lib/libc/stdtime/strftime.c

   1 /*
   2  * Copyright (c) 1989 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Copyright (c) 2011 The FreeBSD Foundation
   6  * All rights reserved.
   7  * Portions of this software were developed by David Chisnall
   8  * under sponsorship from the FreeBSD Foundation.
   9  *
  10  * Redistribution and use in source and binary forms are permitted
  11  * provided that the above copyright notice and this paragraph are
  12  * duplicated in all such forms and that any documentation,
  13  * advertising materials, and other materials related to such
  14  * distribution and use acknowledge that the software was developed
  15  * by the University of California, Berkeley. The name of the
  16  * University may not be used to endorse or promote products derived
  17  * from this software without specific prior written permission.
  18  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  19  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  21  */
  22
  23 #ifndef lint
  24 #ifndef NOID
  25 static const char       elsieid[] = "@(#)strftime.3     8.3";
  26 /*
  27 ** Based on the UCB version with the ID appearing below.
  28 ** This is ANSIish only when "multibyte character == plain character".
  29 */
  30 #endif /* !defined NOID */
  31 #endif /* !defined lint */
  32
  33 #include "namespace.h"
  34 #include "private.h"
  35
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 static const char       sccsid[] = "@(#)strftime.c      5.4 (Berkeley) 3/14/89";
  38 #endif /* LIBC_SCCS and not lint */
  39 #include <sys/cdefs.h>
  40 __FBSDID("$FreeBSD$");
  41
  42 #include "tzfile.h"
  43 #include <fcntl.h>
  44 #include <sys/stat.h>
  45 #include "un-namespace.h"
  46 #include "timelocal.h"
  47
  48 static char *   _add(const char *, char *, const char *);
  49 static char *   _conv(int, const char *, char *, const char *);
  50 static char *   _fmt(const char *, const struct tm *, char *, const char *,
  51                         int *, locale_t);
  52 static char *   _yconv(int, int, int, int, char *, const char *);
  53
  54 extern char *   tzname[];
  55
  56 #ifndef YEAR_2000_NAME
  57 #define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
  58 #endif /* !defined YEAR_2000_NAME */
  59
  60 #define IN_NONE 0
  61 #define IN_SOME 1
  62 #define IN_THIS 2
  63 #define IN_ALL  3
  64
  65 #define PAD_DEFAULT     0
  66 #define PAD_LESS        1
  67 #define PAD_SPACE       2
  68 #define PAD_ZERO        3
  69
  70 static const char fmt_padding[][4][5] = {
  71         /* DEFAULT,     LESS,   SPACE,  ZERO */
  72 #define PAD_FMT_MONTHDAY        0
  73 #define PAD_FMT_HMS             0
  74 #define PAD_FMT_CENTURY         0
  75 #define PAD_FMT_SHORTYEAR       0
  76 #define PAD_FMT_MONTH           0
  77 #define PAD_FMT_WEEKOFYEAR      0
  78 #define PAD_FMT_DAYOFMONTH      0
  79         { "%02d",       "%d",   "%2d",  "%02d" },
  80 #define PAD_FMT_SDAYOFMONTH     1
  81 #define PAD_FMT_SHMS            1
  82         { "%2d",        "%d",   "%2d",  "%02d" },
  83 #define PAD_FMT_DAYOFYEAR       2
  84         { "%03d",       "%d",   "%3d",  "%03d" },
  85 #define PAD_FMT_YEAR            3
  86         { "%04d",       "%d",   "%4d",  "%04d" }
  87 };
  88
  89 size_t
  90 strftime_l(char * __restrict s, size_t maxsize, const char * __restrict format,
  91     const struct tm * __restrict t, locale_t loc)
  92 {
  93         char *  p;
  94         int     warn;
  95         FIX_LOCALE(loc);
  96
  97         tzset();
  98         warn = IN_NONE;
  99         p = _fmt(((format == NULL) ? "%c" : format), t, s, s + maxsize, &warn, loc);
 100 #ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
 101         if (warn != IN_NONE && getenv(YEAR_2000_NAME) != NULL) {
 102                 (void) fprintf_l(stderr, loc, "\n");
 103                 if (format == NULL)
 104                         (void) fprintf_l(stderr, loc, "NULL strftime format ");
 105                 else    (void) fprintf_l(stderr, loc, "strftime format \"%s\" ",
 106                                 format);
 107                 (void) fprintf_l(stderr, loc, "yields only two digits of years in ");
 108                 if (warn == IN_SOME)
 109                         (void) fprintf_l(stderr, loc, "some locales");
 110                 else if (warn == IN_THIS)
 111                         (void) fprintf_l(stderr, loc, "the current locale");
 112                 else    (void) fprintf_l(stderr, loc, "all locales");
 113                 (void) fprintf_l(stderr, loc, "\n");
 114         }
 115 #endif /* !defined NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU */
 116         if (p == s + maxsize)
