lib/libc/time/zdump.c

   1 /*      $NetBSD: zdump.c,v 1.16 2006/12/04 17:24:40 kleink Exp $        */
   2 /*
   3 ** This file is in the public domain, so clarified as of
   4 ** 2009-05-17 by Arthur David Olson.
   5 */
   6
   7 #include <sys/cdefs.h>
   8 #ifndef lint
   9 #ifndef NOID
  10 __RCSID("$NetBSD: zdump.c,v 1.16 2006/12/04 17:24:40 kleink Exp $");
  11 #endif /* !defined NOID */
  12 #endif /* !defined lint */
  13
  14 static char     elsieid[] = "@(#)zdump.c        8.9";
  15
  16 /*
  17 ** This code has been made independent of the rest of the time
  18 ** conversion package to increase confidence in the verification it provides.
  19 ** You can use this code to help in verifying other implementations.
  20 */
  21
  22 #include "stdio.h"      /* for stdout, stderr */
  23 #include "string.h"     /* for strcpy */
  24 #include "sys/types.h"  /* for time_t */
  25 #include "time.h"       /* for struct tm */
  26 #include "stdlib.h"     /* for exit, malloc, atoi */
  27 #include <err.h>
  28 #include "float.h"      /* for FLT_MAX and DBL_MAX */
  29 #include "ctype.h"      /* for isalpha et al. */
  30 #ifndef isascii
  31 #define isascii(x) 1
  32 #endif /* !defined isascii */
  33
  34 #ifndef ZDUMP_LO_YEAR
  35 #define ZDUMP_LO_YEAR   (-500)
  36 #endif /* !defined ZDUMP_LO_YEAR */
  37
  38 #ifndef ZDUMP_HI_YEAR
  39 #define ZDUMP_HI_YEAR   2500
  40 #endif /* !defined ZDUMP_HI_YEAR */
  41
  42 #ifndef MAX_STRING_LENGTH
  43 #define MAX_STRING_LENGTH       1024
  44 #endif /* !defined MAX_STRING_LENGTH */
  45
  46 #ifndef TRUE
  47 #define TRUE            1
  48 #endif /* !defined TRUE */
  49
  50 #ifndef FALSE
  51 #define FALSE           0
  52 #endif /* !defined FALSE */
  53
  54 #ifndef EXIT_SUCCESS
  55 #define EXIT_SUCCESS    0
  56 #endif /* !defined EXIT_SUCCESS */
  57
  58 #ifndef EXIT_FAILURE
  59 #define EXIT_FAILURE    1
  60 #endif /* !defined EXIT_FAILURE */
  61
  62 #ifndef SECSPERMIN
  63 #define SECSPERMIN      60
  64 #endif /* !defined SECSPERMIN */
  65
  66 #ifndef MINSPERHOUR
  67 #define MINSPERHOUR     60
  68 #endif /* !defined MINSPERHOUR */
  69
  70 #ifndef SECSPERHOUR
  71 #define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
  72 #endif /* !defined SECSPERHOUR */
  73
  74 #ifndef HOURSPERDAY
  75 #define HOURSPERDAY     24
  76 #endif /* !defined HOURSPERDAY */
  77
  78 #ifndef EPOCH_YEAR
  79 #define EPOCH_YEAR      1970
  80 #endif /* !defined EPOCH_YEAR */
  81
  82 #ifndef TM_YEAR_BASE
  83 #define TM_YEAR_BASE    1900
  84 #endif /* !defined TM_YEAR_BASE */
  85
  86 #ifndef DAYSPERNYEAR
  87 #define DAYSPERNYEAR    365
  88 #endif /* !defined DAYSPERNYEAR */
  89
  90 #ifndef isleap
  91 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
  92 #endif /* !defined isleap */
  93
  94 #ifndef isleap_sum
  95 /*
  96 ** See tzfile.h for details on isleap_sum.
