xref: /freebsd/lib/libc/stdtime/strftime.c (revision cfd6422a5217410fbd66f7a7a8a64d9d85e61229)
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 *, locale_t);
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 *, locale_t);
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) fputs("NULL strftime format ", stderr);
105 		else	(void) fprintf_l(stderr, loc, "strftime format \"%s\" ",
106 				format);
107 		(void) fputs("yields only two digits of years in ", stderr);
108 		if (warn == IN_SOME)
109 			(void) fputs("some locales", stderr);
110 		else if (warn == IN_THIS)
111 			(void) fputs("the current locale", stderr);
112 		else	(void) fputs("all locales", stderr);
113 		(void) fputs("\n", stderr);
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(const char *format, const struct tm * const t, char *pt,
131     const char * const ptlim, int *warnp, locale_t loc)
132 {
133 	int Ealternative, Oalternative, PadIndex;
134 	struct lc_time_T *tptr = __get_current_time_locale(loc);
135 
136 	for ( ; *format; ++format) {
137 		if (*format == '%') {
138 			Ealternative = 0;
139 			Oalternative = 0;
140 			PadIndex	 = PAD_DEFAULT;
141 label:
142 			switch (*++format) {
143 			case '\0':
144 				--format;
145 				break;
146 			case 'A':
147 				pt = _add((t->tm_wday < 0 ||
148 					t->tm_wday >= DAYSPERWEEK) ?
149 					"?" : tptr->weekday[t->tm_wday],
150 					pt, ptlim);
151 				continue;
152 			case 'a':
153 				pt = _add((t->tm_wday < 0 ||
154 					t->tm_wday >= DAYSPERWEEK) ?
155 					"?" : tptr->wday[t->tm_wday],
156 					pt, ptlim);
157 				continue;
158 			case 'B':
159 				pt = _add((t->tm_mon < 0 ||
160 					t->tm_mon >= MONSPERYEAR) ?
161 					"?" : (Oalternative ? tptr->alt_month :
162 					tptr->month)[t->tm_mon],
163 					pt, ptlim);
164 				continue;
165 			case 'b':
166 			case 'h':
167 				pt = _add((t->tm_mon < 0 ||
168 					t->tm_mon >= MONSPERYEAR) ?
169 					"?" : tptr->mon[t->tm_mon],
170 					pt, ptlim);
171 				continue;
172 			case 'C':
173 				/*
174 				 * %C used to do a...
175 				 *	_fmt("%a %b %e %X %Y", t);
176 				 * ...whereas now POSIX 1003.2 calls for
177 				 * something completely different.
178 				 * (ado, 1993-05-24)
179 				 */
180 				pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
181 					pt, ptlim, loc);
182 				continue;
183 			case 'c':
184 				{
185 				int warn2 = IN_SOME;
186 
187 				pt = _fmt(tptr->c_fmt, t, pt, ptlim, &warn2, loc);
188 				if (warn2 == IN_ALL)
189 					warn2 = IN_THIS;
190 				if (warn2 > *warnp)
191 					*warnp = warn2;
192 				}
193 				continue;
194 			case 'D':
195 				pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp, loc);
196 				continue;
197 			case 'd':
198 				pt = _conv(t->tm_mday,
199 					fmt_padding[PAD_FMT_DAYOFMONTH][PadIndex],
200 					pt, ptlim, loc);
201 				continue;
202 			case 'E':
203 				if (Ealternative || Oalternative)
204 					break;
205 				Ealternative++;
206 				goto label;
207 			case 'O':
208 				/*
209 				 * C99 locale modifiers.
210 				 * The sequences
211 				 *	%Ec %EC %Ex %EX %Ey %EY
212 				 *	%Od %oe %OH %OI %Om %OM
213 				 *	%OS %Ou %OU %OV %Ow %OW %Oy
214 				 * are supposed to provide alternate
215 				 * representations.
