lib/libc/stdtime/strftime.c

   1 /*
   2  * $NetBSD: strftime.c,v 1.19 2009/01/11 02:46:30 christos Exp $
   3  */
   4
   5 /*
   6 ** We don't use these extensions in strftime operation even when
   7 ** supported by the local tzcode configuration.  A strictly
   8 ** conforming C application may leave them in undefined state.
   9 */
  10
  11 #ifdef _LIBC
  12 #undef TM_ZONE
  13 #undef TM_GMTOFF
  14 #endif
  15
  16 /*
  17 ** Copyright (c) 1989, 1993
  18 **      The Regents of the University of California.  All rights reserved.
  19 **
  20 ** Redistribution and use in source and binary forms, with or without
  21 ** modification, are permitted provided that the following conditions
  22 ** are met:
  23 ** 1. Redistributions of source code must retain the above copyright
  24 **    notice, this list of conditions and the following disclaimer.
  25 ** 2. Redistributions in binary form must reproduce the above copyright
  26 **    notice, this list of conditions and the following disclaimer in the
  27 **    documentation and/or other materials provided with the distribution.
  28 ** 3. All advertising materials mentioning features or use of this software
  29 **    must display the following acknowledgement:
  30 **      This product includes software developed by the University of
  31 **      California, Berkeley and its contributors.
  32 ** 4. Neither the name of the University nor the names of its contributors
  33 **    may be used to endorse or promote products derived from this software
  34 **    without specific prior written permission.
  35 **
  36 ** THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  37 ** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  38 ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  39 ** ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  40 ** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  41 ** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  42 ** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  43 ** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  44 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  45 ** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  46 ** SUCH DAMAGE.
  47 */
  48
  49 #include <sys/localedef.h>
  50 #include <fcntl.h>
  51 #include <locale.h>
  52 #include <time.h>
  53
  54 #include "private.h"
  55 #include "tzfile.h"
  56
  57 #define Locale  _CurrentTimeLocale
  58
  59 static char *   _add(const char *, char *, const char *);
  60 static char *   _conv(int, const char *, char *, const char *);
  61 static char *   _fmt(const char *, const struct tm *, char *,
  62                      const char *, int *);
  63 static char *   _yconv(int, int, int, int, char *, const char *);
  64
  65 #define NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
  66
  67 #ifndef YEAR_2000_NAME
  68 #define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
  69 #endif /* !defined YEAR_2000_NAME */
  70
  71 #define IN_NONE 0
  72 #define IN_SOME 1
  73 #define IN_THIS 2
  74 #define IN_ALL  3
  75
  76 size_t
  77 strftime(char * __restrict s, size_t maxsize, const char * __restrict format,
  78          const struct tm * __restrict t)
  79 {
  80         char *  p;
  81         int     warn;
  82
  83         tzset();
  84         warn = IN_NONE;
  85         p = _fmt(((format == NULL) ? "%c" : format), t, s, s + maxsize, &warn);
  86 #ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
  87         if (warn != IN_NONE && getenv(YEAR_2000_NAME) != NULL) {
  88                 fprintf(stderr, "\n");
  89                 if (format == NULL)
  90                         fprintf(stderr, "NULL strftime format ");
  91                 else    fprintf(stderr, "strftime format \"%s\" ",
  92                                 format);
  93                 fprintf(stderr, "yields only two digits of years in ");
  94                 if (warn == IN_SOME)
  95                         fprintf(stderr, "some locales");
  96                 else if (warn == IN_THIS)
  97                         fprintf(stderr, "the current locale");
  98                 else    fprintf(stderr, "all locales");
  99                 fprintf(stderr, "\n");
 100         }
 101 #endif /* !defined NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU */
 102         if (p == s + maxsize)
 103                 return 0;
 104         *p = '\0';
 105         return p - s;
 106 }
 107
 108 static char *
 109 _fmt(const char *format, const struct tm * const t, char *pt,
 110      const char * const ptlim, int * warnp)
 111 {
 112         for ( ; *format; ++format) {
 113                 if (*format == '%') {
 114 label:
 115                         switch (*++format) {
 116                         case '\0':
 117                                 --format;
 118                                 break;
 119                         case 'A':
 120                                 pt = _add((t->tm_wday < 0 ||
 121                                         t->tm_wday >= DAYSPERWEEK) ?
 122                                         "?" : Locale->day[t->tm_wday],
 123                                         pt, ptlim);
 124                                 continue;
 125                         case 'a':
 126                                 pt = _add((t->tm_wday < 0 ||
 127                                         t->tm_wday >= DAYSPERWEEK) ?
