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 #ifdef HAVE_CONFIG_H
23 #include "config.h"
24 #endif
25
26 #include <netdissect-stdinc.h>
27
28 #include <stdio.h>
29
30 #ifdef HAVE_OS_PROTO_H
31 #include "os-proto.h"
32 #endif
33
34 #include "gmt2local.h"
35
36 /*
37 * Returns the difference between gmt and local time in seconds.
38 * Use gmtime() and localtime() to keep things simple.
39 */
40 int32_t
gmt2local(time_t t)41 gmt2local(time_t t)
42 {
43 register int dt, dir;
44 register struct tm *gmt, *loc;
45 struct tm sgmt;
46
47 if (t == 0)
48 t = time(NULL);
49 gmt = &sgmt;
50 *gmt = *gmtime(&t);
51 loc = localtime(&t);
52 dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60 +
53 (loc->tm_min - gmt->tm_min) * 60;
54
55 /*
56 * If the year or julian day is different, we span 00:00 GMT
57 * and must add or subtract a day. Check the year first to
58 * avoid problems when the julian day wraps.
59 */
60 dir = loc->tm_year - gmt->tm_year;
61 if (dir == 0)
62 dir = loc->tm_yday - gmt->tm_yday;
63 dt += dir * 24 * 60 * 60;
64
65 return (dt);
66 }
67