 117                 return 0;
 118         *p = '\0';
 119         return p - s;
 120 }
 121
 122 size_t
 123 strftime(char * __restrict s, size_t maxsize, const char * __restrict format,
 124     const struct tm * __restrict t)
 125 {
 126         return strftime_l(s, maxsize, format, t, __get_locale());
 127 }
 128
 129 static char *
 130 _fmt(format, t, pt, ptlim, warnp, loc)
 131 const char *            format;
 132 const struct tm * const t;
 133 char *                  pt;
 134 const char * const      ptlim;
 135 int *                   warnp;
 136 locale_t        loc;
 137 {
 138         int Ealternative, Oalternative, PadIndex;
 139         struct lc_time_T *tptr = __get_current_time_locale(loc);
 140
 141         for ( ; *format; ++format) {
 142                 if (*format == '%') {
 143                         Ealternative = 0;
 144                         Oalternative = 0;
 145                         PadIndex         = PAD_DEFAULT;
 146 label:
 147                         switch (*++format) {
 148                         case '\0':
 149                                 --format;
 150                                 break;
 151                         case 'A':
 152                                 pt = _add((t->tm_wday < 0 ||
 153                                         t->tm_wday >= DAYSPERWEEK) ?
 154                                         "?" : tptr->weekday[t->tm_wday],
 155                                         pt, ptlim);
 156                                 continue;
 157                         case 'a':
 158                                 pt = _add((t->tm_wday < 0 ||
 159                                         t->tm_wday >= DAYSPERWEEK) ?
 160                                         "?" : tptr->wday[t->tm_wday],
 161                                         pt, ptlim);
 162                                 continue;
 163                         case 'B':
 164                                 pt = _add((t->tm_mon < 0 ||
 165                                         t->tm_mon >= MONSPERYEAR) ?
 166                                         "?" : (Oalternative ? tptr->alt_month :
 167                                         tptr->month)[t->tm_mon],
 168                                         pt, ptlim);
 169                                 continue;
 170                         case 'b':
 171                         case 'h':
 172                                 pt = _add((t->tm_mon < 0 ||
 173                                         t->tm_mon >= MONSPERYEAR) ?
 174                                         "?" : tptr->mon[t->tm_mon],
 175                                         pt, ptlim);
 176                                 continue;
 177                         case 'C':
 178                                 /*
 179                                 ** %C used to do a...
 180                                 **      _fmt("%a %b %e %X %Y", t);
 181                                 ** ...whereas now POSIX 1003.2 calls for
 182                                 ** something completely different.
 183                                 ** (ado, 1993-05-24)
 184                                 */
 185                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
 186                                         pt, ptlim);
 187                                 continue;
 188                         case 'c':
 189                                 {
 190                                 int warn2 = IN_SOME;
 191
 192                                 pt = _fmt(tptr->c_fmt, t, pt, ptlim, &warn2, loc);
 193                                 if (warn2 == IN_ALL)
 194                                         warn2 = IN_THIS;
 195                                 if (warn2 > *warnp)
 196                                         *warnp = warn2;
 197                                 }
 198                                 continue;
 199                         case 'D':
 200                                 pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp, loc);
 201                                 continue;
 202                         case 'd':
 203                                 pt = _conv(t->tm_mday, fmt_padding[PAD_FMT_DAYOFMONTH][PadIndex],
 204                                         pt, ptlim);
 205                                 continue;
 206                         case 'E':
 207                                 if (Ealternative || Oalternative)
 208                                         break;
 209                                 Ealternative++;
 210                                 goto label;
 211                         case 'O':
 212                                 /*
 213                                 ** C99 locale modifiers.