216 				 *
217 				 * FreeBSD extension
218 				 *      %OB
219 				 */
220 				if (Ealternative || Oalternative)
221 					break;
222 				Oalternative++;
223 				goto label;
224 			case 'e':
225 				pt = _conv(t->tm_mday,
226 					fmt_padding[PAD_FMT_SDAYOFMONTH][PadIndex],
227 					pt, ptlim, loc);
228 				continue;
229 			case 'F':
230 				pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp, loc);
231 				continue;
232 			case 'H':
233 				pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_HMS][PadIndex],
234 					pt, ptlim, loc);
235 				continue;
236 			case 'I':
237 				pt = _conv((t->tm_hour % 12) ?
238 					(t->tm_hour % 12) : 12,
239 					fmt_padding[PAD_FMT_HMS][PadIndex],
240 					pt, ptlim, loc);
241 				continue;
242 			case 'j':
243 				pt = _conv(t->tm_yday + 1,
244 					fmt_padding[PAD_FMT_DAYOFYEAR][PadIndex],
245 					pt, ptlim, loc);
246 				continue;
247 			case 'k':
248 				/*
249 				 * This used to be...
250 				 *	_conv(t->tm_hour % 12 ?
251 				 *		t->tm_hour % 12 : 12, 2, ' ');
252 				 * ...and has been changed to the below to
253 				 * match SunOS 4.1.1 and Arnold Robbins'
254 				 * strftime version 3.0. That is, "%k" and
255 				 * "%l" have been swapped.
256 				 * (ado, 1993-05-24)
257 				 */
258 				pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_SHMS][PadIndex],
259 					pt, ptlim, loc);
260 				continue;
261 #ifdef KITCHEN_SINK
262 			case 'K':
263 				/*
264 				** After all this time, still unclaimed!
265 				*/
266 				pt = _add("kitchen sink", pt, ptlim);
267 				continue;
268 #endif /* defined KITCHEN_SINK */
269 			case 'l':
270 				/*
271 				 * This used to be...
272 				 *	_conv(t->tm_hour, 2, ' ');
273 				 * ...and has been changed to the below to
274 				 * match SunOS 4.1.1 and Arnold Robbin's
275 				 * strftime version 3.0. That is, "%k" and
276 				 * "%l" have been swapped.
277 				 * (ado, 1993-05-24)
278 				 */
279 				pt = _conv((t->tm_hour % 12) ?
280 					(t->tm_hour % 12) : 12,
281 					fmt_padding[PAD_FMT_SHMS][PadIndex],
282 					pt, ptlim, loc);
283 				continue;
284 			case 'M':
285 				pt = _conv(t->tm_min, fmt_padding[PAD_FMT_HMS][PadIndex],
286 					pt, ptlim, loc);
287 				continue;
288 			case 'm':
289 				pt = _conv(t->tm_mon + 1,
290 					fmt_padding[PAD_FMT_MONTH][PadIndex],
291 					pt, ptlim, loc);
292 				continue;
293 			case 'n':
294 				pt = _add("\n", pt, ptlim);
295 				continue;
296 			case 'p':
297 				pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
298 					tptr->pm : 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, loc);
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_l(buf, loc, "%ld",
323 							(long) mkt);
324 					else	(void) sprintf_l(buf, loc, "%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],
339 					pt, ptlim, loc);
340 				continue;
341 			case 'u':
342 				/*
343 				 * From Arnold Robbins' strftime version 3.0:
344 				 * "ISO 8601: Weekday as a decimal number
345 				 * [1 (Monday) - 7]"
346 				 * (ado, 1993-05-24)
347 				 */
348 				pt = _conv((t->tm_wday == 0) ?
349 					DAYSPERWEEK : t->tm_wday,
350 					"%d", pt, ptlim, loc);
351 				continue;
352 			case 'V':	/* ISO 8601 week number */
353 			case 'G':	/* ISO 8601 year (four digits) */
354 			case 'g':	/* ISO 8601 year (two digits) */
355 /*
356  * From Arnold Robbins' strftime version 3.0: "the week number of the
357  * year (the first Monday as the first day of week 1) as a decimal number
358  * (01-53)."
359  * (ado, 1993-05-24)
360  *
361  * From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
362  * "Week 01 of a year is per definition the first week which has the
363  * Thursday in this year, which is equivalent to the week which contains
364  * the fourth day of January. In other words, the first week of a new year
365  * is the week which has the majority of its days in the new year. Week 01
366  * might also contain days from the previous year and the week before week
367  * 01 of a year is the last week (52 or 53) of the previous year even if
368  * it contains days from the new year. A week starts with Monday (day 1)
369  * and ends with Sunday (day 7). For example, the first week of the year
370  * 1997 lasts from 1996-12-30 to 1997-01-05..."
