lib/libc/time/strftime.c

   1 /*      $NetBSD: strftime.c,v 1.22 2012/03/20 16:39:08 matt Exp $       */
   2
   3 #include <sys/cdefs.h>
   4 #if defined(LIBC_SCCS) && !defined(lint)
   5 #if 0
   6 static char     elsieid[] = "@(#)strftime.c     7.64";
   7 static char     elsieid[] = "@(#)strftime.c     8.3";
   8 #else
   9 __RCSID("$NetBSD: strftime.c,v 1.22 2012/03/20 16:39:08 matt Exp $");
  10 #endif
  11 #endif /* LIBC_SCCS and not lint */
  12
  13 #include "namespace.h"
  14
  15 /*
  16 ** Based on the UCB version with the ID appearing below.
  17 ** This is ANSIish only when "multibyte character == plain character".
  18 */
  19
  20 #include "private.h"
  21
  22 /*
  23 ** We don't use these extensions in strftime operation even when
  24 ** supported by the local tzcode configuration.  A strictly
  25 ** conforming C application may leave them in undefined state.
  26 */
  27
  28 #ifdef _LIBC
  29 #undef TM_ZONE
  30 #undef TM_GMTOFF
  31 #endif
  32
  33 /*
  34 ** Copyright (c) 1989, 1993
  35 **      The Regents of the University of California.  All rights reserved.
  36 **
  37 ** Redistribution and use in source and binary forms, with or without
  38 ** modification, are permitted provided that the following conditions
  39 ** are met:
  40 ** 1. Redistributions of source code must retain the above copyright
  41 **    notice, this list of conditions and the following disclaimer.
  42 ** 2. Redistributions in binary form must reproduce the above copyright
  43 **    notice, this list of conditions and the following disclaimer in the
  44 **    documentation and/or other materials provided with the distribution.
  45 ** 3. All advertising materials mentioning features or use of this software
  46 **    must display the following acknowledgement:
  47 **      This product includes software developed by the University of
  48 **      California, Berkeley and its contributors.
  49 ** 4. Neither the name of the University nor the names of its contributors
  50 **    may be used to endorse or promote products derived from this software
  51 **    without specific prior written permission.
  52 **
  53 ** THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  54 ** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  55 ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  56 ** ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  57 ** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  58 ** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  59 ** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  60 ** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  61 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  62 ** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  63 ** SUCH DAMAGE.
  64 */
  65
  66 #ifndef LIBC_SCCS
  67 #ifndef lint
  68 static const char       sccsid[] = "@(#)strftime.c      5.4 (Berkeley) 3/14/89";
  69 #endif /* !defined lint */
  70 #endif /* !defined LIBC_SCCS */
  71
  72 #include "tzfile.h"
  73 #include "fcntl.h"
  74 #include "locale.h"
  75
  76 #ifdef __weak_alias
  77 __weak_alias(strftime_z, _strftime_z)
  78 #endif
  79
  80 #include "sys/localedef.h"
  81 #define Locale  _CurrentTimeLocale
  82 #define c_fmt   d_t_fmt
  83
  84 static char *   _add(const char *, char *, const char *);
  85 static char *   _conv(int, const char *, char *, const char *);
  86 static char *   _fmt(const timezone_t, const char *, const struct tm *, char *,
  87                         const char *, int *);
  88 static char *   _yconv(int, int, int, int, char *, const char *);
  89
  90 extern char *   tzname[];
  91
  92 #ifndef YEAR_2000_NAME
  93 #define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
  94 #endif /* !defined YEAR_2000_NAME */
  95
  96 #define IN_NONE 0
  97 #define IN_SOME 1
  98 #define IN_THIS 2
  99 #define IN_ALL  3
 100
 101 size_t
 102 strftime_z(const timezone_t sp, char * const s, const size_t maxsize,
 103     const char * const format, const struct tm * const  t)
 104 {
 105         char *  p;
 106         int     warn;
 107
 108         warn = IN_NONE;
 109         p = _fmt(sp, ((format == NULL) ? "%c" : format), t, s, s + maxsize,
 110             &warn);
 111 #ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
 112         if (warn != IN_NONE && getenv(YEAR_2000_NAME) != NULL) {
 113                 (void) fprintf(stderr, "\n");
 114                 if (format == NULL)
 115                         (void) fprintf(stderr, "NULL strftime format ");
 116                 else    (void) fprintf(stderr, "strftime format \"%s\" ",
 117                                 format);
 118                 (void) fprintf(stderr, "yields only two digits of years in ");
 119                 if (warn == IN_SOME)
 120                         (void) fprintf(stderr, "some locales");
 121                 else if (warn == IN_THIS)
 122                         (void) fprintf(stderr, "the current locale");
 123                 else    (void) fprintf(stderr, "all locales");