 214                                 ** The sequences
 215                                 **      %Ec %EC %Ex %EX %Ey %EY
 216                                 **      %Od %oe %OH %OI %Om %OM
 217                                 **      %OS %Ou %OU %OV %Ow %OW %Oy
 218                                 ** are supposed to provide alternate
 219                                 ** representations.
 220                                 **
 221                                 ** FreeBSD extension
 222                                 **      %OB
 223                                 */
 224                                 if (Ealternative || Oalternative)
 225                                         break;
 226                                 Oalternative++;
 227                                 goto label;
 228                         case 'e':
 229                                 pt = _conv(t->tm_mday,
 230                                         fmt_padding[PAD_FMT_SDAYOFMONTH][PadIndex], pt, ptlim);
 231                                 continue;
 232                         case 'F':
 233                                 pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp, loc);
 234                                 continue;
 235                         case 'H':
 236                                 pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_HMS][PadIndex],
 237                                         pt, ptlim);
 238                                 continue;
 239                         case 'I':
 240                                 pt = _conv((t->tm_hour % 12) ?
 241                                         (t->tm_hour % 12) : 12,
 242                                         fmt_padding[PAD_FMT_HMS][PadIndex], pt, ptlim);
 243                                 continue;
 244                         case 'j':
 245                                 pt = _conv(t->tm_yday + 1,
 246                                         fmt_padding[PAD_FMT_DAYOFYEAR][PadIndex], pt, ptlim);
 247                                 continue;
 248                         case 'k':
 249                                 /*
 250                                 ** This used to be...
 251                                 **      _conv(t->tm_hour % 12 ?
 252                                 **              t->tm_hour % 12 : 12, 2, ' ');
 253                                 ** ...and has been changed to the below to
 254                                 ** match SunOS 4.1.1 and Arnold Robbins'
 255                                 ** strftime version 3.0. That is, "%k" and
 256                                 ** "%l" have been swapped.
 257                                 ** (ado, 1993-05-24)
 258                                 */
 259                                 pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_SHMS][PadIndex],
 260                                         pt, ptlim);
 261                                 continue;
 262 #ifdef KITCHEN_SINK
 263                         case 'K':
 264                                 /*
 265                                 ** After all this time, still unclaimed!
 266                                 */
 267                                 pt = _add("kitchen sink", pt, ptlim);
 268                                 continue;
 269 #endif /* defined KITCHEN_SINK */
 270                         case 'l':
 271                                 /*
 272                                 ** This used to be...
 273                                 **      _conv(t->tm_hour, 2, ' ');
 274                                 ** ...and has been changed to the below to
 275                                 ** match SunOS 4.1.1 and Arnold Robbin's
 276                                 ** strftime version 3.0. That is, "%k" and
 277                                 ** "%l" have been swapped.
 278                                 ** (ado, 1993-05-24)
 279                                 */
 280                                 pt = _conv((t->tm_hour % 12) ?
 281                                         (t->tm_hour % 12) : 12,
 282                                         fmt_padding[PAD_FMT_SHMS][PadIndex], pt, ptlim);
 283                                 continue;
 284                         case 'M':
 285                                 pt = _conv(t->tm_min, fmt_padding[PAD_FMT_HMS][PadIndex],
 286                                         pt, ptlim);
 287                                 continue;
 288                         case 'm':
 289                                 pt = _conv(t->tm_mon + 1,
 290                                         fmt_padding[PAD_FMT_MONTH][PadIndex], pt, ptlim);
 291                                 continue;
 292                         case 'n':
 293                                 pt = _add("\n", pt, ptlim);
 294                                 continue;
 295                         case 'p':
 296                                 pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
 297                                         tptr->pm :
 298                                         tptr->am,
 299                                         pt, ptlim);
 300                                 continue;
 301                         case 'R':
 302                                 pt = _fmt("%H:%M", t, pt, ptlim, warnp, loc);
 303                                 continue;
 304                         case 'r':
 305                                 pt = _fmt(tptr->ampm_fmt, t, pt, ptlim,
 306                                         warnp, loc);
 307                                 continue;
 308                         case 'S':
 309                                 pt = _conv(t->tm_sec, fmt_padding[PAD_FMT_HMS][PadIndex],
 310                                         pt, ptlim);
 311                                 continue;
 312                         case 's':
 313                                 {
 314                                         struct tm       tm;
 315                                         char            buf[INT_STRLEN_MAXIMUM(
 316                                                                 time_t) + 1];
 317                                         time_t          mkt;