371  * (ado, 1996-01-02)
372  */
373 				{
374 					int	year;
375 					int	base;
376 					int	yday;
377 					int	wday;
378 					int	w;
379 
380 					year = t->tm_year;
381 					base = TM_YEAR_BASE;
382 					yday = t->tm_yday;
383 					wday = t->tm_wday;
384 					for ( ; ; ) {
385 						int	len;
386 						int	bot;
387 						int	top;
388 
389 						len = isleap_sum(year, base) ?
390 							DAYSPERLYEAR :
391 							DAYSPERNYEAR;
392 						/*
393 						 * What yday (-3 ... 3) does
394 						 * the ISO year begin on?
395 						 */
396 						bot = ((yday + 11 - wday) %
397 							DAYSPERWEEK) - 3;
398 						/*
399 						 * What yday does the NEXT
400 						 * ISO year begin on?
401 						 */
402 						top = bot -
403 							(len % DAYSPERWEEK);
404 						if (top < -3)
405 							top += DAYSPERWEEK;
406 						top += len;
407 						if (yday >= top) {
408 							++base;
409 							w = 1;
410 							break;
411 						}
412 						if (yday >= bot) {
413 							w = 1 + ((yday - bot) /
414 								DAYSPERWEEK);
415 							break;
416 						}
417 						--base;
418 						yday += isleap_sum(year, base) ?
419 							DAYSPERLYEAR :
420 							DAYSPERNYEAR;
421 					}
422 #ifdef XPG4_1994_04_09
423 					if ((w == 52 &&
424 						t->tm_mon == TM_JANUARY) ||
425 						(w == 1 &&
426 						t->tm_mon == TM_DECEMBER))
427 							w = 53;
428 #endif /* defined XPG4_1994_04_09 */
429 					if (*format == 'V')
430 						pt = _conv(w, fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
431 							pt, ptlim, loc);
432 					else if (*format == 'g') {
433 						*warnp = IN_ALL;
434 						pt = _yconv(year, base, 0, 1,
435 							pt, ptlim, loc);
436 					} else	pt = _yconv(year, base, 1, 1,
437 							pt, ptlim, loc);
438 				}
439 				continue;
440 			case 'v':
441 				/*
442 				 * From Arnold Robbins' strftime version 3.0:
443 				 * "date as dd-bbb-YYYY"
444 				 * (ado, 1993-05-24)
445 				 */
446 				pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp, loc);
447 				continue;
448 			case 'W':
449 				pt = _conv((t->tm_yday + DAYSPERWEEK -
450 					(t->tm_wday ?
451 					(t->tm_wday - 1) :
452 					(DAYSPERWEEK - 1))) / DAYSPERWEEK,
453 					fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
454 					pt, ptlim, loc);
455 				continue;
456 			case 'w':
457 				pt = _conv(t->tm_wday, "%d", pt, ptlim, loc);
458 				continue;
459 			case 'X':
460 				pt = _fmt(tptr->X_fmt, t, pt, ptlim, warnp, loc);
461 				continue;
462 			case 'x':
463 				{
464 				int	warn2 = IN_SOME;
465 
466 				pt = _fmt(tptr->x_fmt, t, pt, ptlim, &warn2, loc);
467 				if (warn2 == IN_ALL)
468 					warn2 = IN_THIS;
469 				if (warn2 > *warnp)
470 					*warnp = warn2;
471 				}
472 				continue;
473 			case 'y':
474 				*warnp = IN_ALL;
475 				pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
476 					pt, ptlim, loc);
477 				continue;
478 			case 'Y':
479 				pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
480 					pt, ptlim, loc);
481 				continue;
482 			case 'Z':
483 #ifdef TM_ZONE
484 				if (t->TM_ZONE != NULL)
485 					pt = _add(t->TM_ZONE, pt, ptlim);
486 				else
487 #endif /* defined TM_ZONE */
488 				if (t->tm_isdst >= 0)
489 					pt = _add(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 				int		diff;
500 				char const *	sign;
501 
502 				if (t->tm_isdst < 0)
