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asctime.c revision 1.20.4.1 
      1 /*	$NetBSD: asctime.c,v 1.20.4.1 2017/04/21 16:53:09 bouyer Exp $	*/
      2 
      3 /*
      4 ** This file is in the public domain, so clarified as of
      5 ** 1996-06-05 by Arthur David Olson.
      6 */
      7 
      8 /*
      9 ** Avoid the temptation to punt entirely to strftime;
     10 ** the output of strftime is supposed to be locale specific
     11 ** whereas the output of asctime is supposed to be constant.
     12 */
     13 
     14 #include <sys/cdefs.h>
     15 #if defined(LIBC_SCCS) && !defined(lint)
     16 #if 0
     17 static char	elsieid[] = "@(#)asctime.c	8.5";
     18 #else
     19 __RCSID("$NetBSD: asctime.c,v 1.20.4.1 2017/04/21 16:53:09 bouyer Exp $");
     20 #endif
     21 #endif /* LIBC_SCCS and not lint */
     22 
     23 /*LINTLIBRARY*/
     24 
     25 #include "namespace.h"
     26 #include "private.h"
     27 
     28 #ifdef __weak_alias
     29 __weak_alias(asctime_r,_asctime_r)
     30 #endif
     31 
     32 /*
     33 ** Some systems only handle "%.2d"; others only handle "%02d";
     34 ** "%02.2d" makes (most) everybody happy.
     35 ** At least some versions of gcc warn about the %02.2d;
     36 ** we conditionalize below to avoid the warning.
     37 */
     38 /*
     39 ** All years associated with 32-bit time_t values are exactly four digits long;
     40 ** some years associated with 64-bit time_t values are not.
     41 ** Vintage programs are coded for years that are always four digits long
     42 ** and may assume that the newline always lands in the same place.
     43 ** For years that are less than four digits, we pad the output with
     44 ** leading zeroes to get the newline in the traditional place.
     45 ** The -4 ensures that we get four characters of output even if
     46 ** we call a strftime variant that produces fewer characters for some years.
     47 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
     48 ** but many implementations pad anyway; most likely the standards are buggy.
     49 */
     50 #ifdef __GNUC__
     51 #define ASCTIME_FMT	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
     52 #else /* !defined __GNUC__ */
     53 #define ASCTIME_FMT	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
     54 #endif /* !defined __GNUC__ */
     55 /*
     56 ** For years that are more than four digits we put extra spaces before the year
     57 ** so that code trying to overwrite the newline won't end up overwriting
     58 ** a digit within a year and truncating the year (operating on the assumption
     59 ** that no output is better than wrong output).
     60 */
     61 #ifdef __GNUC__
     62 #define ASCTIME_FMT_B	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
     63 #else /* !defined __GNUC__ */
     64 #define ASCTIME_FMT_B	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
     65 #endif /* !defined __GNUC__ */
     66 
     67 #define STD_ASCTIME_BUF_SIZE	26
     68 /*
     69 ** Big enough for something such as
     70 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
     71 ** (two three-character abbreviations, five strings denoting integers,
     72 ** seven explicit spaces, two explicit colons, a newline,
     73 ** and a trailing NUL byte).
     74 ** The values above are for systems where an int is 32 bits and are provided
     75 ** as an example; the define below calculates the maximum for the system at
     76 ** hand.
     77 */
     78 #define MAX_ASCTIME_BUF_SIZE	(2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
     79 
     80 static char	buf_asctime[MAX_ASCTIME_BUF_SIZE];
     81 
     82 /*
     83 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
     84 */
     85 
     86 char *
     87 asctime_r(const struct tm *timeptr, char *buf)
     88 {
     89 	static const char	wday_name[][3] = {
     90 		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
     91 	};
     92 	static const char	mon_name[][3] = {
     93 		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
     94 		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
     95 	};
     96 	const char *	wn;
     97 	const char *	mn;
     98 	char			year[INT_STRLEN_MAXIMUM(int) + 2];
     99 	char			result[MAX_ASCTIME_BUF_SIZE];
    100 
    101 	if (timeptr == NULL) {
    102 		errno = EINVAL;
    103 		return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
    104 	}
    105 	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
    106 		wn = "???";
    107 	else	wn = wday_name[timeptr->tm_wday];
    108 	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
    109 		mn = "???";
    110 	else	mn = mon_name[timeptr->tm_mon];
    111 	/*
    112 	** Use strftime's %Y to generate the year, to avoid overflow problems
    113 	** when computing timeptr->tm_year + TM_YEAR_BASE.
    114 	** Assume that strftime is unaffected by other out-of-range members
    115 	** (e.g., timeptr->tm_mday) when processing "%Y".
    116 	*/
    117 	(void) strftime(year, sizeof year, "%Y", timeptr);
    118 	(void) snprintf(result,
    119 		sizeof(result),
    120 		((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
    121 		wn, mn,
    122 		timeptr->tm_mday, timeptr->tm_hour,
    123 		timeptr->tm_min, timeptr->tm_sec,
    124 		year);
    125 	if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
    126 		return strcpy(buf, result);
    127 	else {
    128 		errno = EOVERFLOW;
    129 		return NULL;
    130 	}
    131 }
    132 
    133 /*
    134 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
    135 */
    136 
    137 char *
    138 asctime(const struct tm *timeptr)
    139 {
    140 	return asctime_r(timeptr, buf_asctime);
    141 }
    142