xref: /netbsd-src/lib/libc/time/strftime.c (revision da39824b722dbd84beb9a1ab7e8de6710cc44d4b)
1 /*	$NetBSD: strftime.c,v 1.30 2013/12/26 18:34:28 christos 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 1.30 2013/12/26 18:34:28 christos Exp $");
10 #endif
11 #endif /* LIBC_SCCS and not lint */
12 
13 #include "namespace.h"
14 
15 #include <stddef.h>
16 #include <assert.h>
17 #include <locale.h>
18 #include "setlocale_local.h"
19 
20 /*
21 ** Based on the UCB version with the copyright notice and sccsid
22 ** appearing below.
23 **
24 ** This is ANSIish only when "multibyte character == plain character".
25 */
26 
27 #include "private.h"
28 
29 /*
30 ** We don't use these extensions in strftime operation even when
31 ** supported by the local tzcode configuration.  A strictly
32 ** conforming C application may leave them in undefined state.
33 */
34 
35 #ifdef _LIBC
36 #undef TM_ZONE
37 #undef TM_GMTOFF
38 #endif
39 
40 /*
41 ** Copyright (c) 1989, 1993
42 **	The Regents of the University of California.  All rights reserved.
43 **
44 ** Redistribution and use in source and binary forms, with or without
45 ** modification, are permitted provided that the following conditions
46 ** are met:
47 ** 1. Redistributions of source code must retain the above copyright
48 **    notice, this list of conditions and the following disclaimer.
49 ** 2. Redistributions in binary form must reproduce the above copyright
50 **    notice, this list of conditions and the following disclaimer in the
51 **    documentation and/or other materials provided with the distribution.
52 ** 3. All advertising materials mentioning features or use of this software
53 **    must display the following acknowledgement:
54 **	This product includes software developed by the University of
55 **	California, Berkeley and its contributors.
56 ** 4. Neither the name of the University nor the names of its contributors
57 **    may be used to endorse or promote products derived from this software
58 **    without specific prior written permission.
59 **
60 ** THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
61 ** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
62 ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
63 ** ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
64 ** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
65 ** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
66 ** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
67 ** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
68 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
69 ** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
70 ** SUCH DAMAGE.
71 */
72 
73 #ifndef LIBC_SCCS
74 #ifndef lint
75 static const char	sccsid[] = "@(#)strftime.c	5.4 (Berkeley) 3/14/89";
76 #endif /* !defined lint */
77 #endif /* !defined LIBC_SCCS */
78 
79 #include "tzfile.h"
80 #include "fcntl.h"
81 #include "locale.h"
82 
83 #ifdef __weak_alias
84 __weak_alias(strftime_l, _strftime_l)
85 __weak_alias(strftime_lz, _strftime_lz)
86 __weak_alias(strftime_z, _strftime_z)
87 #endif
88 
89 #include "sys/localedef.h"
90 #define _TIME_LOCALE(loc) \
91     ((_TimeLocale *)((loc)->part_impl[(size_t)LC_TIME]))
92 #define c_fmt   d_t_fmt
93 
94 static char *	_add(const char *, char *, const char *);
95 static char *	_conv(int, const char *, char *, const char *);
96 static char *	_fmt(const timezone_t, const char *, const struct tm *, char *,
97 			const char *, int *, locale_t);
98 static char *	_yconv(int, int, int, int, char *, const char *);
99 
100 extern char *	tzname[];
