf("New\n");
 129         else {
 130                 tomorrow = potm(days + 1);
 131                 if ((int)today == 50)
 132                         (void)printf("%s\n", tomorrow > today ?
 133                             "at the First Quarter" : "at the Last Quarter");
 134                         /* today is 0.5 too big, but it doesn't matter here
 135                          * since the phase is changing fast enough
 136                          */
 137                 else {
 138                         today -= 0.5;           /* Now it might matter */
 139                         (void)printf("%s ", tomorrow > today ?
 140                             "Waxing" : "Waning");
 141                         if (today > 50)
 142                                 (void)printf("Gibbous (%1.0f%% of Full)\n",
 143                                     today);
 144                         else if (today < 50)
 145                                 (void)printf("Crescent (%1.0f%% of Full)\n",
 146                                     today);
 147                 }
 148         }
 149         exit(0);
 150 }
 151
 152 /*
 153  * potm --
 154  *      return phase of the moon
 155  */
 156 double
 157 potm(days)
 158         double days;
 159 {
 160         double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
 161         double A4, lprime, V, ldprime, D, Nm;
 162
 163         N = 360 * days / 365.242191;                            /* sec 46 #3 */
 164         adj360(&N);
 165         Msol = N + EPSILONg - RHOg;                             /* sec 46 #4 */
 166         adj360(&Msol);
 167         Ec = 360 / PI * ECCEN * sin(dtor(Msol));                /* sec 46 #5 */
 168         LambdaSol = N + Ec + EPSILONg;                          /* sec 46 #6 */
 169         adj360(&LambdaSol);
 170         l = 13.1763966 * days + lzero;                          /* sec 65 #4 */
 171         adj360(&l);
 172         Mm = l - (0.1114041 * days) - Pzero;                    /* sec 65 #5 */
 173         adj360(&Mm);
 174         Nm = Nzero - (0.0529539 * days);                        /* sec 65 #6 */
 175         adj360(&Nm);
 176         Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm));        /* sec 65 #7 */
 177         Ac = 0.1858 * sin(dtor(Msol));                          /* sec 65 #8 */
 178         A3 = 0.37 * sin(dtor(Msol));
 179         Mmprime = Mm + Ev - Ac - A3;                            /* sec 65 #9 */
 180         Ec = 6.2886 * sin(dtor(Mmprime));                       /* sec 65 #10 */
 181         A4 = 0.214 * sin(dtor(2 * Mmprime));                    /* sec 65 #11 */
 182         lprime = l + Ev + Ec - Ac + A4;                         /* sec 65 #12 */
 183         V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));       /* sec 65 #13 */
 184         ldprime = lprime + V;                                   /* sec 65 #14 */
 185         D = ldprime - LambdaSol;                                /* sec 67 #2 */
 186         return(50.0 * (1 - cos(dtor(D))));                      /* sec 67 #3 */
 187 }
 188
 189 /*
 190  * dtor --
 191  *      convert degrees to radians
 192  */
 193 double
 194 dtor(deg)
 195         double deg;
 196 {
 197         return(deg * PI / 180);
 198 }
 199
 200 /*
 201  * adj360 --
 202  *      adjust value so 0 <= deg <= 360
 203  */
 204 void
 205 adj360(deg)
 206         double *deg;
 207 {
 208         for (;;)
 209                 if (*deg < 0)
 210                         *deg += 360;
 211                 else if (*deg > 360)
 212                         *deg -= 360;
 213                 else
 214                         break;
 215 }
 216
 217 #define ATOI2(ar)       ((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;
 218 time_t
 219 parsetime(p)
 220         char *p;
 221 {
 222         struct tm *lt;
 223         int bigyear;
 224         int yearset = 0;
 225         time_t tval;
 226         unsigned char *t;
 227
 228         for (t = p; *t; ++t) {
 229                 if (isdigit(*t))
 230                         continue;
 231                 badformat();
 232         }
 233
 234         tval = time(NULL);
 235         lt = localtime(&tval);
 236         lt->tm_sec = 0;
 237         lt->tm_min = 0;
 238
 239         switch (strlen(p)) {
 240         case 10:                                /* yyyy */
 241                 bigyear = ATOI2(p);
 242                 lt->tm_year = bigyear * 100 - 1900;
 243                 yearset = 1;
 244                 /* FALLTHROUGH */
 245         case 8:                                 /* yy */
 246                 if (yearset) {
 247                         lt->tm_year += ATOI2(p);
 248                 } else {
 249                         lt->tm_year = ATOI2(p);
 250                         if (lt->tm_year < 69)           /* hack for 2000 */
 251                                 lt->tm_year += 100;
 252                 }
 253                 /* FALLTHROUGH */
 254         case 6:                                 /* mm */
 255                 lt->tm_mon = ATOI2(p);
 256                 if ((lt->tm_mon > 12) || !lt->tm_mon)
 257                         badformat();
 258                 --lt->tm_mon;                   /* time struct is 0 - 11 */
 259                 /* FALLTHROUGH */
 260         case 4:                                 /* dd */
 261                 lt->tm_mday = ATOI2(p);
 262                 if ((lt->tm_mday > 31) || !lt->tm_mday)
 263                         badformat();
 264                 /* FALLTHROUGH */
 265         case 2:                                 /* HH */
 266                 lt->tm_hour = ATOI2(p);
 267                 if (lt->tm_hour > 23)
 268                         badformat();
 269                 break;
 270         default:
 271                 badformat();
 272         }
 273         /* The calling code needs a valid tm_ydays and this is the easiest
 274          * way to get one */
 275         if ((tval = mktime(lt)) == -1)
 276                 errx(1, "specified date is outside allowed range");
 277         return (tval);
 278 }
 279
 280 void
 281 badformat()
 282 {
 283         warnx("illegal time format");
 284         (void)fprintf(stderr, "usage: pom [[[[[cc]yy]mm]dd]HH]\n");
 285         exit(1);
 286 }