  97 */
  98 #define isleap_sum(a, b)        isleap((a) % 400 + (b) % 400)
  99 #endif /* !defined isleap_sum */
 100
 101 #define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
 102 #define SECSPERNYEAR    (SECSPERDAY * DAYSPERNYEAR)
 103 #define SECSPERLYEAR    (SECSPERNYEAR + SECSPERDAY)
 104
 105 #ifndef HAVE_GETTEXT
 106 #define HAVE_GETTEXT 0
 107 #endif
 108 #if HAVE_GETTEXT
 109 #include "locale.h"     /* for setlocale */
 110 #include "libintl.h"
 111 #endif /* HAVE_GETTEXT */
 112
 113 #ifndef GNUC_or_lint
 114 #ifdef lint
 115 #define GNUC_or_lint
 116 #else /* !defined lint */
 117 #ifdef __GNUC__
 118 #define GNUC_or_lint
 119 #endif /* defined __GNUC__ */
 120 #endif /* !defined lint */
 121 #endif /* !defined GNUC_or_lint */
 122
 123 #ifndef INITIALIZE
 124 #ifdef GNUC_or_lint
 125 #define INITIALIZE(x)   ((x) = 0)
 126 #else /* !defined GNUC_or_lint */
 127 #define INITIALIZE(x)
 128 #endif /* !defined GNUC_or_lint */
 129 #endif /* !defined INITIALIZE */
 130
 131 /*
 132 ** For the benefit of GNU folk...
 133 ** `_(MSGID)' uses the current locale's message library string for MSGID.
 134 ** The default is to use gettext if available, and use MSGID otherwise.
 135 */
 136
 137 #ifndef _
 138 #if HAVE_GETTEXT
 139 #define _(msgid) gettext(msgid)
 140 #else /* !HAVE_GETTEXT */
 141 #define _(msgid) __UNCONST(msgid)
 142 #endif /* !HAVE_GETTEXT */
 143 #endif /* !defined _ */
 144
 145 #ifndef TZ_DOMAIN
 146 #define TZ_DOMAIN "tz"
 147 #endif /* !defined TZ_DOMAIN */
 148
 149 extern char **  environ;
 150 extern int      getopt(int argc, char * const argv[],
 151                         const char * options);
 152 extern char *   optarg;
 153 extern int      optind;
 154
 155 static time_t   absolute_min_time;
 156 static time_t   absolute_max_time;
 157 static size_t   longest;
 158 static char *   progname;
 159 static int      warned;
 160
 161 static const char *     abbr(struct tm * tmp);
 162 static void     abbrok(const char * abbrp, const char * zone);
 163 static long     delta(struct tm * newp, struct tm * oldp);
 164 static void     dumptime(const struct tm * tmp);
 165 static time_t   hunt(char * name, time_t lot, time_t    hit);
 166 int             main(int, char **);
 167 static void     setabsolutes(void);
 168 static void     show(char * zone, time_t t, int v);
 169 static const char *     tformat(void);
 170 static time_t   yeartot(long y);
 171
 172 #ifndef TYPECHECK
 173 #define my_localtime    localtime
 174 #else /* !defined TYPECHECK */
 175 static struct tm *
 176 my_localtime(tp)
 177 time_t *        tp;
 178 {
 179         register struct tm *    tmp;
 180
 181         tmp = localtime(tp);
 182         if (tp != NULL && tmp != NULL) {
 183                 struct tm       tm;
 184                 register time_t t;
 185
 186                 tm = *tmp;
 187                 t = mktime(&tm);
 188                 if (t - *tp >= 1 || *tp - t >= 1) {
 189                         (void) fflush(stdout);
 190                         (void) fprintf(stderr, "\n%s: ", progname);
 191                         (void) fprintf(stderr, tformat(), *tp);
 192                         (void) fprintf(stderr, " ->");
 193                         (void) fprintf(stderr, " year=%d", tmp->tm_year);
 194                         (void) fprintf(stderr, " mon=%d", tmp->tm_mon);
 195                         (void) fprintf(stderr, " mday=%d", tmp->tm_mday);
 196                         (void) fprintf(stderr, " hour=%d", tmp->tm_hour);
 197                         (void) fprintf(stderr, " min=%d", tmp->tm_min);
 198                         (void) fprintf(stderr, " sec=%d", tmp->tm_sec);
 199                         (void) fprintf(stderr, " isdst=%d", tmp->tm_isdst);
 200                         (void) fprintf(stderr, " -> ");
 201                         (void) fprintf(stderr, tformat(), t);
 202                         (void) fprintf(stderr, "\n");
 203                 }
 204         }
 205         return tmp;
 206 }
 207 #endif /* !defined TYPECHECK */
 208
 209 static void
 210 abbrok(abbrp, zone)
 211 const char * const      abbrp;
 212 const char * const      zone;
 213 {
 214         register const char *   cp;
 215         register char *         wp;
 216
 217         if (warned)
 218                 return;
 219         cp = abbrp;
 220         wp = NULL;
 221         while (isascii((unsigned char) *cp) && isalpha((unsigned char) *cp))
 222                 ++cp;
 223         if (cp - abbrp == 0)
 224                 wp = _("lacks alphabetic at start");
 225         else if (cp - abbrp < 3)
 226                 wp = _("has fewer than 3 alphabetics");
