1/*	$OpenBSD: gmt2local.c,v 1.7 2015/11/15 20:35:36 mmcc Exp $	*/
2
3/*
4 * Copyright (c) 1997
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that: (1) source code distributions
9 * retain the above copyright notice and this paragraph in its entirety, (2)
10 * distributions including binary code include the above copyright notice and
11 * this paragraph in its entirety in the documentation or other materials
12 * provided with the distribution, and (3) all advertising materials mentioning
13 * features or use of this software display the following acknowledgement:
14 * ``This product includes software developed by the University of California,
15 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
16 * the University nor the names of its contributors may be used to endorse
17 * or promote products derived from this software without specific prior
18 * written permission.
19 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
20 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
21 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
22 */
23
24#include <sys/types.h>
25#include <sys/time.h>
26
27#include <stdio.h>
28#ifdef TIME_WITH_SYS_TIME
29#include <time.h>
30#endif
31
32#ifdef HAVE_OS_PROTO_H
33#include "os-proto.h"
34#endif
35
36#include "gmt2local.h"
37#include "privsep.h"
38
39/*
40 * Returns the difference between gmt and local time in seconds.
41 * Use gmtime() and localtime() to keep things simple.
42 */
43int32_t
44gmt2local(time_t t)
45{
46	int dt, dir;
47	struct tm *gmt, *loc;
48	struct tm sgmt;
49
50	if (t == 0)
51		t = time(NULL);
52	gmt = &sgmt;
53	*gmt = *gmtime(&t);
54	loc = priv_localtime(&t);
55	dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60 +
56	    (loc->tm_min - gmt->tm_min) * 60;
57
58	/*
59	 * If the year or julian day is different, we span 00:00 GMT
60	 * and must add or subtract a day. Check the year first to
61	 * avoid problems when the julian day wraps.
62	 */
63	dir = loc->tm_year - gmt->tm_year;
64	if (dir == 0)
65		dir = loc->tm_yday - gmt->tm_yday;
66	dt += dir * 24 * 60 * 60;
67
68	return (dt);
69}
70