timezone/zdump.c

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