 124                 (void) fprintf(stderr, "\n");
 125         }
 126 #endif /* !defined NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU */
 127         if (p == s + maxsize)
 128                 return 0;
 129         *p = '\0';
 130         return p - s;
 131 }
 132
 133 static char *
 134 _fmt(const timezone_t sp, const char *format, const struct tm * const t,
 135         char *pt, const char *const ptlim, int *warnp)
 136 {
 137         for ( ; *format; ++format) {
 138                 if (*format == '%') {
 139 label:
 140                         switch (*++format) {
 141                         case '\0':
 142                                 --format;
 143                                 break;
 144                         case 'A':
 145                                 pt = _add((t->tm_wday < 0 ||
 146                                         t->tm_wday >= DAYSPERWEEK) ?
 147                                         "?" : Locale->day[t->tm_wday],
 148                                         pt, ptlim);
 149                                 continue;
 150                         case 'a':
 151                                 pt = _add((t->tm_wday < 0 ||
 152                                         t->tm_wday >= DAYSPERWEEK) ?
 153                                         "?" : Locale->abday[t->tm_wday],
 154                                         pt, ptlim);
 155                                 continue;
 156                         case 'B':
 157                                 pt = _add((t->tm_mon < 0 ||
 158                                         t->tm_mon >= MONSPERYEAR) ?
 159                                         "?" : Locale->mon[t->tm_mon],
 160                                         pt, ptlim);
 161                                 continue;
 162                         case 'b':
 163                         case 'h':
 164                                 pt = _add((t->tm_mon < 0 ||
 165                                         t->tm_mon >= MONSPERYEAR) ?
 166                                         "?" : Locale->abmon[t->tm_mon],
 167                                         pt, ptlim);
 168                                 continue;
 169                         case 'C':
 170                                 /*
 171                                 ** %C used to do a...
 172                                 **      _fmt("%a %b %e %X %Y", t);
 173                                 ** ...whereas now POSIX 1003.2 calls for
 174                                 ** something completely different.
 175                                 ** (ado, 1993-05-24)
 176                                 */
 177                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
 178                                         pt, ptlim);
 179                                 continue;
 180                         case 'c':
 181                                 {
 182                                 int warn2 = IN_SOME;
 183
 184                                 pt = _fmt(sp, Locale->c_fmt, t, pt, ptlim, &warn2);
 185                                 if (warn2 == IN_ALL)
 186                                         warn2 = IN_THIS;
 187                                 if (warn2 > *warnp)
 188                                         *warnp = warn2;
 189                                 }
 190                                 continue;
 191                         case 'D':
 192                                 pt = _fmt(sp, "%m/%d/%y", t, pt, ptlim, warnp);
 193                                 continue;
 194                         case 'd':
 195                                 pt = _conv(t->tm_mday, "%02d", pt, ptlim);
 196                                 continue;
 197                         case 'E':
 198                         case 'O':
 199                                 /*
 200                                 ** C99 locale modifiers.
 201                                 ** The sequences
 202                                 **      %Ec %EC %Ex %EX %Ey %EY
 203                                 **      %Od %oe %OH %OI %Om %OM
 204                                 **      %OS %Ou %OU %OV %Ow %OW %Oy
 205                                 ** are supposed to provide alternate
 206                                 ** representations.
 207                                 */
 208                                 goto label;
 209                         case 'e':
 210                                 pt = _conv(t->tm_mday, "%2d", pt, ptlim);
 211                                 continue;
 212                         case 'F':
 213                                 pt = _fmt(sp, "%Y-%m-%d", t, pt, ptlim, warnp);
 214                                 continue;
 215                         case 'H':
 216                                 pt = _conv(t->tm_hour, "%02d", pt, ptlim);
 217                                 continue;
 218                         case 'I':
 219                                 pt = _conv((t->tm_hour % 12) ?