 318
 319                                         tm = *t;
 320                                         mkt = mktime(&tm);
 321                                         if (TYPE_SIGNED(time_t))
 322                                                 (void) sprintf(buf, "%ld",
 323                                                         (long) mkt);
 324                                         else    (void) sprintf(buf, "%lu",
 325                                                         (unsigned long) mkt);
 326                                         pt = _add(buf, pt, ptlim);
 327                                 }
 328                                 continue;
 329                         case 'T':
 330                                 pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp, loc);
 331                                 continue;
 332                         case 't':
 333                                 pt = _add("\t", pt, ptlim);
 334                                 continue;
 335                         case 'U':
 336                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 337                                         t->tm_wday) / DAYSPERWEEK,
 338                                         fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex], pt, ptlim);
 339                                 continue;
 340                         case 'u':
 341                                 /*
 342                                 ** From Arnold Robbins' strftime version 3.0:
 343                                 ** "ISO 8601: Weekday as a decimal number
 344                                 ** [1 (Monday) - 7]"
 345                                 ** (ado, 1993-05-24)
 346                                 */
 347                                 pt = _conv((t->tm_wday == 0) ?
 348                                         DAYSPERWEEK : t->tm_wday,
 349                                         "%d", pt, ptlim);
 350                                 continue;
 351                         case 'V':       /* ISO 8601 week number */
 352                         case 'G':       /* ISO 8601 year (four digits) */
 353                         case 'g':       /* ISO 8601 year (two digits) */
 354 /*
 355 ** From Arnold Robbins' strftime version 3.0: "the week number of the
 356 ** year (the first Monday as the first day of week 1) as a decimal number
 357 ** (01-53)."
 358 ** (ado, 1993-05-24)
 359 **
 360 ** From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
 361 ** "Week 01 of a year is per definition the first week which has the
 362 ** Thursday in this year, which is equivalent to the week which contains
 363 ** the fourth day of January. In other words, the first week of a new year
 364 ** is the week which has the majority of its days in the new year. Week 01
 365 ** might also contain days from the previous year and the week before week
 366 ** 01 of a year is the last week (52 or 53) of the previous year even if
 367 ** it contains days from the new year. A week starts with Monday (day 1)
 368 ** and ends with Sunday (day 7). For example, the first week of the year
 369 ** 1997 lasts from 1996-12-30 to 1997-01-05..."
 370 ** (ado, 1996-01-02)
 371 */
 372                                 {
 373                                         int     year;
 374                                         int     base;
 375                                         int     yday;
 376                                         int     wday;
 377                                         int     w;
 378
 379                                         year = t->tm_year;
 380                                         base = TM_YEAR_BASE;
 381                                         yday = t->tm_yday;
 382                                         wday = t->tm_wday;
 383                                         for ( ; ; ) {
 384                                                 int     len;
 385                                                 int     bot;
 386                                                 int     top;
 387
 388                                                 len = isleap_sum(year, base) ?
 389                                                         DAYSPERLYEAR :
 390                                                         DAYSPERNYEAR;
 391                                                 /*
 392                                                 ** What yday (-3 ... 3) does
 393                                                 ** the ISO year begin on?
 394                                                 */
 395                                                 bot = ((yday + 11 - wday) %
 396                                                         DAYSPERWEEK) - 3;
 397                                                 /*
 398                                                 ** What yday does the NEXT
 399                                                 ** ISO year begin on?
 400                                                 */
 401                                                 top = bot -
 402                                                         (len % DAYSPERWEEK);
 403                                                 if (top < -3)
 404                                                         top += DAYSPERWEEK;
 405                                                 top += len;
 406                                                 if (yday >= top) {
 407                                                         ++base;
 408                                                         w = 1;
 409                                                         break;
 410                                                 }
 411                                                 if (yday >= bot) {
 412                                                         w = 1 + ((yday - bot) /
 413                                                                 DAYSPERWEEK);
 414                                                         break;
 415                                                 }
 416                                                 --base;
 417                                                 yday += isleap_sum(year, base) ?