101 
102 #ifndef YEAR_2000_NAME
103 #define YEAR_2000_NAME	"CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
104 #endif /* !defined YEAR_2000_NAME */
105 
106 #define IN_NONE	0
107 #define IN_SOME	1
108 #define IN_THIS	2
109 #define IN_ALL	3
110 
111 size_t
112 strftime_z(const timezone_t sp, char * __restrict s, size_t maxsize,
113     const char * __restrict format, const struct tm * __restrict t)
114 {
115 	return strftime_lz(sp, s, maxsize, format, t, _current_locale());
116 }
117 
118 size_t
119 strftime_lz(const timezone_t sp, char *const s, const size_t maxsize,
120     const char *const format, const struct tm *const t, locale_t loc)
121 {
122 	char *	p;
123 	int	warn;
124 
125 	warn = IN_NONE;
126 	p = _fmt(sp, ((format == NULL) ? "%c" : format), t, s, s + maxsize,
127 	    &warn, loc);
128 #ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
129 	if (warn != IN_NONE && getenv(YEAR_2000_NAME) != NULL) {
130 		(void) fprintf(stderr, "\n");
131 		if (format == NULL)
132 			(void) fprintf(stderr, "NULL strftime format ");
133 		else	(void) fprintf(stderr, "strftime format \"%s\" ",
134 				format);
135 		(void) fprintf(stderr, "yields only two digits of years in ");
136 		if (warn == IN_SOME)
137 			(void) fprintf(stderr, "some locales");
138 		else if (warn == IN_THIS)
139 			(void) fprintf(stderr, "the current locale");
140 		else	(void) fprintf(stderr, "all locales");
141 		(void) fprintf(stderr, "\n");
142 	}
143 #endif /* !defined NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU */
144 	if (p == s + maxsize)
145 		return 0;
146 	*p = '\0';
147 	return p - s;
148 }
149 
150 static char *
151 _fmt(const timezone_t sp, const char *format, const struct tm *const t,
152 	char *pt, const char *const ptlim, int *warnp, locale_t loc)
153 {
154 	for ( ; *format; ++format) {
155 		if (*format == '%') {
156 label:
157 			switch (*++format) {
158 			case '\0':
159 				--format;
160 				break;
161 			case 'A':
162 				pt = _add((t->tm_wday < 0 ||
163 					t->tm_wday >= DAYSPERWEEK) ?
164 					"?" : _TIME_LOCALE(loc)->day[t->tm_wday],
165 					pt, ptlim);
166 				continue;
167 			case 'a':
168 				pt = _add((t->tm_wday < 0 ||
169 					t->tm_wday >= DAYSPERWEEK) ?
170 					"?" : _TIME_LOCALE(loc)->abday[t->tm_wday],
171 					pt, ptlim);
172 				continue;
173 			case 'B':
174 				pt = _add((t->tm_mon < 0 ||
175 					t->tm_mon >= MONSPERYEAR) ?
176 					"?" : _TIME_LOCALE(loc)->mon[t->tm_mon],
177 					pt, ptlim);
178 				continue;
179 			case 'b':
180 			case 'h':
181 				pt = _add((t->tm_mon < 0 ||
182 					t->tm_mon >= MONSPERYEAR) ?
183 					"?" : _TIME_LOCALE(loc)->abmon[t->tm_mon],
184 					pt, ptlim);
185 				continue;
186 			case 'C':
187 				/*
188 				** %C used to do a...
189 				**	_fmt("%a %b %e %X %Y", t);
190 				** ...whereas now POSIX 1003.2 calls for
191 				** something completely different.
192 				** (ado, 1993-05-24)
193 				*/
194 				pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
195 					pt, ptlim);
196 				continue;
197 			case 'c':
198 				{
199 				int warn2 = IN_SOME;
200 
201 				pt = _fmt(sp, _TIME_LOCALE(loc)->c_fmt, t, pt,
202 				    ptlim, &warn2, loc);
203 				if (warn2 == IN_ALL)
204 					warn2 = IN_THIS;
205 				if (warn2 > *warnp)
206 					*warnp = warn2;
207 				}
208 				continue;
209 			case 'D':
210 				pt = _fmt(sp, "%m/%d/%y", t, pt, ptlim, warnp,
211 				    loc);
212 				continue;
213 			case 'd':
214 				pt = _conv(t->tm_mday, "%02d", pt, ptlim);
215 				continue;
216 			case 'E':
217 			case 'O':
218 				/*
219 				** C99 locale modifiers.