 227         else if (cp - abbrp > 6)
 228                 wp = _("has more than 6 alphabetics");
 229         if (wp == NULL && (*cp == '+' || *cp == '-')) {
 230                 ++cp;
 231                 if (isascii((unsigned char) *cp) &&
 232                         isdigit((unsigned char) *cp))
 233                                 if (*cp++ == '1' && *cp >= '0' && *cp <= '4')
 234                                         ++cp;
 235                 if (*cp != '\0')
 236                         wp = _("differs from POSIX standard");
 237         }
 238         if (wp == NULL)
 239                 return;
 240         (void) fflush(stdout);
 241         (void) fprintf(stderr,
 242                 _("%s: warning: zone \"%s\" abbreviation \"%s\" %s\n"),
 243                 progname, zone, abbrp, wp);
 244         warned = TRUE;
 245 }
 246
 247 static void
 248 usage(const char *xprogname, FILE *stream, int status)
 249 {
 250         (void) fprintf(stream,
 251 _("%s: usage is %s [ --version ] [ --help ] [ -v ] [ -c [loyear,]hiyear ] zonename ...\n\
 252 \n\
 253 Report bugs to tz@elsie.nci.nih.gov.\n"),
 254                        xprogname, xprogname);
 255         exit(status);
 256 }
 257
 258 int
 259 main(argc, argv)
 260 int     argc;
 261 char *  argv[];
 262 {
 263         register int            i;
 264         register int            c;
 265         register int            vflag;
 266         register char *         cutarg;
 267         register long           cutloyear = ZDUMP_LO_YEAR;
 268         register long           cuthiyear = ZDUMP_HI_YEAR;
 269         register time_t         cutlotime;
 270         register time_t         cuthitime;
 271         register char **        fakeenv;
 272         time_t                  now;
 273         time_t                  t;
 274         time_t                  newt;
 275         struct tm               tm;
 276         struct tm               newtm;
 277         register struct tm *    tmp;
 278         register struct tm *    newtmp;
 279
 280         INITIALIZE(cutlotime);
 281         INITIALIZE(cuthitime);
 282 #if HAVE_GETTEXT
 283         (void) setlocale(LC_ALL, "");
 284 #ifdef TZ_DOMAINDIR
 285         (void) bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
 286 #endif /* defined TEXTDOMAINDIR */
 287         (void) textdomain(TZ_DOMAIN);
 288 #endif /* HAVE_GETTEXT */
 289         progname = argv[0];
 290         for (i = 1; i < argc; ++i)
 291                 if (strcmp(argv[i], "--version") == 0) {
 292                         (void) printf("%s\n", elsieid);
 293                         exit(EXIT_SUCCESS);
 294                 } else if (strcmp(argv[i], "--help") == 0) {
 295                         usage(progname, stdout, EXIT_SUCCESS);
 296                 }
 297         vflag = 0;
 298         cutarg = NULL;
 299         while ((c = getopt(argc, argv, "c:v")) == 'c' || c == 'v')
 300                 if (c == 'v')
 301                         vflag = 1;
 302                 else    cutarg = optarg;
 303         if ((c != EOF && c != -1) ||
 304                 (optind == argc - 1 && strcmp(argv[optind], "=") == 0)) {
 305                         usage(progname, stderr, EXIT_FAILURE);
 306         }
 307         if (vflag) {
 308                 if (cutarg != NULL) {
 309                         long    lo;
 310                         long    hi;
 311                         char    dummy;
 312
 313                         if (sscanf(cutarg, "%ld%c", &hi, &dummy) == 1) {
 314                                 cuthiyear = hi;
 315                         } else if (sscanf(cutarg, "%ld,%ld%c",
 316                                 &lo, &hi, &dummy) == 2) {
 317                                         cutloyear = lo;
 318                                         cuthiyear = hi;
 319                         } else {
 320 (void) fprintf(stderr, _("%s: wild -c argument %s\n"),
 321                                         progname, cutarg);
 322                                 exit(EXIT_FAILURE);
 323                         }
 324                 }
 325                 setabsolutes();
 326                 cutlotime = yeartot(cutloyear);
 327                 cuthitime = yeartot(cuthiyear);
 328         }
 329         (void) time(&now);
 330         longest = 0;
 331         for (i = optind; i < argc; ++i)
 332                 if (strlen(argv[i]) > longest)
 333                         longest = strlen(argv[i]);
 334         {
 335                 register int    from;
 336                 register int    to;
 337
 338                 for (i = 0; environ[i] != NULL; ++i)
 339                         continue;
