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 */
43 int32_t
gmt2local(time_t t)44 gmt2local(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