220 				** The sequences
221 				**	%Ec %EC %Ex %EX %Ey %EY
222 				**	%Od %oe %OH %OI %Om %OM
223 				**	%OS %Ou %OU %OV %Ow %OW %Oy
224 				** are supposed to provide alternate
225 				** representations.
226 				*/
227 				goto label;
228 			case 'e':
229 				pt = _conv(t->tm_mday, "%2d", pt, ptlim);
230 				continue;
231 			case 'F':
232 				pt = _fmt(sp, "%Y-%m-%d", t, pt, ptlim, warnp,
233 				    loc);
234 				continue;
235 			case 'H':
236 				pt = _conv(t->tm_hour, "%02d", pt, ptlim);
237 				continue;
238 			case 'I':
239 				pt = _conv((t->tm_hour % 12) ?
240 					(t->tm_hour % 12) : 12,
241 					"%02d", pt, ptlim);
242 				continue;
243 			case 'j':
244 				pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);
245 				continue;
246 			case 'k':
247 				/*
248 				** This used to be...
249 				**	_conv(t->tm_hour % 12 ?
250 				**		t->tm_hour % 12 : 12, 2, ' ');
251 				** ...and has been changed to the below to
252 				** match SunOS 4.1.1 and Arnold Robbins'
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, "%2d", pt, ptlim);
258 				continue;
259 #ifdef KITCHEN_SINK
260 			case 'K':
261 				/*
262 				** After all this time, still unclaimed!
263 				*/
264 				pt = _add("kitchen sink", pt, ptlim);
265 				continue;
266 #endif /* defined KITCHEN_SINK */
267 			case 'l':
268 				/*
269 				** This used to be...
270 				**	_conv(t->tm_hour, 2, ' ');
271 				** ...and has been changed to the below to
272 				** match SunOS 4.1.1 and Arnold Robbin's
273 				** strftime version 3.0. That is, "%k" and
274 				** "%l" have been swapped.
275 				** (ado, 1993-05-24)
276 				*/
277 				pt = _conv((t->tm_hour % 12) ?
278 					(t->tm_hour % 12) : 12,
279 					"%2d", pt, ptlim);
280 				continue;
281 			case 'M':
282 				pt = _conv(t->tm_min, "%02d", pt, ptlim);
283 				continue;
284 			case 'm':
285 				pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);
286 				continue;
287 			case 'n':
288 				pt = _add("\n", pt, ptlim);
289 				continue;
290 			case 'p':
291 				pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
292 					_TIME_LOCALE(loc)->am_pm[1] :
293 					_TIME_LOCALE(loc)->am_pm[0],
294 					pt, ptlim);
295 				continue;
296 			case 'R':
297 				pt = _fmt(sp, "%H:%M", t, pt, ptlim, warnp,
298 				    loc);
299 				continue;
300 			case 'r':
301 				pt = _fmt(sp, _TIME_LOCALE(loc)->t_fmt_ampm, t,
302 				    pt, ptlim, warnp, loc);
303 				continue;
304 			case 'S':
305 				pt = _conv(t->tm_sec, "%02d", pt, ptlim);
306 				continue;
307 			case 's':
308 				{
309 					struct tm	tm;
310 					char		buf[INT_STRLEN_MAXIMUM(
311 								time_t) + 1];
312 					time_t		mkt;
313 
314 					tm = *t;
315 					mkt = mktime(&tm);
316 					/* CONSTCOND */
317 					if (TYPE_SIGNED(time_t))
318 						(void)snprintf(buf, sizeof(buf),
319 						    "%jd", (intmax_t) mkt);
320 					else	(void)snprintf(buf, sizeof(buf),
321 						    "%ju", (uintmax_t) mkt);
322 					pt = _add(buf, pt, ptlim);
323 				}
324 				continue;
325 			case 'T':
326 				pt = _fmt(sp, "%H:%M:%S", t, pt, ptlim, warnp,
327 				    loc);
328 				continue;
329 			case 't':
330 				pt = _add("\t", pt, ptlim);
331 				continue;
332 			case 'U':
333 				pt = _conv((t->tm_yday + DAYSPERWEEK -
334 					t->tm_wday) / DAYSPERWEEK,
335 					"%02d", pt, ptlim);
336 				continue;
337 			case 'u':
338 				/*
339 				** From Arnold Robbins' strftime version 3.0:
340 				** "ISO 8601: Weekday as a decimal number
341 				** [1 (Monday) - 7]"
342 				** (ado, 1993-05-24)
343 				*/
344 				pt = _conv((t->tm_wday == 0) ?