 340                 fakeenv = (char **) malloc((size_t) ((i + 2) *
 341                         sizeof *fakeenv));
 342                 if (fakeenv == NULL ||
 343                         (fakeenv[0] = (char *) malloc(longest + 4)) == NULL) {
 344                         err(EXIT_FAILURE, "Can't allocated %zu bytes",
 345                             longest + 4);
 346                 }
 347                 to = 0;
 348                 (void)strcpy(fakeenv[to++], "TZ=");     /* XXX strcpy is safe */
 349                 for (from = 0; environ[from] != NULL; ++from)
 350                         if (strncmp(environ[from], "TZ=", 3) != 0)
 351                                 fakeenv[to++] = environ[from];
 352                 fakeenv[to] = NULL;
 353                 environ = fakeenv;
 354         }
 355         for (i = optind; i < argc; ++i) {
 356                 static char     buf[MAX_STRING_LENGTH];
 357
 358                 (void) strcpy(&fakeenv[0][3], argv[i]); /* XXX strcpy is safe */
 359                 if (!vflag) {
 360                         show(argv[i], now, FALSE);
 361                         continue;
 362                 }
 363                 warned = FALSE;
 364                 t = absolute_min_time;
 365                 show(argv[i], t, TRUE);
 366                 t += SECSPERHOUR * HOURSPERDAY;
 367                 show(argv[i], t, TRUE);
 368                 if (t < cutlotime)
 369                         t = cutlotime;
 370                 tmp = my_localtime(&t);
 371                 if (tmp != NULL) {
 372                         tm = *tmp;
 373                         (void) strncpy(buf, abbr(&tm), (sizeof buf) - 1);
 374                 }
 375                 for ( ; ; ) {
 376                         if (t >= cuthitime || t >= cuthitime - SECSPERHOUR * 12)
 377                                 break;
 378                         newt = t + SECSPERHOUR * 12;
 379                         newtmp = localtime(&newt);
 380                         if (newtmp != NULL)
 381                                 newtm = *newtmp;
 382                         if ((tmp == NULL || newtmp == NULL) ? (tmp != newtmp) :
 383                                 (delta(&newtm, &tm) != (newt - t) ||
 384                                 newtm.tm_isdst != tm.tm_isdst ||
 385                                 strcmp(abbr(&newtm), buf) != 0)) {
 386                                         newt = hunt(argv[i], t, newt);
 387                                         newtmp = localtime(&newt);
 388                                         if (newtmp != NULL) {
 389                                                 newtm = *newtmp;
 390                                                 (void) strncpy(buf,
 391                                                         abbr(&newtm),
 392                                                         (sizeof buf) - 1);
 393                                         }
 394                         }
 395                         t = newt;
 396                         tm = newtm;
 397                         tmp = newtmp;
 398                 }
 399                 t = absolute_max_time;
 400                 t -= SECSPERHOUR * HOURSPERDAY;
 401                 show(argv[i], t, TRUE);
 402                 t += SECSPERHOUR * HOURSPERDAY;
 403                 show(argv[i], t, TRUE);
 404         }
 405         if (fflush(stdout) || ferror(stdout)) {
 406                 err(EXIT_FAILURE, _("Error writing standard output"));
 407         }
 408         exit(EXIT_SUCCESS);
 409         /* If exit fails to exit... */
 410         return EXIT_FAILURE;
 411 }
 412
 413 static void
 414 setabsolutes(void)
 415 {
 416         if (0.5 == (time_t) 0.5) {
 417                 /*
 418                 ** time_t is floating.
 419                 */
 420                 if (sizeof (time_t) == sizeof (float)) {
 421                         absolute_min_time = (time_t) -FLT_MAX;
 422                         absolute_max_time = (time_t) FLT_MAX;
 423                 } else if (sizeof (time_t) == sizeof (double)) {
 424                         absolute_min_time = (time_t) -DBL_MAX;
 425                         absolute_max_time = (time_t) DBL_MAX;
 426                 } else {
 427                         (void) fprintf(stderr,
 428 _("%s: use of -v on system with floating time_t other than float or double\n"),
 429                                 progname);
 430                         exit(EXIT_FAILURE);
 431                 }
 432         } else if (0 > (time_t) -1) {
 433                 /*
 434                 ** time_t is signed.  Assume overflow wraps around.