 128                                         "?" : Locale->abday[t->tm_wday],
 129                                         pt, ptlim);
 130                                 continue;
 131                         case 'B':
 132                                 pt = _add((t->tm_mon < 0 ||
 133                                         t->tm_mon >= MONSPERYEAR) ?
 134                                         "?" : Locale->mon[t->tm_mon],
 135                                         pt, ptlim);
 136                                 continue;
 137                         case 'b':
 138                         case 'h':
 139                                 pt = _add((t->tm_mon < 0 ||
 140                                         t->tm_mon >= MONSPERYEAR) ?
 141                                         "?" : Locale->abmon[t->tm_mon],
 142                                         pt, ptlim);
 143                                 continue;
 144                         case 'C':
 145                                 /*
 146                                 ** %C used to do a...
 147                                 **      _fmt("%a %b %e %X %Y", t);
 148                                 ** ...whereas now POSIX 1003.2 calls for
 149                                 ** something completely different.
 150                                 ** (ado, 1993-05-24)
 151                                 */
 152                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
 153                                         pt, ptlim);
 154                                 continue;
 155                         case 'c':
 156                                 {
 157                                 int warn2 = IN_SOME;
 158
 159                                 pt = _fmt(Locale->d_t_fmt, t, pt, ptlim, &warn2);
 160                                 if (warn2 == IN_ALL)
 161                                         warn2 = IN_THIS;
 162                                 if (warn2 > *warnp)
 163                                         *warnp = warn2;
 164                                 }
 165                                 continue;
 166                         case 'D':
 167                                 pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp);
 168                                 continue;
 169                         case 'd':
 170                                 pt = _conv(t->tm_mday, "%02d", pt, ptlim);
 171                                 continue;
 172                         case 'E':
 173                         case 'O':
 174                                 /*
 175                                 ** C99 locale modifiers.
 176                                 ** The sequences
 177                                 **      %Ec %EC %Ex %EX %Ey %EY
 178                                 **      %Od %oe %OH %OI %Om %OM
 179                                 **      %OS %Ou %OU %OV %Ow %OW %Oy
 180                                 ** are supposed to provide alternate
 181                                 ** representations.
 182                                 */
 183                                 goto label;
 184                         case 'e':
 185                                 pt = _conv(t->tm_mday, "%2d", pt, ptlim);
 186                                 continue;
 187                         case 'F':
 188                                 pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);
 189                                 continue;
 190                         case 'H':
 191                                 pt = _conv(t->tm_hour, "%02d", pt, ptlim);
 192                                 continue;
 193                         case 'I':
 194                                 pt = _conv((t->tm_hour % 12) ?
 195                                         (t->tm_hour % 12) : 12,
 196                                         "%02d", pt, ptlim);
 197                                 continue;
 198                         case 'j':
 199                                 pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);
 200                                 continue;
 201                         case 'k':
 202                                 /*
 203                                 ** This used to be...
 204                                 **      _conv(t->tm_hour % 12 ?
 205                                 **              t->tm_hour % 12 : 12, 2, ' ');
 206                                 ** ...and has been changed to the below to
 207                                 ** match SunOS 4.1.1 and Arnold Robbins'
 208                                 ** strftime version 3.0. That is, "%k" and
 209                                 ** "%l" have been swapped.
 210                                 ** (ado, 1993-05-24)
 211                                 */
 212                                 pt = _conv(t->tm_hour, "%2d", pt, ptlim);
 213                                 continue;
 214 #ifdef KITCHEN_SINK
 215                         case 'K':
 216                                 /*
 217                                 ** After all this time, still unclaimed!
 218                                 */
 219                                 pt = _add("kitchen sink", pt, ptlim);
 220                                 continue;
 221 #endif /* defined KITCHEN_SINK */
 222                         case 'l':
 223                                 /*
 224                                 ** This used to be...
 225                                 **      _conv(t->tm_hour, 2, ' ');
 226                                 ** ...and has been changed to the below to
 227                                 ** match SunOS 4.1.1 and Arnold Robbin's
 228                                 ** strftime version 3.0. That is, "%k" and
 229                                 ** "%l" have been swapped.
 230                                 ** (ado, 1993-05-24)
 231                                 */
 232                                 pt = _conv((t->tm_hour % 12) ?