 418                                                         DAYSPERLYEAR :
 419                                                         DAYSPERNYEAR;
 420                                         }
 421 #ifdef XPG4_1994_04_09
 422                                         if ((w == 52 &&
 423                                                 t->tm_mon == TM_JANUARY) ||
 424                                                 (w == 1 &&
 425                                                 t->tm_mon == TM_DECEMBER))
 426                                                         w = 53;
 427 #endif /* defined XPG4_1994_04_09 */
 428                                         if (*format == 'V')
 429                                                 pt = _conv(w, fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
 430                                                         pt, ptlim);
 431                                         else if (*format == 'g') {
 432                                                 *warnp = IN_ALL;
 433                                                 pt = _yconv(year, base, 0, 1,
 434                                                         pt, ptlim);
 435                                         } else  pt = _yconv(year, base, 1, 1,
 436                                                         pt, ptlim);
 437                                 }
 438                                 continue;
 439                         case 'v':
 440                                 /*
 441                                 ** From Arnold Robbins' strftime version 3.0:
 442                                 ** "date as dd-bbb-YYYY"
 443                                 ** (ado, 1993-05-24)
 444                                 */
 445                                 pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp, loc);
 446                                 continue;
 447                         case 'W':
 448                                 pt = _conv((t->tm_yday + DAYSPERWEEK -
 449                                         (t->tm_wday ?
 450                                         (t->tm_wday - 1) :
 451                                         (DAYSPERWEEK - 1))) / DAYSPERWEEK,
 452                                         fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex], pt, ptlim);
 453                                 continue;
 454                         case 'w':
 455                                 pt = _conv(t->tm_wday, "%d", pt, ptlim);
 456                                 continue;
 457                         case 'X':
 458                                 pt = _fmt(tptr->X_fmt, t, pt, ptlim, warnp, loc);
 459                                 continue;
 460                         case 'x':
 461                                 {
 462                                 int     warn2 = IN_SOME;
 463
 464                                 pt = _fmt(tptr->x_fmt, t, pt, ptlim, &warn2, loc);
 465                                 if (warn2 == IN_ALL)
 466                                         warn2 = IN_THIS;
 467                                 if (warn2 > *warnp)
 468                                         *warnp = warn2;
 469                                 }
 470                                 continue;
 471                         case 'y':
 472                                 *warnp = IN_ALL;
 473                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
 474                                         pt, ptlim);
 475                                 continue;
 476                         case 'Y':
 477                                 pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
 478                                         pt, ptlim);
 479                                 continue;
 480                         case 'Z':
 481 #ifdef TM_ZONE
 482                                 if (t->TM_ZONE != NULL)
 483                                         pt = _add(t->TM_ZONE, pt, ptlim);
 484                                 else
 485 #endif /* defined TM_ZONE */
 486                                 if (t->tm_isdst >= 0)
 487                                         pt = _add(tzname[t->tm_isdst != 0],
 488                                                 pt, ptlim);
 489                                 /*
 490                                 ** C99 says that %Z must be replaced by the
 491                                 ** empty string if the time zone is not
 492                                 ** determinable.
 493                                 */
 494                                 continue;
 495                         case 'z':
 496                                 {
 497                                 int             diff;
 498                                 char const *    sign;
 499
 500                                 if (t->tm_isdst < 0)
 501                                         continue;
 502 #ifdef TM_GMTOFF
 503                                 diff = t->TM_GMTOFF;
 504 #else /* !defined TM_GMTOFF */
 505                                 /*
 506                                 ** C99 says that the UTC offset must
 507                                 ** be computed by looking only at
 508                                 ** tm_isdst. This requirement is
 509                                 ** incorrect, since it means the code
 510                                 ** must rely on magic (in this case
 511                                 ** altzone and timezone), and the
 512                                 ** magic might not have the correct
 513                                 ** offset. Doing things correctly is
 514                                 ** tricky and requires disobeying C99;
 515                                 ** see GNU C strftime for details.
 516                                 ** For now, punt and conform to the
 517                                 ** standard, even though it's incorrect.
 518                                 **
 519                                 ** C99 says that %z must be replaced by the
 520                                 ** empty string if the time zone is not
 521                                 ** determinable, so output nothing if the
 522                                 ** appropriate variables are not available.