 220                                         (t->tm_hour % 12) : 12,
 221                                         "%02d", pt, ptlim);
 222                                 continue;
 223                         case 'j':
 224                                 pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);
 225                                 continue;
 226                         case 'k':
 227                                 /*
 228                                 ** This used to be...
 229                                 **      _conv(t->tm_hour % 12 ?
 230                                 **              t->tm_hour % 12 : 12, 2, ' ');
 231                                 ** ...and has been changed to the below to
 232                                 ** match SunOS 4.1.1 and Arnold Robbins'
 233                                 ** strftime version 3.0. That is, "%k" and
 234                                 ** "%l" have been swapped.
 235                                 ** (ado, 1993-05-24)
 236                                 */
 237                                 pt = _conv(t->tm_hour, "%2d", pt, ptlim);
 238                                 continue;
 239 #ifdef KITCHEN_SINK
 240                         case 'K':
 241                                 /*
 242                                 ** After all this time, still unclaimed!
 243                                 */
 244                                 pt = _add("kitchen sink", pt, ptlim);
 245                                 continue;
 246 #endif /* defined KITCHEN_SINK */
 247                         case 'l':
 248                                 /*
 249                                 ** This used to be...
 250                                 **      _conv(t->tm_hour, 2, ' ');
 251                                 ** ...and has been changed to the below to
 252                                 ** match SunOS 4.1.1 and Arnold Robbin's
 253                                 ** strftime version 3.0. That is, "%k" and
 254                                 ** "%l" have been swapped.
 255                                 ** (ado, 1993-05-24)
 256                                 */
 257                                 pt = _conv((t->tm_hour % 12) ?
 258                                         (t->tm_hour % 12) : 12,
 259                                         "%2d", pt, ptlim);
 260                                 continue;
 261                         case 'M':
 262                                 pt = _conv(t->tm_min, "%02d", pt, ptlim);
 263                                 continue;
 264                         case 'm':
 265                                 pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);
 266                                 continue;
 267                         case 'n':
 268                                 pt = _add("\n", pt, ptlim);
 269                                 continue;
 270                         case 'p':
 271                                 pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
 272                                         Locale->am_pm[1] :
 273                                         Locale->am_pm[0],
 274                                         pt, ptlim);
 275                                 continue;
 276                         case 'R':
 277                                 pt = _fmt(sp, "%H:%M", t, pt, ptlim, warnp);
 278                                 continue;
 279                         case 'r':
 280                                 pt = _fmt(sp, Locale->t_fmt_ampm, t, pt, ptlim,
 281                                         warnp);
 282                                 continue;
 283                         case 'S':
 284                                 pt = _conv(t->tm_sec, "%02d", pt, ptlim);
 285                                 continue;
 286                         case 's':
 287                                 {
 288                                         struct tm       tm;
 289                                         char            buf[INT_STRLEN_MAXIMUM(
 290                                                                 time_t) + 1];
 291                                         time_t          mkt;
 292
 293                                         tm = *t;
 294                                         mkt = mktime(&tm);
 295                                         /* CONSTCOND */
 296                                         if (TYPE_SIGNED(time_t))
 297                                                 (void) snprintf(buf, sizeof(buf),
 298                                                     "%lld", (long long) mkt);
 299                                         else    (void) snprintf(buf, sizeof(buf),
 300                                                     "%llu", (unsigned long long)
 301                                                     mkt);
 302                                         pt = _add(buf, pt, ptlim);
 303                                 }
 304                                 continue;
 305                         case 'T':
 306                                 pt = _fmt(sp, "%H:%M:%S", t, pt, ptlim, warnp);
 307                                 continue;
 308                         case 't':
 309                                 pt = _add("\t", pt, ptlim);
 310                                 continue;
 311                         case 'U':
 312                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 313                                         t->tm_wday) / DAYSPERWEEK,
 314                                         "%02d", pt, ptlim);
 315                                 continue;
 316                         case 'u':
 317                                 /*
 318                                 ** From Arnold Robbins' strftime version 3.0:
 319                                 ** "ISO 8601: Weekday as a decimal number
 320                                 ** [1 (Monday) - 7]"
 321                                 ** (ado, 1993-05-24)
 322                                 */
 323                                 pt = _conv((t->tm_wday == 0) ?