 233                                         (t->tm_hour % 12) : 12,
 234                                         "%2d", pt, ptlim);
 235                                 continue;
 236                         case 'M':
 237                                 pt = _conv(t->tm_min, "%02d", pt, ptlim);
 238                                 continue;
 239                         case 'm':
 240                                 pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);
 241                                 continue;
 242                         case 'n':
 243                                 pt = _add("\n", pt, ptlim);
 244                                 continue;
 245                         case 'p':
 246                                 pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
 247                                         Locale->am_pm[1] :
 248                                         Locale->am_pm[0],
 249                                         pt, ptlim);
 250                                 continue;
 251                         case 'R':
 252                                 pt = _fmt("%H:%M", t, pt, ptlim, warnp);
 253                                 continue;
 254                         case 'r':
 255                                 pt = _fmt(Locale->t_fmt_ampm, t, pt, ptlim,
 256                                         warnp);
 257                                 continue;
 258                         case 'S':
 259                                 pt = _conv(t->tm_sec, "%02d", pt, ptlim);
 260                                 continue;
 261                         case 's':
 262                                 {
 263                                         struct tm       tm;
 264                                         char            buf[INT_STRLEN_MAXIMUM(
 265                                                                 time_t) + 1];
 266                                         time_t          mkt;
 267
 268                                         tm = *t;
 269                                         mkt = mktime(&tm);
 270                                         /* CONSTCOND */
 271                                         if (TYPE_SIGNED(time_t))
 272                                                 snprintf(buf, sizeof(buf),
 273                                                     "%ld", (long) mkt);
 274                                         else    snprintf(buf, sizeof(buf),
 275                                                     "%lu", (unsigned long)
 276                                                     mkt);
 277                                         pt = _add(buf, pt, ptlim);
 278                                 }
 279                                 continue;
 280                         case 'T':
 281                                 pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp);
 282                                 continue;
 283                         case 't':
 284                                 pt = _add("\t", pt, ptlim);
 285                                 continue;
 286                         case 'U':
 287                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 288                                         t->tm_wday) / DAYSPERWEEK,
 289                                         "%02d", pt, ptlim);
 290                                 continue;
 291                         case 'u':
 292                                 /*
 293                                 ** From Arnold Robbins' strftime version 3.0:
 294                                 ** "ISO 8601: Weekday as a decimal number
 295                                 ** [1 (Monday) - 7]"
 296                                 ** (ado, 1993-05-24)
 297                                 */
 298                                 pt = _conv((t->tm_wday == 0) ?
 299                                         DAYSPERWEEK : t->tm_wday,
 300                                         "%d", pt, ptlim);
 301                                 continue;
 302                         case 'V':       /* ISO 8601 week number */
 303                         case 'G':       /* ISO 8601 year (four digits) */
 304                         case 'g':       /* ISO 8601 year (two digits) */
 305 /*
 306 ** From Arnold Robbins' strftime version 3.0: "the week number of the
 307 ** year (the first Monday as the first day of week 1) as a decimal number
 308 ** (01-53)."
 309 ** (ado, 1993-05-24)
 310 **
 311 ** From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
 312 ** "Week 01 of a year is per definition the first week which has the
 313 ** Thursday in this year, which is equivalent to the week which contains
 314 ** the fourth day of January. In other words, the first week of a new year
 315 ** is the week which has the majority of its days in the new year. Week 01
 316 ** might also contain days from the previous year and the week before week
 317 ** 01 of a year is the last week (52 or 53) of the previous year even if
 318 ** it contains days from the new year. A week starts with Monday (day 1)
 319 ** and ends with Sunday (day 7). For example, the first week of the year
 320 ** 1997 lasts from 1996-12-30 to 1997-01-05..."
 321 ** (ado, 1996-01-02)
 322 */
 323                                 {
 324                                         int     year;
 325                                         int     base;
 326                                         int     yday;
 327                                         int     wday;
 328                                         int     w;
 329
 330                                         year = t->tm_year;
 331                                         base = TM_YEAR_BASE;
 332                                         yday = t->tm_yday;
 333                                         wday = t->tm_wday;
 334                                         for ( ; ; ) {
 335                                                 int     len;
 336                                                 int     bot;
 337                                                 int     top;
 338
 339                                                 len = isleap_sum(year, base) ?
 340                                                         DAYSPERLYEAR :
 341                                                         DAYSPERNYEAR;
 342                                                 /*
 343                                                 ** What yday (-3 ... 3) does
 344                                                 ** the ISO year begin on?
