1 /*
2 * Copyright (c) 1997
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that: (1) source code distributions
7 * retain the above copyright notice and this paragraph in its entirety, (2)
8 * distributions including binary code include the above copyright notice and
9 * this paragraph in its entirety in the documentation or other materials
10 * provided with the distribution, and (3) all advertising materials mentioning
11 * features or use of this software display the following acknowledgement:
12 * ``This product includes software developed by the University of California,
13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14 * the University nor the names of its contributors may be used to endorse
15 * or promote products derived from this software without specific prior
16 * written permission.
17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20 */
21
22 #ifndef lint
23 static const char rcsid[] _U_ =
24 "@(#) $Header: /tcpdump/master/tcpdump/gmt2local.c,v 1.9 2003-11-16 09:36:09 guy Exp $ (LBL)";
25 #endif
26
27 #ifdef HAVE_CONFIG_H
28 #include "config.h"
29 #endif
30
31 #include <tcpdump-stdinc.h>
32
33 #include <stdio.h>
34
35 #ifdef HAVE_OS_PROTO_H
36 #include "os-proto.h"
37 #endif
38
39 #include "gmt2local.h"
40
41 /*
42 * Returns the difference between gmt and local time in seconds.
43 * Use gmtime() and localtime() to keep things simple.
44 */
45 int32_t
gmt2local(time_t t)46 gmt2local(time_t t)
47 {
48 register int dt, dir;
49 register struct tm *gmt, *loc;
50 struct tm sgmt;
51
52 if (t == 0)
53 t = time(NULL);
54 gmt = &sgmt;
55 *gmt = *gmtime(&t);
56 loc = localtime(&t);
57 dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60 +
58 (loc->tm_min - gmt->tm_min) * 60;
59
60 /*
61 * If the year or julian day is different, we span 00:00 GMT
62 * and must add or subtract a day. Check the year first to
63 * avoid problems when the julian day wraps.
64 */
65 dir = loc->tm_year - gmt->tm_year;
66 if (dir == 0)
67 dir = loc->tm_yday - gmt->tm_yday;
68 dt += dir * 24 * 60 * 60;
69
70 return (dt);
71 }
72