 324                                         DAYSPERWEEK : t->tm_wday,
 325                                         "%d", pt, ptlim);
 326                                 continue;
 327                         case 'V':       /* ISO 8601 week number */
 328                         case 'G':       /* ISO 8601 year (four digits) */
 329                         case 'g':       /* ISO 8601 year (two digits) */
 330 /*
 331 ** From Arnold Robbins' strftime version 3.0: "the week number of the
 332 ** year (the first Monday as the first day of week 1) as a decimal number
 333 ** (01-53)."
 334 ** (ado, 1993-05-24)
 335 **
 336 ** From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
 337 ** "Week 01 of a year is per definition the first week which has the
 338 ** Thursday in this year, which is equivalent to the week which contains
 339 ** the fourth day of January. In other words, the first week of a new year
 340 ** is the week which has the majority of its days in the new year. Week 01
 341 ** might also contain days from the previous year and the week before week
 342 ** 01 of a year is the last week (52 or 53) of the previous year even if
 343 ** it contains days from the new year. A week starts with Monday (day 1)
 344 ** and ends with Sunday (day 7). For example, the first week of the year
 345 ** 1997 lasts from 1996-12-30 to 1997-01-05..."
 346 ** (ado, 1996-01-02)
 347 */
 348                                 {
 349                                         int     year;
 350                                         int     base;
 351                                         int     yday;
 352                                         int     wday;
 353                                         int     w;
 354
 355                                         year = t->tm_year;
 356                                         base = TM_YEAR_BASE;
 357                                         yday = t->tm_yday;
 358                                         wday = t->tm_wday;
 359                                         for ( ; ; ) {
 360                                                 int     len;
 361                                                 int     bot;
 362                                                 int     top;
 363
 364                                                 len = isleap_sum(year, base) ?
 365                                                         DAYSPERLYEAR :
 366                                                         DAYSPERNYEAR;
 367                                                 /*
 368                                                 ** What yday (-3 ... 3) does
 369                                                 ** the ISO year begin on?
 370                                                 */
 371                                                 bot = ((yday + 11 - wday) %
 372                                                         DAYSPERWEEK) - 3;
 373                                                 /*
 374                                                 ** What yday does the NEXT
 375                                                 ** ISO year begin on?
 376                                                 */
 377                                                 top = bot -
 378                                                         (len % DAYSPERWEEK);
 379                                                 if (top < -3)
 380                                                         top += DAYSPERWEEK;
 381                                                 top += len;
 382                                                 if (yday >= top) {
 383                                                         ++base;
 384                                                         w = 1;
 385                                                         break;
 386                                                 }
 387                                                 if (yday >= bot) {
 388                                                         w = 1 + ((yday - bot) /
 389                                                                 DAYSPERWEEK);
 390                                                         break;
 391                                                 }
 392                                                 --base;
 393                                                 yday += isleap_sum(year, base) ?
 394                                                         DAYSPERLYEAR :
 395                                                         DAYSPERNYEAR;
 396                                         }
 397 #ifdef XPG4_1994_04_09
 398                                         if ((w == 52 &&
 399                                                 t->tm_mon == TM_JANUARY) ||
 400                                                 (w == 1 &&
 401                                                 t->tm_mon == TM_DECEMBER))
 402                                                         w = 53;
 403 #endif /* defined XPG4_1994_04_09 */
 404                                         if (*format == 'V')
 405                                                 pt = _conv(w, "%02d",
 406                                                         pt, ptlim);
 407                                         else if (*format == 'g') {
 408                                                 *warnp = IN_ALL;
 409                                                 pt = _yconv(year, base, 0, 1,
 410                                                         pt, ptlim);
 411                                         } else  pt = _yconv(year, base, 1, 1,
 412                                                         pt, ptlim);
 413                                 }
 414                                 continue;
 415                         case 'v':
 416                                 /*
 417                                 ** From Arnold Robbins' strftime version 3.0:
 418                                 ** "date as dd-bbb-YYYY"
 419                                 ** (ado, 1993-05-24)
 420                                 */
 421                                 pt = _fmt(sp, "%e-%b-%Y", t, pt, ptlim, warnp);
 422                                 continue;
 423                         case 'W':
 424                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 425                                         (t->tm_wday ?
