arpadate.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 173 行

#ifndef lint
static	char	*sccsid = "@(#)arpadate.c	4.1	(ULTRIX)	7/2/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1987 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/


# include "conf.h"
# include <time.h>
# include <sys/types.h>
# include "useful.h"

/*
**  ARPADATE -- Create date in ARPANET format
**
**	Parameters:
**		ud -- unix style date string.  if NULL, one is created.
**
**	Returns:
**		pointer to an ARPANET date field
**
**	Side Effects:
**		none
**
**	WARNING:
**		date is stored in a local buffer -- subsequent
**		calls will overwrite.
**
**	Bugs:
**		Timezone is computed from local time, rather than
**		from whereever (and whenever) the message was sent.
**		To do better is very hard.
**
**		Some sites are now inserting the timezone into the
**		local date.  This routine should figure out what
**		the format is and work appropriately.
*/

char *
arpadate(ud)
	register char *ud;
{
	register char *p;
	register char *q;
	register int off;
	register int i;
	register struct tm *lt;
	time_t t;
	struct tm gmt;
	static char b[40];
	extern struct tm *localtime(), *gmtime();
	extern char *ctime();
	extern time_t time();

	/*
	**  Get current time.
	**	This will be used if a null argument is passed and
	**	to resolve the timezone.
	*/

	(void) time(&t);
	if (ud == NULL)
		ud = ctime(&t);

	/*
	**  Crack the UNIX date line in a singularly unoriginal way.
	*/

	q = b;

	p = &ud[0];		/* Mon */
	*q++ = *p++;
	*q++ = *p++;
	*q++ = *p++;
	*q++ = ',';
	*q++ = ' ';

	p = &ud[8];		/* 16 */
	if (*p == ' ')
		p++;
	else
		*q++ = *p++;
	*q++ = *p++;
	*q++ = ' ';

	p = &ud[4];		/* Sep */
	*q++ = *p++;
	*q++ = *p++;
	*q++ = *p++;
	*q++ = ' ';

	p = &ud[22];		/* 79 */
	*q++ = *p++;
	*q++ = *p++;
	*q++ = ' ';

	p = &ud[11];		/* 01:03:52 */
	for (i = 8; i > 0; i--)
		*q++ = *p++;

	/*
	 * should really get the timezone from the time in "ud" (which
	 * is only different if a non-null arg was passed which is different
	 * from the current time), but for all practical purposes, returning
	 * the current local zone will do (its all that is ever needed).
	 */
	gmt = *gmtime(&t);
	lt = localtime(&t);

	off = (lt->tm_hour - gmt.tm_hour) * 60 + lt->tm_min - gmt.tm_min;

	/* assume that offset isn't more than a day ... */
	if (lt->tm_year < gmt.tm_year)
		off -= 24 * 60;
	else if (lt->tm_year > gmt.tm_year)
		off += 24 * 60;
	else if (lt->tm_yday < gmt.tm_yday)
		off -= 24 * 60;
	else if (lt->tm_yday > gmt.tm_yday)
		off += 24 * 60;

	*q++ = ' ';
	if (off == 0) {
		*q++ = 'G';
		*q++ = 'M';
		*q++ = 'T';
	} else {
		if (off < 0) {
			off = -off;
			*q++ = '-';
		} else
			*q++ = '+';

		if (off >= 24*60)		/* should be impossible */
			off = 23*60+59;		/* if not, insert silly value */

		*q++ = (off / 600) + '0';
		*q++ = (off / 60) % 10 + '0';
		off %= 60;
		*q++ = (off / 10) + '0';
		*q++ = (off % 10) + '0';
	}
	*q = '\0';

	return (b);
}