1: /*      $NetBSD: pom.c,v 1.14 2004/01/27 20:30:30 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. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  */
   33: 
   34: #include <sys/cdefs.h>
   35: #ifndef lint
   36: __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
   37:         The Regents of the University of California.  All rights reserved.\n");
   38: #endif /* not lint */
   39: 
   40: #ifndef lint
   41: #if 0
   42: static char sccsid[] = "@(#)pom.c       8.1 (Berkeley) 5/31/93";
   43: #else
   44: __RCSID("$NetBSD: pom.c,v 1.14 2004/01/27 20:30:30 jsm Exp $");
   45: #endif
   46: #endif /* not lint */
   47: 
   48: /*
   49:  * Phase of the Moon.  Calculates the current phase of the moon.
   50:  * Based on routines from `Practical Astronomy with Your Calculator',
   51:  * by Duffett-Smith.  Comments give the section from the book that
   52:  * particular piece of code was adapted from.
   53:  *
   54:  * -- Keith E. Brandt  VIII 1984
   55:  *
   56:  * Updated to the Third Edition of Duffett-Smith's book, Paul Janzen, IX 1998
   57:  *
   58:  */
   59: 
   60: #include <ctype.h>
   61: #include <err.h>
   62: #include <math.h>
   63: #include <stdio.h>
   64: #include <string.h>
   65: #include <stdlib.h>
   66: #include <time.h>
   67: #include <unistd.h>
   68: 
   69: #ifndef PI
   70: #define PI        3.14159265358979323846
   71: #endif
   72: 
   73: /*
   74:  * The EPOCH in the third edition of the book is 1990 Jan 0.0 TDT.
   75:  * In this program, we do not bother to correct for the differences
   76:  * between UTC (as shown by the UNIX clock) and TDT.  (TDT = TAI + 32.184s;
   77:  * TAI-UTC = 32s in Jan 1999.)
   78:  */
   79: #define EPOCH_MINUS_1970        (20 * 365 + 5 - 1) /* 20 years, 5 leaps, back 1 day to Jan 0 */
   80: #define EPSILONg  279.403303    /* solar ecliptic long at EPOCH */
   81: #define RHOg      282.768422       /* solar ecliptic long of perigee at EPOCH */
   82: #define ECCEN     0.016713        /* solar orbit eccentricity */
   83: #define lzero     318.351648      /* lunar mean long at EPOCH */
   84: #define Pzero     36.340410       /* lunar mean long of perigee at EPOCH */
   85: #define Nzero     318.510107      /* lunar mean long of node at EPOCH */
   86: 
   87: void    adj360(double *);
   88: double  dtor(double);
   89: int     main(int, char *[]);
   90: double  potm(double);
   91: time_t  parsetime(char *);
   92: void    badformat(void) __attribute__((__noreturn__));
   93: 
   94: int
   95: main(argc, argv)
   96:         int argc;
   97:         char *argv[];
   98: {
   99:         time_t tmpt, now;
  100:         double days, today, tomorrow;
  101:         char buf[1024];
  102: 
  103:         /* Revoke setgid privileges */
  104:         setregid(getgid(), getgid());
  105: 
  106:         if (time(&now) == (time_t)-1)
  107:                 err(1, "time");
  108:         if (argc > 1) {
  109:                 tmpt = parsetime(argv[1]);
  110:                 strftime(buf, sizeof(buf), "%a %Y %b %e %H:%M:%S (%Z)",
  111:                         localtime(&tmpt));
  112:                 printf("%s:  ", buf);
  113:         } else {
  114:                 tmpt = now;
  115:         }
  116:         days = (tmpt - EPOCH_MINUS_1970 * 86400) / 86400.0;
  117:         today = potm(days) + .5;
  118:         if (tmpt < now)
  119:                 (void)printf("The Moon was ");
  120:         else if (tmpt == now)
  121:                 (void)printf("The Moon is ");
  122:         else
  123:                 (void)printf("The Moon will be ");
  124:         if ((int)today == 100)
  125:                 (void)printf("Full\n");
  126:         else if (!(int)today)
  127:                 (void)printf("New\n");
  128:         else {
  129:                 tomorrow = potm(days + 1);
  130:                 if ((int)today == 50)
  131:                         (void)printf("%s\n", tomorrow > today ?
  132:                             "at the First Quarter" : "at the Last Quarter");
  133:                         /* today is 0.5 too big, but it doesn't matter here
  134:                          * since the phase is changing fast enough
  135:                          */
  136:                 else {
  137:                         today -= 0.5;                /* Now it might matter */
  138:                         (void)printf("%s ", tomorrow > today ?