345 					DAYSPERWEEK : t->tm_wday,
346 					"%d", pt, ptlim);
347 				continue;
348 			case 'V':	/* ISO 8601 week number */
349 			case 'G':	/* ISO 8601 year (four digits) */
350 			case 'g':	/* ISO 8601 year (two digits) */
351 /*
352 ** From Arnold Robbins' strftime version 3.0: "the week number of the
353 ** year (the first Monday as the first day of week 1) as a decimal number
354 ** (01-53)."
355 ** (ado, 1993-05-24)
356 **
357 ** From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
358 ** "Week 01 of a year is per definition the first week which has the
359 ** Thursday in this year, which is equivalent to the week which contains
360 ** the fourth day of January. In other words, the first week of a new year
361 ** is the week which has the majority of its days in the new year. Week 01
362 ** might also contain days from the previous year and the week before week
363 ** 01 of a year is the last week (52 or 53) of the previous year even if
364 ** it contains days from the new year. A week starts with Monday (day 1)
365 ** and ends with Sunday (day 7). For example, the first week of the year
366 ** 1997 lasts from 1996-12-30 to 1997-01-05..."
367 ** (ado, 1996-01-02)
368 */
369 				{
370 					int	year;
371 					int	base;
372 					int	yday;
373 					int	wday;
374 					int	w;
375 
376 					year = t->tm_year;
377 					base = TM_YEAR_BASE;
378 					yday = t->tm_yday;
379 					wday = t->tm_wday;
380 					for ( ; ; ) {
381 						int	len;
382 						int	bot;
383 						int	top;
384 
385 						len = isleap_sum(year, base) ?
386 							DAYSPERLYEAR :
387 							DAYSPERNYEAR;
388 						/*
389 						** What yday (-3 ... 3) does
390 						** the ISO year begin on?
391 						*/
392 						bot = ((yday + 11 - wday) %
393 							DAYSPERWEEK) - 3;
394 						/*
395 						** What yday does the NEXT
396 						** ISO year begin on?
397 						*/
398 						top = bot -
399 							(len % DAYSPERWEEK);
400 						if (top < -3)
401 							top += DAYSPERWEEK;
402 						top += len;
403 						if (yday >= top) {
404 							++base;
405 							w = 1;
406 							break;
407 						}
408 						if (yday >= bot) {
409 							w = 1 + ((yday - bot) /
410 								DAYSPERWEEK);
411 							break;
412 						}
413 						--base;
414 						yday += isleap_sum(year, base) ?
415 							DAYSPERLYEAR :
416 							DAYSPERNYEAR;
417 					}
418 #ifdef XPG4_1994_04_09
419 					if ((w == 52 &&
420 						t->tm_mon == TM_JANUARY) ||
421 						(w == 1 &&
422 						t->tm_mon == TM_DECEMBER))
423 							w = 53;
424 #endif /* defined XPG4_1994_04_09 */
425 					if (*format == 'V')
426 						pt = _conv(w, "%02d",
427 							pt, ptlim);
428 					else if (*format == 'g') {
429 						*warnp = IN_ALL;
430 						pt = _yconv(year, base, 0, 1,
431 							pt, ptlim);
432 					} else	pt = _yconv(year, base, 1, 1,
433 							pt, ptlim);
434 				}
435 				continue;
436 			case 'v':
437 				/*
438 				** From Arnold Robbins' strftime version 3.0:
439 				** "date as dd-bbb-YYYY"
440 				** (ado, 1993-05-24)
441 				*/
442 				pt = _fmt(sp, "%e-%b-%Y", t, pt, ptlim, warnp,
443 				    loc);
444 				continue;
445 			case 'W':
446 				pt = _conv((t->tm_yday + DAYSPERWEEK -
447 					(t->tm_wday ?