503 					continue;
504 #ifdef TM_GMTOFF
505 				diff = t->TM_GMTOFF;
506 #else /* !defined TM_GMTOFF */
507 				/*
508 				 * C99 says that the UTC 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 				if (t->tm_isdst == 0)
527 #ifdef USG_COMPAT
528 					diff = -timezone;
529 #else /* !defined USG_COMPAT */
530 					continue;
531 #endif /* !defined USG_COMPAT */
532 				else
533 #ifdef ALTZONE
534 					diff = -altzone;
535 #else /* !defined ALTZONE */
536 					continue;
537 #endif /* !defined ALTZONE */
538 #endif /* !defined TM_GMTOFF */
539 				if (diff < 0) {
540 					sign = "-";
541 					diff = -diff;
542 				} else
543 					sign = "+";
544 				pt = _add(sign, pt, ptlim);
545 				diff /= SECSPERMIN;
546 				diff = (diff / MINSPERHOUR) * 100 +
547 					(diff % MINSPERHOUR);
548 				pt = _conv(diff,
549 					fmt_padding[PAD_FMT_YEAR][PadIndex],
550 					pt, ptlim, loc);
551 				}
552 				continue;
553 			case '+':
554 				pt = _fmt(tptr->date_fmt, t, pt, ptlim,
555 					warnp, loc);
556 				continue;
557 			case '-':
558 				if (PadIndex != PAD_DEFAULT)
559 					break;
560 				PadIndex = PAD_LESS;
561 				goto label;
562 			case '_':
563 				if (PadIndex != PAD_DEFAULT)
564 					break;
565 				PadIndex = PAD_SPACE;
566 				goto label;
567 			case '0':
568 				if (PadIndex != PAD_DEFAULT)
569 					break;
570 				PadIndex = PAD_ZERO;
571 				goto label;
572 			case '%':
573 			/*
574 			 * X311J/88-090 (4.12.3.5): if conversion char is
575 			 * undefined, behavior is undefined. Print out the
576 			 * character itself as printf(3) also does.
577 			 */
578 			default:
579 				break;
580 			}
581 		}
582 		if (pt == ptlim)
583 			break;
584 		*pt++ = *format;
585 	}
586 	return (pt);
587 }
588 
589 static char *
590 _conv(const int n, const char * const format, char * const pt,
591     const char * const ptlim, locale_t  loc)
592 {
593 	char	buf[INT_STRLEN_MAXIMUM(int) + 1];
594 
595 	(void) sprintf_l(buf, loc, format, n);
596 	return _add(buf, pt, ptlim);
597 }
598 
599 static char *
600 _add(const char *str, char *pt, const char * const ptlim)
601 {
602 	while (pt < ptlim && (*pt = *str++) != '\0')
603 		++pt;
604 	return (pt);
605 }
606 
607 /*
608  * POSIX and the C Standard are unclear or inconsistent about
609  * what %C and %y do if the year is negative or exceeds 9999.
610  * Use the convention that %C concatenated with %y yields the
611  * same output as %Y, and that %Y contains at least 4 bytes,
612  * with more only if necessary.
613  */
614 
615 static char *
616 _yconv(const int a, const int b, const int convert_top, const int convert_yy,
617     char *pt, const char * const ptlim, locale_t  loc)
618 {
619 	register int	lead;
620 	register int	trail;
621 
622 #define	DIVISOR	100
623 	trail = a % DIVISOR + b % DIVISOR;
624 	lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
625 	trail %= DIVISOR;
626 	if (trail < 0 && lead > 0) {
627 		trail += DIVISOR;
628 		--lead;
629 	} else if (lead < 0 && trail > 0) {
630 		trail -= DIVISOR;
631 		++lead;
632 	}
633 	if (convert_top) {
634 		if (lead == 0 && trail < 0)
635 			pt = _add("-0", pt, ptlim);
636 		else	pt = _conv(lead, "%02d", pt, ptlim, loc);
637 	}
638 	if (convert_yy)
639 		pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt,
640 		     ptlim, loc);
641 	return (pt);
642 }
643