xref: /illumos-gate/usr/src/lib/libc/port/locale/strftime.c (revision 72af5a458c3acde8fe8b432dc826b8b100d005d1)

/*
 * Copyright 2013 Garrett D'Amore <garrett@damore.org>
 * Copyright 2010 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley. The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include "lint.h"
#include "tzfile.h"
#include <fcntl.h>
#include <stdint.h>
#include <sys/stat.h>
#include <string.h>
#include <stdio.h>
#include <locale.h>
#include "timelocal.h"
#include "localeimpl.h"

static char *_add(const char *, char *, const char *);
static char *_conv(int, const char *, char *, const char *);
static char *_fmt(locale_t, const char *, const struct tm *, char *,
    const char * const);
static char *_yconv(int, int, int, int, char *, const char *);

extern char *tzname[];

#define	IN_NONE	0
#define	IN_SOME	1
#define	IN_THIS	2
#define	IN_ALL	3

#define	PAD_DEFAULT	0
#define	PAD_LESS	1
#define	PAD_SPACE	2
#define	PAD_ZERO	3

static const char *fmt_padding[][4] = {
	/* DEFAULT,	LESS,	SPACE,	ZERO */
#define	PAD_FMT_MONTHDAY	0
#define	PAD_FMT_HMS		0
#define	PAD_FMT_CENTURY		0
#define	PAD_FMT_SHORTYEAR	0
#define	PAD_FMT_MONTH		0
#define	PAD_FMT_WEEKOFYEAR	0
#define	PAD_FMT_DAYOFMONTH	0
	{ "%02d",	"%d",	"%2d",	"%02d" },
#define	PAD_FMT_SDAYOFMONTH	1
#define	PAD_FMT_SHMS		1
	{ "%2d",	"%d",	"%2d",	"%02d" },
#define	PAD_FMT_DAYOFYEAR	2
	{ "%03d",	"%d",	"%3d",	"%03d" },
#define	PAD_FMT_YEAR		3
	{ "%04d",	"%d",	"%4d",	"%04d" }
};

/*
 * If a caller (such as ascftime) passes in a very large maximum size,
 * the pointer addition here may overflow, wrap around the end of
 * memory, and, if used as-is, would cause subsequent range checks to fail
 * spuriously, resulting in corrupted output even if there is sufficent
 * room in the buffer for the requested format.
 *
 * To prevent this, we replace an overflowed result with the largest
 * possible pointer value.
 */
static char *
_ptlim(char *s, size_t maxsize)
{
	char *e = s + maxsize;

	if (e < s)
		e = (char *)(-sizeof (*e));

	return (e);
}

size_t
strftime_l(char *_RESTRICT_KYWD s, size_t maxsize,
    const char *_RESTRICT_KYWD format, const struct tm *_RESTRICT_KYWD t,
    locale_t loc)
{
	char *p;
	char *e = _ptlim(s, maxsize);

	tzset();
	p = _fmt(loc, ((format == NULL) ? "%c" : format), t, s, e);
	if (p == e)
		return (0);
	*p = '\0';
	return (p - s);
}

size_t
strftime(char *_RESTRICT_KYWD s, size_t maxsize,
    const char *_RESTRICT_KYWD format, const struct tm *_RESTRICT_KYWD t)
{
	return (strftime_l(s, maxsize, format, t, uselocale(NULL)));
}

static char *
_fmt(locale_t loc, const char *format, const struct tm *t, char *pt,
    const char * const ptlim)
{
	int Ealternative, Oalternative, PadIndex;
	const struct lc_time *tptr = loc->time;

#define	PADDING(x)	fmt_padding[x][PadIndex]