448 					(t->tm_wday - 1) :
449 					(DAYSPERWEEK - 1))) / DAYSPERWEEK,
450 					"%02d", pt, ptlim);
451 				continue;
452 			case 'w':
453 				pt = _conv(t->tm_wday, "%d", pt, ptlim);
454 				continue;
455 			case 'X':
456 				pt = _fmt(sp, _TIME_LOCALE(loc)->t_fmt, t, pt,
457 				    ptlim, warnp, loc);
458 				continue;
459 			case 'x':
460 				{
461 				int	warn2 = IN_SOME;
462 
463 				pt = _fmt(sp, _TIME_LOCALE(loc)->d_fmt, t, pt,
464 				    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((sp ?
488 					    tzgetname(sp, t->tm_isdst) :
489 					    tzname[t->tm_isdst != 0]),
490 					    pt, ptlim);
491 				/*
492 				** C99 says that %Z must be replaced by the
493 				** empty string if the time zone is not
494 				** determinable.
495 				*/
496 				continue;
497 			case 'z':
498 				{
499 				long		diff;
500 				char const *	sign;
501 
502 				if (t->tm_isdst < 0)
503 					continue;
504 #ifdef TM_GMTOFF
505 				diff = (int)t->TM_GMTOFF;
506 #else /* !defined TM_GMTOFF */
507 				/*
508 				** C99 says that the UT offset must
509 				** be computed by looking only at
510 				** tm_isdst. This requirement is
511 				** incorrect, since it means the code
512 				** must rely on magic (in this case
513 				** altzone and timezone), and the
514 				** magic might not have the correct
515 				** offset. Doing things correctly is
516 				** tricky and requires disobeying C99;
517 				** see GNU C strftime for details.
518 				** For now, punt and conform to the
519 				** standard, even though it's incorrect.
520 				**
521 				** C99 says that %z must be replaced by the
522 				** empty string if the time zone is not
523 				** determinable, so output nothing if the
524 				** appropriate variables are not available.
525 				*/
526 #ifndef STD_INSPIRED
527 				if (t->tm_isdst == 0)
528 #ifdef USG_COMPAT
529 					diff = -timezone;
530 #else /* !defined USG_COMPAT */
531 					continue;
532 #endif /* !defined USG_COMPAT */
533 				else
534 #ifdef ALTZONE
535 					diff = -altzone;
536 #else /* !defined ALTZONE */
537 					continue;
538 #endif /* !defined ALTZONE */
539 #else /* defined STD_INSPIRED */
540 				{
541 					struct tm tmp;
542 					time_t lct, gct;
543 
544 					/*
545 					** Get calendar time from t
546 					** being treated as local.
547 					*/
548 					tmp = *t; /* mktime discards const */
549 					lct = mktime(&tmp);
550 
551 					if (lct == (time_t)-1)
552 						continue;
553 
554 					/*
555 					** Get calendar time from t
556 					** being treated as GMT.
