asctime.c

[Olson, Arthur David (NIH/NCI)]

Thanks to all for feedback on asctime.c. The version below uses %02.2d for
universality, uses %4ld for years to avoid problems if a year isn't four
digits long, and avoids the use of snprintf (which isn't available on some
systems). There are comments on all these changes. Is it soup yet?

				--ado

/*
** This file is in the public domain, so clarified as of
** 1996-06-05 by Arthur David Olson (arthur_david_olson at nih.gov).
*/

#ifndef lint
#ifndef NOID
static char	elsieid[] = "@(#)asctime.c	7.15";
#endif /* !defined NOID */
#endif /* !defined lint */

/*LINTLIBRARY*/

#include "private.h"
#include "tzfile.h"

#define STANDARD_BUFFER_SIZE	26

/*
** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
*/

char *
asctime_r(timeptr, buf)
register const struct tm *	timeptr;
char *				buf;
{
	static const char	wday_name[][3] = {
		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
	};
	static const char	mon_name[][3] = {
		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
	};
	register const char *	wn;
	register const char *	mn;
	/*
	** Big enough for something such as
	** ??? ???-2147483648 -2147483648:-2147483648:-2147483648
-2147483648\n
	** (two three-character abbreviations, five strings denoting
integers,
	** three explicit spaces, two explicit colons, a newline,
	** and a trailing ASCII nul).
	*/
	char			result[2 * 3 + 5 * INT_STRLEN_MAXIMUM(int) +
					3 + 2 + 1 + 1];

	if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
		wn = "???";
	else	wn = wday_name[timeptr->tm_wday];
	if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
		mn = "???";
	else	mn = mon_name[timeptr->tm_mon];
	/*
	** The format used in the (2004) standard is
	**	"%.3s %.3s%3d %.2d:%.2d:%.2d %d\n"
	** Some systems only handle "%.2d"; others only handle "%02d";
	** "%02.2d" makes (most) everybody happy.
	** All years associated with 32-bit time_t values are exactly
	** four digits long; some years associated with 64-bit time_t
	** values are not four digits long so we throw in the 4 below.
	*/
	/*
	** We avoid using snprintf since it's not available on all systems.
	*/
	(void) sprintf(result, "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %4ld\n",
		wn, mn,
		timeptr->tm_mday, timeptr->tm_hour,
		timeptr->tm_min, timeptr->tm_sec,
		timeptr->tm_year + (long) TM_YEAR_BASE);
	if (strlen(result) >= STANDARD_BUFFER_SIZE) {
		errno = EOVERFLOW;
		return NULL;
	} else {
		(void) strcpy(buf, result);
		return buf;
	}
}

/*
** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
*/

char *
asctime(timeptr)
register const struct tm *	timeptr;
{
	static char		result[STANDARD_BUFFER_SIZE];

	return asctime_r(timeptr, result);
}