 426                                         (t->tm_wday - 1) :
 427                                         (DAYSPERWEEK - 1))) / DAYSPERWEEK,
 428                                         "%02d", pt, ptlim);
 429                                 continue;
 430                         case 'w':
 431                                 pt = _conv(t->tm_wday, "%d", pt, ptlim);
 432                                 continue;
 433                         case 'X':
 434                                 pt = _fmt(sp, Locale->t_fmt, t, pt, ptlim, warnp);
 435                                 continue;
 436                         case 'x':
 437                                 {
 438                                 int     warn2 = IN_SOME;
 439
 440                                 pt = _fmt(sp, Locale->d_fmt, t, pt, ptlim, &warn2);
 441                                 if (warn2 == IN_ALL)
 442                                         warn2 = IN_THIS;
 443                                 if (warn2 > *warnp)
 444                                         *warnp = warn2;
 445                                 }
 446                                 continue;
 447                         case 'y':
 448                                 *warnp = IN_ALL;
 449                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
 450                                         pt, ptlim);
 451                                 continue;
 452                         case 'Y':
 453                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
 454                                         pt, ptlim);
 455                                 continue;
 456                         case 'Z':
 457 #ifdef TM_ZONE
 458                                 if (t->TM_ZONE != NULL)
 459                                         pt = _add(t->TM_ZONE, pt, ptlim);
 460                                 else
 461 #endif /* defined TM_ZONE */
 462                                 if (t->tm_isdst >= 0)
 463                                         pt = _add((sp ?
 464                                             tzgetname(sp, t->tm_isdst) :
 465                                             tzname[t->tm_isdst != 0]),
 466                                             pt, ptlim);
 467                                 /*
 468                                 ** C99 says that %Z must be replaced by the
 469                                 ** empty string if the time zone is not
 470                                 ** determinable.
 471                                 */
 472                                 continue;
 473                         case 'z':
 474                                 {
 475                                 int             diff;
 476                                 char const *    sign;
 477
 478                                 if (t->tm_isdst < 0)
 479                                         continue;
 480 #ifdef TM_GMTOFF
 481                                 diff = (int)t->TM_GMTOFF;
 482 #else /* !defined TM_GMTOFF */
 483                                 /*
 484                                 ** C99 says that the UTC offset must
 485                                 ** be computed by looking only at
 486                                 ** tm_isdst. This requirement is
 487                                 ** incorrect, since it means the code
 488                                 ** must rely on magic (in this case
 489                                 ** altzone and timezone), and the
 490                                 ** magic might not have the correct
 491                                 ** offset. Doing things correctly is
 492                                 ** tricky and requires disobeying C99;
 493                                 ** see GNU C strftime for details.
 494                                 ** For now, punt and conform to the
 495                                 ** standard, even though it's incorrect.
 496                                 **
 497                                 ** C99 says that %z must be replaced by the
 498                                 ** empty string if the time zone is not
 499                                 ** determinable, so output nothing if the
 500                                 ** appropriate variables are not available.
 501                                 */
 502 #ifndef STD_INSPIRED
 503                                 if (t->tm_isdst == 0)
 504 #ifdef USG_COMPAT
 505                                         diff = -timezone;
 506 #else /* !defined USG_COMPAT */
 507                                         continue;
 508 #endif /* !defined USG_COMPAT */
 509                                 else
 510 #ifdef ALTZONE
 511                                         diff = -altzone;
 512 #else /* !defined ALTZONE */
 513                                         continue;
 514 #endif /* !defined ALTZONE */
 515 #else /* defined STD_INSPIRED */
 516                                 {
 517                                         struct tm tmp;
 518                                         time_t lct, gct;
 519
 520                                         /*
 521                                         ** Get calendar time from t
 522                                         ** being treated as local.
 523                                         */
 524                                         tmp = *t; /* mktime discards const */
 525                                         lct = mktime(&tmp);
 526
 527                                         if (lct == (time_t)-1)
 528                                                 continue;
 529
 530                                         /*
 531                                         ** Get calendar time from t
 532                                         ** being treated as GMT.