	for (; *format; ++format) {
		if (*format == '%') {
			Ealternative = 0;
			Oalternative = 0;
			PadIndex	 = PAD_DEFAULT;
label:
			switch (*++format) {
			case '\0':
				--format;
				break;
			case 'A':
				pt = _add((t->tm_wday < 0 ||
				    t->tm_wday >= DAYSPERWEEK) ?
				    "?" : tptr->weekday[t->tm_wday],
				    pt, ptlim);
				continue;
			case 'a':
				pt = _add((t->tm_wday < 0 ||
				    t->tm_wday >= DAYSPERWEEK) ?
				    "?" : tptr->wday[t->tm_wday],
				    pt, ptlim);
				continue;
			case 'B':
				pt = _add((t->tm_mon < 0 ||
				    t->tm_mon >= MONSPERYEAR) ?
				    "?" : (tptr->month)[t->tm_mon],
				    pt, ptlim);
				continue;
			case 'b':
			case 'h':
				pt = _add((t->tm_mon < 0 ||
				    t->tm_mon >= MONSPERYEAR) ?
				    "?" : tptr->mon[t->tm_mon],
				    pt, ptlim);
				continue;
			case 'C':
				/*
				 * %C used to do a...
				 *	_fmt("%a %b %e %X %Y", t);
				 * ...whereas now POSIX 1003.2 calls for
				 * something completely different.
				 * (ado, 1993-05-24)
				 */
				pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
				    pt, ptlim);
				continue;
			case 'c':
				pt = _fmt(loc, tptr->c_fmt, t, pt, ptlim);
				continue;
			case 'D':
				pt = _fmt(loc, "%m/%d/%y", t, pt, ptlim);
				continue;
			case 'd':
				pt = _conv(t->tm_mday,
				    PADDING(PAD_FMT_DAYOFMONTH), pt, ptlim);
				continue;
			case 'E':
				if (Ealternative || Oalternative)
					break;
				Ealternative++;
				goto label;
			case 'O':
				/*
				 * C99 locale modifiers.
				 * The sequences
				 *	%Ec %EC %Ex %EX %Ey %EY
				 *	%Od %oe %OH %OI %Om %OM
				 *	%OS %Ou %OU %OV %Ow %OW %Oy
				 * are supposed to provide alternate
				 * representations.
				 */
				if (Ealternative || Oalternative)
					break;
				Oalternative++;
				goto label;
			case 'e':
				pt = _conv(t->tm_mday,
				    PADDING(PAD_FMT_SDAYOFMONTH), pt, ptlim);
				continue;
			case 'F':
				pt = _fmt(loc, "%Y-%m-%d", t, pt, ptlim);
				continue;
			case 'H':
				pt = _conv(t->tm_hour, PADDING(PAD_FMT_HMS),
				    pt, ptlim);
				continue;
			case 'I':
				pt = _conv((t->tm_hour % 12) ?
				    (t->tm_hour % 12) : 12,
				    PADDING(PAD_FMT_HMS), pt, ptlim);
				continue;
			case 'j':
				pt = _conv(t->tm_yday + 1,
				    PADDING(PAD_FMT_DAYOFYEAR), pt, ptlim);
				continue;
			case 'k':
				/*
				 * This used to be...
				 *	_conv(t->tm_hour % 12 ?
				 *		t->tm_hour % 12 : 12, 2, ' ');
				 * ...and has been changed to the below to
				 * match SunOS 4.1.1 and Arnold Robbins'
				 * strftime version 3.0. That is, "%k" and
				 * "%l" have been swapped.
				 * (ado, 1993-05-24)
				 */
				pt = _conv(t->tm_hour,
				    PADDING(PAD_FMT_SHMS), pt, ptlim);
				continue;
			case 'l':
				/*
				 * This used to be...
				 *	_conv(t->tm_hour, 2, ' ');
				 * ...and has been changed to the below to
				 * match SunOS 4.1.1 and Arnold Robbin's
				 * strftime version 3.0. That is, "%k" and
				 * "%l" have been swapped.
				 * (ado, 1993-05-24)
				 */
				pt = _conv((t->tm_hour % 12) ?
				    (t->tm_hour % 12) : 12,
				    PADDING(PAD_FMT_SHMS), pt, ptlim);
				continue;
			case 'M':
				pt = _conv(t->tm_min, PADDING(PAD_FMT_HMS),
				    pt, ptlim);
				continue;
			case 'm':
				pt = _conv(t->tm_mon + 1,
				    PADDING(PAD_FMT_MONTH),
				    pt, ptlim);
				continue;
			case 'n':
				pt = _add("\n", pt, ptlim);
				continue;
			case 'p':
				pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
				    tptr->pm : tptr->am, pt, ptlim);
				continue;
			case 'R':
				pt = _fmt(loc, "%H:%M", t, pt, ptlim);
				continue;
			case 'r':
				pt = _fmt(loc, tptr->ampm_fmt, t, pt, ptlim);
				continue;
			case 'S':
				pt = _conv(t->tm_sec, PADDING(PAD_FMT_HMS),
				    pt, ptlim);
				continue;