 435                 */
 436                 time_t t = 0;
 437                 time_t t1 = 1;
 438
 439                 while (t < t1) {
 440                         t = t1;
 441                         t1 = 2 * t1 + 1;
 442                 }
 443
 444                 absolute_max_time = t;
 445                 t = -t;
 446                 absolute_min_time = t - 1;
 447                 if (t < absolute_min_time)
 448                         absolute_min_time = t;
 449         } else {
 450                 /*
 451                 ** time_t is unsigned.
 452                 */
 453                 absolute_min_time = 0;
 454                 absolute_max_time = absolute_min_time - 1;
 455         }
 456 }
 457
 458 static time_t
 459 yeartot(y)
 460 const long      y;
 461 {
 462         register long   myy;
 463         register long   seconds;
 464         register time_t t;
 465
 466         myy = EPOCH_YEAR;
 467         t = 0;
 468         while (myy != y) {
 469                 if (myy < y) {
 470                         seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
 471                         ++myy;
 472                         if (t > absolute_max_time - seconds) {
 473                                 t = absolute_max_time;
 474                                 break;
 475                         }
 476                         t += seconds;
 477                 } else {
 478                         --myy;
 479                         seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
 480                         if (t < absolute_min_time + seconds) {
 481                                 t = absolute_min_time;
 482                                 break;
 483                         }
 484                         t -= seconds;
 485                 }
 486         }
 487         return t;
 488 }
 489
 490 static time_t
 491 hunt(char *name, time_t lot, time_t hit)
 492 {
 493         time_t                  t;
 494         long                    diff;
 495         struct tm               lotm;
 496         register struct tm *    lotmp;
 497         struct tm               tm;
 498         register struct tm *    tmp;
 499         char                    loab[MAX_STRING_LENGTH];
 500
 501         lotmp = my_localtime(&lot);
 502         if (lotmp != NULL) {
 503                 lotm = *lotmp;
 504                 (void) strncpy(loab, abbr(&lotm), (sizeof loab) - 1);
 505         }
 506         for ( ; ; ) {
 507                 diff = (long) (hit - lot);
 508                 if (diff < 2)
 509                         break;
 510                 t = lot;
 511                 t += diff / 2;
 512                 if (t <= lot)
 513                         ++t;
 514                 else if (t >= hit)
 515                         --t;
 516                 tmp = my_localtime(&t);
 517                 if (tmp != NULL)
 518                         tm = *tmp;
 519                 if ((lotmp == NULL || tmp == NULL) ? (lotmp == tmp) :
 520                         (delta(&tm, &lotm) == (t - lot) &&
 521                         tm.tm_isdst == lotm.tm_isdst &&
 522                         strcmp(abbr(&tm), loab) == 0)) {
 523                                 lot = t;
 524                                 lotm = tm;
 525                                 lotmp = tmp;
 526                 } else  hit = t;
 527         }
 528         show(name, lot, TRUE);
 529         show(name, hit, TRUE);
 530         return hit;
 531 }
 532
 533 /*
 534 ** Thanks to Paul Eggert for logic used in delta.
