Asctime.c

July 20, 2004

      At the end of this message is a revised version of asctime.c.
There are a couple of standard-related matters.

1. The POSIX standard calls for a struct tm that includes an "int tm_year"
member. If time_t is 64 bits and int is 32 bits, tm_year won't be able to
represent all the years associated with time_t values. Should the standard
address this issue?

2. The standard reads...
	The asctime_r() function shall convert the broken-down time in the
	structure pointed to by tm into a string (of the same form as that
	returned by asctime()) that is placed in the user-supplied buffer
	pointed to by buf (which shall contain at least 26 bytes) and then
	return buf.
...but a 26-byte buffer won't be adequate if a five-digit (or more) year is
involved.
Should the standard address this issue? Should "asctime_r" assume that the
fed-in buffer is at most 26 bytes and avoid overflowing it?

				--ado

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

#ifndef lint
#ifndef NOID
static char	elsieid[] = "@(#)asctime.c	7.11";
#endif /* !defined NOID */
#endif /* !defined lint */

/*LINTLIBRARY*/

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

/*
** 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;

	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"
	** Use "%02d", as it is a bit more portable than "%.2d".
	** Drop each .3 since they're superfluous given how we set wn and
mn.
	*/
	(void) sprintf(buf, "%s %s%3d %02d:%02d:%02d %ld\n",
		wn, mn,
		timeptr->tm_mday, timeptr->tm_hour,
		timeptr->tm_min, timeptr->tm_sec,
		timeptr->tm_year + (long) TM_YEAR_BASE);
	return buf;
}

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

char *
asctime(timeptr)
register const struct tm *	timeptr;
{
	/*
	** 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).
	*/
	static char		result[3 * 2 + 5 * INT_STRLEN_MAXIMUM(int) +
					3 + 2 + 1 + 1];

	return asctime_r(timeptr, result);
}

Asctime.c

Olson, Arthur David (NIH/NCI)