557 					**/
558 					tmp = *t; /* mktime discards const */
559 					gct = timegm(&tmp);
560 
561 					if (gct == (time_t)-1)
562 						continue;
563 
564 					/* LINTED difference will fit int */
565 					diff = (intmax_t)gct - (intmax_t)lct;
566 				}
567 #endif /* defined STD_INSPIRED */
568 #endif /* !defined TM_GMTOFF */
569 				if (diff < 0) {
570 					sign = "-";
571 					diff = -diff;
572 				} else	sign = "+";
573 				pt = _add(sign, pt, ptlim);
574 				diff /= SECSPERMIN;
575 				diff = (diff / MINSPERHOUR) * 100 +
576 					(diff % MINSPERHOUR);
577 				_DIAGASSERT(__type_fit(int, diff));
578 				pt = _conv((int)diff, "%04d", pt, ptlim);
579 				}
580 				continue;
581 #if 0
582 			case '+':
583 				pt = _fmt(sp, _TIME_LOCALE(loc)->date_fmt, t,
584 				    pt, ptlim, warnp, loc);
585 				continue;
586 #endif
587 			case '%':
588 			/*
589 			** X311J/88-090 (4.12.3.5): if conversion char is
590 			** undefined, behavior is undefined. Print out the
591 			** character itself as printf(3) also does.
592 			*/
593 			default:
594 				break;
595 			}
596 		}
597 		if (pt == ptlim)
598 			break;
599 		*pt++ = *format;
600 	}
601 	return pt;
602 }
603 
604 size_t
605 strftime(char * const s, const size_t maxsize,
606     const char * const format, const struct tm * const	t)
607 {
608 	tzset();
609 	return strftime_z(NULL, s, maxsize, format, t);
610 }
611 
612 size_t
613 strftime_l(char * __restrict s, size_t maxsize, const char * __restrict format,
614     const struct tm * __restrict t, locale_t loc)
615 {
616 	tzset();
617 	return strftime_lz(NULL, s, maxsize, format, t, loc);
618 }
619 
620 static char *
621 _conv(const int	n, const char *const format, char *const pt,
622     const char *const ptlim)
623 {
624 	char	buf[INT_STRLEN_MAXIMUM(int) + 1];
625 
626 	(void) snprintf(buf, sizeof(buf), format, n);
627 	return _add(buf, pt, ptlim);
628 }
629 
630 static char *
631 _add(const char *str, char *pt, const char *const ptlim)
632 {
633 	while (pt < ptlim && (*pt = *str++) != '\0')
634 		++pt;
635 	return pt;
636 }
637 
638 /*
639 ** POSIX and the C Standard are unclear or inconsistent about
640 ** what %C and %y do if the year is negative or exceeds 9999.
641 ** Use the convention that %C concatenated with %y yields the
642 ** same output as %Y, and that %Y contains at least 4 bytes,
643 ** with more only if necessary.
644 */
645 
646 static char *
647 _yconv(const int a, const int b, const int convert_top, const int convert_yy,
648     char *pt, const char *const ptlim)
649 {
650 	int	lead;
651 	int	trail;
652 
653 #define DIVISOR	100
654 	trail = a % DIVISOR + b % DIVISOR;
655 	lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
656 	trail %= DIVISOR;
657 	if (trail < 0 && lead > 0) {
658 		trail += DIVISOR;
659 		--lead;
660 	} else if (lead < 0 && trail > 0) {
661 		trail -= DIVISOR;
662 		++lead;
663 	}
664 	if (convert_top) {
665 		if (lead == 0 && trail < 0)
666 			pt = _add("-0", pt, ptlim);
667 		else	pt = _conv(lead, "%02d", pt, ptlim);
668 	}
669 	if (convert_yy)
670 		pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
671 	return pt;
672 }
673 
674 #ifdef LOCALE_HOME
675 static struct lc_time_T *
676 _loc(void)
677 {
678 	static const char	locale_home[] = LOCALE_HOME;
679 	static const char	lc_time[] = "LC_TIME";
680 	static char *		locale_buf;
681 
682 	int			fd;
683 	int			oldsun;	/* "...ain't got nothin' to do..." */
684 	char *			lbuf;
685 	char *			name;
686 	char *			p;
687 	const char **		ap;
688 	const char *		plim;
689 	char			filename[FILENAME_MAX];
690 	struct stat		st;
691 	size_t			namesize;
692 	size_t			bufsize;
693 
694 	/*
695 	** Use localebuf.mon[0] to signal whether locale is already set up.