 535 */
 536
 537 static long
 538 delta(newp, oldp)
 539 struct tm *     newp;
 540 struct tm *     oldp;
 541 {
 542         register long   result;
 543         register int    tmy;
 544
 545         if (newp->tm_year < oldp->tm_year)
 546                 return -delta(oldp, newp);
 547         result = 0;
 548         for (tmy = oldp->tm_year; tmy < newp->tm_year; ++tmy)
 549                 result += DAYSPERNYEAR + isleap_sum(tmy, TM_YEAR_BASE);
 550         result += newp->tm_yday - oldp->tm_yday;
 551         result *= HOURSPERDAY;
 552         result += newp->tm_hour - oldp->tm_hour;
 553         result *= MINSPERHOUR;
 554         result += newp->tm_min - oldp->tm_min;
 555         result *= SECSPERMIN;
 556         result += newp->tm_sec - oldp->tm_sec;
 557         return result;
 558 }
 559
 560 static void
 561 show(char *zone, time_t t, int v)
 562 {
 563         register struct tm *    tmp;
 564
 565         (void) printf("%-*s  ", (int) longest, zone);
 566         if (v) {
 567                 tmp = gmtime(&t);
 568                 if (tmp == NULL) {
 569                         (void) printf(tformat(), t);
 570                 } else {
 571                         dumptime(tmp);
 572                         (void) printf(" UTC");
 573                 }
 574                 (void) printf(" = ");
 575         }
 576         tmp = my_localtime(&t);
 577         dumptime(tmp);
 578         if (tmp != NULL) {
 579                 if (*abbr(tmp) != '\0')
 580                         (void) printf(" %s", abbr(tmp));
 581                 if (v) {
 582                         (void) printf(" isdst=%d", tmp->tm_isdst);
 583 #ifdef TM_GMTOFF
 584                         (void) printf(" gmtoff=%ld", tmp->TM_GMTOFF);
 585 #endif /* defined TM_GMTOFF */
 586                 }
 587         }
 588         (void) printf("\n");
 589         if (tmp != NULL && *abbr(tmp) != '\0')
 590                 abbrok(abbr(tmp), zone);
 591 }
 592
 593 static const char *
 594 abbr(tmp)
 595 struct tm *     tmp;
 596 {
 597         register const char *   result;
 598         static const char       nada;
 599
 600         if (tmp->tm_isdst != 0 && tmp->tm_isdst != 1)
 601                 return &nada;
 602         result = tzname[tmp->tm_isdst];
 603         return (result == NULL) ? &nada : result;
 604 }
 605
 606 /*
 607 ** The code below can fail on certain theoretical systems;
 608 ** it works on all known real-world systems as of 2004-12-30.
 609 */
 610
 611 static const char *
 612 tformat(void)
 613 {
 614         if (0.5 == (time_t) 0.5) {      /* floating */
 615                 if (sizeof (time_t) > sizeof (double))
 616                         return "%Lg";
 617                 return "%g";
 618         }
 619         if (0 > (time_t) -1) {          /* signed */
 620                 if (sizeof (time_t) > sizeof (long))
 621                         return "%lld";
 622                 if (sizeof (time_t) > sizeof (int))
 623                         return "%ld";
 624                 return "%d";
 625         }
 626         if (sizeof (time_t) > sizeof (unsigned long))
 627                 return "%llu";
 628         if (sizeof (time_t) > sizeof (unsigned int))
 629                 return "%lu";
 630         return "%u";
 631 }
 632
 633 static void
 634 dumptime(timeptr)
 635 register const struct tm *      timeptr;
 636 {
 637         static const char       wday_name[][3] = {
 638                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
 639         };
 640         static const char       mon_name[][3] = {
 641                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
 642                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 643         };
 644         register const char *   wn;
 645         register const char *   mn;
 646         register int            lead;
 647         register int            trail;
 648
 649         if (timeptr == NULL) {
 650                 (void) printf("NULL");
 651                 return;
 652         }
 653         /*
 654         ** The packaged versions of localtime and gmtime never put out-of-range
 655         ** values in tm_wday or tm_mon, but since this code might be compiled
 656         ** with other (perhaps experimental) versions, paranoia is in order.
 657         */
 658         if (timeptr->tm_wday < 0 || timeptr->tm_wday >=
 659                 (int) (sizeof wday_name / sizeof wday_name[0]))
 660                         wn = "???";
 661         else            wn = wday_name[timeptr->tm_wday];
 662         if (timeptr->tm_mon < 0 || timeptr->tm_mon >=
 663                 (int) (sizeof mon_name / sizeof mon_name[0]))
 664                         mn = "???";
 665         else            mn = mon_name[timeptr->tm_mon];
 666         (void) printf("%.3s %.3s%3d %.2d:%.2d:%.2d ",
 667                 wn, mn,
 668                 timeptr->tm_mday, timeptr->tm_hour,
 669                 timeptr->tm_min, timeptr->tm_sec);
 670 #define DIVISOR 10
 671         trail = timeptr->tm_year % DIVISOR + TM_YEAR_BASE % DIVISOR;
 672         lead = timeptr->tm_year / DIVISOR + TM_YEAR_BASE / DIVISOR +
 673                 trail / DIVISOR;
 674         trail %= DIVISOR;
 675         if (trail < 0 && lead > 0) {
 676                 trail += DIVISOR;
 677                 --lead;
 678         } else if (lead < 0 && trail > 0) {
 679                 trail -= DIVISOR;
 680                 ++lead;
 681         }
 682         if (lead == 0)
 683                 (void) printf("%d", trail);
 684         else    (void) printf("%d%d", lead, ((trail < 0) ? -trail : trail));
 685 }