 533                                         **/
 534                                         tmp = *t; /* mktime discards const */
 535                                         gct = timegm(&tmp);
 536
 537                                         if (gct == (time_t)-1)
 538                                                 continue;
 539
 540                                         /* LINTED difference will fit int */
 541                                         diff = (intmax_t)gct - (intmax_t)lct;
 542                                 }
 543 #endif /* defined STD_INSPIRED */
 544 #endif /* !defined TM_GMTOFF */
 545                                 if (diff < 0) {
 546                                         sign = "-";
 547                                         diff = -diff;
 548                                 } else  sign = "+";
 549                                 pt = _add(sign, pt, ptlim);
 550                                 diff /= SECSPERMIN;
 551                                 diff = (diff / MINSPERHOUR) * 100 +
 552                                         (diff % MINSPERHOUR);
 553                                 pt = _conv(diff, "%04d", pt, ptlim);
 554                                 }
 555                                 continue;
 556 #ifdef __minix
 557                         case '+':
 558                                 pt = _fmt(sp, Locale->c_fmt, t, pt, ptlim, warnp);
 559                                 continue;
 560 #endif /* !__minix */
 561 #if 0
 562                         case '+':
 563                                 pt = _fmt(sp, Locale->date_fmt, t, pt, ptlim,
 564                                         warnp);
 565                                 continue;
 566 #endif
 567                         case '%':
 568                         /*
 569                         ** X311J/88-090 (4.12.3.5): if conversion char is
 570                         ** undefined, behavior is undefined. Print out the
 571                         ** character itself as printf(3) also does.
 572                         */
 573                         default:
 574                                 break;
 575                         }
 576                 }
 577                 if (pt == ptlim)
 578                         break;
 579                 *pt++ = *format;
 580         }
 581         return pt;
 582 }
 583
 584 size_t
 585 strftime(char * const s, const size_t maxsize,
 586     const char * const format, const struct tm * const  t)
 587 {
 588         tzset();
 589         return strftime_z(NULL, s, maxsize, format, t);
 590 }
 591
 592 static char *
 593 _conv(const int n, const char * const format, char * const pt,
 594     const char * const ptlim)
 595 {
 596         char    buf[INT_STRLEN_MAXIMUM(int) + 1];
 597
 598         (void) snprintf(buf, sizeof(buf), format, n);
 599         return _add(buf, pt, ptlim);
 600 }
 601
 602 static char *
 603 _add(const char *str, char *pt, const char * const ptlim)
 604 {
 605         while (pt < ptlim && (*pt = *str++) != '\0')
 606                 ++pt;
 607         return pt;
 608 }
 609
 610 /*
 611 ** POSIX and the C Standard are unclear or inconsistent about
 612 ** what %C and %y do if the year is negative or exceeds 9999.
 613 ** Use the convention that %C concatenated with %y yields the
 614 ** same output as %Y, and that %Y contains at least 4 bytes,
 615 ** with more only if necessary.
 616 */
 617
 618 static char *
 619 _yconv(const int a, const int b, const int convert_top, const int convert_yy,
 620     char *pt, const char * const ptlim)
 621 {
 622         register int    lead;
 623         register int    trail;
 624
 625 #define DIVISOR 100
 626         trail = a % DIVISOR + b % DIVISOR;
 627         lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
 628         trail %= DIVISOR;
 629         if (trail < 0 && lead > 0) {
 630                 trail += DIVISOR;
 631                 --lead;
 632         } else if (lead < 0 && trail > 0) {
 633                 trail -= DIVISOR;
 634                 ++lead;
 635         }
 636         if (convert_top) {
 637                 if (lead == 0 && trail < 0)
 638                         pt = _add("-0", pt, ptlim);
 639                 else    pt = _conv(lead, "%02d", pt, ptlim);
 640         }
 641         if (convert_yy)
 642                 pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
 643         return pt;
 644 }
 645
 646 #ifdef LOCALE_HOME
 647 static struct lc_time_T *
 648 _loc(void)
 649 {
 650         static const char       locale_home[] = LOCALE_HOME;
 651         static const char       lc_time[] = "LC_TIME";
 652         static char *           locale_buf;
 653
 654         int                     fd;
 655         int                     oldsun; /* "...ain't got nothin' to do..." */
 656         char *                  lbuf;
 657         char *                  name;
 658         char *                  p;
 659         const char **           ap;
 660         const char *            plim;
 661         char                    filename[FILENAME_MAX];
 662         struct stat             st;
 663         size_t                  namesize;
 664         size_t                  bufsize;
 665
 666         /*
 667         ** Use localebuf.mon[0] to signal whether locale is already set up.