			case 's':
			{
				struct tm tm;
				char *buf;

				tm = *t;
				(void) asprintf(&buf, "%ld", mktime(&tm));
				pt = _add(buf, pt, ptlim);
				continue;
			}

			case 'T':
				pt = _fmt(loc, "%H:%M:%S", t, pt, ptlim);
				continue;
			case 't':
				pt = _add("\t", pt, ptlim);
				continue;
			case 'U':
				pt = _conv((t->tm_yday + DAYSPERWEEK -
				    t->tm_wday) / DAYSPERWEEK,
				    PADDING(PAD_FMT_WEEKOFYEAR),
				    pt, ptlim);
				continue;
			case 'u':
				/*
				 * From Arnold Robbins' strftime version 3.0:
				 * "ISO 8601: Weekday as a decimal number
				 * [1 (Monday) - 7]"
				 * (ado, 1993-05-24)
				 */
				pt = _conv((t->tm_wday == 0) ?
				    DAYSPERWEEK : t->tm_wday,
				    "%d", pt, ptlim);
				continue;
			case 'V':	/* ISO 8601 week number */
			case 'G':	/* ISO 8601 year (four digits) */
			case 'g':	/* ISO 8601 year (two digits) */
/*
 * From Arnold Robbins' strftime version 3.0: "the week number of the
 * year (the first Monday as the first day of week 1) as a decimal number
 * (01-53)."
 * (ado, 1993-05-24)
 *
 * From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
 * "Week 01 of a year is per definition the first week which has the
 * Thursday in this year, which is equivalent to the week which contains
 * the fourth day of January. In other words, the first week of a new year
 * is the week which has the majority of its days in the new year. Week 01
 * might also contain days from the previous year and the week before week
 * 01 of a year is the last week (52 or 53) of the previous year even if
 * it contains days from the new year. A week starts with Monday (day 1)
 * and ends with Sunday (day 7). For example, the first week of the year
 * 1997 lasts from 1996-12-30 to 1997-01-05..."
 * (ado, 1996-01-02)
 */
			{
				int	year;
				int	base;
				int	yday;
				int	wday;
				int	w;

				year = t->tm_year;
				base = TM_YEAR_BASE;
				yday = t->tm_yday;
				wday = t->tm_wday;
				for (;;) {
					int	len;
					int	bot;
					int	top;

					len = isleap_sum(year, base) ?
					    DAYSPERLYEAR : DAYSPERNYEAR;
					/*
					 * What yday (-3 ... 3) does
					 * the ISO year begin on?
					 */
					bot = ((yday + 11 - wday) %
					    DAYSPERWEEK) - 3;
					/*
					 * What yday does the NEXT
					 * ISO year begin on?
					 */
					top = bot - (len % DAYSPERWEEK);
					if (top < -3)
						top += DAYSPERWEEK;
					top += len;
					if (yday >= top) {
						++base;
						w = 1;
						break;
					}
					if (yday >= bot) {
						w = 1 + ((yday - bot) /
						    DAYSPERWEEK);
						break;
					}
					--base;
					yday += isleap_sum(year, base) ?
					    DAYSPERLYEAR : DAYSPERNYEAR;
				}
#ifdef XPG4_1994_04_09
				if ((w == 52 && t->tm_mon == TM_JANUARY) ||
				    (w == 1 && t->tm_mon == TM_DECEMBER))
					w = 53;
#endif /* defined XPG4_1994_04_09 */
				if (*format == 'V')
					pt = _conv(w,
					    PADDING(PAD_FMT_WEEKOFYEAR),
					    pt, ptlim);
				else if (*format == 'g') {
					pt = _yconv(year, base, 0, 1,
					    pt, ptlim);
				} else
					pt = _yconv(year, base, 1, 1,
					    pt, ptlim);
			}
				continue;
			case 'v':
				/*
				 * From Arnold Robbins' strftime version 3.0:
				 * "date as dd-bbb-YYYY"
				 * (ado, 1993-05-24)
				 */
				pt = _fmt(loc, "%e-%b-%Y", t, pt, ptlim);
				continue;
			case 'W':
				pt = _conv((t->tm_yday + DAYSPERWEEK -
				    (t->tm_wday ?
				    (t->tm_wday - 1) :
				    (DAYSPERWEEK - 1))) / DAYSPERWEEK,
				    PADDING(PAD_FMT_WEEKOFYEAR),
				    pt, ptlim);
				continue;
			case 'w':
				pt = _conv(t->tm_wday, "%d", pt, ptlim);
				continue;
			case 'X':
				pt = _fmt(loc, tptr->X_fmt, t, pt, ptlim);
				continue;
			case 'x':
				pt = _fmt(loc, tptr->x_fmt, t, pt, ptlim);
				continue;
			case 'y':
				pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
				    pt, ptlim);
				continue;
			case 'Y':
				pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
				    pt, ptlim);
				continue;
			case 'Z':
				if (t->tm_isdst >= 0)
					pt = _add(tzname[t->tm_isdst != 0],
					    pt, ptlim);
				/*
				 * C99 says that %Z must be replaced by the
				 * empty string if the time zone is not
				 * determinable.
				 */
				continue;
			case 'z':
				{
				int		diff;
				char const *	sign;