696 	*/
697 	if (localebuf.mon[0])
698 		return &localebuf;
699 	name = setlocale(LC_TIME, NULL);
700 	if (name == NULL || *name == '\0')
701 		goto no_locale;
702 	/*
703 	** If the locale name is the same as our cache, use the cache.
704 	*/
705 	lbuf = locale_buf;
706 	if (lbuf != NULL && strcmp(name, lbuf) == 0) {
707 		p = lbuf;
708 		for (ap = (const char **) &localebuf;
709 			ap < (const char **) (&localebuf + 1);
710 				++ap)
711 					*ap = p += strlen(p) + 1;
712 		return &localebuf;
713 	}
714 	/*
715 	** Slurp the locale file into the cache.
716 	*/
717 	namesize = strlen(name) + 1;
718 	if (sizeof filename <
719 		((sizeof locale_home) + namesize + (sizeof lc_time)))
720 			goto no_locale;
721 	oldsun = 0;
722 	(void) sprintf(filename, "%s/%s/%s", locale_home, name, lc_time);
723 	fd = open(filename, O_RDONLY);
724 	if (fd < 0) {
725 		/*
726 		** Old Sun systems have a different naming and data convention.
727 		*/
728 		oldsun = 1;
729 		(void) sprintf(filename, "%s/%s/%s", locale_home,
730 			lc_time, name);
731 		fd = open(filename, O_RDONLY);
732 		if (fd < 0)
733 			goto no_locale;
734 	}
735 	if (fstat(fd, &st) != 0)
736 		goto bad_locale;
737 	if (st.st_size <= 0)
738 		goto bad_locale;
739 	bufsize = namesize + st.st_size;
740 	locale_buf = NULL;
741 	lbuf = (lbuf == NULL) ? malloc(bufsize) : realloc(lbuf, bufsize);
742 	if (lbuf == NULL)
743 		goto bad_locale;
744 	(void) strcpy(lbuf, name);
745 	p = lbuf + namesize;
746 	plim = p + st.st_size;
747 	if (read(fd, p, (size_t) st.st_size) != st.st_size)
748 		goto bad_lbuf;
749 	if (close(fd) != 0)
750 		goto bad_lbuf;
751 	/*
752 	** Parse the locale file into localebuf.
753 	*/
754 	if (plim[-1] != '\n')
755 		goto bad_lbuf;
756 	for (ap = (const char **) &localebuf;
757 		ap < (const char **) (&localebuf + 1);
758 			++ap) {
759 				if (p == plim)
760 					goto bad_lbuf;
761 				*ap = p;
762 				while (*p != '\n')
763 					++p;
764 				*p++ = '\0';
765 	}
766 	if (oldsun) {
767 		/*
768 		** SunOS 4 used an obsolescent format; see localdtconv(3).
769 		** c_fmt had the ``short format for dates and times together''
770 		** (SunOS 4 date, "%a %b %e %T %Z %Y" in the C locale);
771 		** date_fmt had the ``long format for dates''
772 		** (SunOS 4 strftime %C, "%A, %B %e, %Y" in the C locale).
773 		** Discard the latter in favor of the former.
774 		*/
775 		localebuf.date_fmt = localebuf.c_fmt;
776 	}
777 	/*
778 	** Record the successful parse in the cache.
779 	*/
780 	locale_buf = lbuf;
781 
782 	return &localebuf;
783 
784 bad_lbuf:
785 	free(lbuf);
786 bad_locale:
787 	(void) close(fd);
788 no_locale:
789 	localebuf = C_time_locale;
790 	locale_buf = NULL;
791 	return &localebuf;
792 }
793 #endif /* defined LOCALE_HOME */
794