2 * Copyright (c) 1990 The Regents of the University of California.
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
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.
21 * $FreeBSD: src/usr.sbin/tcpdump/tcpslice/gwtm2secs.c,v 1.4 1999/08/28 05:11:32 peter Exp $
22 * $DragonFly: src/usr.sbin/tcpdump/tcpslice/gwtm2secs.c,v 1.3 2004/04/23 17:55:11 cpressey Exp $
26 * gwtm2secs.c - convert "tm" structs for Greenwich time to Unix timestamp
31 static int days_in_month[] =
32 /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
33 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
35 #define IS_LEAP_YEAR(year) \
36 (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))
38 time_t gwtm2secs(struct tm *tm)
45 * Allow for year being specified with either 2 digits or 4 digits.
46 * 2-digit years are either 19xx or 20xx - a simple heuristic
47 * distinguishes them, since we can't represent any time < 1970.
57 for (i = 1970; i < year; ++i) {
63 for (i = 0; i < tm->tm_mon; ++i)
64 days += days_in_month[i];
66 if (IS_LEAP_YEAR(year) && tm->tm_mon > 1) /* 1 is February */
69 days += tm->tm_mday - 1; /* -1 since days are numbered starting at 1 */
71 return(days * 86400 + tm->tm_hour * 3600 + tm->tm_min * 60 + tm->tm_sec);