				if (t->tm_isdst < 0)
					continue;
				/*
				 * C99 says that the UTC offset must
				 * be computed by looking only at
				 * tm_isdst. This requirement is
				 * incorrect, since it means the code
				 * must rely on magic (in this case
				 * altzone and timezone), and the
				 * magic might not have the correct
				 * offset. Doing things correctly is
				 * tricky and requires disobeying C99;
				 * see GNU C strftime for details.
				 * For now, punt and conform to the
				 * standard, even though it's incorrect.
				 *
				 * C99 says that %z must be replaced by the
				 * empty string if the time zone is not
				 * determinable, so output nothing if the
				 * appropriate variables are not available.
				 */
				if (t->tm_isdst == 0)
					diff = -timezone;
				else
					diff = -altzone;
				if (diff < 0) {
					sign = "-";
					diff = -diff;
				} else
					sign = "+";
				pt = _add(sign, pt, ptlim);
				diff /= SECSPERMIN;
				diff = (diff / MINSPERHOUR) * 100 +
				    (diff % MINSPERHOUR);
				pt = _conv(diff, PADDING(PAD_FMT_YEAR),
				    pt, ptlim);
				}
				continue;
			case '+':
				pt = _fmt(loc, tptr->date_fmt, t, pt, ptlim);
				continue;
			case '-':
				if (PadIndex != PAD_DEFAULT)
					break;
				PadIndex = PAD_LESS;
				goto label;
			case '_':
				if (PadIndex != PAD_DEFAULT)
					break;
				PadIndex = PAD_SPACE;
				goto label;
			case '0':
				if (PadIndex != PAD_DEFAULT)
					break;
				PadIndex = PAD_ZERO;
				goto label;
			case '%':
			/*
			 * X311J/88-090 (4.12.3.5): if conversion char is
			 * undefined, behavior is undefined. Print out the
			 * character itself as printf(3) also does.
			 */
			default:
				break;
			}
		}
		if (pt == ptlim)
			break;
		*pt++ = *format;
	}
	return (pt);
}

static char *
_conv(const int n, const char *format, char *const pt,
    const char *const ptlim)
{
	char	buf[12];

	(void) sprintf(buf, format, n);
	return (_add(buf, pt, ptlim));
}

static char *
_add(const char *str, char *pt, const char *const ptlim)
{
	while (pt < ptlim && (*pt = *str++) != '\0')
		++pt;
	return (pt);
}

/*
 * POSIX and the C Standard are unclear or inconsistent about
 * what %C and %y do if the year is negative or exceeds 9999.
 * Use the convention that %C concatenated with %y yields the
 * same output as %Y, and that %Y contains at least 4 bytes,
 * with more only if necessary.
 */

static char *
_yconv(const int a, const int b, const int convert_top, const int convert_yy,
    char *pt, const char * const ptlim)
{
	register int	lead;
	register int	trail;

#define	DIVISOR	100
	trail = a % DIVISOR + b % DIVISOR;
	lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
	trail %= DIVISOR;
	if (trail < 0 && lead > 0) {
		trail += DIVISOR;
		--lead;
	} else if (lead < 0 && trail > 0) {
		trail -= DIVISOR;
		++lead;
	}
	if (convert_top) {
		if (lead == 0 && trail < 0)
			pt = _add("-0", pt, ptlim);
		else	pt = _conv(lead, "%02d", pt, ptlim);
	}
	if (convert_yy)
		pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
	return (pt);
}