 345                                                 */
 346                                                 bot = ((yday + 11 - wday) %
 347                                                         DAYSPERWEEK) - 3;
 348                                                 /*
 349                                                 ** What yday does the NEXT
 350                                                 ** ISO year begin on?
 351                                                 */
 352                                                 top = bot -
 353                                                         (len % DAYSPERWEEK);
 354                                                 if (top < -3)
 355                                                         top += DAYSPERWEEK;
 356                                                 top += len;
 357                                                 if (yday >= top) {
 358                                                         ++base;
 359                                                         w = 1;
 360                                                         break;
 361                                                 }
 362                                                 if (yday >= bot) {
 363                                                         w = 1 + ((yday - bot) /
 364                                                                 DAYSPERWEEK);
 365                                                         break;
 366                                                 }
 367                                                 --base;
 368                                                 yday += isleap_sum(year, base) ?
 369                                                         DAYSPERLYEAR :
 370                                                         DAYSPERNYEAR;
 371                                         }
 372 #ifdef XPG4_1994_04_09
 373                                         if ((w == 52 &&
 374                                                 t->tm_mon == TM_JANUARY) ||
 375                                                 (w == 1 &&
 376                                                 t->tm_mon == TM_DECEMBER))
 377                                                         w = 53;
 378 #endif /* defined XPG4_1994_04_09 */
 379                                         if (*format == 'V')
 380                                                 pt = _conv(w, "%02d",
 381                                                         pt, ptlim);
 382                                         else if (*format == 'g') {
 383                                                 *warnp = IN_ALL;
 384                                                 pt = _yconv(year, base, 0, 1,
 385                                                         pt, ptlim);
 386                                         } else  pt = _yconv(year, base, 1, 1,
 387                                                         pt, ptlim);
 388                                 }
 389                                 continue;
 390                         case 'v':
 391                                 /*
 392                                 ** From Arnold Robbins' strftime version 3.0:
 393                                 ** "date as dd-bbb-YYYY"
 394                                 ** (ado, 1993-05-24)
 395                                 */
 396                                 pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp);
 397                                 continue;
 398                         case 'W':
 399                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 400                                         (t->tm_wday ?
 401                                         (t->tm_wday - 1) :
 402                                         (DAYSPERWEEK - 1))) / DAYSPERWEEK,
 403                                         "%02d", pt, ptlim);
 404                                 continue;
 405                         case 'w':
 406                                 pt = _conv(t->tm_wday, "%d", pt, ptlim);
 407                                 continue;
 408                         case 'X':
 409                                 pt = _fmt(Locale->t_fmt, t, pt, ptlim, warnp);
 410                                 continue;
 411                         case 'x':
 412                                 {
 413                                 int     warn2 = IN_SOME;
 414
 415                                 pt = _fmt(Locale->d_fmt, t, pt, ptlim, &warn2);
 416                                 if (warn2 == IN_ALL)
 417                                         warn2 = IN_THIS;
 418                                 if (warn2 > *warnp)
 419                                         *warnp = warn2;
 420                                 }
 421                                 continue;
 422                         case 'y':
 423                                 *warnp = IN_ALL;
 424                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
 425                                         pt, ptlim);
 426                                 continue;
 427                         case 'Y':
 428                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
 429                                         pt, ptlim);
 430                                 continue;
 431                         case 'Z':
 432 #ifdef TM_ZONE
 433                                 if (t->TM_ZONE != NULL)
 434                                         pt = _add(t->TM_ZONE, pt, ptlim);
 435                                 else
 436 #endif /* defined TM_ZONE */
 437                                 if (t->tm_isdst >= 0)
 438                                         pt = _add(tzname[t->tm_isdst != 0],
 439                                                 pt, ptlim);
 440                                 /*
 441                                 ** C99 says that %Z must be replaced by the
 442                                 ** empty string if the time zone is not
 443                                 ** determinable.
 444                                 */
 445                                 continue;
 446                         case 'z':
 447                                 {
 448                                 int             diff;
 449                                 char const *    sign;
 450
 451                                 if (t->tm_isdst < 0)
 452                                         continue;
 453 #ifdef TM_GMTOFF
 454                                 diff = (int)t->TM_GMTOFF;
 455 #else /* !defined TM_GMTOFF */
 456                                 /*
 457                                 ** C99 says that the UTC offset must
 458                                 ** be computed by looking only at
 459                                 ** tm_isdst. This requirement is
 460                                 ** incorrect, since it means the code
 461                                 ** must rely on magic (in this case
 462                                 ** altzone and timezone), and the
 463                                 ** magic might not have the correct
 464                                 ** offset. Doing things correctly is
 465                                 ** tricky and requires disobeying C99;
 466                                 ** see GNU C strftime for details.