 523                                 */
 524                                 if (t->tm_isdst == 0)
 525 #ifdef USG_COMPAT
 526                                         diff = -timezone;
 527 #else /* !defined USG_COMPAT */
 528                                         continue;
 529 #endif /* !defined USG_COMPAT */
 530                                 else
 531 #ifdef ALTZONE
 532                                         diff = -altzone;
 533 #else /* !defined ALTZONE */
 534                                         continue;
 535 #endif /* !defined ALTZONE */
 536 #endif /* !defined TM_GMTOFF */
 537                                 if (diff < 0) {
 538                                         sign = "-";
 539                                         diff = -diff;
 540                                 } else  sign = "+";
 541                                 pt = _add(sign, pt, ptlim);
 542                                 diff /= SECSPERMIN;
 543                                 diff = (diff / MINSPERHOUR) * 100 +
 544                                         (diff % MINSPERHOUR);
 545                                 pt = _conv(diff,
 546                                         fmt_padding[PAD_FMT_YEAR][PadIndex], pt, ptlim);
 547                                 }
 548                                 continue;
 549                         case '+':
 550                                 pt = _fmt(tptr->date_fmt, t, pt, ptlim,
 551                                         warnp, loc);
 552                                 continue;
 553                         case '-':
 554                                 if (PadIndex != PAD_DEFAULT)
 555                                         break;
 556                                 PadIndex = PAD_LESS;
 557                                 goto label;
 558                         case '_':
 559                                 if (PadIndex != PAD_DEFAULT)
 560                                         break;
 561                                 PadIndex = PAD_SPACE;
 562                                 goto label;
 563                         case '0':
 564                                 if (PadIndex != PAD_DEFAULT)
 565                                         break;
 566                                 PadIndex = PAD_ZERO;
 567                                 goto label;
 568                         case '%':
 569                         /*
 570                         ** X311J/88-090 (4.12.3.5): if conversion char is
 571                         ** undefined, behavior is undefined. Print out the
 572                         ** character itself as printf(3) also does.
 573                         */
 574                         default:
 575                                 break;
 576                         }
 577                 }
 578                 if (pt == ptlim)
 579                         break;
 580                 *pt++ = *format;
 581         }
 582         return pt;
 583 }
 584
 585 static char *
 586 _conv(n, format, pt, ptlim)
 587 const int               n;
 588 const char * const      format;
 589 char * const            pt;
 590 const char * const      ptlim;
 591 {
 592         char    buf[INT_STRLEN_MAXIMUM(int) + 1];
 593
 594         (void) sprintf(buf, format, n);
 595         return _add(buf, pt, ptlim);
 596 }
 597
 598 static char *
 599 _add(str, pt, ptlim)
 600 const char *            str;
 601 char *                  pt;
 602 const char * const      ptlim;
 603 {
 604         while (pt < ptlim && (*pt = *str++) != '\0')
 605                 ++pt;
 606         return pt;
 607 }
 608
 609 /*
 610 ** POSIX and the C Standard are unclear or inconsistent about
 611 ** what %C and %y do if the year is negative or exceeds 9999.
 612 ** Use the convention that %C concatenated with %y yields the
 613 ** same output as %Y, and that %Y contains at least 4 bytes,
 614 ** with more only if necessary.
 615 */
 616
 617 static char *
 618 _yconv(a, b, convert_top, convert_yy, pt, ptlim)
 619 const int               a;
 620 const int               b;
 621 const int               convert_top;
 622 const int               convert_yy;
 623 char *                  pt;
 624 const char * const      ptlim;
 625 {
 626         register int    lead;
 627         register int    trail;
 628
 629 #define DIVISOR 100
 630         trail = a % DIVISOR + b % DIVISOR;
 631         lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
 632         trail %= DIVISOR;
 633         if (trail < 0 && lead > 0) {
 634                 trail += DIVISOR;
 635                 --lead;
 636         } else if (lead < 0 && trail > 0) {
 637                 trail -= DIVISOR;
 638                 ++lead;
 639         }
 640         if (convert_top) {
 641                 if (lead == 0 && trail < 0)
 642                         pt = _add("-0", pt, ptlim);
 643                 else    pt = _conv(lead, "%02d", pt, ptlim);
 644         }
 645         if (convert_yy)
 646                 pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
 647         return pt;
 648 }