  139:                             "Waxing" : "Waning");
  140:                         if (today > 50)
  141:                                 (void)printf("Gibbous (%1.0f%% of Full)\n",
  142:                                     today);
  143:                         else if (today < 50)
  144:                                 (void)printf("Crescent (%1.0f%% of Full)\n",
  145:                                     today);
  146:                 }
  147:         }
  148:         exit(0);
  149: }
  150: 
  151: /*
  152:  * potm --
  153:  *      return phase of the moon
  154:  */
  155: double
  156: potm(days)
  157:         double days;
  158: {
  159:         double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
  160:         double A4, lprime, V, ldprime, D, Nm;
  161: 
  162:         N = 360 * days / 365.242191;                           /* sec 46 #3 */
  163:         adj360(&N);
  164:         Msol = N + EPSILONg - RHOg;                            /* sec 46 #4 */
  165:         adj360(&Msol);
  166:         Ec = 360 / PI * ECCEN * sin(dtor(Msol));               /* sec 46 #5 */
  167:         LambdaSol = N + Ec + EPSILONg;                         /* sec 46 #6 */
  168:         adj360(&LambdaSol);
  169:         l = 13.1763966 * days + lzero;                         /* sec 65 #4 */
  170:         adj360(&l);
  171:         Mm = l - (0.1114041 * days) - Pzero;                   /* sec 65 #5 */
  172:         adj360(&Mm);
  173:         Nm = Nzero - (0.0529539 * days);                       /* sec 65 #6 */
  174:         adj360(&Nm);
  175:         Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm));       /* sec 65 #7 */
  176:         Ac = 0.1858 * sin(dtor(Msol));                         /* sec 65 #8 */
  177:         A3 = 0.37 * sin(dtor(Msol));
  178:         Mmprime = Mm + Ev - Ac - A3;                           /* sec 65 #9 */
  179:         Ec = 6.2886 * sin(dtor(Mmprime));                      /* sec 65 #10 */
  180:         A4 = 0.214 * sin(dtor(2 * Mmprime));                   /* sec 65 #11 */
  181:         lprime = l + Ev + Ec - Ac + A4;                                /* sec 65 #12 */
  182:         V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));      /* sec 65 #13 */
  183:         ldprime = lprime + V;                                  /* sec 65 #14 */
  184:         D = ldprime - LambdaSol;                               /* sec 67 #2 */
  185:         return(50.0 * (1 - cos(dtor(D))));                     /* sec 67 #3 */
  186: }
  187: 
  188: /*
  189:  * dtor --
  190:  *      convert degrees to radians
  191:  */
  192: double
  193: dtor(deg)
  194:         double deg;
  195: {
  196:         return(deg * PI / 180);
  197: }
  198: 
  199: /*
  200:  * adj360 --
  201:  *      adjust value so 0 <= deg <= 360
  202:  */
  203: void
  204: adj360(deg)
  205:         double *deg;
  206: {
  207:         for (;;)
  208:                 if (*deg < 0)
  209:                         *deg += 360;
  210:                 else if (*deg > 360)
  211:                         *deg -= 360;
  212:                 else
  213:                         break;
  214: }
  215: 
  216: #define ATOI2(ar)       ((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;
  217: time_t
  218: parsetime(p)
  219:         char *p;
  220: {
  221:         struct tm *lt;
  222:         int bigyear;
  223:         int yearset = 0;
  224:         time_t tval;
  225:         unsigned char *t;
  226:         
  227:         for (t = (unsigned char *)p; *t; ++t) {
  228:                 if (isdigit(*t))
  229:                         continue;
  230:                 badformat();
  231:         }
  232: 
  233:         tval = time(NULL);
  234:         lt = localtime(&tval);
  235:         lt->tm_sec = 0;
  236:         lt->tm_min = 0;
  237: 
  238:         switch (strlen(p)) {
  239:         case 10:                               /* yyyy */
  240:                 bigyear = ATOI2(p);
  241:                 lt->tm_year = bigyear * 100 - 1900;
  242:                 yearset = 1;
  243:                 /* FALLTHROUGH */
  244:         case 8:                                        /* yy */
  245:                 if (yearset) {
  246:                         lt->tm_year += ATOI2(p);
  247:                 } else {
  248:                         lt->tm_year = ATOI2(p);
  249:                         if (lt->tm_year < 69)                /* hack for 2000 */
  250:                                 lt->tm_year += 100;
  251:                 }
  252:                 /* FALLTHROUGH */
  253:         case 6:                                        /* mm */
  254:                 lt->tm_mon = ATOI2(p);
  255:                 if ((lt->tm_mon > 12) || !lt->tm_mon)
  256:                         badformat();
  257:                 --lt->tm_mon;                 /* time struct is 0 - 11 */
  258:                 /* FALLTHROUGH */
  259:         case 4:                                        /* dd */
  260:                 lt->tm_mday = ATOI2(p);
  261:                 if ((lt->tm_mday > 31) || !lt->tm_mday)
  262:                         badformat();
  263:                 /* FALLTHROUGH */
  264:         case 2:                                        /* HH */
  265:                 lt->tm_hour = ATOI2(p);
  266:                 if (lt->tm_hour > 23)
  267:                         badformat();
  268:                 break;
  269:         default:
  270:                 badformat();
  271:         }
  272:         /* The calling code needs a valid tm_ydays and this is the easiest
  273:          * way to get one */
  274:         if ((tval = mktime(lt)) == -1)
  275:                 errx(1, "specified date is outside allowed range");
  276:         return (tval);
  277: }
  278: 
  279: void
  280: badformat()
  281: {
  282:         warnx("illegal time format");
  283:         (void)fprintf(stderr, "usage: pom [[[[[cc]yy]mm]dd]HH]\n");
  284:         exit(1);
  285: }