 467                                 ** For now, punt and conform to the
 468                                 ** standard, even though it's incorrect.
 469                                 **
 470                                 ** C99 says that %z must be replaced by the
 471                                 ** empty string if the time zone is not
 472                                 ** determinable, so output nothing if the
 473                                 ** appropriate variables are not available.
 474                                 */
 475                                 {
 476                                         struct tm tmp;
 477                                         time_t lct, gct;
 478
 479                                         /*
 480                                         ** Get calendar time from t
 481                                         ** being treated as local.
 482                                         */
 483                                         tmp = *t; /* mktime discards const */
 484                                         lct = mktime(&tmp);
 485
 486                                         if (lct == (time_t)-1)
 487                                                 continue;
 488
 489                                         /*
 490                                         ** Get calendar time from t
 491                                         ** being treated as GMT.
 492                                         **/
 493                                         tmp = *t; /* mktime discards const */
 494                                         gct = timegm(&tmp);
 495
 496                                         if (gct == (time_t)-1)
 497                                                 continue;
 498
 499                                         /* LINTED difference will fit int */
 500                                         diff = (intmax_t)gct - (intmax_t)lct;
 501                                 }
 502 #endif /* !defined TM_GMTOFF */
 503                                 if (diff < 0) {
 504                                         sign = "-";
 505                                         diff = -diff;
 506                                 } else  sign = "+";
 507                                 pt = _add(sign, pt, ptlim);
 508                                 diff /= SECSPERMIN;
 509                                 diff = (diff / MINSPERHOUR) * 100 +
 510                                         (diff % MINSPERHOUR);
 511                                 pt = _conv(diff, "%04d", pt, ptlim);
 512                                 }
 513                                 continue;
 514                         case '+':
 515                                 pt = _fmt(Locale->d_t_fmt, t, pt, ptlim,
 516                                         warnp);
 517                                 continue;
 518                         case '%':
 519                         /*
 520                         ** X311J/88-090 (4.12.3.5): if conversion char is
 521                         ** undefined, behavior is undefined. Print out the
 522                         ** character itself as printf(3) also does.
 523                         */
 524                         default:
 525                                 break;
 526                         }
 527                 }
 528                 if (pt == ptlim)
 529                         break;
 530                 *pt++ = *format;
 531         }
 532         return pt;
 533 }
 534
 535 static char *
 536 _conv(const int n, const char * const format, char * const pt,
 537       const char * const ptlim)
 538 {
 539         char    buf[INT_STRLEN_MAXIMUM(int) + 1];
 540
 541         snprintf(buf, sizeof(buf), format, n);
 542         return _add(buf, pt, ptlim);
 543 }
 544
 545 static char *
 546 _add(const char *str, char *pt, const char * const ptlim)
 547 {
 548         while (pt < ptlim && (*pt = *str++) != '\0')
 549                 ++pt;
 550         return pt;
 551 }
 552
 553 /*
 554 ** POSIX and the C Standard are unclear or inconsistent about
 555 ** what %C and %y do if the year is negative or exceeds 9999.
 556 ** Use the convention that %C concatenated with %y yields the
 557 ** same output as %Y, and that %Y contains at least 4 bytes,
 558 ** with more only if necessary.
 559 */
 560
 561 static char *
 562 _yconv(const int a, const int b, const int convert_top, const int convert_yy,
 563        char *pt, const char * const ptlim)
 564 {
 565         int     lead;
 566         int     trail;
 567
 568 #define DIVISOR 100
 569         trail = a % DIVISOR + b % DIVISOR;
 570         lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
 571         trail %= DIVISOR;
 572         if (trail < 0 && lead > 0) {
 573                 trail += DIVISOR;
 574                 --lead;
 575         } else if (lead < 0 && trail > 0) {
 576                 trail -= DIVISOR;
 577                 ++lead;
 578         }
 579         if (convert_top) {
 580                 if (lead == 0 && trail < 0)
 581                         pt = _add("-0", pt, ptlim);
 582                 else    pt = _conv(lead, "%02d", pt, ptlim);
 583         }
 584         if (convert_yy)
 585                 pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
 586         return pt;
 587 }