 668         */
 669         if (localebuf.mon[0])
 670                 return &localebuf;
 671         name = setlocale(LC_TIME, (char *) NULL);
 672         if (name == NULL || *name == '\0')
 673                 goto no_locale;
 674         /*
 675         ** If the locale name is the same as our cache, use the cache.
 676         */
 677         lbuf = locale_buf;
 678         if (lbuf != NULL && strcmp(name, lbuf) == 0) {
 679                 p = lbuf;
 680                 for (ap = (const char **) &localebuf;
 681                         ap < (const char **) (&localebuf + 1);
 682                                 ++ap)
 683                                         *ap = p += strlen(p) + 1;
 684                 return &localebuf;
 685         }
 686         /*
 687         ** Slurp the locale file into the cache.
 688         */
 689         namesize = strlen(name) + 1;
 690         if (sizeof filename <
 691                 ((sizeof locale_home) + namesize + (sizeof lc_time)))
 692                         goto no_locale;
 693         oldsun = 0;
 694         (void) sprintf(filename, "%s/%s/%s", locale_home, name, lc_time);
 695         fd = open(filename, O_RDONLY);
 696         if (fd < 0) {
 697                 /*
 698                 ** Old Sun systems have a different naming and data convention.
 699                 */
 700                 oldsun = 1;
 701                 (void) sprintf(filename, "%s/%s/%s", locale_home,
 702                         lc_time, name);
 703                 fd = open(filename, O_RDONLY);
 704                 if (fd < 0)
 705                         goto no_locale;
 706         }
 707         if (fstat(fd, &st) != 0)
 708                 goto bad_locale;
 709         if (st.st_size <= 0)
 710                 goto bad_locale;
 711         bufsize = namesize + st.st_size;
 712         locale_buf = NULL;
 713         lbuf = (lbuf == NULL) ? malloc(bufsize) : realloc(lbuf, bufsize);
 714         if (lbuf == NULL)
 715                 goto bad_locale;
 716         (void) strcpy(lbuf, name);
 717         p = lbuf + namesize;
 718         plim = p + st.st_size;
 719         if (read(fd, p, (size_t) st.st_size) != st.st_size)
 720                 goto bad_lbuf;
 721         if (close(fd) != 0)
 722                 goto bad_lbuf;
 723         /*
 724         ** Parse the locale file into localebuf.
 725         */
 726         if (plim[-1] != '\n')
 727                 goto bad_lbuf;
 728         for (ap = (const char **) &localebuf;
 729                 ap < (const char **) (&localebuf + 1);
 730                         ++ap) {
 731                                 if (p == plim)
 732                                         goto bad_lbuf;
 733                                 *ap = p;
 734                                 while (*p != '\n')
 735                                         ++p;
 736                                 *p++ = '\0';
 737         }
 738         if (oldsun) {
 739                 /*
 740                 ** SunOS 4 used an obsolescent format; see localdtconv(3).
 741                 ** c_fmt had the ``short format for dates and times together''
 742                 ** (SunOS 4 date, "%a %b %e %T %Z %Y" in the C locale);
 743                 ** date_fmt had the ``long format for dates''
 744                 ** (SunOS 4 strftime %C, "%A, %B %e, %Y" in the C locale).
 745                 ** Discard the latter in favor of the former.
 746                 */
 747                 localebuf.date_fmt = localebuf.c_fmt;
 748         }
 749         /*
 750         ** Record the successful parse in the cache.
 751         */
 752         locale_buf = lbuf;
 753
 754         return &localebuf;
 755
 756 bad_lbuf:
 757         free(lbuf);
 758 bad_locale:
 759         (void) close(fd);
 760 no_locale:
 761         localebuf = C_time_locale;
 762         locale_buf = NULL;
 763         return &localebuf;
 764 }
 765 #endif /* defined LOCALE_HOME */