Home | History | Annotate | Line # | Download | only in time
asctime.c revision 1.18 
      1 /*	$NetBSD: asctime.c,v 1.18 2012/10/28 17:11:33 christos 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 1.18 2012/10/28 17:11:33 christos Exp $");
     20 #endif
     21 #endif /* LIBC_SCCS and not lint */
     22 
     23 /*LINTLIBRARY*/
     24 
     25 #include "namespace.h"
     26 #include "private.h"
     27 #include "tzfile.h"
     28 
     29 #ifdef __weak_alias
     30 __weak_alias(asctime_r,_asctime_r)
     31 #endif
     32 
     33 /*
     34 ** Some systems only handle "%.2d"; others only handle "%02d";
     35 ** "%02.2d" makes (most) everybody happy.
     36 ** At least some versions of gcc warn about the %02.2d;
     37 ** we conditionalize below to avoid the warning.
     38 */
     39 /*
     40 ** All years associated with 32-bit time_t values are exactly four digits long;
     41 ** some years associated with 64-bit time_t values are not.
     42 ** Vintage programs are coded for years that are always four digits long
     43 ** and may assume that the newline always lands in the same place.
     44 ** For years that are less than four digits, we pad the output with
     45 ** leading zeroes to get the newline in the traditional place.
     46 ** The -4 ensures that we get four characters of output even if
     47 ** we call a strftime variant that produces fewer characters for some years.
     48 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
     49 ** but many implementations pad anyway; most likely the standards are buggy.
     50 */
     51 #ifdef __GNUC__
     52 #define ASCTIME_FMT	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
     53 #else /* !defined __GNUC__ */
     54 #define ASCTIME_FMT	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
     55 #endif /* !defined __GNUC__ */
     56 /*
     57 ** For years that are more than four digits we put extra spaces before the year
     58 ** so that code trying to overwrite the newline won't end up overwriting
     59 ** a digit within a year and truncating the year (operating on the assumption
     60 ** that no output is better than wrong output).
     61 */
     62 #ifdef __GNUC__
     63 #define ASCTIME_FMT_B	"%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
     64 #else /* !defined __GNUC__ */
     65 #define ASCTIME_FMT_B	"%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
     66 #endif /* !defined __GNUC__ */
     67 
     68 #define STD_ASCTIME_BUF_SIZE	26
     69 /*
     70 ** Big enough for something such as
     71 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
     72 ** (two three-character abbreviations, five strings denoting integers,
     73 ** seven explicit spaces, two explicit colons, a newline,
     74 ** and a trailing ASCII nul).
     75 ** The values above are for systems where an int is 32 bits and are provided
     76 ** as an example; the define below calculates the maximum for the system at
     77 ** hand.
     78 */
     79 #define MAX_ASCTIME_BUF_SIZE	(2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
     80 
     81 static char	buf_asctime[MAX_ASCTIME_BUF_SIZE];
     82 
     83 /*
     84 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
     85 */
     86 
     87 char *
     88 asctime_r(const struct tm *timeptr, char *buf)
     89 {
     90 	static const char	wday_name[][3] = {
     91 		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
     92 	};
     93 	static const char	mon_name[][3] = {
     94 		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
     95 		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
     96 	};
     97 	const char *	wn;
     98 	const char *	mn;
     99 	char			year[INT_STRLEN_MAXIMUM(int) + 2];
    100 	char			result[MAX_ASCTIME_BUF_SIZE];
    101 
    102 	if (timeptr == NULL) {
    103 		errno = EINVAL;
    104 		return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
    105 	}
    106 	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
    107 		wn = "???";
    108 	else	wn = wday_name[timeptr->tm_wday];
    109 	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
    110 		mn = "???";
    111 	else	mn = mon_name[timeptr->tm_mon];
    112 	/*
    113 	** Use strftime's %Y to generate the year, to avoid overflow problems
    114 	** when computing timeptr->tm_year + TM_YEAR_BASE.
    115 	** Assume that strftime is unaffected by other out-of-range members
    116 	** (e.g., timeptr->tm_mday) when processing "%Y".
    117 	*/
    118 	(void) strftime(year, sizeof year, "%Y", timeptr);
    119 	(void) snprintf(result,
    120 		sizeof(result),
    121 		((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
    122 		wn, mn,
    123 		timeptr->tm_mday, timeptr->tm_hour,
    124 		timeptr->tm_min, timeptr->tm_sec,
    125 		year);
    126 	if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
    127 		return strcpy(buf, result);
    128 	else {
    129 #ifdef EOVERFLOW
    130 		errno = EOVERFLOW;
    131 #else /* !defined EOVERFLOW */
    132 		errno = EINVAL;
    133 #endif /* !defined EOVERFLOW */
    134 		return NULL;
    135 	}
    136 }
    137 
    138 /*
    139 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
    140 */
    141 
    142 char *
    143 asctime(const struct tm *timeptr)
    144 {
    145 	return asctime_r(timeptr, buf_asctime);
    146 }
    147